ORCID Profile
0000-0002-0995-1182
Current Organisation
University of Adelaide
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Biomechanical Engineering | Biomedical Engineering
Expanding Knowledge in Engineering | Road Safety | Injury Control |
Publisher: Elsevier BV
Date: 07-2019
DOI: 10.1016/J.CLINBIOMECH.2019.04.024
Abstract: Quantitative objective measures to determine fusion achievement further enable the comparison of new technologies, such as interbody cage surface enhancement. Our aims were to compare in vivo biomechanical responses of ovine L4/5 lumbar motion segments with two cages: 1) Polyetheretherketone or 2) Polyetheretherketone with a nanosurfaced titanium porous scaffold from Nanovis, Inc. Fourteen Merino sheep randomly received either 1) standard Polyetheretherketone cage or 2) Nanocoated Polyetheretherketone cage at L4/L5 with autologous bone graft. At baseline and one-year follow-up, dynamic spinal stiffness was quantified in vivo using a validated mechanical assessment at 2 Hz, 6 Hz, and 12 Hz. The dorsoventral secant stiffness (k Both implants increased spinal stiffness at 2 Hz (21 and 39%, respectively, p < .005), and at 6 Hz (12 and 27%, p < .0001). Significantly greater spinal stiffness was observed with Nanocoated Polyetheretherketone at one-year for both frequencies (p < .05). No significant differences were observed at 12 Hz within or between groups. L4-L5 dorsoventral accelerations were significantly decreased one year following cage placement only with Nanocoated Polyetheretherketone (p < .05) and greater reductions in acceleration were observed with Nanocoated Polyetheretherketone compared to standard Polyetheretherketone (p < .05). Both cages increased spinal stiffness, yet, nanosurfaced cages resulted in greater spinal stiffness changes and decreases in L4-L5 accelerations. These findings may assist in clinical decision making and post-operative recovery strategies.
Publisher: ASME International
Date: 20-09-2013
DOI: 10.1115/1.4025100
Abstract: Despite considerable effort over the last four decades, research has failed to translate into consistently effective treatment options for spinal cord injury (SCI). This is partly attributed to differences between the injury response of humans and rodent models. Some of this difference could be because the cerebrospinal fluid (CSF) layer of the human spine is relatively large, while that of the rodents is extremely thin. We sought to characterize the fluid impulse induced in the CSF by experimental SCIs of moderate and high human-like severity, and to compare this with previous studies in which fluid impulse has been associated with neural tissue injury. We used a new in vivo pig model (n = 6 per injury group, mean age 124.5 days, 20.9 kg) incorporating four miniature pressure transducers that were implanted in pairs in the subarachnoid space, cranial, and caudal to the injury at 30 mm and 100 mm. Tissue sparing was assessed with Eriochrome Cyanine and Neutral Red staining. The median peak pressures near the injury were 522.5 and 868.8 mmHg (range 96.7–1430.0) and far from the injury were 7.6 and 36.3 mmHg (range 3.8–83.7), for the moderate and high injury severities, respectively. Pressure impulse (mmHg.ms), apparent wave speed, and apparent attenuation factor were also evaluated. The data indicates that the fluid pressure wave may be sufficient to affect the severity and extent of primary tissue damage close to the injury site. However, the CSF pressure was close to normal physiologic values at 100 mm from the injury. The high injury severity animals had less tissue sparing than the moderate injury severity animals this difference was statistically significant only within 1.6 mm of the epicenter. These results indicate that future research seeking to elucidate the mechanical origins of primary tissue damage in SCI should consider the effects of CSF. This pig model provides advantages for basic and preclinical SCI research due to its similarities to human scale, including the existence of a human-like CSF fluid layer.
Publisher: Springer Science and Business Media LLC
Date: 05-2004
Publisher: Elsevier BV
Date: 03-2018
DOI: 10.1016/J.SPINEE.2017.07.175
Abstract: Distractive flexion injuries (DFIs) of the subaxial cervical spine are major contributors to spinal cord injury (SCI). Prompt assessment and early intervention of DFIs associated with SCI are crucial to optimize patient outcome however, neurologic examination of patients with subaxial cervical injury is often difficult, as patients commonly present with reduced levels of consciousness. Therefore, it is important to establish potential associations between injury epidemiology and radiographic features, and neurologic involvement. The aims of this study were to describe the epidemiology and radiographic features of DFIs presenting to a major Australian tertiary hospital and to identify those factors predictive of SCI. The agreement and repeatability of radiographic measures of DFI severity were also investigated. This is a combined retrospective case-control and reliability-agreement study. Two hundred twenty-six patients (median age 40 years [interquartile range = 34] 72.1% male) who presented with a DFI of the subaxial cervical spine between 2003 and 2013 were reviewed. The epidemiology and radiographic features of DFI, and risk factors for SCI were identified. Inter- and intraobserver agreement of radiographic measurements was evaluated. Medical records, radiographs, and computed tomography and magnetic resonance imaging scans were examined, and the presence of SCI was evaluated. Radiographic images were analyzed by two consultant spinal surgeons, and the degree of vertebral translation, facet apposition, spinal canal occlusion, and spinal cord compression were documented. Multivariable logistic regression models identified epidemiology and radiographic features predictive of SCI. Intraclass correlation coefficients (ICCs) examined inter- and intraobserver agreement of radiographic measurements. The majority of patients (56.2%) sustained a unilateral (51.2%) or a bilateral facet (48.8%) dislocation. The C6-C7 vertebral level was most commonly involved (38.5%). Younger adults were over-represented among motor-vehicle accidents, whereas falls contributed to a majority of DFIs sustained by older adults. Greater vertebral translation, together with lower facet apposition, distinguished facet dislocation from subluxation. Dislocation, bilateral facet injury, reduced Glasgow Coma Scale, spinal canal occlusion, and spinal cord compression were predictive of neurologic deficit. Radiographic measurements demonstrated at least a "moderate" agreement (ICC>0.4), with most demonstrating an "almost perfect" reproducibility. This large-scale cohort investigation of DFIs in the cervical spine describes radiographic features that distinguish facet dislocation from subluxation, and associates highly reproducible anatomical and clinical indices to the occurrence of concomitant SCI.
Publisher: Springer Science and Business Media LLC
Date: 05-2004
Publisher: Springer Science and Business Media LLC
Date: 31-12-2022
DOI: 10.1007/S10856-022-06704-0
Abstract: Autologous pericranium is a promising dural graft material. An optimal graft should exhibit similar mechanical properties to the native dura, but the mechanical properties of human pericranium have not been characterized, and studies of the biomechanical performance of human spinal dura are limited. The primary aim of this study was to measure the tensile structural and material properties of the pericranium, in the longitudinal and circumferential directions, and of the dura in each spinal region (cervical, thoracic and lumbar) and in three directions (longitudinal anterior and posterior, and circumferential). The secondary aim was to determine corresponding constitutive stress–strain equations using a one-term Ogden model. A total of 146 specimens were tested from 7 cadavers. Linear regression models assessed the effect of tissue type, region, and orientation on the structural and material properties. Pericranium was isotropic, while spinal dura was anisotropic with higher stiffness and strength in the longitudinal than the circumferential direction. Pericranium had lower strength and modulus than spinal dura across all regions in the longitudinal direction but was stronger and stiffer than dura in the circumferential direction. Spinal dura and pericranium had similar strain at peak force, toe, and yield, across all regions and directions. Human pericranium exhibits isotropic mechanical behavior that lies between that of the longitudinal and circumferential spinal dura. Further studies are required to determine if pericranium grafts behave like native dura under in vivo loading conditions. The Ogden parameters reported may be used for computational modeling of the central nervous system.
Publisher: Journal of Neurosurgery Publishing Group (JNSPG)
Date: 06-2012
DOI: 10.3171/2012.3.SPINE11970
Abstract: Spinal cord injury (SCI) often results in considerable permanent neurological impairment, and unfortunately, the successful translation of effective treatments from laboratory models to human patients is lacking. This may be partially attributed to differences in anatomy, physiology, and scale between humans and rodent models. One potentially important difference between the rodent and human spinal cord is the presence of a significant CSF volume within the intrathecal space around the human cord. While the CSF may “cushion” the spinal cord, pressure waves within the CSF at the time of injury may contribute to the extent and severity of the primary injury. The objective of this study was to develop a model of contusion SCI in a miniature pig and establish the feasibility of measuring spinal CSF pressure during injury. A custom weight-drop device was used to apply thoracic contusion SCI to 17 Yucatan miniature pigs. Impact load and velocity were measured. Using fiber optic pressure transducers implanted in the thecal sac, CSF pressures resulting from 2 injury severities (caused by 50-g and 100-g weights released from a 50-cm height) were measured. The median peak impact loads were 54 N and 132 N for the 50-g and 100-g injuries, respectively. At a nominal 100 mm from the injury epicenter, the authors observed a small negative pressure peak (median −4.6 mm Hg [cranial] and −5.8 mm Hg [caudal] for 50 g −27.6 mm Hg [cranial] and −27.2 mm Hg [caudal] for 100 g) followed by a larger positive pressure peak (median 110.5 mm Hg [cranial] and 77.1 mm Hg [caudal] for 50 g 88.4 mm Hg [cranial] and 67.2 mm Hg [caudal] for 100 g) relative to the preinjury pressure. There were no significant differences in peak pressure between the 2 injury severities or the caudal and cranial transducer locations. A new model of contusion SCI was developed to measure spinal CSF pressures during the SCI event. The results suggest that the Yucatan miniature pig is an appropriate model for studying CSF, spinal cord, and dura interactions during injury. With further development and characterization it may be an appropriate in vivo largeanimal model of SCI to answer questions regarding pathological changes, therapeutic safety, or treatment efficacy, particularly where humanlike dimensions and physiology are important.
Publisher: Wiley
Date: 20-04-2022
DOI: 10.1002/JNR.25049
Abstract: Pathological outcomes of traumatic brain injury (TBI), including diffuse axonal injury, are influenced by the direction, magnitude, and duration of head acceleration during the injury exposure. Ovine models have been used to study injury mechanics and pathological outcomes of TBI. To accurately describe the kinematics of the head during an injury exposure, and better facilitate comparison with human head kinematics, anatomical coordinate systems (ACS) with an origin at the head or brain center of mass (CoM), and axes that align with the ovine Frankfort plane equivalent, are required. The aim of this study was to determine the mass properties of the sheep head and brain, and define an ACS virtual for the head and brain, using anatomical landmarks on the skull with the aforementioned origins and orientation. Three‐dimensional models of 10 merino sheep heads were constructed from computed tomography images, and the coordinates of the head and brain CoMs, relative to a previously reported sheep head coordinate system (ACS physical ), were determined using the Hounsfield unit–mass density relationship. The ACS physical origin was 34.8 ± 3.1 mm posterosuperior of the head CoM and 43.7 ± 1.7 anteroinferior of the brain CoM. Prominent internal anatomical landmarks were then used to define a new ACS (ACS virtual ) with axes aligned with the Frankfort plane equivalent and an origin 10.4 ± 3.2 mm from the head CoM. The CoM and ACS virtual defined in this study will increase the potential for comparison of head kinematics between ovine models and humans, in the context of TBI.
Publisher: Elsevier BV
Date: 02-2020
DOI: 10.1016/J.JBIOMECH.2019.109584
Abstract: Despite the common use of one-handed lifting techniques for activities of daily living, these techniques have received little attention in the biomechanics literature. The braced arm-to-thigh technique (BATT) is a one-handed lifting method in which the dominant hand picks up objects, while the free hand braces the trunk on the ipsilateral thigh. The aim of this study was to compare the BATT to two-handed or unsupported one-handed lifting techniques with loads of 2 and 10 kg, by evaluating trunk motion and spine loading at L4/L5. Twenty healthy participants (30-70 years old) matched in age and sex to 18 participants with low back pain were recruited to the study. A three-axis load cell secured to the distal anterior thigh measured the bracing forces applied by the hand. The OpenSim Lifting Full-Body model was used to estimate trunk kinematics and spinal loading at L4/L5. Linear mixed-effects models were developed to compare trunk angles and L4/L5 moments and forces between lifting techniques. Trunk flexion angles were significantly reduced for the BATT lift compared to one-handed and two-handed stoop lifts (9-20%). However, the BATT also increased asymmetric trunk kinematics and moments at L4/L5. The BATT produced significantly lower moments (28-38%), and compressive (25-32%) and antero-posterior shear (25-45%) forces at L4/L5, compared to unsupported lifting techniques. Bracing the hand on the thigh to support the trunk can substantially reduce low back loading during lifting tasks of 2 to 10 kg.
Publisher: Mary Ann Liebert Inc
Date: 05-2022
Abstract: Spinal cord injury (SCI) frequently results in motor, sensory, and autonomic dysfunction for which there is currently no cure. Recent pre-clinical and clinical research has led to promising advances in treatment however, therapeutics indicating promise in rodents have not translated successfully in human trials, likely due, in part, to gross anatomical and physiological differences between the species. Therefore, large animal models of SCI may facilitate the study of secondary injury processes that are influenced by scale, and may assist the translation of potential therapeutic interventions. The aim of this study was to characterize two severities of thoracic contusion SCI in female domestic pigs, measuring motor function and spinal cord lesion characteristics, over 2 weeks post-SCI. A custom-instrumented weight-drop injury device was used to release a 50 g impactor from 10 cm (
Publisher: Informa UK Limited
Date: 04-02-2019
DOI: 10.1080/10255842.2018.1564819
Abstract: There is currently no validated full-body lifting model publicly available on the OpenSim modelling platform to estimate spinal loads during lifting. In this study, the existing full-body-lumbar-spine model was adapted and validated for lifting motions to produce the lifting full-body model. Back muscle activations predicted by the model closely matched the measured erector spinae activation patterns. Model estimates of intradiscal pressures and in vivo measurements were strongly correlated. The same spine loading trends were observed for model estimates and reported vertebral body implant measurements. These results demonstrate the suitability of this model to evaluate changes in lumbar loading during lifting.
Publisher: MDPI AG
Date: 26-02-2020
DOI: 10.3390/JCM9030626
Abstract: Tibial plateau fractures (TPFs) are challenging, requiring complex open reduction and internal fixation (ORIF) and are often associated with complications including surgical site infections (SSIs). In 2007, we introduced a novel management protocol to treat TPFs which consisted of an angiosome- or perforator-sparing (APS) anterolateral approach followed by unrestricted weight bearing and range of motion. The primary aim of this retrospective study was to investigate complication rates and patient outcomes associated with our new management protocol. In total, 79 TPFs treated between 2004 and 2007 through a classic anterolateral surgical approach formed the “Classic Group” while 66 TPFS treated between 2007 and 2013 formed the “APS Group”. Fracture reduction, maintenance of reduction and patient-reported outcomes were assessed. There was a clinically important improvement in the infection incidence with the APS (1.5%) versus the Classic technique (7.6%) (1/66 versus 2/79 for superficial infections 0/66 versus 4/79 for deep infections). Despite a more aggressive rehabilitation, there was no difference in the fracture reduction over time or the functional outcomes between both groups (p 0.05). The APS anterolateral approach improved the rate of SSIs after TPFs without compromising fracture reduction and stabilisation. We continue to use this new management approach and early unrestricted weight bearing when treating amenable TPFs.
Publisher: Elsevier BV
Date: 07-2017
DOI: 10.1016/J.INJURY.2017.05.024
Abstract: Tibial plateau fractures are complex and the current evidence for postoperative rehabilitation is weak, especially related to the recommended postoperative weight bearing. The primary aim of this study was to investigate if loading in the first 12 weeks of recovery is associated with patient reported outcome measures at 26 and 52 weeks postoperative. We hypothesized that there would be no association between loading and patient reported outcome measures. Seventeen patients, with a minimum of 52-week follow-up following fragment-specific open reduction and internal fixation for tibial plateau fracture, were selected for this retrospective analysis. Postoperatively, patients were advised to load their limb to a maximum of 20kg during the first 6 weeks. Loading data were collected during walking using force platforms. A ratio of limb loading (affected to unaffected) was calculated at 2, 6 and 12 weeks postoperative. Knee Injury and Osteoarthritis Scores were collected at 6, 12, 26 and 52 weeks postoperative. The association between loading ratios and patient reported outcomes were investigated. Compliance with weight bearing recommendations and changes in the patient reported outcome measures are described. Fracture reduction and migration were assessed on plain radiographs. No fractures demonstrated any measurable postoperative migration at 52 weeks. Significant improvements were seen in all patient reported outcome measures over the first 52 weeks, despite poor adherence to postoperative weight bearing restrictions. There were no associations between weight bearing ratio and patient reported outcomes at 52 weeks postoperative. Significant associations were identified between the loading ratio at 2 weeks and knee-related quality of life at six months (R
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 11-2012
Publisher: Springer Science and Business Media LLC
Date: 25-04-2012
Publisher: ASME International
Date: 24-03-2021
DOI: 10.1115/1.4050172
Abstract: Bilateral cervical facet dislocation (BFD) with facet fracture (Fx) often causes tetraplegia but is rarely recreated experimentally, possibly due to a lack of muscle replication. Intervertebral axial compression (due to muscle activation) or distraction (due to inertial loading), when combined with excessive anterior translation, may influence interfacet contact or separation and the subsequent production of BFD with or without Fx. This paper presents a methodology to produce C6/C7 BFD+Fx using anterior shear motion superimposed with 300 N compression or 2.5 mm distraction. The effect of these superimposed axial conditions on six-axis loads, and C6 inferior facet deflections and surface strains, was assessed. Twelve motion segments (70 ± 13 yr) achieved 2.19 mm of supraphysiologic anterior shear without embedding failure (supraphysiologic shear analysis point SSP), and BFD+Fx was produced in all five specimens that reached 20 mm of shear. Linear mixed-effects models (α = 0.05) assessed the effect of axial condition. At the SSP, the compressed specimens experienced higher axial forces, facet shear strains, and sagittal facet deflections, compared to the distracted group. Facet fractures had similar radiographic appearance to those that are observed clinically, suggesting that intervertebral anterior shear motion contributes to BFD+Fx.
Publisher: MDPI AG
Date: 05-12-2016
DOI: 10.3390/MA9120982
Publisher: Elsevier BV
Date: 04-2018
DOI: 10.1016/J.JBIOMECH.2018.02.036
Abstract: Traumatic cervical facet dislocation (CFD) is often associated with devastating spinal cord injury. Facet fractures commonly occur during CFD, yet quantitative measures of facet deflection, strain, stiffness and failure load have not been reported. The aim of this study was to determine the mechanical response of the subaxial cervical facets when loaded in directions thought to be associated with traumatic bilateral CFD - anterior shear and flexion. Thirty-one functional spinal units (6 × C2/3, C3/4, C4/5, and C6/7, 7 × C5/6) were dissected from fourteen human cadaver cervical spines (mean donor age 69 years, range 48-92 eight male). Loading was applied to the inferior facets of the inferior vertebra to simulate the in vivo inter-facet loading experienced during supraphysiologic anterior shear and flexion motion. Specimens were subjected to three cycles of sub-failure loading (10-100 N, 1 mm/s) in each direction, before being failed in a randomly assigned direction (10 mm/s). Facet deflection, surface strains, stiffness, and failure load were measured. Linear mixed-effects models (α = 0.05 random effect of cadaver) accounted for variations in specimen geometry and bone density. Specimen-specific parameters were significantly associated with most outcome measures. Facet stiffness and failure load were significantly greater in the simulated flexion loading direction, and deflection and surface strains were higher in anterior shear at the non-destructive analysis point (47 N applied load). The sub-failure strains and stiffness responses differed between the upper and lower subaxial cervical regions. Failure occurred through the facet tip during anterior shear loading, while failure through the pedicles was most common in flexion.
Publisher: Elsevier BV
Date: 04-2015
DOI: 10.1016/J.JBIOMECH.2015.02.010
Abstract: A three dimensional analytical approach was developed to determine the frictional moment vector generated by the relative sliding of the head-cup bearing couple of a total hip replacement. The frictional moment projection onto the femoral neck was also determined over the loading cycle. Predicted frictional moments for nine combinations of bearing materials and diameters were in close agreement with existing in vitro data. The analytical method was then applied to simplified gait (lubrication conditions of dry and serum), ISO standard gait and physiological level gait loading cycles. ISO standard gait had a total contact force of about two fold of physiological level gait and there was a corresponding increase in the maximum frictional torque on neck from 0.66×BW%m to 0.88×BW%m. For the ISO standard gait, the maximum frictional torque occurred at the same instance of maximum frictional moment and the maximum contact force. In contrast, for the physiological level gait, the frictional torque did not occur at the same instance as the peak load. This suggests that the neck frictional torque is a function of other parameters, such as angle between neck axis and frictional moment vector, as well as the magnitude of the contact force and frictional moment. The developed methodology was able to predict the maximum magnitude and change of directions of moments and the variation of torque at the head neck interface. The data will be useful for experimental studies assessing the fretting behaviour of the head neck junction, by providing appropriate loading data.
Publisher: Springer Science and Business Media LLC
Date: 18-01-2023
DOI: 10.1186/S12987-022-00401-4
Abstract: Detecting changes in pulsatile cerebrospinal fluid (CSF) flow may assist clinical management decisions, but spinal CSF flow is relatively understudied. Traumatic spinal cord injuries (SCI) often cause spinal cord swelling and subarachnoid space (SAS) obstruction, potentially causing pulsatile CSF flow changes. Pigs are emerging as a favoured large animal SCI model therefore, the aim of this study was to characterise CSF flow along the healthy pig spine. Phase-contrast magnetic resonance images (PC-MRI), retrospectively cardiac gated, were acquired for fourteen laterally recumbent, anaesthetised and ventilated, female domestic pigs (22–29 kg). Axial images were obtained at C2/C3, T8/T9, T11/T12 and L1/L2. Dorsal and ventral SAS regions of interest (ROI) were manually segmented. CSF flow and velocity were determined throughout a cardiac cycle. Linear mixed-effects models, with post-hoc comparisons, were used to identify differences in peak systolic/diastolic flow, and maximum velocity (cranial/caudal), across spinal levels and dorsal/ventral SAS. Velocity wave speed from C2/C3 to L1/L2 was calculated. PC-MRI data were obtained for 11/14 animals. Pulsatile CSF flow was observed at all spinal levels. Peak systolic flow was greater at C2/C3 (dorsal: − 0.32 ± 0.14 mL/s, ventral: − 0.15 ± 0.13 mL/s) than T8/T9 dorsally (− 0.04 ± 0.03 mL/s p 0.001), but not different ventrally (− 0.08 ± 0.08 mL/s p = 0.275), and no difference between thoracolumbar levels (p 0.05). Peak diastolic flow was greater at C2/C3 (0.29 ± 0.08 mL/s) compared to T8/T9 (0.03 ± 0.03 mL/s, p 0.001) dorsally, but not different ventrally (p = 1.000). Cranial and caudal maximum velocity at C2/C3 were greater than thoracolumbar levels dorsally (p 0.001), and T8/T9 and L1/L2 ventrally (p = 0.022). Diastolic velocity wave speed was 1.41 ± 0.39 m/s dorsally and 1.22 ± 0.21 m/s ventrally, and systolic velocity wave speed was 1.02 ± 0.25 m/s dorsally and 0.91 ± 0.22 m/s ventrally. In anaesthetised and ventilated domestic pigs, spinal CSF has lower pulsatile flow and slower velocity wave propagation, compared to humans. This study provides baseline CSF flow at spinal levels relevant for future SCI research in this animal model.
Publisher: Public Library of Science (PLoS)
Date: 14-01-2021
DOI: 10.1371/JOURNAL.PONE.0244503
Abstract: Adhesions are often considered to be an inevitable consequence of abdominal and pelvic surgery, jeopardizing the medium and long-term success of these procedures. Numerous strategies have been tested to reduce adhesion formation, however, to date, no surgical or medical therapeutic approaches have been successful in its prevention. This study demonstrates the safety and efficacy of Chitogel with Deferiprone and/or antibacterial Gallium Protoporphyrin in different concentrations in preventing adhesion formation after abdominal surgery. 112 adult (8–10 week old) male Wistar albino rats were subjected to midline laparotomy and caecal abrasion, with 48 rats having an additional enterotomy and suturing. Kaolin (0.005g/ml) was applied to further accelerate adhesion formation. The abrasion model rats were randomized to receive saline, Chitogel, or Chitogel plus Deferiprone (5, 10 or 20 mM), together with Gallium Protoporphyrin (250μg/mL). The abrasion with enterotomy rats were randomised to receive saline, Chitogel or Chitogel with Deferiprone (1 or 5 mM). At day 21, rats were euthanised, and adhesions graded macroscopically and microscopically the tensile strength of the repaired caecum was determined by an investigator blinded to the treatment groups. Chitogel with Deferiprone 5 mM significantly reduced adhesion formation (p .01) when pathologically assessed in a rat abrasion model. Chitogel with Deferiprone 5 mM and 1 mM also significantly reduced adhesions (p .05) after abrasion with enterotomy. Def-Chitogel 1mM treatment did not weaken the enterotomy site with treated sites having significantly better tensile strength compared to control saline treated enterotomy rats. Chitogel with Deferiprone 1 mM constitutes an effective preventative anti-adhesion barrier after abdominal surgery in a rat model. Moreover, this therapeutic combination of agents is safe and does not weaken the healing of the sutured enterotomy site.
Publisher: Elsevier BV
Date: 06-2015
DOI: 10.1016/J.INJURY.2015.02.019
Abstract: Osteoporotic tibial plateau fractures (TPFs) are difficult to treat with either open reduction internal fixation (ORIF) or acute total knee arthroplasty (TKA). They have high complication rates, poor outcomes and often fail in the short- to mid-term. We investigated the use of impaction bone grafting (IBG) as an adjunct to stabilise the fracture in a cohort of osteoporotic TPFs. Nine consecutive osteoporotic TPFs were surgically stabilised with ORIF augmented with IBG or with IBG alone (one pure depression fracture) using on average allograft from 2 femoral heads/case (range 1-4 heads or 25-100 cm(3)). The median bone mineral density T-score of the patients was -2.9 (-2.5 to -4.5). All patients were mobilised weight-bearing as tolerated immediately after surgery and had regular follow-up to a minimum of 2 years where functional scores were taken and gait was assessed. Fracture reduction was assessed on plain radiographs and computed tomography (CT) scans maintenance of fracture reduction was monitored using plain radiographs, CT and radiostereometric analysis (RSA). Bone graft remodelling was assessed by comparison of immediate post-operative CT scans with scans at a minimum of 1 year. All surgeries were uneventful. All patients progressed to full weight bearing within 6 weeks of surgery and regained a normal gait by 3 months. Seven fractures healed with a cranio-caudal migration of less than 3mm (range 0-2.6mm using RSA and 0-2mm using CT). Two fractures had an isolated posterolateral fragment depression of 13.5mm and 9 mm, respectively, which did not affect the overall joint alignment or clinical outcomes at short-term follow-up. At latest CT follow-up, on average 51% of the graft area (range 36-70%) had remodelled into new host bone. Impaction bone grafting shows promising results as an adjunct to the surgical stabilisation of osteoporotic TPFs. In this case series the technique provided enough fracture stability for patients to mobilise weight-bearing as tolerated immediately after surgery and achieve full weight-bearing by the sixth postoperative week. There was no failure of fixation and 7 of the 9 cases healed with minimal fracture displacement.
Publisher: Research Square Platform LLC
Date: 19-08-2022
DOI: 10.21203/RS.3.RS-1966542/V1
Abstract: Background Detecting changes in pulsatile cerebrospinal fluid (CSF) flow may assist clinical management decisions, but spinal CSF flow is relatively understudied. Traumatic spinal cord injuries (SCI) often cause spinal cord swelling and subarachnoid space (SAS) obstruction, potentially causing pulsatile CSF flow changes. Pigs are emerging as a favoured large animal SCI model therefore, the aim of this study was to characterise CSF flow along the healthy pig spine. Methods Phase-contrast magnetic resonance images (PC-MRI), retrospectively cardiac gated, were acquired for fourteen laterally recumbent, anaesthetised and ventilated, female domestic pigs (22–29 kg). Axial images were obtained at C2/C3, T8/T9, T11/T12 and L1/L2. Dorsal and ventral SAS regions of interest (ROI) were manually segmented. CSF flow and velocity were determined throughout a cardiac cycle. Linear mixed-effects models, with post hoc comparisons, were used to identify differences in peak systolic/diastolic flow, and maximum velocity (cranial/caudal), across spinal levels and dorsal/ventral SAS. Velocity wave speed from C2/L3 to L1/L2 was calculated. Results PC-MRI data were obtained for 11/14 animals. Pulsatile CSF flow was observed at all spinal levels. Peak systolic flow was greater at C2/C3 (dorsal: -0.37 ± 0.17 mL/s, ventral: -0.19 ± 0.17 mL/s) than T8/T9 (dorsal: -0.04 ± 0.03 mL/s, ventral: -0.09 ± 0.09 mL/s) in both SAS regions (p 0.001), and not different between thoracolumbar levels (p 0.05). Peak diastolic flow was greater at C2/C3 (0.179 ± 0.06 mL/s) compared to T8/T9 (0.04 ± 0.02 mL/s) dorsally (p 0.001), but not different ventrally (p = 1.000). Caudal maximum velocity at C2/C3 was greater than at thoracolumbar levels dorsally and ventrally (p 0.001), but not different ventrally for cranial maximum velocity (p 0.05). Diastolic velocity wave speed was 1.41 ± 0.39 m/s dorsally and 1.22 ± 0.21 m/s ventrally, and systolic velocity wave speed was 1.02 ± 0.25 m/s dorsally and 0.91 ± 0.22 m/s ventrally. Conclusions In anaesthetised and ventilated domestic pigs, spinal CSF has lower pulsatile flow and slower velocity wave propagation, compared to humans. This study provides baseline CSF flow at spinal levels relevant for future SCI research in this animal model.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 24-08-2022
DOI: 10.1097/CORR.0000000000002327
Abstract: A nanostructured titanium surface that promotes antimicrobial activity and osseointegration would provide the opportunity to create medical implants that can prevent orthopaedic infection and improve bone integration. Although nanostructured surfaces can exhibit antimicrobial activity, it is not known whether these surfaces are safe and conducive to osseointegration. Using a sheep animal model, we sought to determine whether the bony integration of medical-grade, titanium, porous-coated implants with a unique nanostructured surface modification (alkaline heat treatment [AHT]) previously shown to kill bacteria was better than that for a clinically accepted control surface of porous-coated titanium covered with hydroxyapatite (PCHA) after 12 weeks in vivo. The null hypothesis was that there would be no difference between implants with respect to the primary outcomes: interfacial shear strength and percent intersection surface (the percentage of implant surface with bone contact, as defined by a micro-CT protocol), and the secondary outcomes: stiffness, peak load, energy to failure, and micro-CT (bone volume/total volume [BV/TV], trabecular thickness [Tb.Th], and trabecular number [Tb.N]) and histomorphometric (bone-implant contact [BIC]) parameters. Implants of each material (alkaline heat-treated and hydroxyapatite-coated titanium) were surgically inserted into femoral and tibial metaphyseal cancellous bone (16 per implant type interference fit) and in tibial cortices at three diaphyseal locations (24 per implant type line-to-line fit) in eight skeletally mature sheep. At 12 weeks postoperatively, bones were excised to assess osseointegration of AHT and PCHA implants via biomechanical push-through tests, micro-CT, and histomorphometry. Bone composition and remodeling patterns in adult sheep are similar to that of humans, and this model enables comparison of implants with ex vivo outcomes that are not permissible with humans. Comparisons of primary and secondary outcomes were undertaken with linear mixed-effects models that were developed for the cortical and cancellous groups separately and that included a random effect of animals, covariates to adjust for preoperative bodyweight, and implant location (left/right limb, femoral/tibial cancellous, cortical diaphyseal region, and medial/lateral cortex) as appropriate. Significance was set at an alpha of 0.05. The estimated marginal mean interfacial shear strength for cancellous bone, adjusted for covariates, was 1.6 MPa greater for AHT implants (9.3 MPa) than for PCHA implants (7.7 MPa) (95% CI 0.5 to 2.8 p = 0.006). Similarly, the estimated marginal mean interfacial shear strength for cortical bone, adjusted for covariates, was 6.6 MPa greater for AHT implants (25.5 MPa) than for PCHA implants (18.9 MPa) (95% CI 5.0 to 8.1 p 0.001). No difference in the implant-bone percent intersection surface was detected for cancellous sites (cancellous AHT 55.1% and PCHA 58.7% adjusted difference of estimated marginal mean -3.6% [95% CI -8.1% to 0.9%] p = 0.11). In cortical bone, the estimated marginal mean percent intersection surface at the medial site, adjusted for covariates, was 11.8% higher for AHT implants (58.1%) than for PCHA (46.2% [95% CI 7.1% to 16.6%] p 0.001) and was not different at the lateral site (AHT 75.8% and PCHA 74.9% adjusted difference of estimated marginal mean 0.9% [95% CI -3.8% to 5.7%] p = 0.70). These data suggest there is stronger integration of bone on the AHT surface than on the PCHA surface at 12 weeks postimplantation in this sheep model. Given that the AHT implants formed a more robust interface with cortical and cancellous bone than the PCHA implants, a clinical noninferiority study using hip stems with identical geometries can now be performed to compare the same surfaces used in this study. The results of this preclinical study provide an ethical baseline to proceed with such a clinical study given the potential of the alkaline heat-treated surface to reduce periprosthetic joint infection and enhance implant osseointegration.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 07-2012
Publisher: Springer Science and Business Media LLC
Date: 12-11-2022
DOI: 10.1007/S10439-022-03099-5
Abstract: Synthetic surrogate head models are used in biomechanical studies to investigate skull, brain, and cervical spine injury. To ensure appropriate biofidelity of these head models, the stiffness is often tuned so that the surrogate’s response approximates the cadaveric response corridor. Impact parameters such as energy, and loading direction and region, can influence injury prediction measures, such as impact force and head acceleration. An improved understanding of how impact parameters affect the head’s structural response is required for designing better surrogate head models. This study comprises a synthesis and review of all existing ex vivo head stiffness data, and the primary factors that influence the force–deformation response are discussed. Eighteen studies from 1972 to 2019 were identified. Head stiffness statistically varied with age (pediatric vs. adult), loading region, and rate. The contact area of the impactor likely affects stiffness, whereas the impactor mass likely does not. The head’s response to frontal impacts was widely reported, but few studies have evaluated the response to other impact locations and directions. The findings from this review indicate that further work is required to assess the effect of head constraints, loading region, and impactor geometry, across a range of relevant scenarios.
Publisher: Springer Science and Business Media LLC
Date: 26-06-2023
DOI: 10.1007/S10439-023-03294-Y
Abstract: Porcine models in injury biomechanics research often involve measuring head or brain kinematics. Translation of data from porcine models to other biomechanical models requires geometric and inertial properties of the pig head and brain, and a translationally relevant anatomical coordinate system (ACS). In this study, the head and brain mass, center of mass (CoM), and mass moments of inertia (MoI) were characterized, and an ACS was proposed for the pre-adolescent domestic pig. Density-calibrated computed tomography scans were obtained for the heads of eleven Large White × Landrace pigs (18–48 kg) and were segmented. An ACS with a porcine-equivalent Frankfort plane was defined using externally palpable landmarks (right/left frontal process of the zygomatic bone and zygomatic process of the frontal bone). The head and brain constituted 7.80 ± 0.79% and 0.33 ± 0.08% of the body mass, respectively. The head and brain CoMs were primarily ventral and caudal to the ACS origin, respectively. The mean head and brain principal MoI (in the ACS with origin at respective CoM) ranged from 61.7 to 109.7 kg cm 2 , and 0.2 to 0.6 kg cm 2 , respectively. These data may aid the comparison of head and brain kinematics/kinetics data and the translation between porcine and human injury models.
Publisher: Elsevier BV
Date: 05-2009
DOI: 10.1016/J.JBIOMECH.2009.01.036
Abstract: To prevent spinal cord injury, optimize treatments for it, and better understand spinal cord pathologies such as spondylotic myelopathy, the interaction between the spinal column and the spinal cord during injury and pathology must be understood. The spinal cord is a complex and very soft tissue that changes properties rapidly after death and is difficult to model. Our objective was to develop a physical surrogate spinal cord with material properties closely corresponding to the in vivo human spinal cord that would be suitable for studying spinal cord injury under a variety of injurious conditions. Appropriate target material properties were identified from published studies and several candidate surrogate materials were screened, under uniaxial tension, in a materials testing machine. QM Skin 30, a silicone elastomer, was identified as the most appropriate material. Spinal cords manufactured from QM Skin 30 were tested under uniaxial tension and transverse compression. Rectangular specimens of QM Skin 30 were also tested under uniform compression. QM Skin 30 produced surrogate cords with a Young's modulus in tension and compression approximately matching values reported for in vivo animal spinal cords (0.25 and 0.20 MPa, respectively). The tensile and compressive Young's modulus and the behavior of the surrogate cord simulated the nonlinear behavior of the in vivo spinal cord.
Publisher: Elsevier BV
Date: 02-2021
DOI: 10.1016/J.JMBBM.2021.105056
Abstract: The objective of this study was to characterize and compare the mechanical properties of porcine pericranium and spinal dura mater, to evaluate the mechanical suitability of pericranium as a dural graft. Eighty-eight spinal dura (cervical, thoracic, and lumbar regions, in ventral longitudinal, dorsal longitudinal and circumferential orientations) and eighteen pericranium s les (ventral-dorsal, and lateral orientations) from four pigs, were harvested and subjected to uniaxial loading while hydrated. The stiffness, strain at toe-linear regions transition, strain at linear-yield regions transition and other structural and mechanical properties were measured. Stress-strain curves were fitted to a one-term Ogden model and Ogden parameters were calculated. Linear regression models with cluster-robust standard errors were used to assess the effect of region and orientation on material and structural properties. Both spinal dura and pericranium exhibited distinct anisotropy and were stiffer in the longitudinal direction. The tissues exhibited structural and mechanical similarities especially in terms of stiffness and strains in the linear region. Stiffness ranged from 1.28 to 5.32 N/mm for spinal dura and 2.42-3.90 N/mm for pericranium. In the circumferential and longitudinal directions, the stiffness of spinal dura specimens was statistically similar to that of pericranium in the same orientation. The strain at the upper bound of the linear region of longitudinal pericranium (28.0%) was statistically similar to that of any spinal dura specimens (24.4-32.9%). Autologous pericranium has advantageous physical properties for spinal duraplasty. The present study demonstrated that longitudinally oriented pericranium is mechanically compatible with spinal duraplasty procedures. Autologous pericranium grafts will likely support the mechanical loads transmitted from the spinal dura, but further biomechanical analyses are required to study the effect of the lower yield strain of circumferential pericranium compared to spinal dura. Finally, the Ogden parameters calculated for pericranium, and the spinal dura at each spinal level, will be useful for computational models incorporating these soft tissues.
Publisher: Elsevier BV
Date: 04-2012
DOI: 10.1016/J.JBIOMECH.2012.01.025
Abstract: The cerebrospinal fluid (CSF) is thought to protect the spinal cord from physiologic loading however, it is unclear whether this protective role extends to traumatic events in which bone fragments enter the canal at high velocity. A synthetic model of the spinal neural anatomy, with mechanical properties similar to native tissues, was constructed to determine if the thickness of the CSF layer (0, 12.8, 19.2 and 24.8 mm, 10 mm cord) and the velocity (1.2, 2.4, 3.7 and 4.8 m/s) of a 20 g impactor affect mechanical predictors of spinal cord injury (SCI) severity. Cord compression was directly proportional to impact velocity, inversely proportional to CSF dimension and zero for the largest dura size. The cord was compressed by more than 18% of its original diameter for the "no CSF" condition and the small dura size for all velocities. Impact loads were directly proportional to velocity, and inversely proportional to the thickness of the CSF layer. Peak cord tension increased with dura size and velocity. Peak CSF pressure decreased with distance from the impact epicenter for all dura sizes attenuation was proportional to the velocity and greatest for the smallest dura. Increased CSF dimension led to reduced CSF pressure near the impact epicenter but had little effect at the remote sites. The results suggest that a thicker CSF layer may reduce the stress induced in the cord, and therefore metrics of SCI risk may be improved by incorporating thecal sac dimensions. Computational, synthetic, cadaveric and animal models may better simulate the biomechanics of human SCI if fluid interaction is incorporated.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 08-2008
Publisher: Elsevier BV
Date: 05-2014
DOI: 10.1016/J.JSE.2013.08.004
Abstract: The suture bridge (SB) transosseous-equivalent rotator cuff repair reduces re-tear rates compared with single-row or other double-row constructs. However, failure rates continue to be high, especially in large and massive tears. The aim of this study was to assess the biomechanical performance of a new SB repair with use of a medial grasping suture compared with the traditional SB repair. Seven matched pairs of sheep infraspinatus tendons were randomly assigned to either SB or suture bridge with grasping suture (SBGS) repair. Each construct was subjected to cyclic loading and then loaded until failure under displacement control in a materials testing machine. Footprint displacement, ultimate load to failure, and mode of failure were assessed. The rotator cuff footprint displacement was less during tensile loading with the addition of the medial grasping suture. The ultimate load to failure was significantly greater for the SBGS repair group than for the SB repair group (334.0 N vs 79.8 N). The mode of failure was the tendon pulling off the footprint in all cases (type 1 tear). There were no failures in which the tendon tore at the medial row of anchors, leaving part of the tendon still on the footprint (type 2 tear). The addition of a medial grasping suture significantly improved the ultimate load to failure and reduced the footprint displacement of the SB rotator cuff repair in a biomechanical model.
Publisher: Springer Science and Business Media LLC
Date: 21-09-2023
Publisher: Elsevier BV
Date: 2019
DOI: 10.1016/J.JBIOMECH.2018.11.047
Abstract: The subaxial cervical facets are important load-bearing structures, yet little is known about their mechanical response during physiological or traumatic intervertebral motion. Facet loading likely increases when intervertebral motions are superimposed with axial compression forces, increasing the risk of facet fracture. The aim of this study was to measure the mechanical response of the facets when intervertebral axial compression or distraction is superimposed on constrained, non-destructive shear, bending and rotation motions. Twelve C6/C7 motion segments (70 ± 13 yr, nine male) were subjected to constrained quasi-static anterior shear (1 mm), axial rotation (4°), flexion (10°), and lateral bending (5°) motions. Each motion was superimposed with three axial conditions: (1) 50 N compression (2) 300 N compression (simulating neck muscle contraction) and, (3) 2.5 mm distraction. Angular deflections, and principal and shear surface strains, of the bilateral C6 inferior facets were calculated from motion-capture data and rosette strain gauges, respectively. Linear mixed-effects models (α = 0.05) assessed the effect of axial condition. Minimum principal and maximum shear strains were largest in the compressed condition for all motions except for maximum principal strains during axial rotation. For right axial rotation, maximum principal strains were larger for the contralateral facets, and minimum principal strains were larger for the left facets, regardless of axial condition. Sagittal deflections were largest in the compressed conditions during anterior shear and lateral bending motions, when adjusted for facet side.
Publisher: Springer Science and Business Media LLC
Date: 06-11-2021
Publisher: Elsevier BV
Date: 04-2018
DOI: 10.1016/J.CLINBIOMECH.2018.03.019
Abstract: The mechanical interactions occurring between the spinal column and spinal cord during an injury event are complex and variable, and likely have implications for the clinical presentation and prognosis of the in idual. The engineering approaches that have been developed to better understand spinal column and cord interactions during an injury event are discussed. These include injury models utilising human and animal cadaveric specimens, in vivo anaesthetised animals, finite element models, inanimate physical systems and combinations thereof. The paper describes the development of these modelling approaches, discusses the advantages and disadvantages of the various models, and the major outcomes that have had implications for spinal cord injury research and clinical practice. The contribution of these four engineering approaches to understanding the interaction between the biomechanics and biology of spinal cord injury is substantial they have improved our understanding of the factors contributing to the spinal column disruption, the degree of spinal cord deformation or motion, and the resultant neurological deficit and imaging features. Models of the injury event are challenging to produce, but technological advances are likely to improve these models and, consequently, our understanding of the mechanical context in which the biological injury occurs.
Publisher: Mary Ann Liebert Inc
Date: 02-2013
Abstract: Spinal cord injury (SCI) researchers have predominately utilized rodents and mice for in vivo SCI modeling and experimentation. From these small animal models have come many insights into the biology of SCI, and a growing number of novel treatments that promote behavioral recovery. It has, however, been difficult to demonstrate the efficacy of such treatments in human clinical trials. A large animal SCI model that is an intermediary between rodent and human SCI may be a valuable translational research resource for pre-clinically evaluating novel therapies, prior to embarking upon lengthy and expensive clinical trials. Here, we describe the development of such a large animal model. A thoracic spinal cord injury at T10/11 was induced in Yucatan miniature pigs (20-25 kg) using a weight drop device. Varying degrees of injury severity were induced by altering the height of the weight drop (5, 10, 20, 30, 40, and 50 cm). Behavioral recovery over 12 weeks was measured using a newly developed Porcine Thoracic Injury Behavior Scale (PTIBS). This scale distinguished locomotor recovery among animals of different injury severities, with strong intra-observer and inter-observer reliability. Histological analysis of the spinal cords 12 weeks post-injury revealed that animals with the more biomechanically severe injuries had less spared white matter and gray matter and less neurofilament immunoreactivity. Additionally, the PTIBS scores correlated strongly with the extent of tissue sparing through the epicenter of injury. This large animal model of SCI may represent a useful intermediary in the testing of novel pharmacological treatments and cell transplantation strategies.
Publisher: Springer Science and Business Media LLC
Date: 17-11-2021
DOI: 10.1007/S10439-021-02888-8
Abstract: Computational models of experimental data can provide a noninvasive method to estimate spinal facet joint biomechanics. Existing models typically consider each vertebra as one rigid-body and assume uniform facet cartilage thickness. However, facet deflection occurs during motion, and cervical facet cartilage is nonuniform. Multi rigid-body computational models were used to investigate the effect of specimen-specific cartilage profiles on facet contact area estimates. Twelve C6/C7 segments underwent non-destructive intervertebral motions. Kinematics and facet deflections were measured. Three-dimensional models of the vertebra and cartilage thickness estimates were obtained from pre-test CT data. Motion-capture data was applied to two model types (2RB: C6, C7 vertebrae each one rigid body 3RB: left and right C6 posterior elements, and C7 vertebrae, each one rigid body) and maximum facet mesh penetration was compared. Constant thickness cartilage (CTC) and spatially-varying thickness cartilage (SVTC) profiles were applied to the facet surfaces of the 3RB model. Cartilage apposition area (CAA) was compared. Linear mixed-effects models were used for all quantitative comparisons. The 3RB model significantly reduced penetrating mesh elements by accounting for facet deflections (p = 0.001). The CTC profile resulted in incongruent facet articulation, whereas realistic congruence was observed for the SVTC profile. The SVTC profile demonstrated significantly larger CAA than the CTC model (p < 0.001).
Publisher: Springer Science and Business Media LLC
Date: 07-03-2022
DOI: 10.1007/S10439-022-02940-1
Abstract: During cervical spine trauma, complex intervertebral motions can cause a reduction in facet joint cartilage apposition area (CAA), leading to cervical facet dislocation (CFD). Intervertebral compression and distraction likely alter the magnitude and location of CAA, and may influence the risk of facet fracture. The aim of this study was to investigate facet joint CAA resulting from intervertebral distraction (2.5 mm) or compression (50, 300 N) superimposed on shear and bending motions. Intervertebral and facet joint kinematics were applied to multi rigid-body kinematic models of twelve C6/C7 motion segments (70 ± 13 year, nine male) with specimen-specific cartilage profiles. CAA was qualitatively and quantitatively compared between distraction and compression conditions for each motion linear mixed-effects models ( α = 0.05) were applied. Distraction significantly decreased CAA throughout all motions, compared to the compressed conditions ( p 0.001), and shifted the apposition region towards the facet tip. These observations were consistent bilaterally for both asymmetric and symmetric motions. The results indicate that axial neck loads, which are altered by muscle activation and head loading, influences facet apposition. Investigating CAA in longer cervical spine segments subjected to quasistatic or dynamic loading may provide insight into dislocation and fracture mechanisms.
Location: United Kingdom of Great Britain and Northern Ireland
Start Date: 05-2019
End Date: 12-2024
Amount: $537,000.00
Funder: Australian Research Council
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