130 research outputs found
Towards a dynamic experimental model of cervical facet dislocation
No full textSession S2-9: Tissue mechanics / testing. IRC-23-129.Darcy W. Thompson-Bagshaw, Ryan D. Quarrington, Peter A. Cripton, Claire F. Jone
Development of a System for In Vitro Neck Muscle Force Replication in Whole Cervical Spine Experiments
No full textGeometric and Inertial Properties of the Pig Head and Brain in an Anatomical Coordinate System
No full textPorcine 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 cm2, and 0.2 to 0.6 kg cm2, respectively. These data may aid the comparison of head and brain kinematics/kinetics data and the translation between porcine and human injury models.Nikoo Soltan, Gunter P. Siegmund, Peter A. Cripton, Claire F. Jone
Gross morphological changes of the spinal cord immediately after surgical decompression in a large animal model of traumatic spinal cord injury
No full textStudy Design. Quantitative in vivo ultrasound imaging study of spinal cord and dura morphology after acute experimental spinal cord injury (SCI) and decompression in a pig model. Objective. To study the morphological changes of the spinal cord and dura immediately after surgical decompression for acute SCI. Summary of Background Data. Surgical decompression for traumatic SCI is currently a topic of debate. After decompression, relief of bony impingement on the thecal sac and spinal cord can be confirmed intraoperatively. However, postoperative imaging often reveals that the cord has swollen to fill the subarachnoid space. Little is known about the extent and timing of this morphological response. Methods. Yucatan miniature pigs received sham surgery (N = 1) or a moderate (N = 6, 20 g, 2.3 m/s) or high (N = 6, 20 g, 4.7 m/s) severity weight-drop SCI followed by 8 hours of sustained compression (100 g) and 6 hours of postdecompression monitoring. Sagittal-plane ultrasound images were used to quantify spinal cord, dura, and subarachnoid space dimensions preinjury and once per hour after decompression. Results. Animals with a moderate SCI exhibited a residual cord deformation of up to 0.64 mm within 10 minutes of decompression, which tended to resolve during 6 hours because of tissue relaxation and swelling. For animals with high-severity SCIs, cord swelling was immediate and resulted in occlusion of the subarachnoid space within 10 minutes to 5 hours, whereas this occurred for only half of the moderate injury group. Conclusion. Decompression of an acute SCI may result in residual cord deformation followed by gradual swelling or immediate swelling leading to subarachnoid occlusion. The response is dependent on initial injury severity. These observations may partly explain the lack of benefit of decompression in some patients and suggest a need to reduce cord swelling to optimize the clinical outcome after acute SCI.Claire F. Jones, Peter A. Cripton and Brian K. Kwo
The effect of cerebrospinal fluid on the biomechanics of spinal cord: an ex vivo bovine model using bovine and physical surrogate spinal cord
No full textStudy Design. A biomechanical study using ex vivo bovine spinal cord and dura, and a synthetic surrogate spinal cord with bovine dura. Objective. To investigate the effect of cerebrospinal fluid (CSF) on spinal cord deformation characteristics and to evaluate the biofidelity of a new surrogate spinal cord using an ex vivo bovine model of the burst fracture process. Summary of Background Data. Spinal cord injury is associated with significant personal, economic and social costs. The role of CSF during the injury event and its effect on the spinal cord deformation and neurologic injury is not well understood. Such knowledge could inform preventative strategies and clinical interventions and aid the development and validation of experimental and computational models. Methods. The transverse impact of a propelled bone fragment analogue with bovine and surrogate cord models was recorded with high speed video and the images analyzed to determine deformation trajectories. Each cord specimen was tested in 3 states: with dura and CSF, with dura only, and without dura. The effect of these states on deformation magnitude, duration, and energy loss parameters was assessed. Results. The estimated spinal cord deformation was significantly reduced, although not eliminated, in the presence of CSF when compared to the bare state. The duration of deformation was generally increased in the presence of CSF, though this difference was not statistically significant. This may indicate a reduction in the cord-fragment interaction force for a given impulse. The dura was found to have no significant effect on deformation parameters for the bovine spinal cord. The deformation of the surrogate cord gave similar trends for the different states in comparison to the bovine cord, but was significantly less than the bovine spinal cord for all conditions. Conclusion. The results indicate that the protective mechanism of CSF may not eliminate cord deformationunder the high energy transverse impact characteristic of a burst fracture. However, CSF may contribute to a lessening of cord deformation and applied force.Claire F. Jones, Shannon G. Kroeker, Peter A. Cripton, and Richard M. Hal
Orthopaedic implants for preventing hip fracture in a fall : a biomechanical investigation
No full textFall-related hip fractures are common yet devastating injuries with poor outcomes. Conventional prevention approaches may not be effective or fast-acting enough to prevent imminent hip fracture in high-risk individuals; however, the surgical insertion of a prophylactic implant to augment the proximal femur has been demonstrated as clinically feasible. In this thesis I investigate the less-explored aspects of femoral augmentation with a prophylactic implant in a sideways fall from standing, the most common scenario for geriatric hip fracture. Our work encompasses four contributions, the first of which involves developing a method to visualize phenomena occurring at the bone level during a fall impact. We integrated a bilateral high-speed x-ray system into a pre-existing fall simulator and applied it to experiments of seven augmented pelvis-femur specimens. We demonstrated sufficient capture of fracture incidence, kinematic data, and newly documented fracture mechanics in the pelvis in a fall. Second, we evaluated the efficacy and safety of prophylactic intramedullary nailing for hip fracture prevention by building finite element models (FEMs) of six ex vivo specimens in their native state to predict fracture outcome in a fall, and comparing their native fracture severity to experimental outcomes post-augmentation. Prophylactic nailing was not associated with any adverse events or hip fractures, but two pelvis fracture cases were found after fall experiments. Third, we quantified the accuracy of augmented versions of the FEMs in predicting outcomes related to force, pelvis deformations, and fracture. Our validation revealed an acceptable level of accuracy for these models and identified areas for future methodological improvements. Finally, we conducted an FEM study to identify key design features of prophylactic implants for increasing predicted femur force. We found that various implant designs regarding size or stiffness may pose different benefits for different high-risk candidates based on bone density. This work presents a methodology for the evaluation and development of new prophylactic implants for preventing hip fracture in a fall, and provides new insights into the biomechanical response of the femur and pelvis on impact after augmentation. Our results may contribute to the successful clinical use of these devices as an option for hip fracture prevention.Applied Science, Faculty ofBiomedical Engineering, School ofGraduat
The development of an upper cervical spine model for use in an omnidirectional surrogate neck
No full textSafety devices meant to protect the head and neck are often evaluated with the use of an anthropometric test device. Anthropometric test devices are designed for a specific loading scenario and typically are biofidelic only in that application. There is no single surrogate appropriate for the multiplane loading that often occurs in real-world scenarios. In this thesis, I present the development of a surrogate upper cervical spine model (C0-C2 vertebrae) for eventual use in an omnidirectional anthropometric test device neck and its validation under quasi-static loading.
We obtained CT scans from a 31-year-old male with no cervical spine pathologies from Vancouver General Hospital. These scans were segmented, modified and 3D printed in aluminum. The transverse, alar, and nuchal ligaments were replicated in the model as they are believed to be the most deterministic to the kinematics of the region. For testing, a custom spine machine was used to apply pure moments in flexion-extension, lateral bending, and axial rotation to the specimen at quasi-static rates. Movements of the vertebrae were tracked using a motion analysis system. In this way, the applied moments and corresponding movements of the vertebrae can be recorded and evaluated.
Range of motion, neutral zone and mean helical axis of motion were extracted from the resultant moment-rotation plots and compared to the cadaveric literature. Quantitative curve shape analysis was carried out to assess the shape of the prototype moment-rotation curve to those from cadaveric literature. The range of motion and neutral zones in flexion-extension, lateral bending, and axial rotation are within range of the cadaveric results presented. Quantitative curve shape comparisons resulted in biofidelity ratings from fair to excellent. The mean helical axis of motion was aligned with that reported in cadaveric studies in axial rotation and slightly anterior to what was expected in flexion-extension.
Reproducing the kinetic and kinematic responses of surrogate spinal segments will aid in the construction of a biofidelic omnidirectional durable surrogate neck. Such a neck could be used to evaluate, improve, and optimize head and neck safety equipment for transportation, occupational, and sports settings.Applied Science, Faculty ofBiomedical Engineering, School ofGraduat
The pressure distribution of cerebrospinal fluid responds to residual compression and decompression in an animal model of acute spinal cord injury
No full textSTUDY DESIGN: In vivo large animal (pig) model study of cerebrospinal fluid (CSF) pressures after acute experimental spinal cord injury (SCI). OBJECTIVE: To determine how the CSF pressure (CSFP) and CSF pulse pressure amplitude (CSFPPA) cranial and caudal to the injury site change after an acute SCI with subsequent thecal occlusion and decompression. SUMMARY OF BACKGROUND DATA: Lowering intrathecal pressure via CSF drainage is currently instituted to prevent ischemia-induced SCI during thoracoabdominal aortic aneurysm surgery and was recently investigated as a potential intervention for acute traumatic SCI. However, in SCI patients, persistent extradural compression commonly occludes the subarachnoid space. This may generate a CSFP differential across the injury site, which cannot be appreciated with lumbar catheter pressure measurements. METHODS: Anesthetized pigs were subjected to an acute contusive SCI at T11 and 8 hours of sustained compression (n = 12), or sham surgery (n = 2). CSFP was measured cranial and caudal to the injury site, using miniature pressure transducers, during compression and for 6 hours after decompression. RESULTS: The cranial-caudal CSFP differential increased (mean, 0.39 mm Hg/h), predominantly due to increased cranial pressure. On decompression, cranial CSFP decreased (mean, -1.16 mm Hg) and caudal CSFP increased (mean, 0.65 mm Hg). The CSFP differential did not change significantly after decompression. Cranial CSFPPA was greater than caudal CSFPPA, but this differential did not change during compression. On decompression, the caudal CSFPPA increased in some but not all animals. CONCLUSION: Although extradural compression exists at the site of injury, lumbar CSFP may not accurately indicate CSFP cranial to the injury. Decompression may provide immediate, though perhaps partial, resolution of the pressure differential. CSFPPA was not a consistent indicator of decompression in this animal model. These findings may have implications for the design of future clinical protocols in which CSFP is monitored after acute SCI.Claire F. Jones, Robyn S. Newell, Jae H. T. Lee, Peter A. Cripton, and Brian K. Kwo
Cervical cerebrospinal fluid pressure in an in-vivo porcine model of simulated whiplash loading
No full textWhiplash is a common automotive injury and can cause debilitating symptoms including neck stiffness and pain, headaches, and other cognitive/psychological symptoms. The diagnosis, treatment, and prevention of whiplash is challenged by the lack of scientific consensus on the mechanism of injury and source of symptoms. One theorized whiplash injury mechanism postulates that the rapid head/neck motion during a rear-end collision causes pressure transients in the spinal cerebrospinal fluid (CSF) which strain the sensory nerve cells in the cervical dorsal root ganglia. This study aimed to improve understanding of this potential injury mechanism by 1. Developing an in-vivo whiplash injury model to produce controlled and repeatable whiplash exposures, and 2. Correlating the head kinematics in simulated whiplash exposures with the cervical CSF pressure response. A custom test apparatus consisting of programmable servo-motors was developed that could simulate specific programmed whiplash exposures in a porcine model. An in-vivo porcine model was selected due to the gross anatomical and scale similarities to humans, and to enable measuring live spinal CSF pressure. Four anaesthetized Yorkshire pigs underwent surgery to implant three fiber-optic pressure transducers in the cervical intrathecal space. Cranial surgery was also performed to rigidly attach accelerometers and angular rate sensors for measuring head kinematics. Each instrumented animal experienced multiple whiplash exposures where the severity and shape of the whiplash exposure was altered. Relevant head kinematic parameters were extracted and correlated with the cervical CSF pressure response. Qualitatively, all whiplash exposures across the different subjects produced similar patterns of local and global maxima in CSF pressure. Maximum angular rate of the head and Neck Injury Criterion (relates the relative motion of the head and torso) were positively correlated with local pressure maxima, while delay in extension onset was negatively correlated with the local pressure maxima. Additionally, maximum head extension and time to maximum extension were positively, and negatively, correlated with global pressure maxima, respectively. These findings can be used to inform the design of automotive safety systems such as active anti-whiplash seats to reduce the pressure amplitudes in the cervical spine and risk of injury during whiplash exposures.Applied Science, Faculty ofMechanical Engineering, Department ofGraduat
Cervical spine posture, but not head-end motion constraints, governs the kinematic and kinetic response in sub-injurious axial impacts
No full textAvailable online 22 December 2025Head-first impacts can produce traumatic cervical spine injuries resulting in tetraplegia. These injury patterns are thought to relate to the alignment of the loading vector relative to the spinal column. Pre-impact posture and subsequent head and intervertebral kinematics, including spinal buckling and head motion relative to the spine and torso, can generate complex spinal configurations. These motions often precede injury onset and can be observed with ex vivo models in which applied loads remain below injury thresholds. This study examined the kinematic response of the cervical spine to dynamic axial compression at sub-injurious severities, enabling interand intra-specimen comparisons across varying initial spinal postures and head motion constraints. Human cervical spine specimens (N = 7) were subjected to repeated 1 m/s axial impacts, while the applied head constraint (sagittal rotation and/or anterior translation) and initial posture (anterior eccentricity and curvature) were varied. Pre-impact head–T1 eccentricity and curvature, head-end motion during impact, intervertebral kinematics, and impact loads were recorded. Head-end anterior translation and flexion rotation were minimal across all constraint conditions ( 0.05). In contrast, greater initial curvature and eccentricity reduced stiffness and peak force, and increased deformation (p < 0.05). Greater initial curvature also produced larger changes in intervertebral flexion-extension during impact (p < 0.05). These results demonstrate that pre-impact posture dictates the cervical spine’s sub-injurious axial response at discrete anterior eccentricities, which may be further explored using computational models validated using this dataset.Darcy W. Thompson-Bagshaw, Ryan D. Quarrington, Peter A. Cripton, Claire F. Jone
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