ORCID Profile
0000-0002-5067-0833
Current Organisation
University of British Columbia
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Biomechanical Engineering | Biomedical Engineering
Expanding Knowledge in Engineering | Road Safety | Injury Control |
Publisher: Springer Science and Business Media LLC
Date: 03-2005
DOI: 10.1007/S00335-004-2419-8
Abstract: We used a 9.6 K cattle muscle/fat cDNA microarray to study gene expression differences between the longuissimus dorsi (LD) muscle of Japanese Black (JB) and Holstein (HOL) cattle. JB cattle exhibit an unusual ability to accumulate intramuscular adipose tissue with fat melting points lower than that in other breeds. The LD biopsies from three JB (Tajima strain) and three HOL animals were used in this breed comparison. Seventeen genes were identified as preferentially expressed in LD s les from JB and seven genes were found to be expressed more highly in HOL. The expression of six selected differentially expressed genes was confirmed by quantitative real-time PCR. The genes more highly expressed in JB are associated with unsaturated fatty acid synthesis, fat deposition, and the thyroid hormone pathway. These results are consistent with the increased amounts and proportions of monounsaturated fatty acids observed in the muscle of JB animals. By discovering as yet uncharacterized genes that are differentially regulated in this comparison, the work may lead us to a better understanding of the regulatory pathways involved in the development of intramuscular adipose tissue.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 10-2006
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 10-2001
DOI: 10.1097/00007632-200110150-00012
Abstract: An in vitro biomechanical study. To develop and evaluate a new in vitro whole cervical spine model that provides to the specimen, in vivo-like mechanical characteristics. In vitro studies of kinematics, kinetics, and trauma using isolated spine specimens (head-T1 vertebra) have usually applied upward force to the head, resulting in tensile spine forces, contrary to the physiological compressive forces present in vivo. Further, the in vitro load-displacement curves have never been compared with the corresponding in vivo data. A novel muscle force replication (MFR) system is presented. It consists of a set of compressive forces applied to the various vertebrae and occiput of a whole cervical spine specimen. Two protocols, with and without MFR, were evaluated using standardized flexibility testing. Ranges of motion (ROM) and load-displacement curves were documented, and contrasted with similar in vivo data. Results for the MFR were found to be similar to the in vivo measurements, with respect to the intersegmental and whole neck motions as well as the load-displacement curves, thus validating the MFR approach. The new model advances the in vitro testing, which uses whole cervical spine specimens.
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: ASME International
Date: 15-03-2016
DOI: 10.1115/1.4032799
Abstract: Strain gages are commonly used to measure bone strain, but only provide strain at a single location. Digital image correlation (DIC) is an optical technique that provides the displacement, and therefore strain, over an entire region of interest on the bone surface. This study compares vertebral body strains measured using strain gages and DIC. The anterior surfaces of 15 cadaveric porcine vertebrae were prepared with a strain rosette and a speckled paint pattern for DIC. The vertebrae were loaded in compression with a materials testing machine, and two high-resolution cameras were used to image the anterior surface of the bones. The mean noise levels for the strain rosette and DIC were 1 με and 24 με, respectively. Bland–Altman analysis was used to compare strain from the DIC and rosette (excluding 44% of trials with some evidence of strain rosette failure or debonding) the mean difference ± 2 standard deviations (SDs) was −108 με ± 702 με for the minimum (compressive) principal strain and −53 με ± 332 με for the maximum (tensile) principal strain. Although the DIC has higher noise, it avoids the relatively high risk we observed of strain gage debonding. These results can be used to develop guidelines for selecting a method to measure strain on bone.
Publisher: Elsevier BV
Date: 11-2016
DOI: 10.1016/J.MEDENGPHY.2016.08.010
Abstract: Finite element analysis (FEA) of bones scanned with Quantitative Computed Tomography (QCT) can improve early detection of osteoporosis. The accuracy of these models partially depends on the assigned material properties, but anisotropy of the trabecular bone cannot be fully captured due to insufficient resolution of QCT. The inclusion of anisotropy measured from high resolution peripheral QCT (HR-pQCT) could potentially improve QCT-based FEA of the femur, although no improvements have yet been demonstrated in previous experimental studies. This study analyzed the effects of adding anisotropy to clinical resolution femur models by constructing six sets of FE models (two isotropic and four anisotropic) for each specimen from a set of sixteen femurs that were experimentally tested in sideways fall loading with a strain gauge on the superior femoral neck. Two different modulus-density relationships were tested, both with and without anisotropy derived from mean intercept length analysis of HR-pQCT scans. Comparing iso- and anisotropic models to the experimental data resulted in nearly identical correlation and highly similar linear regressions for both whole bone stiffness and strain gauge measurements. Anisotropic models contained consistently greater principal compressive strains, approximately 14% in magnitude, in certain internal elements located in the femoral neck, greater trochanter, and femoral head. In summary, anisotropy had minimal impact on macroscopic measurements, but did alter internal strain behavior. This suggests that organ level QCT-based FE models measuring femoral stiffness have little to gain from the addition of anisotropy, but studies considering failure of internal structures should consider including anisotropy to their models.
Publisher: Springer Science and Business Media LLC
Date: 22-11-2014
Publisher: Springer Science and Business Media LLC
Date: 25-04-2012
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 2002
DOI: 10.1097/00007632-200201010-00011
Abstract: An in vitro flexibility study of C2-T1 specimens under compressive preload. To determine three-dimensional flexibility test moments needed to obtain spinal kinematics representative of the in vivo spine studies. Most previous three-dimensional in vitro cervical spine studies have used equal moments in all three planes to evaluate spinal flexibilities. Recent advances have made it possible to apply physiologic compressive preload. It is unclear what moments should be applied to these preloaded spine segments to simulate in vivo kinematics. Six fresh human cadaveric cervical spine specimens (C2-T1) were used. The preload (100 N) was applied by flexible cables, which passed through guides attached to each vertebra. Flexibility tests of flexion-extension and bilateral axial torsion and lateral bending were performed. Two protocols were compared, 1:1:1 with equal pure moments of 1 Nm for each direction and 2:4:2 with pure moments of 2 Nm for flexion-extension and lateral bending and 4 Nm for axial torsion. Ranges of motion were calculated from the flexibility tests. The 2:4:2 protocol resulted in significantly better agreement with in vivo data than did the 1:1:1 protocol. In flexion-extension, the 2 Nm value was within 17% of the average in vivo value. In axial torsion, the 4 Nm value was within 22% of the in vivo average. In lateral bending, the 2 Nm value was within 15% of the in vivo average. To obtain human in vivo-like kinematics using 100 N preload, the 2:4:2 protocol is to be recommended.
Publisher: Elsevier BV
Date: 09-2011
DOI: 10.1016/J.JBIOMECH.2011.06.015
Abstract: The relationship between bony spinal column and spinal cord injury during an injury event is not well understood. While several studies have measured spinal canal occlusion during axial impact, there has been limited work done to quantify the spinal cord compression or deformation during simulated injury. Because the cord is a viscoelastic solid it may provide resistance to bone fragments, ligaments or other elements that move into the canal and impinge it during column injury. This would differentiate the measurement of cord compression from the measurement of occlusion of an empty canal. In the present study, a novel method of visualizing and quantifying spinal cord deformation during dynamic head-first impact of ex vivo human cervical spine specimens (N=6) was developed. A radiodense, biofidelic surrogate spinal cord was imaged in the spinal canal using high speed cineradiography at 1000 frames per second. The dorsal-ventral diameter of the cord was measured at 1.5mm increments along its length for each frame of the radiographic footage. The resulting cord deformations were used to determine the theoretical neurological outcome of the impact based on published in vivo ferret studies. The corresponding probability of recovery for the spinal cord deformations in these tests ranged between 8% for atlantoaxial dislocation injury and 95% for mid-cervical spine hyperextension injury (based on the ferret data). Clinically relevant spinal column fracture patterns were produced in this study.
Publisher: Elsevier BV
Date: 05-2012
DOI: 10.1016/J.CLINBIOMECH.2011.11.001
Abstract: Vertebral compression fracture repair aims to relieve pain and improve function by restoring vertebral structure and biomechanics, but is still associated with risks arising from polymethylmethacrylate cement extravasation. The Kiva® Vertebral Compression Fracture Treatment System, a stacked coil implant made of polyetheretherketone and delivered over a guide-wire, is a novel device designed to provide height restoration and mechanical stabilization, while improving cement containment and minimizing disruption of cancellous bone. The objective of this study was to determine whether the Kiva system is as effective as balloon kyphoplasty at restoring mechanical properties in osteoporotic vertebral compression fractures. Wedge fractures were created in the middle vertebra of fourteen osteoporotic three-vertebra spine segments and then repaired with either the Kiva or kyphoplasty procedure. Height, stiffness and displacement under compression of the spine segments were measured for four conditions: intact, fractured, augmented, and post-cyclic eccentric loading (50,000cycles, 200-500N, 30mm anterior lever arm). No significant differences were seen between the two procedures for height restoration, stiffness at high or low loads, or displacement under compression. However, the Kiva System required an average of 66% less cement than kyphoplasty to achieve these outcomes (mean 2.6 (SD 0.4) mL v. mean 7.5 (SD 0.8) mL 0 P<0.01). Extravasations and excessive posterior cement flow were also significantly lower with Kiva (0/7 v. 4/7 P<.05). Kiva exhibits similar biomechanical performance to balloon kyphoplasty, but may reduce the risk of extravasation through the containment mechanism of the implant design and by reducing cement volume.
Publisher: Elsevier BV
Date: 02-2015
DOI: 10.1016/J.BONE.2014.10.001
Abstract: Bone can be viewed as a nano-fibrous composite with complex hierarchical structures. Its deformation and fracture behaviors depend on both the local structure and the type of stress applied. In contrast to the extensive studies on bone fracture under compression and tension, there is a lack of knowledge on the fracture process under shear, a stress state often exists in hip fracture. This study investigated the mechanical behavior of human cortical bone under shear, with the focus on the relation between the fracture pattern and the microstructure. Iosipescu shear tests were performed on notched rectangular bar specimens made from human cortical bone. They were prepared at different angles (i.e. 0°, 30°, 60° and 90°) with respect to the long axis of the femoral shaft. The results showed that human cortical bone behaved as an anisotropic material under shear with the highest shear strength (~50MPa) obtained when shearing perpendicular to the Haversian systems or secondary osteons. Digital image correlation (DIC) analysis found that shear strain concentration bands had a close association with long bone axis with an average deviation of 11.8° to 18.5°. The fracture pattern was also greatly affected by the structure with the crack path generally following the direction of the long axes of osteons. More importantly, we observed unique peripheral arc-shaped microcracks within osteons, using laser scanning confocal microscopy (LSCM). They were generally long cracks that developed within a lamella without crossing the boundaries. This microcracking pattern clearly differed from that created under either compressive or tensile stress: these arc-shaped microcracks tended to be located away from the Haversian canals in early-stage damaged osteons, with ~70% developing in the outer third osteonal wall. Further study by second harmonic generation (SHG) and two-photon excitation fluorescence (TPEF) microscopy revealed a strong influence of the organization of collagen fibrils on shear microcracking. This study concluded that shear-induced microcracking of human cortical bone follows a unique pattern that is governed by the lamellar structure of the osteons.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 02-2005
DOI: 10.1097/01.BSD.0000138694.56012.CE
Abstract: It remains unclear whether adjacent vertebral body fractures are related to the natural progression of osteoporosis or if adjacent fractures are a consequence of augmentation with bone cement. Experimental or computational studies have not completely addressed the biomechanical effects of kyphoplasty on adjacent levels immediately following augmentation. This study presents a validated two-functional spinal unit (FSU) T12-L2 finite element model with a simulated kyphoplasty augmentation in L1 to predict stresses and strains within the bone cement and bone of the treated and adjacent nontreated vertebral bodies. The findings from this multiple-FSU study and a recent retrospective clinical study suggest that changes in stresses and strains in levels adjacent to a kyphoplasty-treated level are minimal. Furthermore, the stress and strain levels found in the treated levels are less than injury tolerance limits of cancellous and cortical bone. Therefore, subsequent adjacent level fractures may be related to the underlying etiology (weakening of the bone) rather than the surgical intervention.
Publisher: Elsevier BV
Date: 07-2008
DOI: 10.1016/J.AAP.2008.03.007
Abstract: Chance fractures of the skeletally immature spine classically occur in frontal motor vehicle accidents (MVAs) when the occupants are restrained by a lap belt only and undergo traumatic hyperflexion of the torso during the impact. We retrospectively examined all MVA-related Chance fractures at British Columbia's Children's Hospital since 1986, by collecting injury and seat-belt use information from chart data and imaging studies. Twenty-six patients were included in the study, 14 wore a lap belt only, seven wore a three-point restraint properly, and five were reportedly misusing the shoulder portion of a three-point restraint. The subjects ranged in age from 3 to 16 with a mean age of 10.6 years. Eleven of the 26 (42%) patients sustained abdominal viscera injuries, seven of the 26 patients suffered neurologic injury (spinal cord and/or spinal nerve injury) associated with their spinal fracture, with two cases of complete paralysis, and there was a 38% incidence of head injury. Concomitant injuries (i.e. to the head, abdomen and abdominal contents) tended to be mitigated by the presence of a properly worn shoulder restraint. This leads to the conclusion that Chance fractures can be sustained even when the occupant is using a shoulder belt to restrain their torso. The mechanism responsible for this is unknown. This may indicate that Chance fractures can be caused by a lesser degree of torso hyperflexion than previously thought. Alternatively, we also speculate that Chance fractures can occur while the torso is restrained by the shoulder belt if the hips submarine beneath the lap belt and the torso experiences hyperflexion secondary to forward excursion of the pelvis and legs during the collision. Future work is necessary to confirm these mechanisms and to find ways to prevent them. These studies will need to use computational or experimental child surrogates that can sit in a slouched posture and submarine during a collision.
Publisher: Springer Science and Business Media LLC
Date: 27-11-2017
DOI: 10.1007/S10439-017-1952-Z
Abstract: The limitations of areal bone mineral density measurements for identifying at-risk in iduals have led to the development of alternative screening methods for hip fracture risk including the use of geometrical measurements from the proximal femur and subject specific finite element analysis (FEA) for predicting femoral strength, based on quantitative CT data (qCT). However, these methods need more development to gain widespread clinical applications. This study had three aims: To investigate whether proximal femur geometrical parameters correlate with obtained femur peak force during the impact testing to examine whether or not failure of the proximal femur initiates in the cancellous (trabecular) bone and finally, to examine whether or not surface fracture initiates in the places where holes perforate the cortex of the proximal femur. We found that cortical thickness around the trochanteric-fossa is significantly correlated to the peak force obtained from simulated sideways falling (R
Publisher: Springer Science and Business Media LLC
Date: 06-10-2009
Publisher: Elsevier BV
Date: 03-2014
DOI: 10.1016/J.JBIOMECH.2013.12.001
Abstract: Current neck injury criteria do not include limits for lateral bending combined with axial compression and this has been observed as a clinically relevant mechanism, particularly for rollover motor vehicle crashes. The primary objectives of this study were to evaluate the effects of lateral eccentricity (the perpendicular distance from the axial force to the centre of the spine) on peak loads, kinematics, and spinal canal occlusions of subaxial cervical spine specimens tested in dynamic axial compression (0.5 m/s). Twelve 3-vertebra human cadaver cervical spine specimens were tested in two groups: low and high eccentricity with initial eccentricities of 1 and 150% of the lateral diameter of the vertebral body. Six-axis loads inferior to the specimen, kinematics of the superior-most vertebra, and spinal canal occlusions were measured. High speed video was collected and acoustic emission (AE) sensors were used to define the time of injury. The effects of eccentricity on peak loads, kinematics, and canal occlusions were evaluated using unpaired Student t-tests. The high eccentricity group had lower peak axial forces (1544 ± 629 vs. 4296 ± 1693 N), inferior displacements (0.2 ± 1.0 vs. 6.6 ± 2.0 mm), and canal occlusions (27 ± 5 vs. 53 ± 15%) and higher peak ipsilateral bending moments (53 ± 17 vs. 3 ± 18 Nm), ipsilateral bending rotations (22 ± 3 vs. 1 ± 2°), and ipsilateral displacements (4.5 ± 1.4 vs. -1.0 ± 1.3 mm, p<0.05 for all comparisons). These results provide new insights to develop prevention, recognition, and treatment strategies for compressive cervical spine injuries with lateral eccentricities.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 07-2014
Publisher: Springer Science and Business Media LLC
Date: 13-11-2013
DOI: 10.1038/503S13A
Publisher: Elsevier BV
Date: 04-2001
DOI: 10.1016/S0021-9290(00)00205-0
Abstract: A novel technique to measure in vitro disc pressures in human cervical spine specimens was developed. A miniature pressure transducer was used and an insertion technique was designed to minimise artefacts due to insertion. The technique was used to measure the intradiscal pressure in cervical spines loaded in pure axial compression. The resulting pressure varied linearly with the applied compressive force with coefficients of determination (r(2)) greater than 0.99 for each of the four specimens. Peak pressures between 2.4 and 3.5MPa were recorded under 800N of compression.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 02-2007
Publisher: BMJ
Date: 08-06-2011
DOI: 10.1136/INJURYPREV-2011-040071
Abstract: Bicycling may be less appealing in parts of the world where cycling is less safe. Differences between jurisdictions suggest route design is key to improving safety and increasing ridership. Previous studies faced difficulties in effectively assessing denominators for risk calculations and controlling confounding. This paper describes the advantages of the case-crossover design of the Bicyclists' Injuries and the Cycling Environment study to address these challenges to observational studies of cycling safety. Injured cyclists were recruited from the emergency departments of five hospitals in Vancouver and Toronto, Canada. In 18 months, 690 participants were successfully recruited and interviewed. Each participant was interviewed to map the route of their injury trip, identify the injury site and select two control sites at random from the same route. Infrastructural characteristics at each study site were scored by site observers who were blinded as to whether sites were crash or comparison sites. Analyses will compare infrastructural variables between case and control sites with conditional logistic regression. This study presents a novel application of the case-crossover design to the evaluation of relationships between infrastructure and cycling safety while controlling confounders and exposure to risk. It is hoped that the value of this method and the efficiency of the recruitment process will encourage replication in other locations, to expand the range of cycling infrastructure compared and to facilitate evidence-based cycling infrastructure choices that can make cycling safer and more appealing.
Publisher: Society for Neuroscience
Date: 09-2017
DOI: 10.1523/ENEURO.0164-17.2017
Abstract: Diffuse axonal injury (DAI) is a hallmark of traumatic brain injury (TBI) pathology. Recently, the Closed Head Injury Model of Engineered Rotational Acceleration (CHIMERA) was developed to generate an experimental model of DAI in a mouse. The characterization of DAI using diffusion tensor magnetic resonance imaging (MRI diffusion tensor imaging, DTI) may provide a useful set of outcome measures for preclinical and clinical studies. The objective of this study was to identify the complex neurobiological underpinnings of DTI features following DAI using a comprehensive and quantitative evaluation of DTI and histopathology in the CHIMERA mouse model. A consistent neuroanatomical pattern of pathology in specific white matter tracts was identified across ex vivo DTI maps and photomicrographs of histology. These observations were confirmed by voxelwise and regional analysis of DTI maps, demonstrating reduced fractional anisotropy (FA) in distinct regions such as the optic tract. Similar regions were identified by quantitative histology and exhibited axonal damage as well as robust gliosis. Additional analysis using a machine-learning algorithm was performed to identify regions and metrics important for injury classification in a manner free from potential user bias. This analysis found that diffusion metrics were able to identify injured brains almost with the same degree of accuracy as the histology metrics. Good agreement between regions detected as abnormal by histology and MRI was also found. The findings of this work elucidate the complexity of cellular changes that give rise to imaging abnormalities and provide a comprehensive and quantitative evaluation of the relative importance of DTI and histological measures to detect brain injury.
Publisher: Elsevier BV
Date: 11-2012
DOI: 10.1016/J.MEDENGPHY.2011.12.016
Abstract: Low-stiffness posterior fusion devices for the lumbar spine have been developed to treat degenerative spinal conditions. However, the demands on an implant vary between a stable motion segment and one which exhibits a significant degree of sagittal plane instability. Shear motion in the antero-posterior direction is a relevant mode of instability for clinical conditions such as degenerative lumbar spondylolisthesis. Shear load-sharing between the implant and spine in conditions of antero-posterior instability has not been studied, nor have there been comparisons between traditional rigid implants and novel low-stiffness implants. The objective of this study was to develop a method to measure in vitro shear forces on three clinically relevant fusion implants when they are applied to an unstable model of degenerative spondylolisthesis in a human cadaver spine. Uniaxial strain gauges were affixed to the surface of the implants and a spine-segment-specific calibration method was used to calibrate the strain output to an applied shear force. The accuracy of the force measurements was within 3.4N for all implant types and the repeatability was within 5.4N. The force measurement technique was sufficiently accurate and reliable to conclude that it is suitable for use in in vitro experiments to measure implant shear force.
Publisher: Springer Science and Business Media LLC
Date: 04-1995
DOI: 10.1007/BF00278923
Publisher: Springer Science and Business Media LLC
Date: 10-05-2015
Publisher: Informa UK Limited
Date: 10-10-2022
Publisher: Mary Ann Liebert Inc
Date: 15-12-2016
Abstract: In the military environment, injured soldiers undergoing medical evacuation via helicopter or mine-resistant ambush-protected vehicle (MRAP) are subjected to vibration and shock inherent to the transport vehicle. We conducted the present study to assess the consequences of such vibration on the acutely injured spinal cord. We used a porcine model of spinal cord injury (SCI). After a T10 contusion-compression injury, animals were subjected to 1) no vibration (n = 7-8), 2) whole body vibration at frequencies and litudes simulating helicopter transport (n = 8), or 3) whole body vibration simulating ground transportation in an MRAP ambulance (n = 7). Hindlimb locomotor function (using Porcine Thoracic Injury Behavior Scale [PTIBS]), Eriochrome Cyanine histochemistry and biochemical analysis of inflammatory and neural damage markers were analyzed. Cerebrospinal fluid (CSF) expression levels for monocyte chemoattractant protein-1 (MCP-1), interleukin (IL)-6, IL-8, and glial fibrillary acidic protein (GFAP) were similar between the helicopter or MRAP group and the unvibrated controls. Spared white/gray matter tended to be lower in the MRAP-vibrated animals than in the unvibrated controls, especially rostral to the epicenter. However, spared white/gray matter in the helicopter-vibrated group appeared normal. Although there was a relationship between the extent of sparing and the extent of locomotor recovery, no significant differences were found in PTIBS scores between the groups. In summary, exposures to vibration in the context of ground (MRAP) or aeromedical (helicopter) transportation did not significantly impair functional outcome in our large animal model of SCI. However, MRAP vibration was associated with increased tissue damage around the injury site, warranting caution around exposure to vehicle vibration acutely after SCI.
Publisher: Springer Science and Business Media LLC
Date: 07-05-2004
Publisher: Wiley
Date: 30-03-2016
DOI: 10.1002/JOR.23093
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 07-2009
Publisher: Elsevier BV
Date: 03-2018
Publisher: BMJ
Date: 23-12-2016
DOI: 10.1136/BJSPORTS-2015-095006
Abstract: The Whistler Sliding Centre (WSC) in British Columbia, Canada, has played host to many events including the 2010 Winter Olympics. This study was performed to better understand sliding sport incident (crash, coming off sled, etc) and injury prevalence and provide novel insights into the effect of slider experience and track-specific influences on injury risk and severity. Track documentation and medical records over 4 years (2007 track inception to 2011) were used to form 3 databases, including over 43,200 runs (all sliding disciplines). Statistics were generated relating incident and injury to start location, crash location and slider experience as well as to understand injury characteristics. Overall injury rate was found to be 0.5%, with more severe injury occurring in <0.1% of the total number of runs. More frequent and severe injuries were observed at lower track locations. Of 2605 different sliders, 73.6% performed 1-29 runs down the track. Increased slider experience was generally found to reduce the frequency of injury. Lacerations, abrasions and contusions represented 52% of all injuries. A fatality represented the most severe injury on the track and was the result of track ejection. By investigating the influence of start location, incident location and slider experience on incident and injury frequency and severity, a better understanding has been achieved of the inherent risks involved in sliding sports. Incident monitoring, with particular focus on track ejection, should be an emphasis of sliding tracks.
Publisher: Elsevier BV
Date: 06-2012
DOI: 10.1016/J.JBIOMECH.2012.03.025
Abstract: Acoustic emission (AE) sensors are a reliable tool in detecting fracture however they have not been used to differentiate between compressive osseous and tensile ligamentous failures in the spine. This study evaluated the effectiveness of AE data in detecting the time of injury of ligamentum flavum (LF) and vertebral body (VB) specimens tested in tension and compression, respectively, and in differentiating between these failures. AE signals were collected while LF (n=7) and VB (n=7) specimens from human cadavers were tested in tension and compression (0.4m/s), respectively. Times of injury (time of peak AE litude) were compared to those using traditional methods (VB: time of peak force, LF: visual evidence in high speed video). Peak AE signal litudes and frequencies (using Fourier and wavelet transformations) for the LF and VB specimens were compared. In each group, six specimens failed (VB, fracture LF, periosteal stripping or attenuation) and one did not. Time of injury using AE signals for VB and LF specimens produced average absolute differences to traditional methods of 0.7 (SD=0.2) ms and 2.4 (SD=1.5) ms (representing 14% and 20% of the average loading time), respectively. AE signals from VB fractures had higher litudes and frequencies than those from LF failures (average peak litude 87.7 (SD=6.9) dB vs. 71.8 (SD=9.8)dB for the inferior sensor, p<0.05 median characteristic frequency from the inferior sensor 97 (interquartile range, IQR, 41) kHz vs. 31 (IQR 2) kHz, p<0.05). These findings demonstrate that AE signals could be used to delineate complex failures of the spine.
Publisher: Wiley
Date: 21-01-2015
DOI: 10.1002/JOR.22792
Abstract: Many pathologies involving disc degeneration are treated with surgery and spinal implants. It is important to understand how the spine behaves mechanically as a function of disc degeneration. Shear loading is especially relevant in the natural and surgically stabilized lumbar spine. The objective of our study was to determine the effect of disc degeneration on anterior translation of the lumbar spine under shear loading. We tested 30 human cadaveric functional spinal units (L3-4 and L4-5) in anterior shear loading. First, the specimens were imaged in a 1.5 T magnetic resonance scanner. The discs were graded according to the Pfirrmann classification. The specimens were then loaded up to 250 N in anterior shear with an axial compression force of 300 N. Motion of the vertebrae was captured with an optoelectronic camera system. Inter- and intra-observer reliability for disc grading was determined (Cohen's and Fleiss' Kappa), and a non-parametric test was performed on the translation data to characterize the effect of disc degeneration on this parameter. We found fair to moderate agreement between and within observers for the disc grading. We found no significant effect of disc degeneration on anterior shear translation (Kruskal-Wallis ANOVA). Our results indicate that disc degeneration, as classified with the Pfirrmann scale, does not predict lumbar spinal motion in shear.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 2000
DOI: 10.1097/00007632-200001150-00006
Abstract: Load sharing in stabilized spinal segments was evaluated using sequential injury and stabilization with a posterior instrumentation system under an in vitro flexibility protocol. To analyze the partitioning of applied loads between anatomic and implanted structures of lumbar functional spinal units stabilized with a posterior instrumentation system. To identify surgical indications for which the risk of fixator breakage in vivo is high. Relatively few groups have experimentally measured the in vitro and in vivo forces and/or moments supported by posterior instrumentation systems, and no analysis, of the load sharing in these systems has been performed. This information will provide novel insight into implant fatigue life, and the degree to which the spinal anatomy is shielded from the applied load and will allow the verification of mathematical models for new injury scenarios. Specimen kinematics were determined using an optoelectronic tracking system. Intradiscal pressure and the forces and moments supported by the implants were measured using, respectively, a needle-mounted pressure sensor and strain gauges mounted on the spinal implants. A large majority of the applied moments were supported by an equal and opposite force pair between the intervertebral disc and fixator rods in flexion and extension and an equal and opposite force pair between the left and right fixator rods in lateral bending. Torsional moments were shared approximately equally between the posterior elements, intervertebral disc, an equal and opposite shear force pair in the transverse plane between the right and left fixators and internal fixator moments. When posterior instrumentation devices are used to stabilize severe anterior column injuries, they are at risk of fracture secondary to reversed bending moments.
Publisher: Elsevier BV
Date: 06-2014
DOI: 10.1016/J.MEDENGPHY.2014.02.019
Abstract: The majority of people who sustain hip fractures after a fall to the side would not have been identified using current screening techniques such as areal bone mineral density. Identifying them, however, is essential so that appropriate pharmacological or lifestyle interventions can be implemented. A protocol, demonstrated on a single specimen, is introduced, comprising the following components in vitro biofidelic drop tower testing of a proximal femur high-speed image analysis through digital image correlation detailed accounting of the energy present during the drop tower test organ level finite element simulations of the drop tower test micro level finite element simulations of critical volumes of interest in the trabecular bone. Fracture in the femoral specimen initiated in the superior part of the neck. Measured fracture load was 3760N, compared to 4871N predicted based on the finite element analysis. Digital image correlation showed compressive surface strains as high as 7.1% prior to fracture. Voxel level results were consistent with high-speed video data and helped identify hidden local structural weaknesses. We found using a drop tower test protocol that a femoral neck fracture can be created with a fall velocity and energy representative of a sideways fall from standing. Additionally, we found that the nested explicit finite element method used allowed us to identify local structural weaknesses associated with femur fracture initiation.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 11-2012
Publisher: Springer Science and Business Media LLC
Date: 06-10-2009
Publisher: Springer Science and Business Media LLC
Date: 21-08-2016
DOI: 10.1007/S10439-015-1412-6
Abstract: The spinal cord undergoes physical deformation during traumatic spinal cord injury (TSCI), which results in biological damage. This study demonstrates a novel approach, using magnetic resonance imaging and image registration techniques, to quantify the three-dimensional deformation of the cervical spinal cord in an in vivo rat model. Twenty-four male rats were subjected to one of two clinically relevant mechanisms of TSCI (i.e. contusion and dislocation) inside of a MR scanner using a novel apparatus, enabling imaging of the deformed spinal cords. The displacement fields demonstrated qualitative differences between injury mechanisms. Three-dimensional Lagrangian strain fields were calculated, and the results from the contusion injury mechanism were deemed most reliable. Strain field error was assessed using a Monte Carlo approach, which showed that simulated normal strain error experienced a bias, whereas shear strain error did not. In contusion injury, a large region of dorso-ventral compressive strain was observed under the impactor which extended into the ventral region of the spinal cord. High tensile lateral strains under the impactor and compressive lateral strains in the lateral white matter were also observed in contusion. The ability to directly observe and quantify in vivo spinal cord deformation informs our knowledge of the mechanics of TSCI.
Publisher: ASME International
Date: 24-09-2013
DOI: 10.1115/1.4024822
Abstract: Current understanding of the biomechanics of cervical spine injuries in head-first impact is based on decades of epidemiology, mathematical models, and in vitro experimental studies. Recent mathematical modeling suggests that muscle activation and muscle forces influence injury risk and mechanics in head-first impact. It is also known that muscle forces are central to the overall physiologic stability of the cervical spine. Despite this knowledge, the vast majority of in vitro head-first impact models do not incorporate musculature. We hypothesize that the simulation of the stabilizing mechanisms of musculature during head-first osteoligamentous cervical spine experiments will influence the resulting kinematics and injury mechanisms. Therefore, the objective of this study was to document differences in the kinematics, kinetics, and injuries of ex vivo osteoligamentous human cervical spine and surrogate head complexes that were instrumented with simulated musculature relative to specimens that were not instrumented with musculature. We simulated a head-first impact (3 m/s impact speed) using cervical spines and surrogate head specimens (n = 12). Six spines were instrumented with a follower load to simulate in vivo compressive muscle forces, while six were not. The principal finding was that the axial coupling of the cervical column between the head and the base of the cervical spine (T1) was increased in specimens with follower load. Increased axial coupling was indicated by a significantly reduced time between head impact and peak neck reaction force (p = 0.004) (and time to injury (p = 0.009)) in complexes with follower load relative to complexes without follower load. Kinematic reconstruction of vertebral motions indicated that all specimens experienced hyperextension and the spectrum of injuries in all specimens were consistent with a primary hyperextension injury mechanism. These preliminary results suggest that simulating follower load that may be similar to in vivo muscle forces results in significantly different impact kinetics than in similar biomechanical tests where musculature is not simulated.
Publisher: Springer Science and Business Media LLC
Date: 05-05-1998
Abstract: One goal of interbody fusion is to increase the height of the degenerated disc space. Interbody cages in particular have been promoted with the claim that they can maintain the disc space better than other methods. There are many factors that can affect the disc height maintenance, including graft or cage design, the quality of the surrounding bone and the presence of supplementary posterior fixation. The present study is an in vitro biomechanical investigation of the compressive behaviour of three different interbody cage designs in a human cadaveric model. The effect of bone density and posterior instrumentation were assessed. Thirty-six lumbar functional spinal units were instrumented with one of three interbody cages: (1) a porous titanium implant with endplate fit (Stratec), (2) a porous, rectangular carbon-fibre implant (Brantigan) and (3) a porous, cylindrical threaded implant (Ray). Posterior instrumentation (USS) was applied to half of the specimens. All specimens were subjected to axial compression displacement until failure. Correlations between both the failure load and the load at 3 mm displacement with the bone density measurements were observed. Neither the cage design nor the presence of posterior instrumentation had a significant effect on the failure load. The loads at 3 mm were slightly less for the Stratec cage, implying lower axial stiffness, but were not different with posterior instrumentation. The large range of observed failure loads overlaps the potential in vivo compressive loads, implying that failure of the bone-implant interface may occur clinically. Preoperative measurements of bone density may be an effective tool to predict settling around interbody cages.
Publisher: Springer Science and Business Media LLC
Date: 12-10-2005
Publisher: SAGE Publications
Date: 02-2008
Abstract: Experimental measurement of the load-bearing patterns of the facet joints in the lumbar spine remains a challenge, thereby limiting the assessment of facet joint function under various surgical conditions and the validation of computational models. The extra-articular strain (EAS) technique, a non-invasive measurement of the contact load, has been used for unilateral facet joints but does not incorporate strain coupling, i.e. ipsilateral EASs due to forces on the contralateral facet joint. The objectives of the present study were to establish a bilateral model for facet contact force measurement using the EAS technique and to determine its effectiveness in measuring these facet joint contact forces during three-dimensional flexibility tests in the lumbar spine. Specific goals were to assess the accuracy and repeatability of the technique and to assess the effect of soft-tissue artefacts. In the accuracy and repeatability tests, ten uniaxial strain gauges were bonded to the external surface of the inferior facets of L3 of ten fresh lumbar spine specimens. Two pressure-sensitive sensors (Tekscan) were inserted into the joints after the capsules were cut. Facet contact forces were measured with the EAS and Tekscan techniques for each specimen in flexion, extension, axial rotation, and lateral bending under a ±7.5 N m pure moment. Four of the ten specimens were tested five times in axial rotation and extension for repeatability. These same specimens were disarticulated and known forces were applied across the facet joint using a manual probe (direct accuracy) and a materials-testing system (disarticulated accuracy). In soft-tissue artefact tests, a separate set of six lumbar spine specimens was used to document the virtual facet joint contact forces during a flexibility test following removal of the superior facet processes. Linear strain coupling was observed in all specimens. The average peak facet joint contact forces during flexibility testing was greatest in axial rotation (71±25 N), followed by extension (27±35 N) and lateral bending (25±28 N), and they were most repeatable in axial rotation (coefficient of variation, 5 per cent). The EAS accuracy was about 20 per cent in the direct accuracy assessment and about 30 per cent in the disarticulated accuracy test. The latter was very similar to the Tekscan accuracy in the same test. Virtual facet loads (r.m.s.) were small in axial rotation (12 N) and lateral bending (20 N), but relatively large in flexion (34 N) and extension (35 N). The results suggested that the bilateral EAS model could be used to determine the facet joint contact forces in axial rotation but may result in considerable error in flexion, extension, and lateral bending.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 07-2012
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 2007
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: 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: 07-2016
DOI: 10.1016/J.MEDENGPHY.2016.03.006
Abstract: Contributing to slow advance of finite element (FE) simulations for hip fracture risk prediction, into clinical practice, could be a lack of consensus in the biomechanics community on how to map properties to the models. Thus, the aim of the present study was first, to systematically quantify the influence of the modulus-density relationship (E-ρ) and the material mapping method (MMM) on the predicted mechanical response of the proximal femur in a side-ways fall (SWF) loading configuration and second, to perform a model-to-model comparison of the predicted mechanical response within the femoral neck for all the specimens tested in the present study, using three different modelling techniques that have yielded good validation outcome in terms of surface strain prediction and whole bone response according to the literature. We found the outcome to be highly dependent on both the E-ρ relationship and the MMM. In addition, we found that the three modelling techniques that have resulted in good validation outcome in the literature yielded different principal strain prediction both on the surface as well as internally in the femoral neck region of the specimens modelled in the present study. We conclude that there exists a need to carry out a more comprehensive validation study for the SWF loading mode to identify which combination of MMMs and E-ρ relationship leads to the best match for whole bone and local mechanical response. The MMMs tested in the present study have been made publicly available at ome/mitk-gem.
Publisher: Informa UK Limited
Date: 26-05-2016
DOI: 10.1080/14763141.2016.1163414
Abstract: Ice hockey body checks involving direct shoulder-to-head contact frequently result in head injury. In the current study, we examined the effect of shoulder pad style on the likelihood of head injury from a shoulder-to-head check. Shoulder-to-head body checks were simulated by swinging a modified Hybrid-III anthropomorphic test device (ATD) with and without shoulder pads into a stationary Hybrid-III ATD at 21 km/h. Tests were conducted with three different styles of shoulder pads (traditional, integrated and tethered) and without shoulder pads for the purpose of control. Head response kinematics for the stationary ATD were measured. Compared to the case of no shoulder pads, the three different pad styles significantly (p < 0.05) reduced peak resultant linear head accelerations of the stationary ATD by 35-56%. The integrated shoulder pads reduced linear head accelerations by an additional 18-21% beyond the other two styles of shoulder pads. The data presented here suggest that shoulder pads can be designed to help protect the head of the struck player in a shoulder-to-head check.
Publisher: Public Library of Science (PLoS)
Date: 19-01-2016
Publisher: Springer Science and Business Media LLC
Date: 10-03-2012
Publisher: Elsevier BV
Date: 08-2001
DOI: 10.1016/S0021-9290(01)00054-9
Abstract: Interdisciplinary communication of three-dimensional kinematic data arising from in vitro biomechanical tests is challenging. Complex kinematic representations such as the helical axes of motion (HAM) add to the challenge. The difficulty increases further when other quantities (i.e. load or tissue strain data) are combined with the kinematic data. The objectives of this study were to develop a method to graphically replay and animate in vitro biomechanical tests including HAM data. This will allow intuitive interpretation of kinematic and other data independent of the viewer's area of expertise. The value of this method was verified with a biomechanical test investigating load-sharing of the cervical spine. Three 3.0 mm aluminium spheres were glued to each of the two vertebrae from a C2-3 segment of a human cervical spine. Before the biomechanical tests, CT scans were made of the specimen (slice thickness=1.0 mm and slice spacing=1.5 mm). The specimens were subjected to right axial torsion moments (2.0 Nm). Strain rosettes mounted to the anterior surface of the C3 vertebral body and bilaterally beneath the facet joints on C3 were used to estimate the force flow through the specimen. The locations of the aluminium spheres were digitised using a space pointer and the motion analysis system. Kinematics were measured using an optoelectronic motion analysis system. HAMs were calculated to describe the specimen kinematics. The digitised aluminium sphere locations were used to match the CT and biomechanical test data (RMS errors between the CT and experimental points were less than 1.0 mm). The biomechanical tests were "replayed" by animating reconstructed CT models in accordance with the recorded experimental kinematics, using custom software. The animated test replays allowed intuitive analysis of the kinematic data in relation to the strain data. This technique improves the ability of experts from disparate backgrounds to interpret and discuss this type of biomechanical data.
Publisher: Elsevier BV
Date: 2015
DOI: 10.1016/J.JBIOMECH.2014.11.042
Abstract: Current screening techniques based on areal bone mineral density (aBMD) measurements are unable to identify the majority of people who sustain hip fractures. Biomechanical examination of such events may help determine what predisposes a hip to be susceptible to fracture. Recently, drop-tower simulations of in-vitro sideways falls have allowed the study of the mechanical response of the proximal human femur at realistic impact speeds. This technique has created an opportunity to validate explicit finite element (FE) models against dynamic test data. This study compared the outcomes of 15 human femoral specimens fractured using a drop tower with complementary specimen-specific explicit FE analysis. Correlation coefficient and root mean square error (RMSE) were found to be moderate for whole bone stiffness comparison (R(2)=0.3476 and 22.85% respectively). No correlation was found between experimentally and computationally predicted peak force, however, energy absorption comparison produced moderate correlation and RMSE (R(2)=0.4781 and 29.14% respectively). By comparing predicted strain maps to high speed video data we demonstrated the ability of the FE models to detect vulnerable portions of the bones. Based on our observations, we conclude that there exists a need to extend the current apparent level material models for bone to cover higher strain rates than previously tested experimentally.
Publisher: Elsevier BV
Date: 02-2014
Publisher: Elsevier BV
Date: 02-2018
DOI: 10.1016/J.JMBBM.2017.10.033
Abstract: Sideways falls are largely responsible for the highly prevalent osteoporotic hip fractures in today's society. These injuries are dynamic events, therefore dynamic FE models validated with dynamic ex vivo experiments provide a more realistic simulation than simple quasi-static analysis. Drop tower experiments using cadaveric specimens were used to identify the material mapping strategy that provided the most realistic mechanical response under impact loading. The present study tested the addition of compression-tension asymmetry, tensile bone damage, and cortical-specific strain rate dependency to the material mapping strategy of fifteen dynamic FE models of the proximal femur, and found improved correlations and reduced error for whole bone stiffness (R
Publisher: BMJ
Date: 06-2012
Publisher: Springer Science and Business Media LLC
Date: 02-1996
DOI: 10.1007/BF00307831
Abstract: Natalizumab treatment provides a model for non-inflammation-induced disease progression in multiple sclerosis (MS). To study serum contactin-1 (sCNTN1) as a novel biomarker for disease progression in natalizumab-treated relapsing-remitting MS (RRMS) patients. Eighty-nine natalizumab-treated RRMS patients with minimum follow-up of 3 years were included. sCNTN1 was analyzed at baseline (before natalizumab initiation), 3, 12, 24 months (M) and last follow-up (median 5.2 years) and compared to 222 healthy controls (HC) and 15 primary progressive MS patients (PPMS). Results were compared between patients with progressive, stable, or improved disability according to EDSS-plus criteria. Median sCNTN1 levels (ng/mL,) in RRMS (baseline: 10.7, 3M: 9.7, 12M: 10.4, 24M: 10.8 last follow-up: 9.7) were significantly lower compared to HC (12.5 Lower baseline sCNTN1 concentrations were associated with long-term disability progression during natalizumab treatment, making it a possible blood-based prognostic biomarker for RRMS.
Publisher: Springer Science and Business Media LLC
Date: 14-04-2023
Publisher: Informa UK Limited
Date: 06-2012
DOI: 10.1080/15459624.2012.679853
Abstract: Occupational whole-body vibration is often studied as a risk factor for conditions that may arise soon after exposure, but only rarely have studies examined associations with conditions arising long after occupational exposure has ceased. We aimed to develop a method of constructing previous occupational whole-body vibration exposure metrics from self-reported data collected for a case-control study of Parkinson's disease. A detailed job history and exposure interview was administered to 808 residents of British Columbia, Canada (403 people with Parkinson's disease and 405 healthy controls). Participants were prompted to report exposure to whole-body vibrating equipment. We limited the data to exposure reports deemed to be above background exposures and used the whole-body vibration literature (typically reporting on seated vector sum measurements) to assign intensity (acceleration) values to each type of equipment reported. We created four metrics of exposure (duration of exposure, most intense equipment exposure, and two dose metrics combining duration and intensity) and examined their distributions and correlations. We tested the role of age and gender in predicting whole-body vibration exposure. Thirty-six percent of participants had at least one previous occupational exposure to whole-body vibrating equipment. Because less than half of participants reported exposure, all continuous metrics exhibited positively skewed distributions, although the distribution of most intense equipment exposure was more symmetrically distributed among the exposed. The arithmetic mean of duration of exposure among those exposed was 14.0 (standard deviation, SD: 14.2) work years, while the geometric mean was 6.8 (geometric SD, GSD: 4.5). The intensity of the most intense equipment exposure (among the exposed) had an arithmetic mean of 0.9 (SD: 0.3) m·s(-2) and a geometric mean of 0.8 (GSD: 1.4). Male gender and older age were both associated with exposure, although the effect of age was attenuated after adjustment for gender. The methods developed allowed us to create continuous metrics of whole-body vibration retrospectively, displaying useful variance for epidemiologic studies.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 11-1996
DOI: 10.1097/00007632-199611150-00005
Abstract: An in vitro biomechanical investigation in the human lumbar spine focuses on the functional significance of vertebral bone density and intervertebral disc degenerations. To determine that interrelationship between vertebral bone density and intervertebral disc degeneration, their effect on normal spine motion, and their significance in the biotechnical performance of interbody fixation techniques. A relationship between vertebral bone density and intervertebral disc degeneration has been suggested, but a definitive relationship has not been established. The effect of vertebral bone density and intervertebral disc degeneration on interbody stabilization remains unknown despite the rapidly increasing use of this surgical method for patients with chronic low back pain. The vertebral bone density and intervertebral disc degeneration of 72 functional spinal units were determined using dual energy x-ray absorptiometry scans and macroscopic grading, respectively. A three-dimensional flexibility test was performed on 24 functional spinal units in the intact and stabilised conditions. The compressive behavior of the bone-implant interface was evaluated in 48 functional spinal units. The vertebral bone density in moderately degenerated disc was significantly lower than at all other levels of intervertebral disc degeneration. Increasing intervertebral disc degeneration resulted in more axial rotation and less lateral bending. In flexion-extension and lateral bending, better vertebral bone resulted in significantly better stabilization. This trend was observed also in axial compression in which higher failure loads were observed with greater bone densities. The authors conclude a significant relationship exists between bone density and disc degeneration, bone density is a highly important factor in the performance of interbody stabilization, and disc degeneration, is of moderate importance in signal motion.
Publisher: BMJ
Date: 14-02-2013
Publisher: Informa UK Limited
Date: 14-06-2010
DOI: 10.1080/15389581003614870
Abstract: To evaluate a prototype sagittal plane surrogate neck model designed to provide a biofidelic response to head-first impacts with a straightened cervical posture. Published biomechanical studies were used in the design to define the range of motion (ROM) and stiffness in both flexion-extension rotation and axial compression. The neck was tested in a series of head-first impacts on a drop tower to investigate the temporal aspects of the kinetic axial force response for the head and neck. A separate series of flexion-extension tests was conducted in a spinal motion simulator to assess its ROM and bending stiffness. In impacts with a 104 N axial preload, the surrogate head and neck displayed a bimodal response to force development in agreement with published studies of cadaveric head-first impacts. In bending without an axial preload, the neck had an ROM and bending stiffness representative of cadaveric human spines and it included a large neutral zone, but with the incremental addition of axial preload these metrics were somewhat reduced. The model appears suitable for studying the scenario of sagittal plane, aligned column impacts. Further design refinements are required to provide biofidelity in both sagittal bending and head-first impacts using a single level of axial preload. This would be necessary to study impact scenarios where considerable sagittal plane neck rotation occurs at impact. The model has identified some key concepts that must be considered for continued design and improvement of a dedicated dummy neck for head-first impacts.
Publisher: Elsevier BV
Date: 08-2009
DOI: 10.1016/J.JBIOMECH.2009.05.001
Abstract: Results of recent imaging studies and theoretical models suggest that the superior femoral neck is a location of local weakness due to an age-related thinning of the cortex, and thus the site of hip fracture initiation. The purpose of this study was to experimentally determine the spatial and temporal characteristics of the macroscopic failure process during a simulated hip fracture that would occur as a result of a sideways fall. Twelve fresh frozen human cadaveric femora were used in this study. The femora were fractured in an apparatus designed to simulate a fall on the greater trochanter. Image sequences of the surface events related to the fractures were captured using two high-speed video cameras at 9111 Hz. The videos were analyzed with respect to time and load to determine the location and sequence of these events occurring in the proximal femur. The mean failure load was 4032 N (SD 370 N). The first surface events were identified in the superior femoral neck in eleven of the twelve specimens. Nine of these specimens fractured in a clear two-step process that initiated with a failure in the superior femoral neck, followed by a failure in the inferior femoral neck. This cadaveric model of hip fracture empirically confirms hypotheses that suggested that hip fractures initiate with a failure in the superior femoral neck where stresses are primarily compressive during a sideways fall impact, followed by a failure in the inferior neck where stresses are primarily tensile. Our results confirm the superolateral neck of the femur as an important region of interest for future hip fracture screening, prevention and treatment research.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 08-2008
Publisher: Elsevier BV
Date: 09-2014
DOI: 10.1016/J.AAP.2014.02.016
Abstract: Cycling is a popular form of recreation and method of commuting with clear health benefits. However, cycling is not without risk. In Canada, cycling injuries are more common than in any other summer sport and according to the US National Highway and Traffic Safety Administration, 52,000 cyclists were injured in the US in 2010. Head injuries account for approximately two-thirds of hospital admissions and three-quarters of fatal injuries among injured cyclists. In many jurisdictions and across all age levels, helmets have been adopted to mitigate risk of serious head injuries among cyclists and the majority of epidemiological literature suggests that helmets effectively reduce risk of injury. Critics have raised questions over the actual efficacy of helmets by pointing to weaknesses in existing helmet epidemiology including selection bias and lack of appropriate control for the type of impact sustained by the cyclist and the severity of the head impact. These criticisms demonstrate the difficulty in conducting epidemiology studies that will be regarded as definitive and the need for complementary biomechanical studies where confounding factors can be adequately controlled. In the bicycle helmet context, there is a paucity of biomechanical data comparing helmeted to unhelmeted head impacts and, to our knowledge, there is no data of this type available with contemporary helmets. In this research, our objective was to perform biomechanical testing of paired helmeted and unhelmeted head impacts using a validated anthropomorphic test headform and a range of drop heights between 0.5m and 3.0m, while measuring headform acceleration and Head Injury Criterion (HIC). In the 2m (6.3m/s) drops, the middle of our drop height range, the helmet reduced peak accelerations from 824g (unhelmeted) to 181g (helmeted) and HIC was reduced from 9667 (unhelmeted) to 1250 (helmeted). At realistic impact speeds of 5.4m/s (1.5m drop) and 6.3m/s (2.0m drop), bicycle helmets changed the probability of severe brain injury from extremely likely (99.9% risk at both 5.4 and 6.3m/s) to unlikely (9.3% and 30.6% risk at 1.5m and 2.0m drops respectively). These biomechanical results for acceleration and HIC, and the corresponding results for reduced risk of severe brain injury show that contemporary bicycle helmets are highly effective at reducing head injury metrics and the risk for severe brain injury in head impacts characteristic of bicycle crashes.
Publisher: Springer Science and Business Media LLC
Date: 12-2014
Publisher: Springer Science and Business Media LLC
Date: 2004
DOI: 10.1007/S00132-003-0581-4
Abstract: The study quantified the stress levels in treated and untreated vertebral bodies following kyphoplasty. Three-dimensional FE models of treated and untreated T11, T12, L1, and L2 vertebral bodies were evaluated to examine the stress levels within the bone and bone cement. A validated T12-L1 model was used to investigate the effect of kyphoplasty treatment on adjacent vertebral stresses and strains. Using the single vertebral models, bone cement modulus changes had minimal effect on the stresses in the bone or the cement. The presence of bone cement had a minimal effect on the stress magnitudes or distribution in the adjacent T12 vertebra. This study provides quantification of the stress levels in bone cement and bone in vertebral bodies treated with kyphoplasty under in vivo-like loading conditions. The presence of bone cement immediately following kyphoplasty has only a slight effect on the stress magnitudes or distributions in adjacent vertebrae.
Publisher: Springer Science and Business Media LLC
Date: 30-07-2015
Publisher: BMJ
Date: 05-01-2015
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: 2008
DOI: 10.1016/J.JBIOMECH.2007.07.015
Abstract: Methods were developed to measure intervertebral disc pressure using optical fibre-Bragg gratings (FBGs). The FBG sensor was calibrated for hydrostatic pressure in a purpose-built apparatus and the average sensitivity was determined to be -5.7 +/- 0.085 pm/MPa (mean +/- SD). The average coefficient of determination (r(2)) for the calibration data was 0.99, and the average hysteresis of the sensor was 2.13% of full scale. The FBG was used to measure intradiscal pressure response to compressive load in five lumbar functional spine units. The pressure measured by the FBG sensor varied linearly with applied compressive load with coefficients of determination ranging from 0.84 to 0.97. The FBG sensor's sensitivity to compressive load ranged from 0.702 +/- 0.043 kPa/N (mean +/- SD) in a L1-L2 specimen, to 1.07 +/- 0.069 kPa/N in a L4-L5 specimen. These measurements agree with those of previous studies in lumbar spines. Two strain gauge pressure sensors were also used to measure intradiscal pressure response to compressive load. The measured pressure sensitivity to load ranged from 0.251 kPa/N (L4-L5) to 0.850 kPa/N (L2-L3). The average difference in pressure sensitivity to load between Sensors 1 and 2 was 12.9% of the value for Sensor 1, with a range from 1.1% to 20.4%, which suggests that disc pressure was not purely hydrostatic. This may have contributed to the difference between the responses of the FBG and strain gauge sensors.
Publisher: Springer Science and Business Media LLC
Date: 25-10-2015
DOI: 10.1007/S00586-014-3612-4
Abstract: Determine the effects of dynamic injurious axial compression applied at various lateral eccentricities (lateral distance to the centre of the spine) on mechanical flexibilities and structural injury patterns of the cervical spine. 13 three-vertebra human cadaver cervical spine specimens (6 C3-5, 3 C4-6, 2 C5-7, 2 C6-T1) were subjected to pure moment flexibility tests (±1.5 Nm) before and after impact trauma was applied in two groups: low and high lateral eccentricity (1 and 150 % of the lateral diameter of the vertebral body, respectively). Relative range of motion (ROM) and relative neutral zone (NZ) were calculated as the ratio of post and pre-trauma values. Injuries were diagnosed by a spine surgeon and scored. Classification functions were developed using discriminant analysis. Low and high eccentric loading resulted in primarily bony fractures and soft tissue injuries, respectively. Axial impacts with high lateral eccentricities resulted in greater spinal motion in lateral bending [median relative ROM 3.5 (interquartile range, IQR 2.3) vs. 1.4 (IQR 0.5) and median relative NZ 4.7 (IQR 3.7) vs. 2.3 (IQR 1.1)] and in axial rotation [median relative ROM 5.3 (IQR 13.7) vs. 1.3 (IQR 0.5), p < 0.05 for all comparisons] than those that resulted from low eccentricity impacts. The developed classification functions had 92 % classification accuracy. Dynamic axial compression loading of the cervical spine with high lateral eccentricities produced primarily soft tissue injuries resulting in more post-injury spinal flexibility in lateral bending and axial rotation than that associated with the bony fractures resulting from low eccentricity impacts.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 10-2008
Publisher: Elsevier BV
Date: 2008
DOI: 10.1016/J.JBIOMECH.2007.06.030
Abstract: Mechanical constraints to spine motion can arise in a variety of real-world situations such as when shoulder belts prevent anterior translation of the thorax during automotive collisions. The effect of such constraint on spinal column-spinal cord interaction during injury remains unknown. The purpose of the present study was to compare maximal dynamic spinal canal occlusion, measured via a specialized transducer, in cadaveric upper thoracic spine specimens under a variety of anterior-posterior constraint conditions. Four injury models were produced using 24 cadaveric spine specimens (T1-T4). Incremental compressive trauma was applied under constrained (i.e. blocked anterior-posterior translation) flexion-compression, pure-compression and extension-compression, and under unconstrained (i.e. free anterior-posterior translation) flexion-compression. All displacements were applied at 500 mm/s. For all three constrained trauma groups, complete transducer occlusion occurred between 20 and 30 mm of compressive displacement. The extension-compression caused transducer occlusion significantly less than the other constrained models (p < 0.022) at 20 mm compression. For unconstrained flexion-compression, a compression of up to 50 mm resulted in a mean of 26% transducer occlusion. The constrained pure-compression tests led to burst fracture with significant body height loss at T2. The constrained flexion-compression and extension-compression tests caused fracture-dislocation injury at the T2-T3 level. Constrained trauma clearly led to more spinal canal occlusion than the unconstrained in these models, and more severe injury to the spinal column. The results add to our understanding of the effect of column injury pattern on spinal cord injury. This information has clear implications for the design of injury prevention devices.
Publisher: Informa UK Limited
Date: 09-2008
DOI: 10.1080/17457300802340980
Abstract: The objective of this research was to describe the use and incorrect use of child restraint systems in Manitoba, Canada. In 2004, a team of inspectors made up of Royal Canadian Mounted Police officers and trained car seat technicians from the Manitoba child seat coalition conducted a descriptive survey of types and frequency of child restraint systems' incorrect use. The setting was 10 roadside inspection sites located around the city of Winnipeg, Manitoba. The subjects were parents and primary caregivers of children using child restraint systems. The main outcome measured was the reported appropriate use rate as determined by the compliance to safety standards for correct installation and use of child restraints. A total of 340 child restraint systems were assessed. The overall rate of incorrect use was 70%. The errors present in stage III systems (booster seats) are much lower than the errors present in stage I systems (rear-facing child safety seats) and stage II systems (forward-facing child safety seats). The data presented illustrate that incorrect use of child restraint systems in the province of Manitoba is a large problem and must be dealt with immediately in order to ensure child safety now and in the future. Community-wide information and enhanced enforcement c aigns, consisting of activities such as mass media, information and publicity, child restraint systems displays and special enforcement strategies (check points, dedicated law enforcement officials, alternative penalties) should be used to increase the correct use of child restraint systems. Failure to use child restraint systems properly can contribute to serious injury or death of a child.
Publisher: Springer Science and Business Media LLC
Date: 16-07-2015
DOI: 10.1007/S00198-014-2812-4
Abstract: Through experiments that simulated sideways falls with a mechanical hip impact simulator, we demonstrated the protective effect of hip abductor muscle forces in reducing peak stresses at the femoral neck and the corresponding risk for hip fracture. Over 90% of hip fractures are due to falls, and an improved understanding the factors that separate injurious and non-injurious falls (via their influence on the peak stress generated at the femoral neck) may lead to improved risk assessment and prevention strategies. The purpose of this study was to measure the effect of muscle forces spanning the hip, and knee boundary conditions, on peak forces and estimated stresses at the femoral neck during simulated falls with a mechanical system. We simulated hip abductor muscle forces and knee boundary conditions with a mechanical hip impact simulator and measured forces and stresses at the femoral neck during sideways falls. Peak compressive and tensile stresses, shear force, bending moment, and axial force are each associated with hip abductor muscle forces and knee boundary conditions (p < 0.0005). When muscle force increased from 400 to 1,200 N, peak compressive and tensile stresses decreased 24 and 56%, respectively. These effects were similar to the magnitude of decline in fracture strength associated with osteoporosis and arose from the tension-band effect of the muscle in reducing the bending moment by 37%. Furthermore, peak compressive and tensile stresses averaged 40 and 51% lower, respectively, in the free knee than fixed knee condition. Contraction of the hip abductor muscles at the moment of impact during a fall, and landing with the knee free of constraints, substantially reduced peak compressive and tensile stresses at the femoral neck and risk for femoral fracture in a sideways fall.
Publisher: Elsevier BV
Date: 04-2013
DOI: 10.1016/J.JBIOMECH.2013.02.025
Abstract: Finite element (FE) analysis based on quantitative computed tomography (QCT) images is an emerging tool to estimate bone strength in a specific patient or specimen however, it is limited by the computational power required and the associated time required to generate and solve the models. Thus, our objective was to develop a fast, validated method to estimate whole bone structural stiffness and failure load in addition to a sensitivity analysis of varying boundary conditions. We performed QCT scans on twenty fresh-frozen proximal femurs (age: 77±13 years) and mechanically tested the femurs in a configuration that simulated a sideways fall on the hip. We used custom software to generate the FE models with boundary conditions corresponding to the mechanical tests and solved the linear models to estimate bone structural stiffness and estimated failure load. For the sensitivity analysis, we varied the internal rotation angle of the femoral neck from -30° to 45° at 15° intervals and estimated structural stiffness at each angle. We found both the FE estimates of structural stiffness (R(2)=0.89, p<0.01) and failure load (R(2)=0.81, p<0.01) to be in high agreement with the values found by mechanical testing. An important advantage of these methods was that the models of approximately 500,000 elements took less than 11 min to solve using a standard desktop workstation. In this study we developed and validated a method to quickly and accurately estimate proximal femur structural stiffness and failure load using QCT-driven FE methods.
Publisher: Springer Science and Business Media LLC
Date: 28-04-2020
DOI: 10.1038/S41598-020-63974-W
Abstract: There is currently no established injury criterion for the spine in compression with lateral load components despite this load combination commonly contributing to spinal injuries in rollover vehicle crashes, falls and sports. This study aimed to determine an injury criterion and accompanying tolerance values for cervical spine segments in axial compression applied with varying coronal plane eccentricity. Thirty-three human cadaveric functional spinal units were subjected to axial compression at three magnitudes of lateral eccentricity of the applied force. Injury was identified by high-speed video and graded by spine surgeons. Linear regression was used to define neck injury tolerance values based on a criterion incorporating coronal plane loads accounting for specimen sex, age, size and bone density. Larger coronal plane eccentricity at injury was associated with smaller resultant coronal plane force. The level of coronal plane eccentricity at failure appears to distinguish between the types of injuries sustained, with hard tissue structure injuries more common at low levels of eccentricity and soft tissue structure injuries more common at high levels of eccentricity. There was no relationship between axial force and lateral bending moment at injury which has been previously proposed as an injury criterion. These results provide the foundation for designing and evaluating strategies and devices for preventing severe spinal injuries.
Publisher: Elsevier BV
Date: 03-2018
DOI: 10.1016/J.BONE.2017.12.020
Abstract: Hip fractures pose a major health problem throughout the world due to their devastating impact. Current theories for why these injuries are so prevalent in the elderly point to an increased propensity to fall and decreases in bone mass with ageing. However, the fracture mechanisms, particularly the stress and strain conditions leading to bone failure at the hip remain unclear. Here, we directly examined the cortical bone from clinical intra-capsular hip fractures at a microscopic level, and found strong evidence of compression induced failure in the superior cortex. A total of 143 sections obtained from 24 femoral neck s les that were retrieved from 24 fracturing patients at surgery were examined using laser scanning confocal microscopy (LSCM) after fluorescein staining. The stained microcracks showed significantly higher density in the superior cortex than in the inferior cortex, indicating a greater magnitude of strain in the superior femoral neck during the failure-associated deformation and fracture process. The predominant stress state for each section was reconstructed based on the unique correlation between the microcrack pattern and the stress state. Specifically, we found clear evidence of longitudinal compression and buckling as the primary failure mechanisms in the superior cortex. These findings demonstrate the importance of microcrack analysis in studying clinical hip fractures, and point to the central role of the superior cortex failure as an important aspect of the failure initiation in clinical intra-capsular hip fractures.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 08-2012
Publisher: Mary Ann Liebert Inc
Date: 15-12-2017
Abstract: Traumatic spinal cord injury (SCI) triggers many perturbations within the injured cord, such as decreased perfusion, reduced tissue oxygenation, increased hydrostatic pressure, and disrupted bioenergetics. While much attention is directed to neuroprotective interventions that might alleviate these early pathophysiologic responses to traumatic injury, the temporo-spatial characteristics of these responses within the injured cord are not well documented. In this study, we utilized our Yucatan mini-pig model of traumatic SCI to characterize intraparenchymal hemodynamic and metabolic changes within the spinal cord for 1 week post-injury. Animals were subjected to a contusion/compression SCI at T10. Prior to injury, probes for microdialysis and the measurement of spinal cord blood flow (SCBF), oxygenation (in partial pressure of oxygen PaPO
Publisher: Elsevier BV
Date: 11-2014
DOI: 10.1016/J.JBIOMECH.2014.06.040
Abstract: Understanding proximal femur fracture may yield new targets for fracture prevention screening and treatment. The goal of this study was to characterize force-displacement and failure behaviours in the proximal femur between displacement control and impact loading fall simulations. Twenty-one human proximal femurs were tested in two ways, first to a sub-failure load at a constant displacement rate, then to fracture in an impact fall simulator. Comparisons of sub-failure energy and stiffness were made between the tests at the same compressive force. Additionally, the impact failure tests were compared with previous, constant displacement rate failure tests (at 2 and 100mm/s) in terms of energy, yield force, and stiffness. Loading and displacement rates were characterized and related to specimen stiffness in the impact tests. No differences were observed between the sub-failure constant displacement and impact tests in the aforementioned metrics. Comparisons between failure tests showed that the impact group had the lowest absorbed energy, 24% lower maximum force and 160% higher stiffness than the 100mm/s group (p<0.01 for all), but suffered from low statistical power to differentiate the donor age and specimen BMD. Loading and displacement rates for the specimens tested using impact varied during each test and between specimens and did not show appreciable viscoelasticity. These results indicate that constant displacement rate testing may help understand sub-failure mechanical behaviour, but may not elucidate failure behaviours. The differences between the impact and constant displacement rate fall simulations have important ramifications for interpreting the results of previous experiments.
Publisher: Wiley
Date: 30-10-2021
DOI: 10.1002/JOR.25196
Abstract: To evaluate the biomechanical properties of the upper thoracic spine in anterior–posterior shear loading at various displacement rates. These data broaden our understanding of thoracic spine biomechanics and inform efforts to model the spine and spinal cord injuries. Seven T1–T2 thoracic functional spinal units were loaded non‐destructively by a pure shear force up to 200 N, starting from a neutral posture. Tests were run in both posterior and anterior directions, at displacement rates of 1, 10, and 100 mm/s. The three‐dimensional motion of the specimen was recorded at 1000 Hz. In idual and averaged load–displacement curves were generated and specimen stiffnesses were calculated. Due to a nonlinear response of the specimens, stiffness was defined separately for both the lower half and the upper half of the specimen range of motion. Specimens were significantly stiffer in the anterior direction than in the posterior direction, across all rates. At low displacements, the anterior stiffness averaged 230 N/mm, 76% higher than the low displacement posterior stiffness of 131 N/mm. At high displacements, anterior stiffness averaged 258 N/mm, 51% stiffer than the high displacement posterior stiffness of 171 N/mm. Shear displacement rate had a small effect on the load response, with the 100 mm/s rate causing a mildly stiffer response at low displacements in the anterior direction. Overall, the load–displacement response exhibited pseudo‐quadratic behavior at 1 and 10 mm/s but became more linear at 100 mm/s. The shear stiffness in the upper thoracic spine is greatest in the anterior loading direction, being 51%–76% greater than posterior, most likely due to facet interactions. The effect of the shear displacement rate is low.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 04-2012
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: Elsevier BV
Date: 12-2000
DOI: 10.1016/S0021-9290(00)00145-7
Abstract: Presently, there is little consensus about how, or even if, axial preload should be incorporated in spine flexibility tests in order to simulate the compressive loads naturally present in vivo. Some preload application methods are suspected of producing unwanted "artefact" forces as the specimen rotates and, in doing so, influencing the resulting kinematics. The objective of this study was to quantitatively compare four distinct types of preload which have roots in contemporary experimental practice. The specific quantities compared were the reaction moments and forces resulting at the intervertebral disc and specimen kinematics. The preload types incorporated increasing amounts of caudal constraint on the preload application vector ranging from an unconstrained dead-load arrangement to an apparatus that allowed the vector to follow rotations of the specimen. Six human cadaveric spine segments were tested (1-L1/L2, 3-L2/L3, 1-L3/L4 and 1-L4/L5). Pure moments were applied to the specimens with each of the four different types of compressive preload. Kinematic response was measured using an opto-electronic motion analysis system. A six-axis load cell was used to measure reaction forces and moments. Artefact reaction moments and shear forces were significantly affected by preload application method and magnitude. Unconstrained preload methods produced high artefact moments and low artefact shear forces while more constrained methods did the opposite. A mechanical trade-off is suggested by our results, whereby unwanted moment can only be prevented at the cost of shear force production. When comparing spine flexibility studies, caution should be exercised to ensure preload was applied in a similar manner for all studies. Unwanted moments or forces induced as a result of preload application method may render the comparison of two seemingly similar studies inappropriate.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 15-11-2017
Publisher: Informa UK Limited
Date: 20-04-2016
DOI: 10.1080/10255842.2015.1032944
Abstract: Visualization and analysis of the rodent spinal cord subject to experimental spinal cord injury (SCI) has almost completely been limited to naked-eye observations, and a single measure of gross spinal cord motion due to injury. This study introduces a novel method which utilizes MRI to quantify the deformation of the rodent spinal cord due to imposed, clinically-relevant injuries - specifically, cervical contusion and dislocation mechanisms. The image registration methods were developed using the Advanced Normalization Tools package, which incorporate rigid, affine and deformable registration steps. The proposed method is validated against a fiducial-based, 'gold-standard' measure of spinal cord tissue motion. The validation analysis yielded accuracy (and precision) values of 62 μm (49 μm), 73 μm (79 μm) and 112 μm (110 μm), for the medio-lateral, dorso-ventral and cranio-caudal directions, respectively. The internal morphological change of the spinal cord has never before been quantified, experimentally. This study demonstrates the capability of this method and its potential for future application to in vivo rodent models of SCI.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 06-2013
Publisher: Springer Science and Business Media LLC
Date: 11-09-2012
Publisher: Mary Ann Liebert Inc
Date: 15-06-2015
Abstract: Whole-body vibration has been identified as a potential stressor to spinal cord injury (SCI) patients during pre-hospital transportation. However, the effect that such vibration has on the acutely injured spinal cord is largely unknown, particularly in the frequency domain of 5 Hz in which resonance of the spine occurs. The objective of the study was to investigate the consequences of resonance vibration on the injured spinal cord. Using our previously characterized porcine model of SCI, we subjected animals to resonance vibration (5.7±0.46 Hz) or no vibration for a period of 1.5 or 3.0 h. Locomotor function was assessed weekly and cerebrospinal fluid (CSF) s les were collected to assess different inflammatory and injury severity markers. Spinal cords were evaluated histologically to quantify preserved white and gray matter. No significant differences were found between groups for CSF levels of monocyte chemotactic protein-1, interleukin 6 (IL-6) and lL-8. Glial fibrillary acidic protein levels were lower in the resonance vibration group, compared with the non-vibrated control group. Spared white matter tissue was increased within the vibrated group at 7 d post-injury but this difference was not apparent at the 12-week time-point. No significant difference was observed in locomotor recovery following resonance vibration of the spine. Here, we demonstrate that exposure to resonance vibration for 1.5 or 3 h following SCI in our porcine model is not detrimental to the functional or histological outcomes. Our observation that a 3.0-h period of vibration at resonance frequency induces modest histological improvement at one week post-injury warrants further study.
Publisher: CSIRO Publishing
Date: 2005
DOI: 10.1071/EA05058
Abstract: Japanese Black cattle are characterised by a unique ability to deposit intramuscular fat with lower melting temperature. In this study, 3 consecutive biopsies from Longissimus muscle tissue were taken and RNA isolated from 3 Japanese Black (Tajima strain) and 3 Holstein animals at age 11–20 months. The gene expression changes in these s les were analysed using a bovine fat/muscle cDNA microarray. A mixed-ANOVA model was fitted to the intensity signals. A total of 335 (4.8%) array elements were identified as differentially expressed genes in this breed × time comparison study. Genes preferentially expressed in Japanese Black are associated with mono-unsaturated fatty acid synthesis, fat deposition, adipogenesis development and muscle regulation, while ex les of genes preferentially expressed in Holstein come from functional classes involved in connective tissue and skeletal muscle development. The gene expression differences detected between the Longissimus muscle of the 2 breeds give important clues to the molecular basis for the unique features of the Japanese Black breed, such as the onset and rate of adipose tissue development, metabolic differences, and signalling pathways involved in converting carbohydrate to lipid during lipogenesis. These findings will impact on industry management strategies designed to manipulate intramuscular adipose development at different development stages to gain maximum return for beef products.
Publisher: Springer Science and Business Media LLC
Date: 06-01-2015
DOI: 10.1007/S00586-014-3735-7
Abstract: Dynamic implants have been developed to address potential adjacent level effects due to rigid instrumentation. Rates of revision surgeries may be reduced by using improved implants in the primary surgery. Prior to clinical use, implants should be rigorously tested ex vivo. The objective of our study was to characterize the load-sharing and kinematic behavior of a novel low-stiffness spinal implant. A human cadaveric model of degenerative spondylolisthesis was tested in shear. Lumbar functional spinal units (N = 15) were tested under a static 300 N axial compression force and a cyclic anterior shear force (5-250 N). Translation was tracked with a motion capture system. A novel implant was compared to three standard implants with shear stiffness ranging from low to high. All implants were instrumented with strain gauges to measure the supported shear force. Each implant was affixed to each specimen, and the specimens were tested intact and in two progressively destabilized states. Specimen condition and implant type affected implant load-sharing and specimen translation (p 0.2). The novel implant behaved similarly to the medium-stiffness implant in both load-sharing and translation despite having a different design and stiffness. Complex implant design and specimen-implant interaction necessitate pre-clinical testing of novel implants. Further in vitro testing in axial rotation and flexion-extension is recommended as they are highly relevant loading directions for non-rigid implants.
Publisher: American Public Health Association
Date: 12-2012
Abstract: Objectives. We compared cycling injury risks of 14 route types and other route infrastructure features. Methods. We recruited 690 city residents injured while cycling in Toronto or Vancouver, Canada. A case-crossover design compared route infrastructure at each injury site to that of a randomly selected control site from the same trip. Results. Of 14 route types, cycle tracks had the lowest risk (adjusted odds ratio [OR] = 0.11 95% confidence interval [CI] = 0.02, 0.54), about one ninth the risk of the reference: major streets with parked cars and no bike infrastructure. Risks on major streets were lower without parked cars (adjusted OR = 0.63 95% CI = 0.41, 0.96) and with bike lanes (adjusted OR = 0.54 95% CI = 0.29, 1.01). Local streets also had lower risks (adjusted OR = 0.51 95% CI = 0.31, 0.84). Other infrastructure characteristics were associated with increased risks: streetcar or train tracks (adjusted OR = 3.0 95% CI = 1.8, 5.1), downhill grades (adjusted OR = 2.3 95% CI = 1.7, 3.1), and construction (adjusted OR = 1.9 95% CI = 1.3, 2.9). Conclusions. The lower risks on quiet streets and with bike-specific infrastructure along busy streets support the route-design approach used in many northern European countries. Transportation infrastructure with lower bicycling injury risks merits public health support to reduce injuries and promote cycling.
Publisher: Elsevier BV
Date: 04-2019
DOI: 10.1016/J.CLINBIOMECH.2018.04.014
Abstract: Head-first impacts with an aligned cervical spine cause some of the most severe types of injuries due to the risk of fractures and associated spinal cord injury. Sports, such as football, mountain biking and horseback riding, contribute to the incidence of spinal cord injury but there is potential to reduce the risk of these injuries through a helmet-mounted device. A novel device, the Pro-Neck-Tor mechanism, was incorporated into a commercial football helmet and tested in head-first impact experiments. The Pro-Neck-Tor connects an inner and outer helmet shell, which upon head-first impact of a certain load, induces motion of the head away from the path of the following torso. Impacts were performed onto three impact surface angles with a flexion-inducing Pro-Neck-Tor mechanism. Based on averaged data, the Pro-Neck-Tor provided a significant and consistent reduction in peak compressive neck forces compared to the unmodified football helmet in the conditions tested. In some impact conditions, the Pro-Neck-Tor increased the peak sagittal plane neck bending moments and impulse over that observed for the unmodified helmet. The Pro-Neck-Tor with flexion escape is capable of lowering axial neck forces in head-first impacts compared to a conventional helmet by guiding the cervical column away from an aligned posture and into an eccentric loading scenario which published studies suggests frequently leads to no injury or to a less severe injury. Continued development and testing of the device are needed to optimize the altered neck loading and to drive the design toward a commercial configuration.
Publisher: Springer Science and Business Media LLC
Date: 21-10-2009
Publisher: Elsevier BV
Date: 04-2018
DOI: 10.1016/J.JBIOMECH.2018.01.036
Abstract: Little is known about the internal mechanics of the in vivo spinal cord during injury. The objective of this study was to develop a method of tracking internal and surface deformation of in vivo rat spinal cord during compression using radiography. Since neural tissue is radio-translucent, radio-opaque markers were injected into the spinal cord. Two tantalum beads (260 µm) were injected into the cord (dorsal and ventral) at C5 of nine anesthetized rats. Four beads were glued to the lateral surface of the cord, caudal and cranial to the injection site. A compression plate was displaced 0.5 mm, 2 mm, and 3 mm into the spinal cord and lateral X-ray images were taken before, during, and after each compression for measuring bead displacements. Potential bead migration was monitored for by comparing displacements of the internal and glued surface beads. Dorsal beads moved significantly more than ventral beads with a range in averages of 0.57-0.71 mm and 0.31-0.35 mm respectively. Bead displacements during 0.5 mm compressions were significantly lower than 2 mm and 3 mm compressions. There was no statistically significant migration of the internal beads. The results indicate the merit of this technique for measuring in vivo spinal cord deformation. The pattern of bead displacements illustrates the complex internal and surface deformations of the spinal cord during transverse compression. This information is needed for validating physical and finite element spinal cord surrogates and to define relationships between loading parameters, internal cord deformation, and biological and functional outcomes.
Publisher: Elsevier BV
Date: 2017
DOI: 10.1016/J.JMBBM.2016.10.002
Abstract: The purpose of this study was to load cadaveric vertebral bodies (n=6) in compression and compare the response, measured with digital image correlation (DIC) on the cortex, with the predicted response from specimen-specific vertebral finite element (FE) models. Five modulus-density relationships were evaluated, and for the strongest modulus-density relationship, the correlation between the DIC and FE displacements had R
Publisher: ASME International
Date: 04-10-2013
DOI: 10.1115/1.4025390
Abstract: A new method for laboratory testing of human proximal femora in conditions simulating a sideways fall was developed. Additionally, in order to analyze the strain state in future cadaveric tests, digital image correlation (DIC) was validated as a tool for strain field measurement on the bone of the femoral neck. A fall simulator which included models for the body mass, combined lateral femur and pelvis mass, pelvis stiffness, and trochanteric soft tissue was designed. The characteristics of each element were derived and developed based on human data from the literature. The simulator was verified by loading a state-of-the-art surrogate femur and comparing the resulting force-time trace to published, human volunteer experiments. To validate the DIC, 20 human proximal femora were prepared with a strain rosette and speckle paint pattern, and loaded to 50% of their predicted failure load at a low compression rate. Strain rosettes were taken as the gold standard, and minimum principal strains from the DIC and the rosettes were compared using descriptive statistics. The initial slope of the force-time curve obtained in the fall simulator matched published human volunteer data, with local peaks superimposed in the model due to internal vibrations of the spring used to model the pelvis stiffness. Global force magnitude and temporal characteristics were within 2% of published volunteer experiments. The DIC minimum principal strains were found to be accurate to 127±239μɛ. These tools will allow more biofidelic laboratory simulation of falls to the side, and more detailed analysis of proximal femur failure mechanisms using human cadaver specimens.
Publisher: Elsevier BV
Date: 10-2019
DOI: 10.1016/J.JBIOMECH.2019.07.023
Abstract: Computational models of the human brain are widely used in the evaluation and development of helmets and other protective equipment. These models are often attempted to be validated using cadaver tissue displacements despite studies showing neural tissue degrades quickly after death. Addressing this limitation, this study aimed to develop a technique for quantifying living brain motion in vivo using a closed head impact animal model of traumatic brain injury (TBI) called CHIMERA. We implanted radiopaque markers within the brain of three adult ferrets and resealed the skull while the animals were anesthetized. We affixed additional markers to the skull to track skull kinematics. The CHIMERA device delivered controlled, repeatable head impacts to the head of the animals while the impacts were fluoroscopically stereo-visualized. We observed that 1.5 mm stainless steel fiducials (∼8 times the density of the brain) migrated from their implanted positions while neutral density targets remained in their implanted position post-impact. Brain motion relative to the skull was quantified in neutral density target tests and showed increasing relative motion at higher head impact severities. We observed the motion of the brain lagged behind that of the skull, similar to previous studies. This technique can be used to obtain a comprehensive dataset of in vivo brain motion to validate computational models reflecting the mechanical properties of the living brain. The technique would also allow the mechanical response of in vivo brain tissue to be compared to cadaveric preparations for investigating the fidelity of current human computational brain models.
Publisher: Elsevier BV
Date: 11-2013
DOI: 10.1016/J.JBIOMECH.2013.08.013
Abstract: Rollover crashes are dynamic and complex events in which head impacts with the roof can cause catastrophic neck injuries. Ex vivo and computational models are valuable in understanding, and ultimately preventing, these injuries. Although neck posture and muscle activity influence the resulting injury, there is currently no in vivo data describing these parameters immediately prior to a head-first impact. The specific objectives of this study were to determine the in vivo neck vertebral alignment and muscle activation levels when upside down, a condition that occurs during a rollover. Eleven human subjects (6F, 5M) were tested while seated upright and inverted in a custom-built apparatus. Vertebral alignment was measured using fluoroscopy and muscle activity was recorded using surface and indwelling electrodes in eight superficial and deep neck muscles. In vivo vertebral alignment and muscle activation levels differed between the upright and inverted conditions. When inverted and relaxed, the neck was more lordotic, C1 was aligned posterior to C7, the Frankfort plane was extended, and the activity of six muscles increased compared to upright and relaxed. When inverted subjects were asked to look forward to eliminate head extension, flexor muscle activity increased, C7 was more flexed, and C1 was aligned anterior to C7 versus upright and relaxed. Combined with the large inter-subject variability observed, these findings indicate that cadaveric or computational models designed to study injuries and prevention devices while inverted need to consider a variety of postures and muscle conditions to be relevant to the in vivo situation.
Publisher: The Company of Biologists
Date: 2013
DOI: 10.1242/DMM.011320
Abstract: Traumatic brain injury (TBI) is a major worldwide healthcare problem. Despite promising outcomes from many preclinical studies, the failure of several clinical studies to identify effective therapeutic and pharmacological approaches for TBI suggests that methods to improve the translational potential of preclinical studies are highly desirable. Rodent models of TBI are increasingly in demand for preclinical research, particularly for closed head injury (CHI), which mimics the most common type of TBI observed clinically. Although seemingly simple to establish, CHI models are particularly prone to experimental variability. Promisingly, bioengineering-oriented research has advanced our understanding of the nature of the mechanical forces and resulting head and brain motion during TBI. However, many neuroscience-oriented laboratories lack guidance with respect to fundamental biomechanical principles of TBI. Here, we review key historical and current literature that is relevant to the investigation of TBI from clinical, physiological and biomechanical perspectives, and comment on how the current challenges associated with rodent TBI models, particularly those involving CHI, could be improved.
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: ASME International
Date: 31-10-2014
DOI: 10.1115/1.4028817
Abstract: The tolerance of the spine to bending moments, used for evaluation of injury prevention devices, is often determined through eccentric axial compression experiments using segments of the cadaver spine. Preliminary experiments in our laboratory demonstrated that eccentric axial compression resulted in “unexpected” (artifact) moments. The aim of this study was to evaluate the static and dynamic effects of test configuration on bending moments during eccentric axial compression typical in cadaver spine segment testing. Specific objectives were to create dynamic equilibrium equations for the loads measured inferior to the specimen, experimentally verify these equations, and compare moment responses from various test configurations using synthetic (rubber) and human cadaver specimens. The equilibrium equations were verified by performing quasi-static (5 mm/s) and dynamic experiments (0.4 m/s) on a rubber specimen and comparing calculated shear forces and bending moments to those measured using a six-axis load cell. Moment responses were compared for hinge joint, linear slider and hinge joint, and roller joint configurations tested at quasi-static and dynamic rates. Calculated shear force and bending moment curves had similar shapes to those measured. Calculated values in the first local minima differed from those measured by 3% and 15%, respectively, in the dynamic test, and these occurred within 1.5 ms of those measured. In the rubber specimen experiments, for the hinge joint (translation constrained), quasi-static and dynamic posterior eccentric compression resulted in flexion (unexpected) moments. For the slider and hinge joints and the roller joints (translation unconstrained), extension (“expected”) moments were measured quasi-statically and initial flexion (unexpected) moments were measured dynamically. In the cadaver experiments with roller joints, anterior and posterior eccentricities resulted in extension moments, which were unexpected and expected, for those configurations, respectively. The unexpected moments were due to the inertia of the superior mounting structures. This study has shown that eccentric axial compression produces unexpected moments due to translation constraints at all loading rates and due to the inertia of the superior mounting structures in dynamic experiments. It may be incorrect to assume that bending moments are equal to the product of compression force and eccentricity, particularly where the test configuration involves translational constraints and where the experiments are dynamic. In order to reduce inertial moment artifacts, the mass, and moment of inertia of any loading jig structures that rotate with the specimen should be minimized. Also, the distance between these structures and the load cell should be reduced.
Publisher: Mary Ann Liebert Inc
Date: 15-09-2016
Abstract: During traumatic spinal cord injury (SCI), the spinal cord is subject to external displacements that result in damage of neural tissues. These displacements produce complex internal deformations, or strains, of the spinal cord parenchyma. The aim of this study is to determine a relationship between these internal strains during SCI and primary damage to spinal cord gray matter (GM) in an in vivo rat contusion model. Using magnetic resonance imaging and novel image registration methods, we measured three-dimensional (3D) mechanical strain in in vivo rat cervical spinal cord (n = 12) during an imposed contusion injury. We then assessed expression of the neuronal transcription factor, neuronal nuclei (NeuN), in ventral horns of GM (at the epicenter of injury as well as at intervals cranially and caudally), immediately post-injury. We found that minimum principal strain was most strongly correlated with loss of NeuN stain across all animals (R(2) = 0.19), but varied in strength between in idual animals (R(2) = 0.06-0.52). Craniocaudal distribution of anatomical damage was similar to measured strain distribution. A Monte Carlo simulation was used to assess strain field error, and minimum principal strain (which ranged from 8% to 36% in GM ventral horns) exhibited a standard deviation of 2.6% attributed to the simulated error. This study is the first to measure 3D deformation of the spinal cord and relate it to patterns of ensuing tissue damage in an in vivo model. It provides a platform on which to build future studies addressing the tolerance of spinal cord tissue to mechanical deformation.
Start Date: 05-2019
End Date: 12-2024
Amount: $537,000.00
Funder: Australian Research Council
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