ORCID Profile
0000-0002-1108-6503
Current Organisations
University Of Strathclyde
,
Queensland University of Technology
,
University of Bristol
Does something not look right? The information on this page has been harvested from data sources that may not be up to date. We continue to work with information providers to improve coverage and quality. To report an issue, use the Feedback Form.
Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Biomedical Engineering | Biomechanical Engineering | Orthopaedics | Rehabilitation Engineering | Image Processing | Paediatrics | Biomechanics | Biomaterials | Engineering/Technology Instrumentation | Cardiology (Incl. Cardiovascular Diseases) | Medical Physics |
ANZSRC Socio-Economic Objective (SEO)
Skeletal system and disorders (incl. arthritis) | Medical instrumentation | Surgical methods and procedures | Clinical health not specific to particular organs, diseases and conditions | Nervous system and disorders | Health related to ageing | Cardiovascular system and diseases | Child health | Integrated systems | Machinery and equipment not elsewhere classified
Related Links
Publications
Timing of pulsed electromagnetic field stimulation does not affect the promotion of bone cell development
Publisher: Wiley
Date: 27-09-2005
DOI: 10.1002/BEM.20166
Abstract: Pulsed electromagnetic field (PEMF) devices have been used clinically to promote the healing of surgically resistant fractures in vivo. However, there is a sparsity of data on how the timing of an applied PEMF effects the osteogenic cells that would be present within the fracture gap. The purpose of this study was to examine the response of osteoblast-like cells to a PEMF stimulus, mimicking that of a clinically available device, using four protocols for the timing of the stimulus. The PEMF signal consisted of a 5 ms pulse burst (containing 20 pulses) repeated at 15 Hz. Cultures of a human osteosarcoma cell line, SaOS-2, were exposed to the four timing protocols, each conducted over 3 days. Protocol one stimulated the cells for 8 h each day, protocol two stimulated the cells for 24 h on the first day, protocol three stimulated the cells for 24 h on the second day, and protocol four stimulated the cells for 24 h on the third day. Cells were seeded with either 25,000 or 50,000 cells/well (24-well cell culture plates). All assays showed reduced proliferation and increased differentiation (alkaline phosphatase activity) in the PEMF stimulated cultures compared with the control cultures, except for protocol four alkaline phosphatase measurements. No clear trend was observed between the four protocols however this may be due to cell density. The results indicated that an osteoblast-like cell line is responsive to a 15 Hz PEMF stimulus, which will stimulate the cell line to into an increasing state of maturity.
Functional outcome of transfemoral amputees fitted with an osseointegrated fixation: Temporal gait characteristics
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 2010
Artificial lumbar intervertebral disc replacement: Accepted practice or experimental surgery?
Publisher: Informa UK Limited
Date: 11-2010
DOI: 10.1586/ERD.10.60
Abstract: A review of the literature suggests that implanting current artificial discs for degenerative disc disease at one level of the lumbar spine is as safe and effective as fusion, but is not a substantially better procedure. There are no controlled trials of multilevel implantation, and the literature suggests that this should, therefore, be considered experimental surgery. There is evidence that adjacent levels are not protected from degeneration, and degeneration of the zygapophysial joints at the operated level may occur. The concept of motion preservation is unproven and needs to be reviewed.
Growing rod analysis for the fusionless correction of early onset scoliosis (EOS)
Publisher: Springer Science and Business Media LLC
Date: 19-01-2014
Guest Editorial: Recent progress in artificial organs and regenerative medicine in Japan
Publisher: Wiley
Date: 05-2010
Categorization of activities of daily living of lower limb amputees during short-term use of a portable kinetic recording system: A preliminary study
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 2011
Are coupled rotations in the lumbar spine largely due to the osseo-ligamentous anatomy?—A modeling study
Publisher: Informa UK Limited
Date: 02-2008
DOI: 10.1080/10255840701552143
Abstract: Prior studies have found that primary rotations in the lumbar spine are accompanied by coupled out-of-plane rotations. However, it is not clear whether these accompanying rotations are primarily due to passive (discs, ligaments and facet joints) or active (muscles) spinal anatomy. The aim of this study was to use a finite element (FE) model of the lumbar spine to predict three-dimensional coupled rotations between the lumbar vertebrae, due to passive spinal structures alone. The FE model was subjected to physiologically observed whole lumbar spine rotations about in vivo centres of rotation. Model predictions were validated by comparison of intra-discal pressures and primary rotations with in vivo measurements and these showed close agreement. Predicted coupled rotations matched in vivo measurements for all primary motions except lateral bending. We suggest that coupled rotations accompanying primary motions in the sagittal (flexion/extension) and transverse (axial rotation) planes are primarily due to passive spinal structures. For lateral bending the muscles most likely play a key role in the coupled rotation of the spine.
Simulation and enhancement of a cardiovascular device test rig
Publisher: Informa UK Limited
Date: 03-2010
DOI: 10.1057/JOS.2009.15
Dynamic back movement measured using a three-dimensional television system
Publisher: Elsevier BV
Date: 1987
DOI: 10.1016/0021-9290(87)90323-X
Abstract: A technique for the measurement of rotational human back movements in three dimensions has been developed. The spatial coordinates of reflective markers on rigs attached to the back surface were calculated using a calibrated television/computer system. A mathematical analysis of the change in these coordinates, as subjects performed set manoeuvres, was developed to provide unique descriptions of the rotational movements in terms of clinical angles related to anatomical frames of reference. The technique produced angles of rotation with maximum errors about any axis of +/- 2 degrees, with a root mean square error of less than 1 degree. The analysis of back movements using surface markers was shown to be feasible from studies of six volunteers who demonstrated consistent patterns of movement which were similar to previously reported patterns of spinal movement measured radiographically.
Power spectrum analysis of human femoral rotations during gait
Publisher: Springer Science and Business Media LLC
Date: 09-1997
DOI: 10.1007/BF02525540
Abstract: We are living in a terrifying pandemic caused by Sars-CoV-2, in which patients with diabetes mellitus have, from the beginning, been identified as having a high risk of hospitalization and mortality. This viral disease is not limited to the respiratory system, but also affects, among other organs, the central nervous system. Furthermore, we already know that in iduals with diabetes mellitus exhibit signs of astrocyte dysfunction and are more likely to develop cognitive deficits and even dementia. It is now being realized that COVID-19 incurs long-term effects and that those infected can develop several neurological and psychiatric manifestations. As this virus seriously compromises cell metabolism by triggering several mechanisms leading to the unfolded protein response (UPR), which involves endoplasmic reticulum Ca
Abnormal motion in spondylolytic spondylolisthesis
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 05-2005
DOI: 10.1097/01.BRS.0000162400.06685.37
Abstract: A retrospective, cohort study of the kinematics of the lumbar spine of patients with spondylolisthesis compared with asymptomatic normal subjects. To determine if abnormal motion could be detected in the radiographs of patients with spondylolisthesis. Contrary to the prevailing conviction that lumbar segments affected by lytic spondylolisthesis are unstable, multiple studies have failed to find evidence of increased or abnormal motion at these segments. However, these studies did not use techniques that might reveal abnormalities in the quality of motion, as opposed to its magnitude. The flexion-extension radiographs of 13 patients with spondylolytic spondylolisthesis were analyzed to determine the location of their instantaneous centers of rotation, and their magnitudes of translation and sagittal rotation. Normative data were obtained by applying the same techniques to the radiographs of 20 asymptomatic subjects. All but 1 of the 13 patients had at least one segment with abnormal motion. Only one patient had excessive translation at the lytic segment. Five patients had minor abnormalities affecting either the lytic segment or ones above, and 6 had paradoxical motion at the lytic segment in which the center of rotation was located above L5, instead of below, and in which L5 translated backward instead of forward during flexion. A proportion of patients with spondylolisthesis had highly abnormal movements but ones with normal magnitudes of motion. Determining the instantaneous axes of rotation reveals the abnormal quality of motion.
Development of a multi-scale finite element model of the osteoporotic lumbar vertebral body for the investigation of apparent level vertebra mechanics and micro-level trabecular mechanics
Publisher: Elsevier BV
Date: 07-2010
DOI: 10.1016/J.MEDENGPHY.2010.04.006
Abstract: Osteoporotic spinal fractures are a major concern in ageing Western societies. This study develops a multi-scale finite element (FE) model of the osteoporotic lumbar vertebral body to study the mechanics of vertebral compression fracture at both the apparent (whole vertebral body) and micro-structural (internal trabecular bone core) levels. Model predictions were verified against experimental data, and found to provide a reasonably good representation of the mechanics of the osteoporotic vertebral body. This novel modelling methodology will allow detailed investigation of how trabecular bone loss in osteoporosis affects vertebral stiffness and strength in the lumbar spine.
A biomechanical investigation of dual growing rods used for fusionless scoliosis correction
Publisher: Elsevier BV
Date: 2015
DOI: 10.1016/J.CLINBIOMECH.2014.11.008
Abstract: The use of dual growing rods is a fusionless surgical approach to the treatment of early onset scoliosis which aims to harness potential growth and correct spinal deformity. The purpose of this study was to compare the in-vitro biomechanical response of two different dual rod designs under axial rotation loading. Six porcine spines were dissected into seven level thoracolumbar multi-segment units. Each specimen was mounted and tested in a biaxial Instron machine, undergoing nondestructive left and right axial rotation to peak moments of 4 Nm at a constant rotation rate of 8 deg. s(-1). A motion tracking system (Optotrak) measured 3D displacements of in idual vertebrae. Each spine was tested in an un-instrumented state first and then with appropriately sized semi-constrained and 'rigid' growing rods in alternating sequence. The range of motion, neutral zone size and stiffness were calculated from the moment-rotation curves and intervertebral range of motion was calculated from Optotrak data. Irrespective of test sequence, rigid rods showed a significant reduction of total rotation across all instrumented levels (with increased stiffness) whilst semi-constrained rods exhibited similar rotational behavior to the un-instrumented spines (P<0.05). An 11.1% and 8.0% increase in stiffness for left and right axial rotation respectively and 14.9% reduction in total range of motion were recorded with dual rigid rods compared with semi-constrained rods. Based on these findings, the Semi-constrained growing rods were shown to not increase axial rotation stiffness compared with un-instrumented spines. This is thought to provide a more physiological environment for the growing spine compared to dual rigid rod constructs.
Thermomechanical investigation of the cortical bone analogue in third-generation Sawbones femurs
Publisher: SAGE Publications
Date: 02-2007
Abstract: The mechanical properties of the short glass fibre reinforced (SGFR) epoxy resin used as the cortical bone analogue in the third-generation Sawbones femurs were investigated for use within orthopaedic benchtop tests. Tensile and four-point bending tests were used to assess the material properties of the SGFR epoxy at both room (22° C) and body temperatures (37° C). The 20 standardized specimens used for the materials testing were machined from third-generation Sawbones femurs. The flexural properties of the specimens were determined using ASTM D6272-02 and the tensile properties were obtained using ASTM D638-02. The mean (and standard deviation, or SD) values of the modulus of elasticity in four-point bending for room and body temperature specimens of 7.8 (0.64) GPa and 2.8 (0.66) GPa respectively were significantly different ( P 0.001). The mean (and SD) values of the modulus of elasticity in tension for the room and body temperature specimens of 9.4 (0.8) GPa and 5.4 (1.3) GPa respectively were also significantly different ( P = 0.02). The modulus of elasticity of SGFR epoxy is highly temperature dependent. A reduction in the modulus of elasticity of up to 63 per cent was observed when increasing the temperature of the specimens from room to body temperature. SGFR epoxy Sawbones do not accurately represent the material properties of bone at body temperature.
Load on osseointegrated fixation of a transfemoral amputee during a fall: Loading, descent, impact and recovery analysis
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 03-2010
DOI: 10.3109/03093640903585024
Abstract: Falling represents a health risk for lower limb utees fitted with an osseointegrated fixation mainly because of the potential damage to the fixation. The purpose of this study was to characterize a real forward fall that occurred inadvertently to a transfemoral utee fitted with an osseointegrated fixation while attending a gait measurement session to assess the load applied on the residuum. The objective was to analyze the load applied on the fixation with an emphasis on the sequence of events, the pattern and the magnitude of the forces and moments. The load was measured directly at 200 Hz using a six-channel transducer. Complementary video footage was also studied. The fall was ided into four phases: Loading (240 ms), descent (620 ms), impact (365 ms) and recovery (2495 ms). The main impact forces and moments occurred 870 ms and 915 ms after the heel contact, and corresponded to 133% BW and 17 % BWm, or 1.2 and 11.2 times the maximum forces and moments applied during the previous steps of the participant, respectively. This study provided key information to engineers and clinicians facing the challenge to design equipment, and rehabilitation and exercise programs to restore safely the locomotion of lower limb utees.
Temperature dependence of the tensile properties of interspinous ligaments of sheep
Publisher: Elsevier BV
Date: 1986
DOI: 10.1016/0141-5425(86)90032-4
Abstract: The dependence on temperature of the tensile properties of interspinous ligaments was examined to establish whether in vitro studies at room temperature reflect behaviour in vivo at higher temperatures. Specimens consisting of sheep interspinous ligaments attached to their adjacent spinous processes were mounted in specially designed holding devices in an Instron material testing machine the specimens were immersed in saline and tests were conducted at four temperatures between 19 degrees C and 46 degrees C. Control tests demonstrated the repeated testing to a load up to half the fail load did not affect the response of the ligaments. No difference was found in the mechanical characteristics of the ligaments at the different temperatures but the ligaments expanded at the higher temperatures, resulting in an increase in extension over which they demonstrated an initial low stiffness characteristic. Thus although temperature did not directly affect the response of the ligaments to load, the thermal expansion of the soft tissue elements may have implications for the function and mobility of spinal joints if measured at room rather than body temperature.
The BiVACOR rotary biventricular assist device : concept and in vitro investigation
Publisher: Wiley
Date: 10-2008
DOI: 10.1111/J.1525-1594.2008.00633.X
Abstract: The BiVACOR is a novel rotary Biventricular Assist Device (BiVAD) undergoing development to treat global end-stage heart failure. The design includes left and right vanes positioned on a shared rotating hub to form a double-sided magnetically and hydrodynamically suspended centrifugal impeller. The performance of the device was assessed in a pulsatile mock circulation loop replicating end-stage biventricular heart failure, and was shown to restore flow from pathological (2 L/min) to normal levels (5 L/min). A novel technique to balance the left/right outflow of the BiVAD was also investigated, for which a maximum relative left to right outflow differential of 1.8 L/min was achieved at normal physiologic afterloads. The in vitro results encourage device progression to in vivo animal studies. Successful development of this BiVAD will provide a suitably miniature device for patients who require biventricular assistance.
Frank-starling control of a left ventricular assist device
Publisher: IEEE
Date: 08-2011
Measurement of back and spinal mobility
Publisher: Elsevier BV
Date: 02-1986
Nonlinear finite element analysis of anular lesions in the L4/5 intervertebral disc
Publisher: Elsevier BV
Date: 2007
DOI: 10.1016/J.JBIOMECH.2007.01.007
Abstract: Degenerate intervertebral discs exhibit both material and structural changes. Structural defects (lesions) develop in the anulus fibrosus with age. While degeneration has been simulated in numerous previous studies, the effects of structural lesions on disc mechanics are not well known. In this study, a finite element model (FEM) of the L4/5 intervertebral disc was developed in order to study the effects of anular lesions and loss of hydrostatic pressure in the nucleus pulposus on the disc mechanics. Models were developed to simulate both healthy and degenerate discs. Degeneration was simulated with either rim, radial or circumferential anular lesions and by equating nucleus pressure to zero. The anulus fibrosus ground substance was represented as a nonlinear incompressible material using a second-order polynomial, hyperelastic strain energy equation. Hyperelastic material parameters were derived from experimentation on sheep discs. Endplates were assumed to be rigid, and annulus lamellae were assumed to be vertical in the unloaded state. Loading conditions corresponding to physiological ranges of rotational motion were applied to the models and peak rotation moments compared between models. Loss of nucleus pulposus pressure had a much greater effect on the disc mechanics than the presence of anular lesions. This indicated that the development of anular lesions alone (prior to degeneration of the nucleus) has minimal effect on disc mechanics, but that disc stiffness is significantly reduced by the loss of hydrostatic pressure in the nucleus. With the degeneration of the nucleus, the outer innervated anulus or surrounding osteo-ligamentous anatomy may therefore experience increased strains.
Movements of the lumbar spine measured by three-dimensional X-ray analysis
Publisher: Elsevier BV
Date: 04-1982
DOI: 10.1016/0141-5425(82)90070-X
Abstract: Techniques for the calculation from biplanar radiographs of the three-dimensional coordinates of anatomical landmarks on human lumbar vertebrae, and of the movements in three dimensions of the vertebrae between different positions of the spine are presented. The calculation of three-dimensional coordinates uses a calibration procedure based on direct linear transformation. Coordinate systems are used to define the orientations of each vertebra, and movements are derived from coordinate transformations between neighbouring vertebrae. The root mean square error in determining the absolute locations of anatomical landmarks was found to be less than 1 mm. For the movements of one vertebra relative to its neighbour the root mean square errors for translations were less than 2 mm and for rotations were less than 1.5 degrees. The system has been used to assess patients after spinal fusions and is currently being used in the diagnosis and assessment of patients with specific pathologies.
Mediation of biomaterial-cell interactions by adsorbed proteins: A review
Publisher: Mary Ann Liebert Inc
Date: 2005
Abstract: An appropriate cellular response to implanted surfaces is essential for tissue regeneration and integration. It is well described that implanted materials are immediately coated with proteins from blood and interstitial fluids, and it is through this adsorbed layer that cells sense foreign surfaces. Hence, it is the adsorbed proteins, rather than the surface itself, to which cells initially respond. Diverse studies using a range of materials have demonstrated the pivotal role of extracellular adhesion proteins--fibronectin and vitronectin in particular--in cell adhesion, morphology, and migration. These events underlie the subsequent responses required for tissue repair, with the nature of cell surface interactions contributing to survival, growth, and differentiation. The pattern in which adhesion proteins and other bioactive molecules adsorb thus elicits cellular reactions specific to the underlying physicochemical properties of the material. Accordingly, in vitro studies generally demonstrate favorable cell responses to charged, hydrophilic surfaces, corresponding to superior adsorption and bioactivity of adhesion proteins. This review illustrates the mediation of cell responses to biomaterials by adsorbed proteins, in the context of osteoblasts and selected materials used in orthopedic implants and bone tissue engineering. It is recognized, however, that the periimplant environment in vivo will differ substantially from the cell-biomaterial interface in vitro. Hence, one of the key issues yet to be resolved is that of the interface composition actually encountered by osteoblasts within the sequence of inflammation and bone regeneration.
The reliability of postural sway measures using the 3SPACE tracker
Publisher: Elsevier BV
Date: 09-1996
DOI: 10.1016/0268-0033(96)00009-5
Abstract: OBJECTIVE: To investigate the reliability of three-dimensional postural control sway measures, in a normal population, using an electromagnetic device. DESIGN: A repeated measures design was used within and between sessions. BACKGROUND: Electromagnetic measurement has been proposed as a method of measuring postural sway however, reliability within a normal population has not been shown. METHOD: An electromagnetic device, the 3SPACE Tracker, measured postural sway at the pelvis using sway path length and displacements in the anterior-posterior, medial-lateral and vertical direction. Ten subjects performed a postural control task involving two trials for six different sensory conditions, on two separate occasions, two weeks apart. RESULTS: The reliability of the technique was demonstrated by the repeatability of results for in idual subjects within and between sessions. In idual subjects and sensory conditions were discriminated. Sway path length was the most consistent of the measures used. CONCLUSIONS: Three dimensional measures of postural sway are reliable and discriminatory in a normal population.
Comparison of Silicate-Substituted Calcium Phosphate (Actifuse) with Recombinant Human Bone Morphogenetic Protein-2 (Infuse) in Posterolateral Instrumented Lumbar Fusion
Publisher: SAGE Publications
Date: 12-2015
Abstract: Randomized controlled trial. The aim of this study was to assess the efficacy of the bone grafting substitute silicate-substituted calcium phosphate (SiCaP) compared with recombinant human bone morphogenetic protein 2 (rhBMP-2) and to evaluate the clinical outcomes over a period of 2 years. Patients undergoing PLF surgery for DDD at a single center were recruited and randomized to one of two groups: SiCaP ( n = 9) or rhBMP-2 ( n = 10). One patient withdrew prior to randomization and another from the rhBMP-2 group after randomization. The radiologic and clinical outcomes were examined and compared. Fusion was assessed at 12 months with computed tomography and plain radiographs. Clinical outcomes were evaluated by recording measures of pain, quality of life, disability, and neurologic status from 6 weeks to 2 years postoperatively. In the SiCaP and rhBMP-2 groups, fusion was observed in 9/9 and 8/9 patients, respectively. Pain and disability scores were reduced and quality of life increased in both groups. Leg pain, disability, and satisfaction scores were similar between the groups at each postoperative point however, back pain was less at 6 weeks and quality of life was higher at 6 months in the SiCaP group than the rhBMP-2 group. SiCaP and rhBMP-2 were comparable in terms of achieving successful bone growth and fusion. Both groups achieved similar alleviation of pain and improved quality of life and neurologic, satisfaction, and return to work outcomes following PLF surgery.
A three-dimensional mathematical model of the thoracolumbar fascia and an estimate of its biomechanical effect
Publisher: Elsevier BV
Date: 10-2010
DOI: 10.1016/J.JBIOMECH.2010.06.022
Abstract: The thoracolumbar fascia (TLF) provides a means of attachment to the lumbar spine for several muscles including the transverse abdominis, and parts of the latissimus dorsi and internal oblique muscles. Previous biomechanical models of the lumbar spine either tend to omit the TLF on the assumption that its contribution would be negligible or incorporate only part of the TLF. Here, a three-dimensional model of the posterior and middle layers of the TLF is presented to enable its action to be included in future three-dimensional models of the spine. It is used illustratively to estimate the biomechanical influence of this structure on the lumbar spine. The formulation of the model allows the lines of action of the fibres comprising the fascia to be calculated for any posture whilst ensuring that anatomical constraints are satisfied. Application of the model suggests that the TLF produces moments primarily in flexion and extension. The simulated results demonstrate that the abdominal muscles, acting via the TLF, are capable of contributing extension moments comparable to those produced by other smaller muscles associated with the lumbar spine.
Predicting the fatigue life of internal fracture fixation plates
Publisher: Elsevier BV
Date: 07-2008
The long-term wear of retrieved McKee-Farrar metal-on-metal total hip prostheses
Publisher: Elsevier BV
Date: 04-2005
DOI: 10.1016/J.ARTH.2004.09.028
Abstract: Twenty-four cobalt-chrome alloy McKee-Farrar matching acetabular and femoral components were retrieved at revision total hip arthroplasty. The average time in situ was 16 years. Wear and loss of sphericity was very low. Polishing wear (type 1), fine abrasive (type 2), multidirectional dull abrasive (type 3), and unidirectional dull abrasive wear (type 4) of the articulating surfaces were identified. The mean percent area of femoral heads occupied by types 2, 3, and 4 wear was 18%, 5%, and 2%, respectively. There was no association between the type and distribution of wear and the time in situ. Impingement damage was evident on 9 implant pairs. The extent and types of wear described in this paper will be useful when analyzing the patterns of surface damage of newer designs of metal-on-metal articulations.
Computational fluid dynamic analysis of intracranial aneurysmal bleb formation
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 13-08-2013
DOI: 10.1227/NEU.0000000000000137
Abstract: The management of unruptured aneurysms is controversial, with the decision to treat influenced by aneurysm characteristics including size and morphology. Aneurysmal bleb formation is thought to be associated with an increased risk of rupture. To correlate computational fluid dynamic (CFD) indices with bleb formation. Anatomic models were constructed from 3-dimensional rotational angiography data in 27 patients with cerebral aneurysms harboring a single bleb. Additional models representing the aneurysm before bleb formation were constructed by digitally removing the bleb. We characterized hemodynamic features of models both with and without the blebs using CFDs. Flow structure, wall shear stress (WSS), pressure, and oscillatory shear index (OSI) were analyzed. There was a statistically significant association between bleb location at or adjacent to the point of maximal WSS (74%, P = .019), irrespective of rupture status. Aneurysmal blebs were related to the inflow or outflow jet in 89% of cases (P & .001), whereas 11% were unrelated. Maximal wall pressure and OSI were not significantly related to bleb location. The bleb region attained a lower WSS after its formation in 96% of cases (P & .001) and was also lower than the average aneurysm WSS in 86% of cases (P & .001). Cerebral aneurysm blebs generally form at or adjacent to the point of maximal WSS and are aligned with major flow structures. Wall pressure and OSI do not contribute to determining bleb location. The measurement of WSS using CFD models may potentially predict bleb formation and thus improve the assessment of rupture risk in unruptured aneurysms.
Mechanical Function of the Nucleus Pulposus of the Intervertebral Disc under High Rates of Loading
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 08-2019
Mechanical function of the human lumbar interspinous and supraspinous ligaments
Publisher: Elsevier BV
Date: 07-1990
DOI: 10.1016/0141-5425(90)90010-K
Abstract: The mechanical function of the interspinous and supraspinous ligaments has been examined by simulating, on excised specimens, the deformation caused during forward flexion of the spine in real life. The load extension curves showed that during the first half of flexion the ligaments carried very little load but towards the end of the range of flexion they resisted up to 134N. When the supraspinous ligament was sectioned the interspinous ligament alone resisted 75% of this load. Testing at high strain rates showed an increase in load-carrying capacity of up to 30%. The maximum extension moment that can be produced by these ligaments was calculated to be approximately 7 Nm, or 5% of the moment the back muscles can produce across any intervertebral joint. Hence, during active lifting, these ligaments in isolation provide little mechanical assistance.
Bioengineering Activities in the Department of Orthopaedic Surgery and Trauma, Royal Adelaide Hospital, Adelaide, South Australia
Publisher: SAGE Publications
Date: 12-1991
DOI: 10.1243/PIME_PROC_1991_205_302_02
Abstract: This paper outlines the main areas of bioengineering research in the Department of Orthopaedic Surgery and Trauma at the Royal Adelaide Hospital, South Australia.
A naturally shaped silicone ventricle evaluated in a mock circulation loop: A preliminary study
Publisher: Informa UK Limited
Date: 2009
DOI: 10.1080/03091900802184072
Abstract: Mock circulation loops are used to evaluate the performance of cardiac assist devices prior to animal and clinical testing. A compressible, translucent silicone ventricle chamber that mimics the exact size, shape and motion of a failing heart is desired to assist in flow visualization studies around inflow cannulae during VAD support. The aim of this study was therefore to design and construct a naturally shaped flexible left ventricle and evaluate its performance in a mock circulation loop. The ventricle shape was constructed by the use of CT images taken from a patient experiencing cardiomyopathic heart failure and used to create a 3D image and subsequent mould to produce a silicone ventricle. Different cardiac conditions were successfully simulated to validate the ventricle performance, including rest, left heart failure and VAD support.
Evaluation of modal analysis techniques using physical models to detect osseointegration of implants in transfemoral amputees
Publisher: IEEE
Date: 08-2011
Ageing performance of a compliant layer bearing acetabular prosthesis in an ovine hip arthroplasty model
Publisher: Elsevier BV
Date: 09-2006
DOI: 10.1016/J.ARTH.2005.07.023
Abstract: The wear performance of a polyurethane compliant layer (CL) material formed into an acetabular component and implanted into a sheep model of cemented total hip arthroplasty was assessed at 6, 12, 24, and 48 months. Four (11%) of 36 acetabular components debonded from the cement and one component was slightly loose at the cement-bone interface. There was no macroscopic evidence of fracture, wear, or deformation of the CL material on the articular surface of the acetabular components. Small numbers of polymeric wear particles was found in the hip synovial tissues of 10 sheep, most commonly in the early time groups, and were likely associated with initial wear of surface asperities. The wear performance of the CL was unchanged during a 48-month implantation period.
Bilateral femoral rotations measured during walking
Publisher: Elsevier BV
Date: 09-1996
DOI: 10.1016/0268-0033(95)00073-9
Abstract: The aim of this study was to develop and assess a method of analysis of femoral rotations to describe and summarize an in idual's gait. Twelve normal subjects underwent walking trials at both natural and slow speeds, controlled by a metronome. The three-dimensional rotations of each femur were measured, simultaneously, during walking using a 3SPACE Tracker. The phase lags between the three rotations for each leg, obtained by cross-correlations, provided the primary data. The device was found to be reliable and gave significant test--retest repeatability. The analyses provided summary parameters describing mathematically the patterns of rotations and showed there was repeatability within and between sessions. A strong systematic subject effect in all analyses indicated that these parameters provide a highly specific description of how an in idual walks.
A new approach for assigning bone material properties from CT images into finite element models
Publisher: Elsevier BV
Date: 03-2010
DOI: 10.1016/J.JBIOMECH.2009.10.040
Abstract: Generation of subject-specific finite element (FE) models from computed tomography (CT) datasets is of significance for application of the FE analysis to bone structures. A great challenge that remains is the automatic assignment of bone material properties from CT Hounsfield Units into finite element models. This paper proposes a new assignment approach, in which material properties are directly assigned to each integration point. Instead of modifying the dataset of FE models, the proposed approach ides the assignment procedure into two steps: generating the data file of the image intensity of a bone in a MATLAB program and reading the file into ABAQUS via user subroutines. Its accuracy has been validated by assigning the density of a bone phantom into a FE model. The proposed approach has been applied to the FE model of a sheep tibia and its applicability tested on a variety of element types. The proposed assignment approach is simple and illustrative. It can be easily modified to fit users' situations.
The effect of repeated loading and freeze-thaw cycling on immature bovine thoracic motion segment stiffness
Publisher: SAGE Publications
Date: 10-2014
Abstract: There is growing interest in the biomechanics of “fusionless” implant constructs used for deformity correction in the thoracic spine however, there are questions over the comparability of in vitro biomechanical studies from different research groups due to the various methods used for specimen preparation, testing and data collection. The aim of this study was to identify the effect of two key factors on the stiffness of immature bovine thoracic spine motion segments: (1) repeated cyclic loading and (2) multiple freeze–thaw cycles, to aid in the planning and interpretation of in vitro studies. Two groups of thoracic spine motion segments from 6- to 8-week-old calves were tested in flexion/extension, right/left lateral bending and right/left axial rotation under moment control. Group A was tested with continuous repeated cyclic loading for 500 cycles with data recorded at cycles 3, 5, 10, 25, 50, 100, 200, 300, 400 and 500. Group (B) was tested after each of five freeze–thaw sequences, with data collected from the 10th load cycle in each sequence. Results of testing showed that for Group A: flexion/extension stiffness reduced significantly over the 500 load cycles (−22% p = 0.001), but there was no significant change between the 5th and 200th load cycles. Lateral bending stiffness decreased significantly (−18% p = 0.009) over the 500 load cycles, but there was no significant change in axial rotation stiffness ( p = 0.137). Group B: there was no significant difference between mean stiffness over the five freeze–thaw sequences in flexion/extension ( p = 0.813) and a near-significant reduction in mean stiffness in axial rotation (−6% p = 0.07). However, there was a statistically significant increase in stiffness in lateral bending (+30% p = 0.007). Study findings indicate that comparison of in vitro testing results for immature thoracic bovine spine segments between studies can be performed with up to 200 load cycles without significant changes in stiffness. However, when testing protocols require greater than 200 cycles, or when repeated freeze–thaw cycles are involved, it is important to account for the effect of cumulative load and freeze–thaw cycles on spine segment stiffness.
Measurement of human back movements in three dimensions by opto-electronic devices
Publisher: Elsevier BV
Date: 11-1987
DOI: 10.1016/0268-0033(87)90082-9
Abstract: Two systems for the measurement of the movement of retro-reflective markers in three-dimensional space have been used to measure rotations of the human back. Both the CODA-3 and the VICON devices used are available commercially. Both devices were shown to be capable of producing reproducible data on three-dimensional rotations. However, neither system was shown to be ideal due to the difficulty of maintaining the markers in the field of view. In particular, the CODA-3 system was found to be severely limited in this application due to the problem of cross-over conflict between the retro-reflective prisms that results in the loss of data. The VICON system was found to be more flexible but data analysis requires an interactive input from the operator and so can be very time consuming.
How Can Models of Motor Control Be Useful for Understanding Low Back Pain?
Publisher: Elsevier
Date: 2013
Three-dimensional kinematics of the human back
Publisher: Elsevier BV
Date: 11-1990
In Vitro Human Monocycle Response to Wear Particles of Titanium Alloy Containing Vanadium or Niobium
Publisher: British Editorial Society of Bone & Joint Surgery
Date: 03-1997
DOI: 10.1302/0301-620X.79B2.0790311
Abstract: Our aim was to determine whether in vitro studies would detect differences in the cellular response to wear particles of two titanium alloys commonly used in the manufacture of joint replacement prostheses. Particles were of the order of 1 μm in diameter representative of those found adjacent to failed prostheses. Exposure of human monocytes to titanium 6-aluminium 4- vanadium (TiAlV) at concentrations of 4 x 10 7 particles/ml produced a mean prostaglandin E 2 release of 2627.6 pM this was significantly higher than the 317.4 pM induced by titanium 6-aluminium 7-niobium alloy (TiAlNb) particles (p = 0.006). Commercially-pure titanium particles induced a release of 347.8 pM. In addition, TiAlV stimulated significantly more release of the other cell mediators, interleukin-1, tumour necrosis factor and interleukin-6. At lower concentrations of particles there was less mediator release and less obvious differences between materials. None of the materials caused significant toxicity. The levels of inflammatory mediators released by phagocytic cells in response to wear particles may influence the amount of periprosthetic bone loss. Our findings have shown that in vitro studies can detect differences in cellular response induced by particles of similar titanium alloys in common clinical use, although in vivo studies have shown little difference. While in vitro studies should not be used as the only form of assessment, they must be considered when assessing the relative biocompatibility of different implant materials.
Posterior intertransverse fusion assessed clinically and with biplanar radiography
Publisher: Springer Science and Business Media LLC
Date: 06-1985
DOI: 10.1007/BF00267032
Abstract: Data from the Czech national registry were analysed retrospectively to describe treatment outcomes for capecitabine and oxaliplatin (XELOX) regimen with bevacizumab versus 5-fluorouracil, leucovorin, and oxaliplatin (FOLFOX) regimen with bevacizumab in the first-line therapy for metastatic colorectal cancer (mCRC). A national registry containing anonymised in idual data on patients treated with targeted therapies was used as a data source. In total, 2,191 mCRC patients who received a first-line therapy with bevacizumab combined with either FOLFOX regimen (n = 1,218, 55.6%) or XELOX regimen (n = 973, 44.4%) were included in the present analysis. No statistically significant difference in survival was observed between the two groups, with median overall survival (OS) of 27.0 months (95% confidence interval [CI] 24.6-29.5 months) and 30.6 months (95% CI 27.8-33.4 months) for FOLFOX/bevacizumab and XELOX/bevacizumab, respectively (p = 0.281). Median progression-free survival (PFS) was 11.4 months (95% CI 10.7-12.1 months) for FOLFOX/bevacizumab and 11.5 months (95% CI 10.8-12.3 months) for XELOX/bevacizumab (p = 0.337). The number of metastatic sites was identified as the most significant predictor of PFS and, together with the presence/absence of metastatic disease at diagnosis, also for OS. According to this large registry-based analysis, XELOX and FOLFOX regimens have similar effectiveness for use in combination with bevacizumab in the first-line treatment of mCRC. Multiple metastatic sites and the presence of metastatic disease at diagnosis were the strongest negative predictors of OS regardless of backbone chemotherapy regimen.
Optimizing the response from a passively controlled biventricular assist device
Publisher: Wiley
Date: 05-2010
DOI: 10.1111/J.1525-1594.2009.00870.X
Abstract: Recent studies into rotary biventricular support have indicated that inadequate left/right flow balancing may lead to vascular congestion and/or ventricular suckdown. The implementation of a passive controller that automatically adjusts left/right flow during total and partial cardiac support would improve physiological interaction. This has encouraged the development of a biventricular assist device (BiVAD) prototype that achieves passive control of the two rotary pumps' hydraulic output by way of a nonrotating double pressure plate configuration, the hub, suspended between the ventricular assist device (VAD) impellers. Fluctuations in either the VAD's inlet or outlet pressure will cause the hub to translate, and in doing so, affect each pump's hydraulic outputs. In order to achieve partial support, the floating assembly needed to respond to pathologic blood pressure signals while being insensitive to residual ventricular function. An incorporated mechanical spring-mass-d er assembly affects the passive response to optimize the dynamic interaction between the prototype and the supported cardiovascular system. It was found that increasing the d ing from a medium to a high level was effective in filtering out the higher frequency ventricular pressure signals, reducing a modified litude ratio by up to 72%. A spring response was also identified as being inherent in the passive response and was characterized as being highly nonlinear at the extremes of the floating assembly's translation range. The results from this study introduce a new means of BiVAD control as well as the characterization of a fully passive mechanical physiological controller.
Soft layer lubrication of artificial hip joints
Publisher: Wiley
Date: 04-1988
Quantifying Progressive Anterior Overgrowth in the Thoracic Vertebrae of Adolescent Idiopathic Scoliosis Patients
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 04-2016
Biomechanics of the spine
Publisher: Elsevier BV
Date: 04-1989
A passively controlled biventricular support device
Publisher: Wiley
Date: 06-2010
DOI: 10.1111/J.1525-1594.2009.00897.X
Abstract: Clinical studies have reported the balancing of pump outputs to be a serious control issue for rotary biventricular support (BiVS) systems. Poor reliability of long-term, blood immersed pressure sensors encouraged the development of a new control strategy to improve their viability. A rotary BiVS device was designed and constructed with a mechanical passive controller to autoregulate pump outputs to emulate the native baroreceptor response. In vitro testing in a dual circuit, hydraulic mock circulation loop showed that the prototype was able to maintain arterial pressures when subjected to sudden induced hemodynamic destabilization. However, inlet suction was observed when sudden simulated hypertension briefly reduced venous return to the cannulated ventricle. The results have encouraged further development of the device as a means to create an inherently stable, fully passive biventricular support device.
Engineering the perfect mattress: The influence of substrate mechanics on deep tissue stresses in supine
Publisher: Elsevier BV
Date: 12-2023
Rotational mobility of the human back in forward flexion
Publisher: Elsevier BV
Date: 05-1989
DOI: 10.1016/0141-5425(89)90145-3
Abstract: This paper describes the measurement of the ability of the human back to twist when in flexed postures using a new electromagnetic measurement device. The mobility of the lumbar spine in 12 normal male subjects was investigated and it was demonstrated that increased rotation was possible when in a flexed posture. This suggests that the intervertebral disc may be vulnerable to torsion when twisting is combined with sub-maximal sagittal flexion.
In vitro evaluation of a compliant inflow cannula reservoir to reduce suction events with extracorporeal rotary ventricular assist device support
Publisher: Wiley
Date: 08-2011
DOI: 10.1111/J.1525-1594.2011.01311.X
Abstract: Limited preload sensitivity of rotary left ventricular assist devices (LVADs) renders patients susceptible to harmful atrial or ventricular suction events. Active control systems may be used to rectify this problem however, they usually depend on unreliable sensors or potentially inaccurate inferred data from, for ex le, motor current. This study aimed to characterize the performance of a collapsible inflow cannula reservoir as a passive control system to eliminate suction events in extracorporeal, rotary LVAD support. The reservoir was evaluated in a mock circulation loop against a rigid cannula under conditions of reduced preload and increased LVAD speed in both atrial and ventricular cannulation scenarios. Both cases demonstrated the ease with which chamber suction events can occur with a rigid cannula and confirm that the addition of the reservoir maintained positive chamber volumes with reduced preload and high LVAD speeds. Reservoir performance was dependent on height with respect to the cannulated chamber, with lower placement required in atrial cannulation due to reduced filling pressures. This study concluded that a collapsible inflow cannula is capable of minimizing suction events in extracorporeal, rotary LVAD support.
A graphical presentation of three-dimensional joint mobility
Publisher: Elsevier BV
Date: 02-1987
DOI: 10.1016/0268-0033(87)90040-4
Abstract: Reduction of joint mobility in humans is a very common medical condition which results from trauma or joint disease. However, there is currently no satisfactory way of plotting the three-dimensional rotations which completely define this mobility. The most usual method of presenting the results from the many systems for measuring joint mobility is to plot graphs of the three angles of rotation, in idually, against time, or to plot two angles of rotation against one another. However, this latter excludes the third angle of rotation which has to be presented separately. This paper suggests a technique known as the hemispherical projection method for the plotting of three-dimensional joint mobility data. The technique is derived from the fields of structural geology and rock mechanics where it is used for presenting and analysing orientation information on discontinuity planes in rock. Data from human hip and spine movements have now been successfully plotted using a microcomputer. This will provide an opportunity for straightforward comparison of movements between in iduals and patient groups using the shape of the output graphs as a clinical aid. In addition, it is suggested that 'indices of mobility' may be derived from the plots. These indices could be used to quantify joint disability using the area enclosed by, and the asymmetry of, the plot.
Load-induced changes in the diffusion tensor of ovine anulus fibrosus: A pilot MRI study
Publisher: Wiley
Date: 07-11-2017
DOI: 10.1002/JMRI.25531
Abstract: To assess the feasibility of diffusion tensor imaging (DTI) for evaluating changes in anulus fibrosus (AF) microstructure following uniaxial compression. Six axially aligned s les of AF were obtained from a merino sheep disc two each from the anterior, lateral, and posterior regions. The s les were mechanically loaded in axial compression during five cycles at a rate and maximum compressive strain that reflected physiological conditions. DTI was conducted at 7T for each s le before and after mechanical testing. The mechanical response of all s les in unconfined compression was nonlinear. A stiffer response during the first loading cycle, compared to the remaining cycles, was observed. Change in diffusion parameters appeared to be region-dependent. The mean fractional anisotropy increased following mechanical testing. This was smallest in the lateral (2% and 9%) and largest in the anterior and posterior s les (17-25%). The mean average diffusivity remained relatively constant (<2%) after mechanical testing in the lateral and posterior s les, but increased (by 5%) in the anterior s les. The mean angle made by the principal eigenvector with the spine axis in the lateral s les was 73° and remained relatively constant (<2%) following mechanical testing. This angle was smaller in the anterior (55°) and posterior (47°) regions and increased by 6-16° following mechanical testing. These preliminary results suggest that axial compression reorients the collagen fibers, such that they become more consistently aligned parallel to the plane of the endplates. 1 Technical Efficacy: Stage 1 J. MAGN. RESON. IMAGING 2017 :1723-1735.
A robotic testing facility for the measurement of the mechanics of spinal joints
Publisher: SAGE Publications
Date: 03-2007
Abstract: A robotic testing facility for the measurement of joint mechanics was used to determine the significance of tears in the intervertebral disc on the mechanics of the spinal joint. Ten lumbar joints of sheep were dynamically loaded and manipulated. Comparisons were made between the behaviour of the intervertebral disc in flexion and extension at two test speeds. The influence of the posterior elements and of rim lesions was assessed by testing the joint immediately before and after removal of the posterior elements and after the creation of a 40 N mm × 10 mm rim lesion in the disc. Stiffness of the spinal joint dropped significantly upon removal of the posterior elements, from 0.81 to 0.23 N m/deg for flexion and from 0.65 to 0.40 N m/deg for extension. Maximum moments dropped 37 per cent for flexion and 63 per cent for extension. The rim lesion caused a further significant stiffness reduction to 0.21 and 0.31 N m/deg respectively. Maximum moments reduced a further 12 per cent and 16 per cent respectively. A higher test speed (2 deg/s instead of 0.5 deg/s) usually did not change these results significantly. The novel six-degrees-of-freedom robotic testing facility used in this study was demonstrated to be an effective system for studying the mechanics of complex biological joints.
Radiographic and histologic analysis of cemented double tapered femoral stems
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 10-1998
DOI: 10.1097/00003086-199810000-00024
Abstract: The macroscopic, radiographic, and histologic features of the prosthesis-cement and cementbone interfaces and adjacent bone were studied in 21 cemented hemiarthroplasties in sheep that had lived until sacrifice at 9 months. The features were compared with those immediately after implantation of the stem in the contralateral femur. The femoral stem was a double taper that was either polished collarless, matte collarless, or matte collared. There was no prosthesis to cement debonding or cement to bone radiolucent line immediately after implantation, and there was excellent interdigitation at the cement-bone interface. After 9 months there was no evidence of prosthesis to cement debonding and no stem with definite loosening. At 9 months after implantation there was evidence of bone remodeling with new bone filling what were presumed to be gaps at the cement-bone interface from immediately after implantation. Radiolucent lines at the cement-bone interface were found to represent trabeculation of the cortical bone rather than the presence of a complete fibrous interface, which was not seen. There was no difference between stem types. Sheep have been shown to be useful in a model of cemented hip arthroplasty and, although no differences were seen between stem types at 9 months after implantation, long term differences cannot be excluded.
Understanding how axial loads on the spine influence segmental biomechanics for idiopathic scoliosis patients: A magnetic resonance imaging study
Publisher: Elsevier BV
Date: 02-2016
DOI: 10.1016/J.CLINBIOMECH.2015.11.007
Abstract: Segmental biomechanics of the scoliotic spine are important since the overall spinal deformity is comprised of the cumulative coronal and axial rotations of in idual joints. This study investigates the coronal plane segmental biomechanics for adolescent idiopathic scoliosis patients in response to physiologically relevant axial compression. In idual spinal joint compliance in the coronal plane was measured for a series of 15 idiopathic scoliosis patients using axially loaded magnetic resonance imaging. Each patient was first imaged in the supine position with no axial load, and then again following application of an axial compressive load. Coronal plane disc wedge angles in the unloaded and loaded configurations were measured. Joint moments exerted by the axial compressive load were used to derive estimates of in idual joint compliance. The mean standing major Cobb angle for this patient series was 46°. Mean intra-observer measurement error for endplate inclination was 1.6°. Following loading, initially highly wedged discs demonstrated a smaller change in wedge angle, than less wedged discs for certain spinal levels (+2,+1,-2 relative to the apex, (p<0.05)). Highly wedged discs were observed near the apex of the curve, which corresponded to lower joint compliance in the apical region. While in idual patients exhibit substantial variability in disc wedge angles and joint compliance, overall there is a pattern of increased disc wedging near the curve apex, and reduced joint compliance in this region. Approaches such as this can provide valuable biomechanical data on in vivo spinal biomechanics of the scoliotic spine, for analysis of deformity progression and surgical planning.
Re-design of the Exeter V40 long-stem femoral component for ease of removal
Publisher: SAGE Publications
Date: 02-2007
Abstract: Clinical experience shows that removal of the Exeter long-stem femoral component (220 mm, 240 mm, 260 mm) of total hip arthroplasty is extremely difficult, often requiring splitting of the femur. To identify the reason for this, measurements of stem geometry and force required to pull the stems out of the cement mantle were conducted on three original Exeter long-stem and one standard femoral components. All implants required an initial force of approximately 4 kN for release from the cement. The long-stem components then required much larger forces and hence much higher expenditure of energy to pull them clear of the cement. This was attributed to the reverse taper seen on the nominally cylindrical distal section of the long-stem components. Following re-design of the manufacturing process to ensure the taper continued to the implant's distal tip, four further implants were tested. These demonstrated the requirement for initial cement release but then required no further energy expenditure similar to the standard stem. This study clearly demonstrated that the original difficulty in removing these long stems was owing to the manufacturing process resulting in a reverse taper on the distal stem. The adoption of recommended manufacturing changes to ensure the taper continues to the distal tip removed this difficulty.
Mechanical consequences of annular tears and subsequent intervertebral disc degeneration
Publisher: Elsevier BV
Date: 07-1994
DOI: 10.1016/0268-0033(94)90001-9
Abstract: The relationship between degeneration of the intervertebral disc and changes to its mechanics is unclear. The aim of this study was to examine, in a sheep model, the effect of creating a lesion in the outer, anterior annulus on the mechanics of the intervertebral joint complex and the disc. Forty-one 2-year-old Merino wethers were allocated randomly into a control group or an annular lesion group and additionally to non-survivors which were sacrificed immediately or survivors sacrificed 6 months later. The annular lesion group had incisions made in two non-adjacent intervertebral discs and a plate was secured across the vertebrae at one level. Mechanical tests were performed on specimens consisting of the two vertebrae, the intervening disc and associated ligaments. Stiffness of the specimens was measured in flexion, extension, and in pure torsion. The tests were conducted first on the intact intervertebral joints and then after removal of the zygapophyseal joints and the interspinous and supraspinous ligaments. The results showed that the creation of an annular lesion caused immediate changes to the mechanics of the disc. In torsion, where no axis of rotation was imposed on the joints, there was a clear reduction in stiffness compared with controls. After 6 months the discs in the lesion groups approached the stiffness of the controls. The plates had a marked effect on the stiffness of the joints in flexion and extension, but after 6 months this difference was not apparent. The mechanics of the intact joints were not affected immediately by the lesion but after 6 months they were less stiff than the controls. There was clear evidence of a progressive degenerative response in the nucleus in all discs with a lesion. The addition of a plate to limit movement did not markedly affect this biological response to the injury but there was some evidence that after 6 months there were fewer degenerative changes to the zygapophyseal joints in the plated specimens. Recovery of the mechanical integrity of the disc was more marked in the joints that were plated, supporting the concept that limiting motion of an injured intervertebral disc facilitates a healing response in the annulus.
A compact mock circulation loop for the in vitro testing of cardiovascular devices
Publisher: Wiley
Date: 30-09-2010
DOI: 10.1111/J.1525-1594.2010.01088.X
Abstract: In vitro cardiovascular device performance evaluation in a mock circulation loop (MCL) is a necessary step prior to in vivo testing. A MCL that accurately represents the physiology of the cardiovascular system accelerates the assessment of the device's ability to treat pathological conditions. To serve this purpose, a compact MCL measuring 600 × 600 × 600 mm (L × W × H) was constructed in conjunction with a computer mathematical simulation. This approach allowed the effective selection of physical loop characteristics, such as pneumatic drive parameters, to create pressure and flow, and pipe dimensions to replicate the resistance, compliance, and fluid inertia of the native cardiovascular system. The resulting five-element MCL reproduced the physiological hemodynamics of a healthy and failing heart by altering ventricle contractility, vascular resistance/compliance, heart rate, and vascular volume. The effects of interpatient anatomical variability, such as septal defects and valvular disease, were also assessed. Cardiovascular hemodynamic pressures (arterial, venous, atrial, ventricular), flows (systemic, bronchial, pulmonary), and volumes (ventricular, stroke) were analyzed in real time. The objective of this study is to describe the developmental stages of the compact MCL and demonstrate its value as a research tool for the accelerated development of cardiovascular devices.
Sequential Magnetic Resonance Imaging Reveals Individual Level Deformities of Vertebrae and Discs in the Growing Scoliotic Spine
Publisher: Springer Science and Business Media LLC
Date: 05-2017
DOI: 10.1016/J.JSPD.2016.10.002
Abstract: The aim of this study was to measure contributions of in idual vertebra and disc wedging to coronal Cobb angle in the growing scoliotic spine using sequential magnetic resonance imaging (MRI). Clinically, the Cobb angle measures the overall curve in the coronal plane but does not measure in idual vertebra and disc wedging. It was hypothesized that patients whose deformity progresses will have different patterns of coronal wedging in vertebrae and discs to those of patients whose deformities remain stable. A group of adolescent idiopathic scoliosis (AIS) patients each received two to four MRI scans (spaced 3-12 months apart). The coronal plane wedge angles of each vertebra and disc in the major curve were measured for each scan, and the proportions and patterns of wedging in vertebrae and discs were analyzed for subgroups of patients whose spinal deformity did and did not progress during the study period. Sixteen patients were included in the study the mean patient age was 12.9 years (standard deviation 1.7 years). All patients were classified as right-sided major thoracic Lenke Type 1 curves (9 type 1A, 4 type 1B, and 3 type 1C). Cobb angle progression of ≥5° between scans was seen in 56% of patients. Although there were measurable changes in the wedging of in idual vertebrae and discs in all patients, there was no consistent pattern of deformity progression between patients who progressed and those who did not. The patterns of progression found in this study did not support the hypothesis of wedging commencing in the discs and then transferring to the vertebrae. Sequential MRI data showed complex patterns of deformity progression. Changes to the wedging of in idual vertebrae and discs may occur in patients who have no increase in Cobb angle therefore, the Cobb method alone may be insufficient to capture the complex mechanisms of deformity progression.
The effect of soft tissue properties on overall biomechanical response of a human lumbar motion segment: a preliminary finite element study
Publisher: WIT Press
Date: 05-09-2007
DOI: 10.2495/BIO070101
Predicting spinal profile using 3D non-contact surface scanning: Changes in surface topography as a predictor of internal spinal alignment
Publisher: Public Library of Science (PLoS)
Date: 26-09-2019
Gravity-induced torque and intravertebral rotation in idiopathic scoliosis
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 2008
Is There Asymmetry Between the Concave and Convex Pedicles in Adolescent Idiopathic Scoliosis? A CT Investigation
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 03-2017
In Vitro Analysis of Exeter Stem Torsional Stability
Publisher: Elsevier BV
Date: 10-2007
DOI: 10.1016/J.ARTH.2007.03.012
Abstract: The effect of cyclic loading on the torsional stiffness of a polished double-tapered femoral stem was investigated in vitro. Initial torsional stability was compared with torsional stability after cyclic loading. Stems were removed from the cement mantle and reinserted without the use of additional cement. Torsional stability was measured after reinsertion and after further cyclic loading. Subsidence of the stem was observed. No difference in torsional stiffness was observed during loading. No difference between the stiffness before extraction and after reinsertion was observed. Torsional stiffness of an Exeter stem does not decrease after axial subsidence under cyclic loading. Stability is retained after reinsertion into the original cement mantle. Debonding of the Exeter stem is not associated with rotational instability of the implant.
A semiautomatic method to identify vertebral end plate lesions (Schmorl's nodes)
Publisher: Elsevier BV
Date: 07-2015
DOI: 10.1016/J.SPINEE.2015.04.027
Abstract: There are differences in the definitions of end plate lesions (EPLs), often referred to as Schmorl's nodes, that may, to some extent, account for the large range of reported prevalence (3.8%-76%). The purpose of this study was to develop a technique to measure the size, prevalence, and location of EPLs in a consistent manner. This study proposed a method using a detection algorithm that was applied to five adolescent females (average age, 15.1 [range, 13.0-19.2] years) with idiopathic scoliosis (average major Cobb angle, 60° [range, 55°-67°]). Existing low-dose, computed tomography scans were segmented semiautomatically to extract three-dimensional morphology of each vertebral end plate. Any remaining attachments to the posterior elements of adjacent vertebrae or end plates were then manually sectioned. An automatic algorithm was used to determine the presence and position of EPLs. End plate lesions were identified in 15 of the 170 (8.8%) end plates analyzed with an average depth of 3.1 mm. Eleven of the 15 EPLs were seen in the lumbar spine. The algorithm was found to be most sensitive to changes in the minimum EPL gradient at the edges of the EPL. This study describes an imaging analysis technique for consistent measurement of the prevalence, location, and size of EPLs. The technique can be used to analyze large populations without observer errors in EPL definitions.
THE AXIAL TORQUE OF THE LUMBAR BACK MUSCLES: TORSION STRENGTH OF THE BACK MUSCLES
Publisher: Wiley
Date: 03-1993
DOI: 10.1111/J.1445-2197.1993.TB00520.X
Abstract: The maximal, axial torque generated by the lumbar back muscles was determined by modelling the action of the 49 fascicles of longissimus thoracis, iliocostalis lumborum and the lumbar multifidus on radiographs of the lumbar spine of nine young male subjects in upright standing and in full lumbar flexion. No single fascicle exerted more than 2 Nm of axial torque in the upright posture, and the collective torque of all muscles acting a segment did not exceed 5 Nm. All torques were considerably less in full flexion. The lumbar back muscles exert very little torque on the lumbar spine, and contribute only about 5% of the total torque involved in trunk rotation. None of the lumbar back muscles can be considered a rotator. The oblique abdominal muscles are the principal rotators of the trunk. Preventative and rehabilitation programmes concerned with torsion injuries should focus on the abdominal muscles rather than the back muscles for stability in axial rotation.
Is vertebral rotation correction maintained after thoracoscopic anterior scoliosis surgery? A low-dose computed tomography study
Publisher: Springer Science and Business Media LLC
Date: 17-08-2017
The effect of trabecular micro-architecture on vertebra biomechanics: A finite element investigation
Publisher: WIT Press
Date: 05-09-2007
DOI: 10.2495/BIO070111
Correlations between the mechanical properties, radiology and histomorphometry of human femoral bone
Publisher: Elsevier BV
Date: 08-1992
DOI: 10.1016/0268-0033(92)90030-8
Abstract: Initial fixation of the femoral components of total hip replacements is related to the mechanical integrity of the bone within the proximal femur. This preliminary study examined the correlations between the mechanical properties, histomorphometry, and radiology of bone core specimens taken from the proximal femora of cadavers and of patients undergoing total hip replacement surgery. Measurements and subjective assessments of the femoral bone from radiographs were shown to have poor correlation with both compressive mechanical properties and bone volume measurements. However, the mechanical properties of the bone core specimens and the histomorphometric measurements correlated well with the bone density measured by single-photon absorptiometry, indicating that this type of imaging technique may be of value in determining bone quality prior to surgery. The prediction of the mechanical properties of the proximal femur by preoperative imaging may have direct bearing on the type of femoral component to be used in total hip replacement. Preoperative assessment of bone quality would allow the surgeon to predict the likely fixation obtainable with different designs.
FE stress analysis of the interface between the bone and an osseointegrated implant for amputees - Implications to refine the rehabilitation program
Publisher: Elsevier BV
Date: 12-2008
DOI: 10.1016/J.CLINBIOMECH.2008.06.012
Abstract: The direct anchorage of lower-limb prosthesis to the bone has been shown to be an excellent alternative for utees experiencing complications in using a conventional prosthetic socket. During rehabilitation phase, utees are asked to apply static loading on the abutment perpendicular to a weigh scale to prepare the bone to tolerate the forces likely to be developed during walking. The weigh scale measures only the vertical force. A different loading protocol can affect the bone-implant interface stresses and the outcome of the rehabilitation. This study developed a Finite Element model to study the stresses in the bone adjacent to the implant. Three loading conditions were applied based on the experimentally measured load: (1) vertical force applied along the long axis of the limb, corresponding to the load clinically prescribed in the weight bearing exercise (2) loads applied on the three axes, corresponding to the "true" load measured simultaneously by a tri-axial load transducer during the same exercise and (3) loads experienced during independent walking. The model revealed that the weigh scale might in fact be applying much higher and less uniform stresses on the bone than expected. During walking, high stress occurred at various locations of the implanted region, which was different from the patterns of stress distribution during weight bearing exercises. The difference in stress among three loading conditions implies that tri-axial load should be monitored during the weight bearing exercises and carefully prescribed.
Using MRI for the imaging of long bones: first experiences
Publisher: Elsevier BV
Date: 07-2008
Minimizing spine autofusion with the use of semiconstrained growing rods for early onset scoliosis in children
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 11-2018
DOI: 10.1097/BPO.0000000000001242
Abstract: A new growing rod (GR) design, the semiconstrained growing rod (SCGR), with the added advantage of axial rotation freedom within the components, has been introduced at our center which has been shown to be growth friendly. We hypothesize that the SCGR system would reduce autofusion in vivo, thereby maximizing the coronal plane correction, T1-S1 growth, and the final correction achieved at definitive fusion for children with an early onset scoliosis. In total, 28 patients had either single or dual 5.5 mm diameter SCGR placed minimally invasively through a submuscular approach. Surgical lengthening procedures occurred approximately every 6 months until the definitive fusion procedure was performed for 18 patients. Scoliosis, kyphosis, and lordosis angles, T1-S1 trunk length, and any complications encountered were evaluated. For the full cohort, before GR insertion, the mean major Cobb curve angle was 72.4 degrees (SD, 18.8 range, 45 to 120), mean T1-S1 trunk length was 282 mm (SD, 59 range, 129 to 365), and at the latest follow-up (mean 6.9 y, SD 3.3, range 2.0 to 13.0), 38.8 degrees (SD, 17.5 range 10 to 90) and 377 mm (SD, 62 range, 225 to 487), respectively. For the subset of 18 patients who have had their final instrumented fusion surgery, the definitive surgery procedure alone produced a correction of the major Cobb curve angle by mean 20.3 degrees (SD, 16.1 P .0001), and an increase in the T1-S1 trunk length of mean 31.7 mm (SD, 23.1 P .0001). There were 14 complications involving 11 of the 28 patients, giving rise to 5 unplanned surgical interventions and 1 case where GR treatment was abandoned. SCGR patients exhibited statistically significant increase in T1-S1 trunk length and statistically significant decrease in the severity of scoliosis over the course of GR treatment and again, importantly, with the definitive fusion surgery, suggesting that autofusion had been minimized during GR treatment with relatively low complication rates. Level IV—case series.
Finite Element Modeling to Aid in Refining the Rehabilitation of Amputees Using Osseointegrated Prostheses
Publisher: No publisher found
Date: 2007
Implant retrieval studies of the wear and loosening of prosthetic joints: A review
Publisher: Elsevier BV
Date: 07-2000
Mechanobiology of Bone Development and Computational Simulations
Publisher: Springer London
Date: 2010
A comparison of four techniques to measure anterior and posterior vertebral body heights and sagittal plane wedge angles in adolescent idiopathic scoliosis
Publisher: Springer Science and Business Media LLC
Date: 30-06-2016
DOI: 10.1007/S11517-016-1520-Y
Abstract: Adolescent idiopathic scoliosis (AIS) is a three-dimensional (3D) spinal deformity of unknown aetiology. Increased growth of the anterior part of the vertebrae known as anterior overgrowth has been proposed as a potential driver for AIS initiation and progression. To date, there has been no objective evaluation of the 3D measurement techniques used to identify this phenomenon and the majority of previous studies use 2D planar assessments which contain inherent projection errors due to the vertebral rotation which is part of the AIS deformity. In this study, vertebral body (VB) heights and wedge angles were measured in a test group of AIS patients and healthy controls using four different image analysis and measurement techniques. Significant differences were seen between the techniques in terms of VB heights and VB wedge angles. The low variability, and the fact that the rotation and tilt of the deformed VBs are taken into account, suggests that the proposed technique using the full 3D orientation of the vertebrae is the most reliable method to measure anterior and posterior VB heights and sagittal plane wedge angles in 3D image data sets. These results have relevance for future investigations that aim to quantify anterior overgrowth in AIS patients for comparison with healthy controls.
Supine to standing Cobb angle change in idiopathic scoliosis: The effect of endplate pre-selection
Publisher: Springer Science and Business Media LLC
Date: 08-10-2014
The mechanical response of the ovine lumbar anulus fibrosus to uniaxial, biaxial and shear loads
Publisher: Elsevier BV
Date: 02-2010
DOI: 10.1016/J.JMBBM.2009.09.002
Abstract: Analytical and computational models of the intervertebral disc (IVD) are commonly employed to enhance understanding of the biomechanics of the human spine and spinal motion segments. The accuracy of these models in predicting physiological behaviour of the spine is intrinsically reliant on the accuracy of the material constitutive representations employed to represent the spinal tissues. There is a paucity of detailed mechanical data describing the material response of the reinforced-ground matrix in the anulus fibrosus of the IVD. In the present study, the 'reinforced-ground matrix' was defined as the matrix with the collagen fibres embedded but not actively bearing axial load, thus incorporating the contribution of the fibre-fibre and fibre-matrix interactions. To determine mechanical parameters for the anulus ground matrix, mechanical tests were carried out on specimens of ovine anulus, under unconfined uniaxial compression, simple shear and biaxial compression. Test specimens of ovine anulus fibrosus were obtained with an adjacent layer of vertebral bone/cartilage on the superior and inferior specimen surface. Specimen geometry was such that there were no continuous collagen fibres coupling the two endplates. S les were sub ided according to disc region - anterior, lateral and posterior - to determine the regional inhomogeneity in the anulus mechanical response. Specimens were loaded at a strain rate sufficient to avoid fluid outflow from the tissue and typical stress-strain responses under the initial load application and under repeated loading were determined for each of the three loading types. The response of the anulus tissue to the initial and repeated load cycles was significantly different for all load types, except biaxial compression in the anterior anulus. Since the maximum applied strain exceeded the damage strain for the tissue, experimental results for repeated loading reflected the mechanical ability of the tissue to carry load, subsequent to the initiation of damage. To our knowledge, this is the first study to provide experimental data describing the response of the 'reinforced-ground matrix' to biaxial compression. Additionally, it is novel in defining a study objective to determine the regionally inhomogeneous response of the 'reinforced-ground matrix' under an extensive range of loading conditions suitable for mechanical characterisation of the tissue. The results presented facilitate the development of more detailed and comprehensive constitutive descriptions for the large strain nonlinear elastic or hyperelastic response of the anulus ground matrix.
Simulation of the nutrient supply in fracture healing
Publisher: Elsevier BV
Date: 11-2009
DOI: 10.1016/J.JBIOMECH.2009.07.010
Abstract: The healing process for bone fractures is sensitive to mechanical stability and blood supply at the fracture site. Most currently available mechanobiological algorithms of bone healing are based solely on mechanical stimuli, while the explicit analysis of revascularization and its influences on the healing process have not been thoroughly investigated in the literature. In this paper, revascularization was described by two separate processes: angiogenesis and nutrition supply. The mathematical models for angiogenesis and nutrition supply have been proposed and integrated into an existing fuzzy algorithm of fracture healing. The computational algorithm of fracture healing, consisting of stress analysis, analyses of angiogenesis and nutrient supply, and tissue differentiation, has been tested on and compared with animal experimental results published previously. The simulation results showed that, for a small and medium-sized fracture gap, the nutrient supply is sufficient for bone healing, for a large fracture gap, non-union may be induced either by deficient nutrient supply or inadequate mechanical conditions. The comparisons with experimental results demonstrated that the improved computational algorithm is able to simulate a broad spectrum of fracture healing cases and to predict and explain delayed unions and non-union induced by large gap sizes and different mechanical conditions. The new algorithm will allow the simulation of more realistic clinical fracture healing cases with various fracture gaps and geometries and may be helpful to optimise implants and methods for fracture fixation.
Apparatus for monitoring load bearing rehabilitation exercises of a transfemoral amputee fitted with an osseointegrated fixation: A proof-of-concept study
Publisher: Elsevier BV
Date: 02-2010
DOI: 10.1016/J.GAITPOST.2009.10.010
Abstract: The purpose of this proof-of-concept study was to determine the relevance of direct measurements to monitor the load applied on the osseointegrated fixation of transfemoral utees during static load bearing exercises. The objectives were (A) to introduce an apparatus using a three-dimensional load transducer, (B) to present a range of derived information relevant to clinicians, (C) to report on the outcomes of a pilot study and (D) to compare the measurements from the transducer with those from the current method using a weighing scale. One transfemoral utee fitted with an osseointegrated implant was asked to apply 10 kg, 20 kg, 40 kg and 80 kg on the fixation, using self-monitoring with the weighing scale. The loading was directly measured with a portable kinetic system including a six-channel transducer, external interface circuitry and a laptop. As the load prescribed increased from 10 kg to 80 kg, the forces and moments applied on and around the antero-posterior axis increased by four-fold anteriorly and 14-fold medially, respectively. The forces and moments applied on and around the medio-lateral axis increased by nine-fold laterally and 16-fold from anterior to posterior, respectively. The long axis of the fixation was overloaded and underloaded in 17% and 83% of the trials, respectively, by up to + or - 10%. This proof-of-concept study presents an apparatus that can be used by clinicians facing the challenge of improving basic knowledge on osseointegration, for the design of equipment for load bearing exercises and for rehabilitation programs.
Computational investigations of mechanical failures of internal plate fixation
Publisher: SAGE Publications
Date: 08-10-2010
Abstract: This paper investigated the biomechanics of two clinical cases of bone fracture treatments. Both fractures were treated with the same locking compression plate but with different numbers of screws as well as different plate materials. The fracture treated with 12 screws (rigid fixation) failed at 7 weeks with the plate breaking the fracture with six screws (flexible fixation) endured the entire healing process. It was hypothesized that the plate failure in the unsuccessful case was due to the material fatigue induced by stress concentration in the plate. As the two clinical cases had different fracture locations and different plate materials, finite element simulations were undertaken for each fractured bone fixed by both a rigid and a flexible method. This enabled comparisons to be made between the rigid and flexible fixation methods. The fatigue life was assessed for each fixation method. The results showed that the stress in the rigid fixation methods could be significantly higher than that in flexible fixation methods. The fatigue analyses showed that, with the stress level in flexible fixation (i.e. with fewer screws), the plate was able to endure 2000 days, and that the plate in rigid fixation could fail by fatigue fracture in 20 days. The paper concludes that the rigid fixation method resulted in serious stress concentrations in the plate, which induced fatigue failure. The flexible fixation gave sufficient stability and was better for fracture healing.
Are coupled rotations in the lumbar spine largely due to the osseo-ligamentous anatomy? – A modelling study
Publisher: Informa UK Limited
Date: 04-2008
Replication of the Frank-Starling response in a mock circulation loop
Publisher: IEEE
Date: 08-2011
Load-induced changes in the diffusion tensor of ovine anulus fibrosus: A pilot MRI study
Publisher: Wiley
Date: 12-05-2017
DOI: 10.1002/JMRI.25759
Evaluation of inflow cannulation site for implantation of right-sided rotary ventricular assist device
Publisher: Wiley
Date: 29-04-2013
DOI: 10.1111/AOR.12067
Abstract: Right heart dysfunction is one of the most serious complications following implantation of a left ventricular assist device, often leading to the requirement for short- or long-term right ventricular assist device (RVAD) support. The inflow cannulation site induces major hemodynamic changes and so there is a need to optimize the site used depending on the patient's condition. Therefore, this study evaluated and compared the hemodynamic influence of right atrial cannulation (RAC) and right ventricular cannulation (RVC) inflow sites. An in vitro variable heart failure mock circulation loop was used to compare RAC and RVC in mild and severe biventricular heart failure (BHF) conditions. In the severe BHF condition, higher ventricular ejection fraction (RAC: 13.6%, RVC: 32.7%) and thus improved heart chamber and RVAD washout were observed with RVC, which suggested this strategy might be preferable for long-term support (i.e., bridge-to-transplant or destination therapy) to reduce the risk of thrombus formation. In the mild BHF condition, higher pulmonary valve flow (RAC: 3.33 L/min, RVC: 1.97 L/min) and lower right ventricular stroke work (RAC: 0.10 W, RVC: 0.13 W) and volumes were recorded with RAC. These results indicate an improved potential for myocardial recovery, thus RAC should be chosen in this condition. This in vitro study suggests that RVAD inflow cannulation site should be chosen on a patient-specific basis with a view to the support strategy to promote myocardial recovery or reduce the risk of long-term complications.
Kinetics of transfemoral amputees with osseointegrated fixation performing common activities of daily living
Publisher: Elsevier BV
Date: 07-2007
DOI: 10.1016/J.CLINBIOMECH.2007.02.005
Abstract: Direct anchorage of a lower-limb prosthesis to the bone through an implanted fixation (osseointegration) has been suggested as an excellent alternative for utees experiencing complications from use of a conventional socket-type prosthesis. However, an attempt needs to be made to optimize the mechanical design of the fixation and refine the rehabilitation program. Understanding the load applied on the fixation is a crucial step towards this goal. The load applied on the osseointegrated fixation of nine transfemoral utees was measured using a load transducer, when the utees performed activities which included straight-line level walking, ascending and descending stairs and a r as well as walking around a circle. Force and moment patterns along each gait cycle, magnitudes and time of occurrence of the local extrema of the load, as well as impulses were analysed. Managing a r and stairs, and walking around a circle did not produce a significant increase (P>0.05) in load compared to straight-line level walking. The patterns of the moment about the medio-lateral axis were different among the six activities which may reflect the different strategies used in controlling the prosthetic knee joint. This study increases the understanding of biomechanics of bone-anchored osseointegrated prostheses. The loading data provided will be useful in designing the osseointegrated fixation to increase the fatigue life and to refine the rehabilitation protocol.
A diffusion and T2 relaxation MRI study of the ovine lumbar intervertebral disc under compression in vitro
Publisher: IOP Publishing
Date: 31-07-2004
DOI: 10.1088/0031-9155/49/16/006
Abstract: The ovine lumbar intervertebral disc is a useful model for the human lumbar disc. We present preliminary estimates of diffusion coefficients and T2 relaxation times in a pilot MRI study of the ovine lumbar intervertebral disc during uniaxial compression in vitro, and identify factors that h er the ability to accurately monitor the temporal evolution of the effective diffusion tensor at high spatial resolution.
Direct measurement of hoop strains in the intact and torn human medial meniscus
Publisher: Elsevier BV
Date: 07-1996
DOI: 10.1016/0268-0033(96)00003-4
Abstract: OBJECTIVE: To measure the circumferential or hoop strains generated in the medial meniscus during loading of the knee joint and to examine the effect of longitudinal and radial tears in the meniscus on these strain values. DESIGN: An in vitro investigation measuring the circumferential strains in the medial menisci of cadaveric human knees as they were loaded in a materials testing machine. BACKGROUND: The menisci transmit approximately 50% of the load through the knee, the rest being transmitted by direct contact of the articular cartilage. Damage to the menisci will alter the pattern of load transmission as will meniscectomy. This study examined the changes in the mechanics of the meniscus in situ as a result of simulated tears to assess the effect of its load carrying capacity and the implications of surgery to remove part or all of a damaged meniscus. METHODS: Nineteen human cadaveric knees were tested. Windows were made in the joint capsule and strain gauges inserted into the anterior, middle and posterior sections of the medial meniscus. The knees were then loaded to three times body weight at speeds of 50 and 500 mm/min, with the knee joint at 0 degrees and 30 degrees of flexion. The tests were repeated following the creation of a longitudinal or a radial tear in the meniscus. RESULTS: The intact menisci showed significantly less strain in the posterior section compared to the anterior and middle sections (P < 0.003, with strains of 1.54%, 2.86% and 2.65% respectively). With a longitudinal tear this pattern changed with strains decreasing anteriorly and increasing posteriorly. There were also significant differences at different angles of knee joint flexion not seen in the intact meniscus. 50% radial tears reduced the strains anteriorly whilst a complete radial tear completely defunctioned the meniscus. CONCLUSIONS: This study has shown that there are significantly different hoop strains produced in different sections of the medial meniscus under load and the patterns of strain distribution are disturbed by meniscal tears. RELEVANCE: These results provide important data for mathematical models which must include non-uniform behaviour. They also have implications for the surgical management of torn menisci. Undamaged portions should be preserved and the integrity of the circumferential fibres maintained to ensure the menisci retain a load bearing capability.
Comparison of two numerical approaches for bone remodelling
Publisher: Elsevier BV
Date: 2007
DOI: 10.1016/J.MEDENGPHY.2005.12.008
Abstract: This paper addresses the "checkerboard" phenomenon, which occurs in numerical simulation of bone remodelling. It attempts to answer the question: is an element-based approach suitable for bone remodelling? Two different numerical approaches, the element-based and the node-based finite element analyses, are implemented using ABAQUS. A comparison of the numerical results demonstrates that the checkerboard phenomenon occurs only in the element-based finite element analyses the node-based approach eradicates the checkerboard phenomenon but requires much more computational time. This study shows that it is essential to enforce the continuity of bone density across the element boundaries. As the node-based approach requires much more computational time, the first-order Adams-Bashforth integration method is introduced to reduce computational cost. The comparisons with Euler's forward method demonstrate that the first-order Adams-Bashforth method indeed enhances accuracy and reduces computational cost. This study concludes that the node-based approach with the first-order Adams-Bashforth integration scheme is to be recommended for computational bone remodelling studies.
Clinical Implications of Stiffness and Strength Changes in Fracture Healing
Publisher: British Editorial Society of Bone & Joint Surgery
Date: 1997
DOI: 10.1302/0301-620X.79B1.0790009
Abstract: In the assessment of fracture healing by monitoring stiffness with vibrational analysis or instrumented external fixators, it has been assumed that there is a workable correlation between stiffness and strength. We used four-point bending tests to study time-related changes in stiffness and strength in healing tibial fractures in sheep. We aimed to test the validity of the measurement of stiffness to assess fracture strength. At each duration of healing examined, we found marked variations in stiffness and strength. Stiffness was shown to be load-dependent: measurements at higher loads reflected ultimate strength more accurately. There was a biphasic relationship between stiffness and strength: at first there was a strong correlation regardless of loading conditions, but in the second phase, which included the period of ‘clinical healing’, stiffness and strength were not significantly correlated. We conclude that the monitoring of stiffness is useful primarily in assessing progress towards union but is inherently limited as an assessment of strength at the time of clinical union. Any interpretation of stiffness must take into account the load conditions.
Parametric equations to represent the profile of the human intervertebral disc in the transverse plane
Publisher: Springer Science and Business Media LLC
Date: 21-08-2007
DOI: 10.1007/S11517-007-0242-6
Abstract: Computational and finite element models of the spine are used to investigate spine and disc mechanics. Subject specific data for the transverse profile of the disc could improve the geometric accuracy of these models. The current study aimed to develop a mathematical algorithm to describe the profile of the disc components, using subject-specific data points. Using data points measured from pictures of human intervertebral discs sectioned in the transverse plane, parametric formulae were derived that mapped the outer profile of the anulus and nucleus. The computed anulus and nucleus profile were a similar shape to the discs from which they were derived. The computed total disc area was similar to the experimental data. The nucleus:disc area ratios were sensitive to the data points defined for each disc. The developed formulae can be easily implemented to provide patient specific data for the disc profile in computational models of the spine.
The riverine bioreactor: An integrative perspective on biological decomposition of organic matter across riverine habitats
Publisher: Elsevier BV
Date: 06-2021
Relative Roles of Cortical and Trabecular Thinning in Reducing Osteoporotic Vertebral Body Stiffness: A Modeling Study
Publisher: Springer Berlin Heidelberg
Date: 2009
New method for the non-invasive three-dimensional measurement of human back movement
Publisher: Elsevier BV
Date: 05-1989
DOI: 10.1016/0268-0033(89)90042-9
Abstract: A new method for the non-invasive three-dimensional measurement of human lumbar movement is described. The electro-magnetic 3space Isotrak system was found to be accurate and reliable, having a total r.m.s. error for rotations of less than o·2°. The system was able to produce consistent plots of subjects' movement patterns and it is proposed that this system should be evaluated in respect of its discriminatory and predictive potential in clinical studies of low back disorders. It may then become a useful tool in the routine clinical assessment of patients with spinal disorders, providing a complete quantification of back kinematics quickly and efficiently.
Development of a biaxial compression device for biological samples: Preliminary experimental results for a closed cell foam
Publisher: Elsevier BV
Date: 07-2009
DOI: 10.1016/J.JMBBM.2008.10.011
Abstract: Biological tissues are subjected to complex loading states in vivo and in order to define constitutive equations that effectively simulate their mechanical behaviour under these loads, it is necessary to obtain data on the tissue's response to multiaxial loading. Single axis and shear testing of biological tissues is often carried out, but biaxial testing is less common. We sought to design and commission a biaxial compression testing device, capable of obtaining repeatable data for biological s les. The apparatus comprised a sealed stainless steel pressure vessel specifically designed such that a state of hydrostatic compression could be created on the test specimen while simultaneously unloading the s le along one axis with an equilibrating tensile pressure. Thus a state of equibiaxial compression was created perpendicular to the long axis of a rectangular s le. For the purpose of calibration and commissioning of the vessel, rectangular s les of closed cell ethylene vinyl acetate (EVA) foam were tested. Each s le was subjected to repeated loading, and nine separate biaxial experiments were carried out to a maximum pressure of 204 kPa (30 psi), with a relaxation time of two hours between them. Calibration testing demonstrated the force applied to the s les had a maximum error of 0.026 N (0.423% of maximum applied force). Under repeated loading, the foam s le demonstrated lower stiffness during the first load cycle. Following this cycle, an increased stiffness, repeatable response was observed with successive loading. While the experimental protocol was developed for EVA foam, preliminary results on this material suggest that this device may be capable of providing test data for biological tissue s les. The load response of the foam was characteristic of closed cell foams, with consolidation during the early loading cycles, then a repeatable load-displacement response upon repeated loading. The repeatability of the test results demonstrated the ability of the test device to provide reproducible test data and the low experimental error in the force demonstrated the reliability of the test data.
Graphical presentation of the range of hip and knee rotations for clinical evaluation of gait
Publisher: Elsevier BV
Date: 2001
DOI: 10.1016/S0268-0033(00)00069-3
Abstract: This paper reports a method of using a multi-axis graph to represent the range of rotations at the hip and knee joints during gait for clinical evaluation of a patient's performance. The multi-axis graph uses 12 symmetrically arranged axes to represent each component of range of rotations at the hip and knee joints of both legs. The range of joint rotations of thirteen normal subjects and two patients were measured using an electromagnetic motion tracking system with four foot switches. The range of joint rotations of normal subjects shows a symmetrical star in the multi-axis graph. Abnormal function of a patient shows an asymmetrical star. This representation provides a simple way to examine a patient's performance in a time effective manner. Relevance. In clinical practice, the multi-axis representation of joint rotations can be used as an initial evaluation of a patient's performance to identify problems for further investigation.
Disc lesions and the mechanics of the intervertebral joint complex
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 12-2000
DOI: 10.1097/00007632-200012010-00010
Abstract: Correlations between tears in the disc and the mechanics of both the intervertebral joint and vertebral body bone were analyzed. To examine the effect of disc degeneration on the mechanics of spinal motion segments. Degeneration of the intervertebral disc results in changes to the mechanics of the spine. The actual effect of tear type and size on the mechanics of the intervertebral joint is unknown. Thirty spinal specimens (median age, 68 years) were ided into T12-L1, L2-L3, and L4-L5 motion segments. Mechanical tests recorded stiffness in flexion, extension, and torsion. Disc morphology was ascertained by taking three transverse sections of the disc and mapping and measuring the concentric tears, radial tears, and rim lesions. The severity of each tear type within each disc then was quantified. Bone cubes from the adjacent vertebral bodies were tested in compression to determine the elastic moduli and tested to failure in the longitudinal direction. Groups with tears were older and had reduced bone elastic moduli than groups without tears. Extension stiffness for the intact joint tended to increase with increasing tear severity. A decrease in torsional stiffness was present with increased severity of rim lesions at both L2-L3 and L4-L5. Tears in the intervertebral disc are reflected in a reduction in vertebral bone elastic modulus and in changes in the mechanics of the intervertebral joints in flexion, extension, and torsion.
The role of quadratus lumborum asymmetry in the occurrence of lesions in the lumbar vertebrae of cricket fast bowlers
Publisher: Elsevier BV
Date: 10-2007
DOI: 10.1016/J.MEDENGPHY.2006.09.010
Abstract: In cricket fast bowlers an increased incidence of stress fractures or lesions in the L4 pars interarticularis is observed, which shows a strong statistical correlation with the presence of hypertrophy in the contralateral Quadratus Lumborum (QL) muscle. This study aims to find a physical explanation for this correlation. A mathematical model was used to estimate the forces and moments on the L3 and L4 vertebrae in six postures attained during fast bowling. These forces and moments were used in finite element models to estimate the stresses in the pars interarticularis. Two scenarios were examined per posture: symmetric QL muscles, and right QL muscle volume 30% enlarged. Influence of muscle activation was also investigated. QL asymmetry only correlates with significant stress increases when stress levels are relatively low. When stress levels are high, due to extreme posture or muscle activation, asymmetry only causes small stress changes, suggesting that asymmetry is not the cause of stress fractures in the pars. There are even indications that asymmetry might help to reduce stresses, but more detailed knowledge of the size and activation of the lumbar muscles is needed to confirm this.
Three-dimensional analysis of active cervical motion: The effect of age and gender
Publisher: Elsevier BV
Date: 06-1996
DOI: 10.1016/0268-0033(95)00072-0
Abstract: OBJECTIVE: To describe the effects of age and gender on three-dimensional (3D) active cervical spine motion. DESIGN: This was a descriptive study. BACKGROUND: This study expanded on previous investigations of age and gender effects on single plane motion of the cervical spine. METHODS: Sixty female and 60 male asymptomatic, normal volunteers, aged between 20 and 59 years, were examined in a standardized seated position. The 3 SPACE Isotrak system was used to measure simultaneous 3D motion of the cervical spine. RESULTS: The mean range of all the primary movements decreased significantly with age. For flexion/extension the greatest decrease occurred between the 20- and 30-year-olds, whereas for both lateral flexion and rotation, significant differences were demonstrated in subjects aged two decades apart. The coupling of motion associated with rotation was significantly related to age. CONCLUSION: Age had a significant effect on all of the primary movements. Age had less effect on the range of the coupled movements, in that the only movements to be affected were lateral flexion and extension occurring during cervical rotation. Gender had no marked effect on the primary or the coupled movements. RELEVANCE: This study provides normative data for the effects of age and gender on three-dimensional analysis of active cervical spine motion, which can be used for comparison with specific patient populations. The high level of intra-subject test-retest reliability renders the3 SPACE system of value for clinical measurement of movement pre- and post-treatment intervention for cervical spine disorders.
Evaluation of inflow cannulation site for implantation of right-sided rotary ventricular assist device
Publisher: Wiley
Date: 29-04-2013
DOI: 10.1111/AOR.12067
Abstract: Right heart dysfunction is one of the most serious complications following implantation of a left ventricular assist device, often leading to the requirement for short- or long-term right ventricular assist device (RVAD) support. The inflow cannulation site induces major hemodynamic changes and so there is a need to optimize the site used depending on the patient's condition. Therefore, this study evaluated and compared the hemodynamic influence of right atrial cannulation (RAC) and right ventricular cannulation (RVC) inflow sites. An in vitro variable heart failure mock circulation loop was used to compare RAC and RVC in mild and severe biventricular heart failure (BHF) conditions. In the severe BHF condition, higher ventricular ejection fraction (RAC: 13.6%, RVC: 32.7%) and thus improved heart chamber and RVAD washout were observed with RVC, which suggested this strategy might be preferable for long-term support (i.e., bridge-to-transplant or destination therapy) to reduce the risk of thrombus formation. In the mild BHF condition, higher pulmonary valve flow (RAC: 3.33 L/min, RVC: 1.97 L/min) and lower right ventricular stroke work (RAC: 0.10 W, RVC: 0.13 W) and volumes were recorded with RAC. These results indicate an improved potential for myocardial recovery, thus RAC should be chosen in this condition. This in vitro study suggests that RVAD inflow cannulation site should be chosen on a patient-specific basis with a view to the support strategy to promote myocardial recovery or reduce the risk of long-term complications.
Three-dimensional lumbar spine postures measured by magnetic resonance imaging reconstruction
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 05-2007
Stress analysis of interbody fusion - Finite element modelling of intervertebral implant and vertebral body
Publisher: Elsevier BV
Date: 05-2003
DOI: 10.1016/S0268-0033(03)00022-6
Abstract: To investigate stresses in cage type interbody fusion systems during compressive loading.Design. The study uses finite element methods to investigate predicted stresses. Previously published experimental material properties are used as inputs to the numerical simulation. Interbody spinal fusion procedures using cage style intervertebral implants often cause subsidence failure of the vertebral endplate, resulting in potential pain and mechanical instability of the fusion system. Finite element models were developed to simulate compressive load transfer between interbody implants and adjacent vertebral body. The vertebral body was modelled using separate finite element mesh regions for cancellous core and cortical shell, with the meshes tied together at the core/shell interface. Coulomb friction was implemented to model the contact between implants and vertebral endplate.Results. Simulation results predicted endplate stresses of approximately 12 times the nominal contact pressure due to differing deformation stiffnesses of the implant and endplate structures. Reduction of the cancellous core elastic modulus to simulate severely osteoporotic bone resulted in endplate stresses up to three times higher than the values for an intact cancellous core. In this study, finite element analysis was used to investigate the stresses in interbody fusion systems. Published vertebral loads corresponding to certain activities were shown to generate endplate stresses which approach and exceed the failure stress for cortical bone. Endplate stresses are strongly dependent on the modulus of the underlying cancellous core. Endplate subsidence failure can potentially occur at the corners of existing cage-type interbody implants under physiological compressive loads. Matching material properties between cortical endplate and implant does not guarantee optimal contact conditions, and overall bending stiffness should be assessed.
Characterization of progressive changes in pedicle morphometry and neurovascular anatomy during growth in adolescent idiopathic scoliosis versus adolescents without scoliosis
Publisher: Springer Science and Business Media LLC
Date: 17-06-2020
Difficulties in estimating muscle forces from muscle cross-sectional area: An example using the psoas major muscle
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 07-1999
DOI: 10.1097/00007632-199907150-00016
Abstract: Most biomechanical models use muscle cross-sectional area (CSA) as an indicator of maximum isometric muscle force. In general, there are multiple estimates of CSA for the same muscle. For ex le, numerous studies have estimated the CSA of the psoas major muscle using different subject populations and positions. However, few studies have combined the available information to obtain an overall estimate of CSA or investigated the effect different subject characteristics may have on CSA. In the present update, nine studies that reported psoas major CSA or physiologic CSA were compared with respect to subject characteristics, methodology, and results. Corrections to cadaveric data were made to adjust physiologic CSA to CSA. Comparison of reported values for living subjects indicated that females have smaller mean CSA than males for the psoas major muscle and that body size does not significantly influence muscle CSA in males. Areas derived from cadaveric data were smaller than similar studies on living subjects, possibly because of subject age, removal of tendinous and fatty components of fascicles, and lack of detailed data for fascicle angles in the supine position. Results indicate that researchers who use muscle CSA in biomechanical models should carefully assess the appropriateness of the data used, particularly in relation to potential sex differences and the influence of postural changes on CSA.
Anatomic fitting of total artificial hearts for in vivo evaluation
Publisher: Wiley
Date: 05-03-2013
DOI: 10.1111/AOR.12060
Abstract: Successful anatomic fitting of a total artificial heart (TAH) is vital to achieve optimal pump hemodynamics after device implantation. Although many anatomic fitting studies have been completed in humans prior to clinical trials, few reports exist that detail the experience in animals for in vivo device evaluation. Optimal hemodynamics are crucial throughout the in vivo phase to direct design iterations and ultimately validate device performance prior to pivotal human trials. In vivo evaluation in a sheep model allows a realistically sized representation of a smaller patient, for which smaller third-generation TAHs have the potential to treat. Our study aimed to assess the anatomic fit of a single device rotary TAH in sheep prior to animal trials and to use the data to develop a three-dimensional, computer-aided design (CAD)-operated anatomic fitting tool for future TAH development. Following excision of the native ventricles above the atrio-ventricular groove, a prototype TAH was inserted within the chest cavity of six sheep (28-40 kg). Adjustable rods representing inlet and outlet conduits were oriented toward the center of each atrial chamber and the great vessels, with conduit lengths and angles recorded for future analysis. A three-dimensional, CAD-operated anatomic fitting tool was then developed, based on the results of this study, and used to determine the inflow and outflow conduit orientation of the TAH. The mean diameters of the sheep left atrium, right atrium, aorta, and pulmonary artery were 39, 33, 12, and 11 mm, respectively. The center-to-center distance and outer-edge-to-outer-edge distance between the atria, found to be 39 ± 9 mm and 72 ± 17 mm in this study, were identified as the most critical geometries for successful TAH connection. This geometric constraint restricts the maximum separation allowable between left and right inlet ports of a TAH to ensure successful alignment within the available atrial circumference.
Ability of modal analysis to detect osseointegration of implants in transfemoral amputees: A physical model study
Publisher: Springer Science and Business Media LLC
Date: 06-10-2013
DOI: 10.1007/S11517-012-0962-0
Abstract: Owing to the successful use of non-invasive vibration analysis to monitor the progression of dental implant healing and stabilization, it is now being considered as a method to monitor femoral implants in transfemoral utees. This study uses composite femur-implant physical models to investigate the ability of modal analysis to detect changes at the interface between the implant and bone simulating those that occur during osseointegration. Using electromagnetic shaker excitation, differences were detected in the resonant frequencies and mode shapes of the model when the implant fit in the bone was altered to simulate the two interface cases considered: firm and loose fixation. The study showed that it is beneficial to examine higher resonant frequencies and their mode shapes (rather than the fundamental frequency only) when assessing fixation. The influence of the model boundary conditions on the modal parameters was also demonstrated. Further work is required to more accurately model the mechanical changes occurring at the bone-implant interface in vivo, as well as further refinement of the model boundary conditions to appropriately represent the in vivo conditions. Nevertheless, the ability to detect changes in the model dynamic properties demonstrates the potential of modal analysis in this application and warrants further investigation.
Mechanobiology of Bone Development and Computational Simulations
Publisher: No publisher found
Date: 2010
Gravity-induced coronal plane joint moments in adolescent idiopathic scoliosis
Publisher: Springer Science and Business Media LLC
Date: 12-2015
Modelling external bone adaptation using evolutionary structural optimisation
Publisher: Springer Science and Business Media LLC
Date: 25-08-2007
DOI: 10.1007/S10237-006-0055-9
Abstract: External remodelling is significant in the bone healing process, and it is essential to predict the bone external shape in the design of artificial bone grafts. This paper demonstrates the effectiveness of the evolutionary structural optimisation (ESO) method for the simulation of bone morphology. A two-dimensional ESO strategy is developed which is capable of finding the modified bone topology beginning with any geometry under any loading conditions. The morphology of bone structure is described by the quantitative bone adaptation theory, which is integrated with the finite element method. The evolutionary topology optimisation process is introduced to find the bone shape. A rectangle, which occupies a larger space than the external shape of the bone structure, is specified as a design domain the evolutionary process iteratively eliminates and redistributes material throughout the domain to obtain an optimum arrangement of bone materials. The technique has been tested on a wide range of ex les. In this paper, the formation of trabecular bone architecture around an implant is studied as another ex le, the growth of the coronal section of a vertebral body is predicted. The ex les support the assertion that the external shape of bone structure can be successfully predicted by the proposed ESO procedure.
Metal debris from bony resection in knee arthroplasty - Is it an issue? Experiments in pigs
Publisher: Medical Journals Sweden AB
Date: 2005
DOI: 10.1080/17453670510041448
Abstract: Metal particles are generated during bone preparation in knee arthroplasty. These particles may produce third-body wear, or may have a role in osteolysis. Knowledge of their characteristics may help in the development of methods to reduce the amount of metal debris during bone cutting procedures. We performed bony resection of the distal femur and proximal tibia on 15 pig knees, simulating a total knee arthroplasty (TKA). Metal debris was collected from the saw blades, cutting blocks and bone surfaces and cleaned for microanalysis. The average loss of metal from the saw blades was 1.13 mg. The average volume of a wear particle was 3.4 x 10(-16) m(3). From this, it was estimated that approximately 500,000 particles are released from the saw blade alone. Material analysis of the particles indicated that the majority originated from the metallic cutting guides, suggesting that many millions of wear particles would be generated during the surgical procedure. Two particle shapes predominated: platelet shape and ploughed shape. Wear particles are produced during resection for a TKA. These may enter the artificial articulation and cause accelerated wear and macrophage activation. Redesign of cutting blocks and saw blades may reduce the amount of debris produced during surgery.
The effect of endplate preselection when measuring supine versus standing cobb angle change in idiopathic scoliosis
Publisher: Springer Science and Business Media LLC
Date: 19-01-2014
Clinical Biomechanics is 35 years old
Publisher: Elsevier BV
Date: 08-2021
Coupled rotations in the lumbar spine—are these a consequence of passive spinal anatomy?
Publisher: WIT Press
Date: 05-09-2007
DOI: 10.2495/BIO070091
Predicting spinal column profile from surface topography via 3D non-contact surface scanning
Publisher: Public Library of Science (PLoS)
Date: 23-03-2023
DOI: 10.1371/JOURNAL.PONE.0282634
Abstract: 3D Non-Contact surface scanning (3DSS) is used in both biomechanical and clinical studies to capture accurate 3D images of the human torso, and to better understand the shape and posture of the spine–both healthy and pathological. This study sought to determine the efficacy and accuracy of using 3DSS of the posterior torso, to determine the curvature of the spinal column in the lateral lying position. A cohort of 50 healthy adults underwent 3DSS and Magnetic Resonance Imaging (MRI) to correlate the contours of the external spine surface with the internal spinal column. The correlation analysis was composed of two phases: (1) MRI vertebral points vs MRI external spine surface markers and (2) MRI external spine surface markers vs 3DSS external spine surface markers. The first phase compared the profiles of fiducial markers (vitamin capsules) adhered to the skin surface over the spinous processes against the coordinates of the spinous processes–assessing the linear distance between the profiles, and similarity of curvature, in the sagittal and coronal planes. The second phase compared 3DSS external spine surface markers with the MRI external spine surface markers in both planes, with further qualitative assessment for postural changes. The distance between the MRI vertebral points and MRI external spine surface markers showed strong statistically significant correlation with BMI in both sagittal and coronal planes. Kolmogorov-Smirnov (KS) tests showed similar no significant difference in curvature, k, in almost all participants on both planes. In the second phase, the coronal 3DSS external spine surface profiles were statistically different to the MRI external spine surface markers in 44% of participants. Qualitative assessment showed postural changes between MRI and 3DSS measurements in these participants. These study findings demonstrate the utility and accuracy of using anatomical landmarks overlaid on the spinous processes, to identify the position of the spinal bones using 3DSS. Using this method, it will be possible to predict the internal spinal curvature from surface topography, provided that the thickness of the overlaying subcutaneous adipose layer is considered, thus enabling postural analysis of spinal shape and curvature to be carried out in biomechanical and clinical studies without the need for radiographic imaging.
Segmental torso masses in adolescent idiopathic scoliosis
Publisher: Elsevier BV
Date: 08-2014
DOI: 10.1016/J.CLINBIOMECH.2014.06.002
Abstract: Adolescent idiopathic scoliosis is the most common type of spinal deformity whose aetiology remains unclear. Studies suggest that gravitational forces in the standing position play an important role in scoliosis progression, therefore anthropometric data is required to develop biomechanical models of the deformity. Few studies have analysed the trunk by vertebral level and none have performed investigations of the scoliotic trunk. The aim of this study was to determine the centroid, thickness, volume and estimated mass, for sections of the scoliotic trunk. Existing low-dose CT scans were used to estimate vertebral level-by-level torso masses for 20 female adolescent idiopathic scoliosis patients. ImageJ processing software was used to analyse the CT images and enable estimation of the segmental torso mass corresponding to each vertebral level. The patients' mean age was 15.0 (SD 2.7) years with mean major Cobb angle of 52 (SD 5.9)° and mean patient weight of 58.2 (SD 11.6) kg. The magnitude of torso segment mass corresponding to each vertebral level increased by 150% from 0.6kg at T1 to 1.5kg at L5. Similarly, segmental thickness from T1-L5 increased inferiorly from a mean 18.5 (SD 2.2) mm at T1 to 32.8 (SD 3.4) mm at L5. The mean total trunk mass, as a percentage of total body mass, was 27.8 (SD 0.5) % which was close to values reported in previous literature. This study provides new anthropometric reference data on segmental (vertebral level-by-level) torso mass in adolescent idiopathic scoliosis patients, useful for biomechanical models of scoliosis progression and treatment.
A compliant, banded outflow cannula for decreased afterload sensitivity of rotary right ventricular assist devices
Publisher: Wiley
Date: 09-07-2015
DOI: 10.1111/AOR.12338
Abstract: Biventricular support with dual rotary ventricular assist devices (VADs) has been implemented clinically with restriction of the right VAD (RVAD) outflow cannula to artificially increase afterload and, therefore, operate within recommended design speed ranges. However, the low preload and high afterload sensitivity of these devices increase the susceptibility of suction events. Active control systems are prone to sensor drift or inaccurate inferred (sensor-less) data, therefore an alternative solution may be of benefit. This study presents the in vitro evaluation of a compliant outflow cannula designed to passively decrease the afterload sensitivity of rotary RVADs and minimize left-sided suction events. A one-way fluid-structure interaction model was initially used to produce a design with suitable flow dynamics and radial deformation. The resultant geometry was cast with different initial cross-sectional restrictions and concentrations of a softening diluent before evaluation in a mock circulation loop. Pulmonary vascular resistance (PVR) was increased from 50 dyne s/cm(5) until left-sided suction events occurred with each compliant cannula and a rigid, 4.5 mm diameter outflow cannula for comparison. Early suction events (PVR ∼ 300 dyne s/cm(5) ) were observed with the rigid outflow cannula. Addition of the compliant section with an initial 3 mm diameter restriction and 10% diluent expanded the outflow restriction as PVR increased, thus increasing RVAD flow rate and preventing left-sided suction events at PVR levels beyond 1000 dyne s/cm(5) . Therefore, the compliant, restricted outflow cannula provided a passive control system to assist in the prevention of suction events with rotary biventricular support while maintaining pump speeds within normal ranges of operation.
Defining the Neutral Zone of sheep intervertebral joints during dynamic motions: An in vitro study
Publisher: Elsevier BV
Date: 02-2003
DOI: 10.1016/S0268-0033(02)00180-8
Abstract: To make an experimental assessment of the Neutral Zone of intervertebral joints during dynamic spinal motion in flexion/extension, lateral bending and axial rotation and to develop a criterion for its definition. Dynamic mechanical testing of sheep intervertebral joints with a six-degree of freedom robotic facility under position control. The Neutral Zone is defined as a region of no or little resistance to motion in the middle of an intervertebral joint's range of movement. Previous studies have used quasi-static loading regimes that do not model physiological activity. This study simulated physiological movements using a robotic testing facility to address this issue. Five spines from mature sheep were used and three motion segments were tested from each spine. The robotic facility enabled the testing regime to be defined for each in idual joint based on its geometry. The joints were tested by cycling through the full range of physiological movement in flexion/extension, lateral bending and axial rotation. A Neutral Zone was found to exist during dynamic movements only in flexion/extension. The results suggested that a Neutral Zone does not exist in lateral bending or axial rotation. The zygapophysial joints were shown to be significant in determining the mechanics of the intervertebral joints as their removal increased the Neutral Zone in all cases. A new criterion for defining the size of the Neutral Zone during dynamic motion was proposed and its implications for spinal movements in life discussed. A Neutral Zone exists in flexion/extension during dynamic movements of intervertebral joints and is a feature of the natural range of joint motion. This has important implications for the muscular control of the spine consisting of several intrinsically lax joints stacked on one another. The existence of a Neutral Zone is a feature of the natural range of joint motion and requires complex control of intervertebral joints by the spinal muscles. Defining the biomechanical response throughout the physiological range of motion (RoM) is important in understanding possible injury and rehabilitation mechanisms.
Morphometric analysis of the thoracic intervertebral foramen osseous anatomy in adolescent idiopathic scoliosis using low-dose computed tomography
Publisher: Springer Science and Business Media LLC
Date: 05-2016
DOI: 10.1016/J.JSPD.2015.10.004
Abstract: The dimensions of the thoracic intervertebral foramen in adolescent idiopathic scoliosis (AIS) have not previously been quantified. Better understanding of the dimensions of the foramen may be useful in surgical planning. This study describes a reproducible method for measurement of the thoracic foramen in AIS using computed tomography (CT). In 23 preoperative female patients with Lenke 1 type AIS with right-side convexity major curves confined to the thoracic spine the foraminal height (FH), foraminal width (FW), pedicle to superior articular process distance (P-SAP), and cross-sectional foraminal area (FA) were measured using multiplanar reconstructed CT. Measurements were made at entrance, midpoint, and exit of the thoracic foramina from T1-T2 to T11-T12. Results were also correlated with dependent variables of major curve Cobb angle measured on X-ray and CT, age, weight, Lenke classification subtype, Risser grade, and number of spinal levels in the major curve. The FH, FW, P-SAP, and FA dimensions and ratios are all significantly larger on the convexity of the major curve and maximal at or close to the apex. Mean thoracic foraminal dimensions change in a predictable manner relative to position on the major thoracic curve. There was no statistically significant correlation with the measured foraminal dimensions or ratios and the in idual dependent variables. The average ratio of convexity to concavity dimensions at the apex foramina for entrance, midpoint, and exit, respectively, are FH (1.50, 1.38, 1.25), FW (1.28, 1.30, 0.98), FA (2.06, 1.84, 1.32), and P-SAP (1.61, 1.47, 1.30). Foraminal dimensions of the thoracic spine are significantly affected by AIS. Foraminal dimensions have a predictable convexity-to-concavity ratio relative to the proximity to the major curve apex. Surgeons should be aware of these anatomical differences during scoliosis correction surgery.
Atrial Versus Ventricular Cannulation for a Rotary Ventricular Assist Device
Publisher: Wiley
Date: 09-2010
DOI: 10.1111/J.1525-1594.2010.01093.X
Abstract: The ventricular assist device inflow cannulation site is the primary interface between the device and the patient. Connecting these cannulae to either atria or ventricles induces major changes in flow dynamics however, there are little data available on precise quantification of these changes. The objective of this investigation was to quantify the difference in ventricular/vascular hemodynamics during a range of left heart failure conditions with either atrial (AC) or ventricular (VC) inflow cannulation in a mock circulation loop with a rotary left VAD. Ventricular ejection fraction (EF), stroke work, and pump flow rates were found to be consistently lower with AC compared with VC over all simulated heart failure conditions. Adequate ventricular ejection remained with AC under low levels of mechanical support however, the reduced EF in cases of severe heart failure may increase the risk of thromboembolic events. AC is therefore more suitable for class III, bridge to recovery patients, while VC is appropriate for class IV, bridge to transplant/destination patients.
Anatomy and biomechanics of psoas major
Publisher: Elsevier BV
Date: 05-1992
Computational model of the lumbar spine musculature: Implications of spinal surgery
Publisher: Elsevier BV
Date: 02-2011
DOI: 10.1016/J.CLINBIOMECH.2010.09.017
Abstract: The development of a comprehensive and detailed model of the musculature of the lumbar region is required if biomechanical models are to accurately predict the forces and moments experienced by the lumbar spine. A new anatomical model representing the nine major muscles of the lumbar spine and the thoracolumbar fascia is presented. These nine muscles are modeled as numerous fascicles, each with its own force producing potential based on size and line of action. The simulated spine is fully deformable, allowing rotation in any direction, while respecting the physical constraints imposed by the skeletal structure. Maximal moments were predicted by implementing the model using a pseudo force distribution algorithm. Three types of surgery that affect the spinal musculature were simulated: posterior spinal surgery, anterior surgery, and total hip replacement. Predicted moments matched published data from maximum isometric exertions in male volunteers. The biomechanical changes for the three different types of surgery demonstrated several common features: decreased spinal compression and production of asymmetric moments during symmetric tasks. This type of analysis provides new opportunities to explore the effect of different patterns of muscle activity including muscle injury on the biomechanics of the spine.
The effect of vertebral body stapling on spine biomechanics and structure using a bovine model
Publisher: Elsevier BV
Date: 04-2020
A biological basis for instantaneous centres of rotation of the vertebral column
Publisher: SAGE Publications
Date: 09-1995
DOI: 10.1243/PIME_PROC_1995_209_341_02
Abstract: The instantaneous centre of rotation has proven to be a useful parameter of vertebral motion. The normal location of instantaneous centres has been determined in cadavers and in normal volunteers for the cervical, thoracic and lumbar spines, and abnormal location of centres has been shown to correlate with spinal pain. However, to date, an instantaneous centre has constituted no more than a convenient mathematical summary of vertebral kinematics. It has defied resolution into biologically meaningful parameters. This study offers a novel model of vertebral motion in which the instantaneous centre of rotation can be shown to be a function of the location of the centre of reaction of a vertebra, and the intrinsic rotation and translation it undergoes. These parameters are strictly linked by equations that determine the location of an axis of rotation. These equations allow aberrations in the location of an axis to be interpreted in terms of the anatomical and pathological factors that affect the centre of reaction of the vertebra and the rotation and translation it undergoes.
A comparison of vertebral venous networks in adolescent idiopathic scoliosis patients and healthy controls
Publisher: Springer Science and Business Media LLC
Date: 06-06-2016
DOI: 10.1007/S00276-016-1709-7
Abstract: Cadaveric studies have previously documented a typical pattern of venous drainage within vertebral bodies (VBs), comprised primarily of the basivertebral vein. These studies, however, are limited by the number of s les available. MRI is able to provide 3D images of soft tissue structures in the spine, including the basivertebral vein without the use of contrast in both healthy controls and subjects with abnormal anatomy such as adolescent idiopathic scoliosis (AIS). This study aimed to quantify the venous networks within VBs of 15 healthy adolescent controls and 15 AIS patients. Five transverse slices through the VBs were examined simultaneously and the observable vascular network traced. The length of the network on the left and right sides of the VB was calculated, and the spatial patterning assessed level-by-level within each subject. Significant differences were seen in the left/right distribution of vessels in both the control and AIS subjects, with both groups having greater length on the right side of all of their VBs. No difference was seen between AIS and control subjects in any region. Large in idual variations in patterns were seen in both groups however, the control group showed more consistent spatial patterning of the vascular networks across levels in comparison to the AIS group. The length of the basivertebral vein was seen to have a significant bias to the right hand side of the VB in both healthy and AIS adolescents. The spatial pattern of this vein showed large variations in branching both within and across in iduals. No significant differences were seen between AIS and control subjects, suggesting both that this network is preserved in deformed AIS vertebrae, and that the vertebral venous system does not play a role in the etiology of AIS.
The mechanical effects of intervertebral disc lesions
Publisher: Elsevier BV
Date: 06-2004
An experimental and finite element poroelastic creep response analysis of an intervertebral hydrogel disc model in axial compression
Publisher: Springer Science and Business Media LLC
Date: 07-2005
DOI: 10.1007/S10856-005-2538-0
Abstract: A hydrogel intervertebral disc (IVD) model consisting of an inner nucleus core and an outer anulus ring was manufactured from 30 and 35% by weight Poly(vinyl alcohol) hydrogel (PVA-H) concentrations and subjected to axial compression in between saturated porous endplates at 200 N for 11 h, 30 min. Repeat experiments (n=4) on different s les (N=2) show good reproducibility of fluid loss and axial deformation. An axisymmetric nonlinear poroelastic finite element model with variable permeability was developed using commercial finite element software to compare axial deformation and predicted fluid loss with experimental data. The FE predictions indicate differential fluid loss similar to that of biological IVDs, with the nucleus losing more water than the anulus, and there is overall good agreement between experimental and finite element predicted fluid loss. The stress distribution pattern indicates important similarities with the biological IVD that includes stress transference from the nucleus to the anulus upon sustained loading and renders it suitable as a model that can be used in future studies to better understand the role of fluid and stress in biological IVDs.
Modelling the line of action for the oblique abdominal muscles using an elliptical torso model
Publisher: Elsevier BV
Date: 09-2001
DOI: 10.1016/S0021-9290(01)00079-3
Abstract: When modelling the line of action of a muscle, anatomical considerations must be included if the model is to realistically mimic the muscle behaviour. The internal and external oblique muscles are ex les of muscles that do not follow a straight line between origin and insertion, instead having to wrap around the torso. A model is presented which describes the shape of the torso using a right elliptical cylinder of varying dimensions. The muscle lines of action are then calculated based on this underlying torso shape. The model has been successfully fitted to the data reported by Stokes and Gardner-Morse (Journal of Biomechanics 32(3) (1999) 311). When compared to a linear model, the use of the torso model results in a 15% increase in the axial twist moment, and decreases in the lateral bend and extension moments (5% and 2%, respectively), able to be generated by the internal and external oblique muscles combined in upright stance. These differences become larger (up to 37%) when the torso is flexed, extended or twisted. The structure of the torso model allows it to be used to model any posture without significant increases in the overall model complexity.
Passive control of a biventricular assist device with compliant inflow cannulae
Publisher: Wiley
Date: 08-2012
DOI: 10.1111/J.1525-1594.2012.01504.X
Abstract: Rotary ventricular assist device (VAD) support of the cardiovascular system is susceptible to suction events due to the limited preload sensitivity of these devices. This may be of particular concern with rotary biventricular support (BiVAD) where the native, flow balancing Starling response is diminished in both ventricles. The reliability of sensor and sensorless-based control systems which aim to control VAD flow based on preload has limitations, and, thus, an alternative solution is desired. This study introduces a compliant inflow cannula (CIC) which could improve the preload sensitivity of a rotary VAD by passively altering VAD flow depending on preload. To evaluate the design, both the CIC and a standard rigid inflow cannula were inserted into a mock circulation loop to enable biventricular heart failure support using configurations of atrial and ventricular inflow, and arterial outflow cannulation. A range of left (LVAD) and right VAD (RVAD) rotational speeds were tested as well as step changes in systemic ulmonary vascular resistance to alter relative preloads, with resulting flow rates recorded. Simulated suction events were observed, particularly at higher VAD speeds, during support with the rigid inflow cannula, while the CIC prevented suction events under all circumstances. The compliant section passively restricted its internal diameter as preload was reduced, which increased the VAD circuit resistance and thus reduced VAD flow. Therefore, a CIC could potentially be used as a passive control system to prevent suction events in rotary left, right, and biventricular support.
Kinematics and movement sequencing during flexion of the lumbar spine
Publisher: Elsevier BV
Date: 07-1999
DOI: 10.1016/S0268-0033(98)00109-0
Abstract: This study investigated the sequence of intervertebral joint movements and range of motion during three tasks involving lumbar flexion. Position sensors were used to measure position and rotation of lumbar vertebrae during unconstrained flexion. In the development of mathematical models, numerous assumptions need to be made. Few studies have attempted to assess the validity of the assumptions regarding kinematics in models of the lumbar spine. Position sensors were attached to the skin overlying the lumbar vertebrae of 14 volunteers. Volunteers performed three flexion tasks unconstrained flexion from upright standing, with and without a mass of 5 kg held close to the body, and the transition from upright standing to a seated position. Four definitive movement sequences were identified for those subjects with consistency between replicates 'top down' motion (where the top of the lumbar spine starts to move first and the bottom moves last), 'bottom up' (where the bottom of the lumbar spine moves first and the top moves last), 'all together' (where all segments commence movement together), and 'middle last' (where the middle segments of the lumbar spine are last to commence movement). Subjects not fitting one of these sequences were categorised into a miscellaneous group. Only two subjects exhibited the same sequence for each of the three tasks, while other subjects exhibited two or three different sequences for the three tasks, or showed a lack of consistency for one of the tasks. The results from this study indicate that there is no single movement sequence exhibited by the s le population. Incorrect assumptions which are incorporated into mathematical models have the potential to influence model output. Given that output from spinal models is often used to assess ergonomic issues such as safe lifting loads, validation of the assumptions is essential.
The role of the middle lumbar fascia on spinal mechanics: A human biomechanical assessment
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 15-04-2017
Stereo radiography of lumbar spine motion
Publisher: Medical Journals Sweden AB
Date: 1985
DOI: 10.3109/17453678509154154
Abstract: The technique of Biplanar Radiography for the computer analysis of orthogonal radiographs of the human spine enables the calculation of three-dimensional coordinates for anatomical landmarks on the vertebrae. Three-dimensional intervertebral movements are deduced from the changes in the relative orientations of the vertebrae as a subject moves from one position to another. The three-dimensional coordinates of the anatomical landmarks on the vertebrae were found to have an RMS error of less than 1 mm. The RMS errors for translational movements were less than 2 mm and for rotations were less than 1.5 degrees. This study of normal subjects has defined the ranges of voluntary flexion and extension, axial rotation, and lateral bending in the lumbar spines of young males. The range of flexion plus extension at each lumbar intervertebral joint is approximately 14 degrees with the L4/5 level being slightly more mobile than the others. There are approximately 2 degrees of axial rotation at each joint with L3/4 and L4/5 being slightly more mobile. Lateral bending of approximately 10 degrees occurs at the upper three levels while there is significantly less movement of 6 degrees and 3 degrees at L4/5 and L5/S1 respectively. In flexion and extension accompanying axial rotation of 2 degrees or more and lateral bending of 3 degrees or more occurred rarely and any larger accompanying rotation at an intervertebral joint should be considered abnormal. During twisting and side bending axial rotation to the right is accompanied by lateral bending to the left and vice versa at the three upper levels. At L5/S1 axial rotation and lateral bending generally accompany each other in the same direction while L4/5 is a transitional level. During lateral bending there is also generally extension at the upper levels and flexion at L5/S1. The measurement in vivo of the accompanying rotations in the other planes has demonstrated that there is no simple mechanical coupling of the rotations. Finally, this study has provided a base line of normal movements to which the movements seen in pathological conditions can be compared.
Mechanical properties of the human anterior cruciate ligament
Publisher: Elsevier BV
Date: 10-1995
DOI: 10.1016/0268-0033(95)98193-X
Abstract: The aim was to measure the stiffness and strength of the femur-anterior cruciate ligament-tibia complex tested in a physiological manner with a force exerted anteriorly on the tibia, at knee joint flexion angles of 0 degrees, 10 degrees and 30 degrees and at speeds of 50 and 500 mm/min. Ligaments were preconditioned by cycling five times, with data from the fifth cycle used to determine the stiffness of the ligament in a low-load range. The ligaments were then tested to failure with the knee at 30 degrees flexion. The specimens were ided into two groups, middle-aged (40-60) and old (>60). For each group no statistical difference was observed between stiffness of the ligament at different joint flexion angles or speeds. Seven of the 21 specimens in the older age group failed by avulsion at the bone-ligament interface. All the other specimens failed by tears in the substance of the ligament. Ultimate failure load was found to have a significant correlation with bodyweight. It was 1.6 and 1.3 times bodyweight for the middle-aged and older age groups respectively. This study has highlighted the importance of identifying different modes of failure, of making corrections for bodyweight and testing in a physiological manner. The results allow a better understanding of the mechanical behaviour of the anterior cruciate ligament and provide design data for anterior cruciate ligament grafts and prostheses. RELEVANCE:--Our clinical experience indicates that the anterior cruciate ligament is frequently ruptured during uncoordinated contraction of the quadriceps mechanism. The results of this study, in which the mechanical properties of the anterior cruciate ligament have been measured with force exerted anteriorly on the tibia, allow a more complete understanding of the mechanical behaviour of the anterior cruciate ligament and provide design data for anterior cruciate ligament grafts and prostheses.
Foreword
Publisher: Medical Journals Sweden AB
Date: 1985
Failure strengths of different meniscal suturing techniques
Publisher: Elsevier BV
Date: 04-1995
DOI: 10.1016/0749-8063(95)90059-4
Abstract: The aim of this study was to measure the failure strengths of three arthroscopic meniscal suturing methods. The techniques investigated were a single horizontal loop, a double vertical loop, and a single vertical loop. Eleven human, lateral menisci obtained at autopsy were cut with a scalpel to simulate peripheral longitudinal tears. The menisci were then repaired with one suture at a time, using each of the three methods in turn. The two parts of the meniscus were then pulled apart using a computer-controlled materials testing machine until failure occurred, either by the suture itself failing or by the suture pulling out because of tearing of the meniscus. The horizontal sutures had a mean failure strength of 29.3 N, whereas the double vertical loop failed at 63.2 N and the single vertical loop at 67.3 N. The horizontal loop sutures and the double vertical loop sutures all failed by pulling out of the meniscus. The single vertical loop sutures failed by rupture of the suture itself. This study showed the superior mechanical characteristics of the single vertical loop suturing system over the other techniques tested. Owing to the more consistent failure strength, decreased costs, and shorter surgical time over the double vertical loop system, the single vertical loop technique is recommended for arthroscopic meniscal repair.
Finite Element Modeling to Aid in Refining the Rehabilitation of Amputees Using Osseointegrated Prostheses
Publisher: Springer Berlin Heidelberg
Date: 2007
Evaluation of left ventricular assist device performance and hydraulic force in a complete mock circulation loop
Publisher: Wiley
Date: 24-06-2005
DOI: 10.1111/J.1525-1594.2005.29093.X
Abstract: Centrifugal pump performance characteristics are vital in determining the ability of a prototype left ventricular assist device (LVAD) to meet the physiological circulation requirements of the cardiovascular system. These characteristics influence the static hydraulic forces encountered by the pump impeller, which determine the required load stiffness of suspension type bearings to minimize impeller touchdown. Performance investigations were conducted on an LVAD design while characterizing the impeller static hydraulic forces of various impeller/volute configurations. The pumps were inserted into a complete systemic and pulmonary mock circulation rig configured to provide suitable nonpulsatile or simulated pulsatile left heart failure environments. The single volute and closed shroud impeller configuration exhibited lowest radial (0.01 N) and axial (3 N) force at nonpulsatile design flow conditions, respectively. Normal hemodynamic conditions of 5.1 L/min at 94 mm Hg were re-established upon inserting the device into the left heart failure environment, where the pump operated along the nonpulsatile characteristic curve for 2200 rpm. The operational limits on this curve were dictated by the required pressure differential across the pump during systolic and diastolic periods. The reduction of left atrial pressure (25 to 8 mm Hg) indicated the alleviation of pulmonary congestion. The ability for the LVAD to support circulation in a left heart failure environment was successfully demonstrated in the mock circulation loop. The impeller hydraulic force characteristics attained will aid the bearing designer to select the best volute and impeller configuration to minimize impeller touchdown in magnetic, hydrodynamic or mechanical type bearing applications.
Mechanical tension as a driver of connective tissue growth in vitro
Publisher: Elsevier BV
Date: 07-1970
DOI: 10.1016/J.MEHY.2014.03.031
Abstract: We propose the progressive mechanical expansion of cell-derived tissue analogues as a novel, growth-based approach to in vitro tissue engineering. The prevailing approach to producing tissue in vitro is to culture cells in an exogenous "scaffold" that provides a basic structure and mechanical support. This necessarily pre-defines the final size of the implantable material, and specific signals must be provided to stimulate appropriate cell growth, differentiation and matrix formation. In contrast, surgical skin expansion, driven by increments of stretch, produces increasing quantities of tissue without trauma or inflammation. This suggests that connective tissue cells have the innate ability to produce growth in response to elevated tension. We posit that this capacity is maintained in vitro, and that order-of-magnitude growth may be similarly attained in self-assembling cultures of cells and their own extracellular matrix. The hypothesis that growth of connective tissue analogues can be induced by mechanical expansion in vitro may be ided into three components: (1) tension stimulates cell proliferation and extracellular matrix synthesis (2) the corresponding volume increase will relax the tension imparted by a fixed displacement (3) the repeated application of static stretch will produce sustained growth and a tissue structure adapted to the tensile loading. Connective tissues exist in a state of residual tension, which is actively maintained by resident cells such as fibroblasts. Studies in vitro and in vivo have demonstrated that cellular survival, reproduction, and matrix synthesis and degradation are regulated by the mechanical environment. Order-of-magnitude increases in both bone and skin volume have been achieved clinically through staged expansion protocols, demonstrating that tension-driven growth can be sustained over prolonged periods. Furthermore, cell-derived tissue analogues have demonstrated mechanically advantageous structural adaptation in response to applied loading. Together, these data suggest that a program of incremental stretch constitutes an appealing way to replicate tissue growth in cell culture, by harnessing the constituent cells' innate mechanical responsiveness. In addition to offering a platform to study the growth and structural adaptation of connective tissues, tension-driven growth presents a novel approach to in vitro tissue engineering. Because the supporting structure is secreted and organised by the cells themselves, growth is not restricted by a "scaffold" of fixed size. This also minimises potential adverse reactions to exogenous materials upon implantation. Most importantly, we posit that the growth induced by progressive stretch will allow substantial volumes of connective tissue to be produced from relatively small initial cell numbers.
Related Organisations
University Of Strathclyde
Location: United Kingdom of Great Britain and Northern Ireland
University Of Bristol
Location: United Kingdom of Great Britain and Northern Ireland
Related Funding Activities
The Australian Research Network For Medical Devices: Advanced Technology Solutions For Patients And Practitioners
Start Date: 2003
End Date: 2003
Funder: Australian Research Council
View Funded ActivityA Multi-Axis Biomaterials Testing Facility
Start Date: 2006
End Date: 2006
Funder: Australian Research Council
View Funded ActivityInnovative Approach To Design A New Osseointegrated Implant For Transfemoral Amputees With Better Resistance To Fractures
Start Date: 2004
End Date: 2006
Funder: Australian Research Council
View Funded ActivityDiscovery Projects - Grant ID: DP0211324
Start Date: 03-2002
End Date: 08-2006
Amount: $352,000.00
Funder: Australian Research Council
View Funded ActivityLinkage Projects - Grant ID: LP0347500
Start Date: 01-2003
End Date: 12-2007
Amount: $69,099.00
Funder: Australian Research Council
View Funded ActivityDiscovery Projects - Grant ID: DP0663282
Start Date: 2006
End Date: 12-2009
Amount: $340,000.00
Funder: Australian Research Council
View Funded ActivityLinkage Infrastructure, Equipment And Facilities - Grant ID: LE0668506
Start Date: 2006
End Date: 12-2006
Amount: $150,000.00
Funder: Australian Research Council
View Funded ActivitySpecial Research Initiatives - Grant ID: SR0354734
Start Date: 2004
End Date: 12-2004
Amount: $10,000.00
Funder: Australian Research Council
View Funded ActivityLinkage Projects - Grant ID: LP0455577
Start Date: 04-2005
End Date: 06-2008
Amount: $70,668.00
Funder: Australian Research Council
View Funded ActivityLinkage Projects - Grant ID: LP0455481
Start Date: 12-2004
End Date: 12-2008
Amount: $209,000.00
Funder: Australian Research Council
View Funded ActivityDiscovery Projects - Grant ID: DP0345667
Start Date: 04-2003
End Date: 12-2006
Amount: $254,500.00
Funder: Australian Research Council
View Funded Activity