ORCID Profile
0000-0002-0633-2482
Does something not look right? The information on this page has been harvested from data sources that may not be up to date. We continue to work with information providers to improve coverage and quality. To report an issue, use the Feedback Form.
Publisher: The University of Adelaide
Date: 2022
DOI: 10.25909/20544636
Publisher: The University of Adelaide
Date: 2022
DOI: 10.25909/20544657
Publisher: The University of Adelaide
Date: 2022
DOI: 10.25909/20544618
Publisher: Elsevier BV
Date: 03-2018
DOI: 10.1016/J.SPINEE.2017.07.175
Abstract: Distractive flexion injuries (DFIs) of the subaxial cervical spine are major contributors to spinal cord injury (SCI). Prompt assessment and early intervention of DFIs associated with SCI are crucial to optimize patient outcome however, neurologic examination of patients with subaxial cervical injury is often difficult, as patients commonly present with reduced levels of consciousness. Therefore, it is important to establish potential associations between injury epidemiology and radiographic features, and neurologic involvement. The aims of this study were to describe the epidemiology and radiographic features of DFIs presenting to a major Australian tertiary hospital and to identify those factors predictive of SCI. The agreement and repeatability of radiographic measures of DFI severity were also investigated. This is a combined retrospective case-control and reliability-agreement study. Two hundred twenty-six patients (median age 40 years [interquartile range = 34] 72.1% male) who presented with a DFI of the subaxial cervical spine between 2003 and 2013 were reviewed. The epidemiology and radiographic features of DFI, and risk factors for SCI were identified. Inter- and intraobserver agreement of radiographic measurements was evaluated. Medical records, radiographs, and computed tomography and magnetic resonance imaging scans were examined, and the presence of SCI was evaluated. Radiographic images were analyzed by two consultant spinal surgeons, and the degree of vertebral translation, facet apposition, spinal canal occlusion, and spinal cord compression were documented. Multivariable logistic regression models identified epidemiology and radiographic features predictive of SCI. Intraclass correlation coefficients (ICCs) examined inter- and intraobserver agreement of radiographic measurements. The majority of patients (56.2%) sustained a unilateral (51.2%) or a bilateral facet (48.8%) dislocation. The C6-C7 vertebral level was most commonly involved (38.5%). Younger adults were over-represented among motor-vehicle accidents, whereas falls contributed to a majority of DFIs sustained by older adults. Greater vertebral translation, together with lower facet apposition, distinguished facet dislocation from subluxation. Dislocation, bilateral facet injury, reduced Glasgow Coma Scale, spinal canal occlusion, and spinal cord compression were predictive of neurologic deficit. Radiographic measurements demonstrated at least a "moderate" agreement (ICC>0.4), with most demonstrating an "almost perfect" reproducibility. This large-scale cohort investigation of DFIs in the cervical spine describes radiographic features that distinguish facet dislocation from subluxation, and associates highly reproducible anatomical and clinical indices to the occurrence of concomitant SCI.
Publisher: Cold Spring Harbor Laboratory
Date: 13-09-2021
DOI: 10.1101/2021.09.13.459432
Abstract: Over-activity of transforming growth factor β1 (TGFβ1) in subchondral bone has a direct causal role in rodent models of knee osteoarthritis (OA), which can be blocked by TGFβ1 neutralisation. In this study, we investigated whether the spatially distributed level of active TGFβ1 in human subchondral bone associates with the characteristic structural, cellular and molecular parameters of human knee OA. Subchondral bone s les (35 OA arthroplasty patients, aged 69±9 years) were obtained from regions below either macroscopically present or denuded cartilage. Bone s les were processed to determine the concentration of active TGFβ1 (ELISA) and gene-specific mRNA expression (RT-PCR). Synchrotron micro-CT imaging was utilised to assess the bone microstructure, bone mineralization, the osteocyte lacunar network and bone matrix vascularity. Finally, s les were histologically examined for cartilage OARSI grading, quantification of tartrate resistant acid phosphatase positive cells and bone marrow micro-vasculature. Subchondral bone below severely degenerated/depleted cartilage, characterised by impaired bone matrix quality due to sclerotic microarchitecture, disorganised collagen, high heterogeneity of the mineral distribution, contained increased concentrations of active TGFβ1, compared to adjacent areas with more intact cartilage. In addition, increased levels of active TGFβ1 related directly to increased bone volume while increased OARSI grade associated directly with morphometric characteristics (size, shape and orientation) of osteocyte lacunae. These results indicate that increased active TGFβ1 associates spatially with impaired bone quality and the disease severity of human OA. This study therefore suggests that TGFβ1 could be a therapeutic target to prevent or reduce human disease progression.
Publisher: Springer Science and Business Media LLC
Date: 31-12-2022
DOI: 10.1007/S10856-022-06704-0
Abstract: Autologous pericranium is a promising dural graft material. An optimal graft should exhibit similar mechanical properties to the native dura, but the mechanical properties of human pericranium have not been characterized, and studies of the biomechanical performance of human spinal dura are limited. The primary aim of this study was to measure the tensile structural and material properties of the pericranium, in the longitudinal and circumferential directions, and of the dura in each spinal region (cervical, thoracic and lumbar) and in three directions (longitudinal anterior and posterior, and circumferential). The secondary aim was to determine corresponding constitutive stress–strain equations using a one-term Ogden model. A total of 146 specimens were tested from 7 cadavers. Linear regression models assessed the effect of tissue type, region, and orientation on the structural and material properties. Pericranium was isotropic, while spinal dura was anisotropic with higher stiffness and strength in the longitudinal than the circumferential direction. Pericranium had lower strength and modulus than spinal dura across all regions in the longitudinal direction but was stronger and stiffer than dura in the circumferential direction. Spinal dura and pericranium had similar strain at peak force, toe, and yield, across all regions and directions. Human pericranium exhibits isotropic mechanical behavior that lies between that of the longitudinal and circumferential spinal dura. Further studies are required to determine if pericranium grafts behave like native dura under in vivo loading conditions. The Ogden parameters reported may be used for computational modeling of the central nervous system.
Publisher: Wiley
Date: 20-04-2022
DOI: 10.1002/JNR.25049
Abstract: Pathological outcomes of traumatic brain injury (TBI), including diffuse axonal injury, are influenced by the direction, magnitude, and duration of head acceleration during the injury exposure. Ovine models have been used to study injury mechanics and pathological outcomes of TBI. To accurately describe the kinematics of the head during an injury exposure, and better facilitate comparison with human head kinematics, anatomical coordinate systems (ACS) with an origin at the head or brain center of mass (CoM), and axes that align with the ovine Frankfort plane equivalent, are required. The aim of this study was to determine the mass properties of the sheep head and brain, and define an ACS virtual for the head and brain, using anatomical landmarks on the skull with the aforementioned origins and orientation. Three‐dimensional models of 10 merino sheep heads were constructed from computed tomography images, and the coordinates of the head and brain CoMs, relative to a previously reported sheep head coordinate system (ACS physical ), were determined using the Hounsfield unit–mass density relationship. The ACS physical origin was 34.8 ± 3.1 mm posterosuperior of the head CoM and 43.7 ± 1.7 anteroinferior of the brain CoM. Prominent internal anatomical landmarks were then used to define a new ACS (ACS virtual ) with axes aligned with the Frankfort plane equivalent and an origin 10.4 ± 3.2 mm from the head CoM. The CoM and ACS virtual defined in this study will increase the potential for comparison of head kinematics between ovine models and humans, in the context of TBI.
Publisher: Cold Spring Harbor Laboratory
Date: 20-01-2023
DOI: 10.1101/2023.01.18.524641
Abstract: It is unclear if different factors influence osteoarthritis (OA) progression and the changes characterising OA disease in hip and knee. We investigated the difference between hip OA and knee OA at the subchondral bone tissue and cellular level, relative to the degree of cartilage degeneration. Bone s les were collected from 11 patients (aged 70±8 years) undergoing knee arthroplasty and 8 patients (aged 64±12 years) undergoing hip arthroplasty surgery. Bone microstructure, osteocyte-lacunar network and bone matrix vascularity were evaluated using synchrotron micro-CT imaging. S les were additionally examined histologically to determine osteocyte density, viability, and connectivity. After adjustment for donor gender and age, associations between the extent of cartilage degeneration, bone volume fraction [8.7, 95% CI (3.4, 14.1)], trabecular number [1.5, 95% CI (0.8, 2.3)], osteocyte lacunar density [4714.9 95% CI (2079.1, 7350.6)] and trabecular separation [-0.06, 95% CI (0.01, 0.1)] were found in both knee and hip OA. When compared to knee OA, hip OA was characterised by higher trabecular thickness [0.006, 95% CI (-4, 0.01)], larger but less spheric osteocyte lacunae [47.3 95% CI (11.2, 83.4), -0.04 95% CI (-0.6, -0.01), respectively], lower vascular canal density [-22.8 95% CI (-35.4, -10.3)] lower osteocyte density [-84.9 95% CI (-102.4, -67.4)], and less senescent but more apoptotic osteocytes [-2.4 95% CI (-3.6, -1.2), 24.9 95% CI (17.7, 32.1)], respectively. Subchondral bone from hip OA and knee OA exhibits different characteristics at the tissue and cellular levels, suggesting different mechanisms of OA progression between the hip and knee joints.
Publisher: The University of Adelaide
Date: 2022
DOI: 10.25909/20544681
Publisher: The University of Adelaide
Date: 2022
DOI: 10.25909/20545053
Publisher: ASME International
Date: 24-03-2021
DOI: 10.1115/1.4050172
Abstract: Bilateral cervical facet dislocation (BFD) with facet fracture (Fx) often causes tetraplegia but is rarely recreated experimentally, possibly due to a lack of muscle replication. Intervertebral axial compression (due to muscle activation) or distraction (due to inertial loading), when combined with excessive anterior translation, may influence interfacet contact or separation and the subsequent production of BFD with or without Fx. This paper presents a methodology to produce C6/C7 BFD+Fx using anterior shear motion superimposed with 300 N compression or 2.5 mm distraction. The effect of these superimposed axial conditions on six-axis loads, and C6 inferior facet deflections and surface strains, was assessed. Twelve motion segments (70 ± 13 yr) achieved 2.19 mm of supraphysiologic anterior shear without embedding failure (supraphysiologic shear analysis point SSP), and BFD+Fx was produced in all five specimens that reached 20 mm of shear. Linear mixed-effects models (α = 0.05) assessed the effect of axial condition. At the SSP, the compressed specimens experienced higher axial forces, facet shear strains, and sagittal facet deflections, compared to the distracted group. Facet fractures had similar radiographic appearance to those that are observed clinically, suggesting that intervertebral anterior shear motion contributes to BFD+Fx.
Publisher: Elsevier BV
Date: 04-2018
DOI: 10.1016/J.JBIOMECH.2018.02.036
Abstract: Traumatic cervical facet dislocation (CFD) is often associated with devastating spinal cord injury. Facet fractures commonly occur during CFD, yet quantitative measures of facet deflection, strain, stiffness and failure load have not been reported. The aim of this study was to determine the mechanical response of the subaxial cervical facets when loaded in directions thought to be associated with traumatic bilateral CFD - anterior shear and flexion. Thirty-one functional spinal units (6 × C2/3, C3/4, C4/5, and C6/7, 7 × C5/6) were dissected from fourteen human cadaver cervical spines (mean donor age 69 years, range 48-92 eight male). Loading was applied to the inferior facets of the inferior vertebra to simulate the in vivo inter-facet loading experienced during supraphysiologic anterior shear and flexion motion. Specimens were subjected to three cycles of sub-failure loading (10-100 N, 1 mm/s) in each direction, before being failed in a randomly assigned direction (10 mm/s). Facet deflection, surface strains, stiffness, and failure load were measured. Linear mixed-effects models (α = 0.05 random effect of cadaver) accounted for variations in specimen geometry and bone density. Specimen-specific parameters were significantly associated with most outcome measures. Facet stiffness and failure load were significantly greater in the simulated flexion loading direction, and deflection and surface strains were higher in anterior shear at the non-destructive analysis point (47 N applied load). The sub-failure strains and stiffness responses differed between the upper and lower subaxial cervical regions. Failure occurred through the facet tip during anterior shear loading, while failure through the pedicles was most common in flexion.
Publisher: Elsevier BV
Date: 06-2022
DOI: 10.1016/J.JOCA.2022.03.004
Abstract: The association between the spatially distributed level of active TGFβ1 in human subchondral bone, and the characteristic structural and cellular parameters of human knee OA, was assessed. Paired subchondral bone s les from 35 OA arthroplasty patients, (15 men and 20 women, aged 69 ± 9 years) were obtained from beneath macroscopically present (CA+) or denuded cartilage (CA-) to determine the concentration of active TGFβ1 (ELISA) and its relationship to bone quality (synchrotron micro-CT), cellularity, and vascularization (histology). Bone s les beneath (CA-) regions had significantly increased concentrations of active TGFβ1 protein (mean difference: 26.4 95% CI: [3.2, 49.7]), when compared to bone in CA + regions. Trabecular Bone below (CA-) regions had increased bone volume (median difference: 4.3 96.49% CI: [-1.7, 17.8]), increased trabecular number (1.5 [0.006, 2.6], decreased trabecular separation (-0.05 [-0.1,-0.005]), and increased bone mineral density (394.5 [65.7, 723.3]) comparing to (CA+) regions. Further, (CA-) bone regions showed increased osteocyte density (0.012 [0.006, 0.018]), with larger osteocyte lacunae (39.8 [7.8, 71.7]) that were less spherical (-0.02 [-0.04, -0.003]), and increased bone matrix vascularity (12.4 [0.3, 24.5]) compared to (CA+). In addition, increased levels of active TGFβ1 related to increased bone volume (0.04 [-0.11, 0.9]), while increased OARSI grade associated with lacunar volume (-44.1 [-71.1, -17.2]), and orientation (2.7 [0.8, 4.6]). Increased concentration of active TGFβ1 in the subchondral bone of human knee OA associates spatially with impaired bone quality and disease severity, suggesting that TGFβ1 is a potential therapeutic target to prevent or reduce human OA disease progression.
Publisher: The University of Adelaide
Date: 2022
DOI: 10.25909/20545335
Publisher: Springer Science and Business Media LLC
Date: 18-01-2023
DOI: 10.1186/S12987-022-00401-4
Abstract: Detecting changes in pulsatile cerebrospinal fluid (CSF) flow may assist clinical management decisions, but spinal CSF flow is relatively understudied. Traumatic spinal cord injuries (SCI) often cause spinal cord swelling and subarachnoid space (SAS) obstruction, potentially causing pulsatile CSF flow changes. Pigs are emerging as a favoured large animal SCI model therefore, the aim of this study was to characterise CSF flow along the healthy pig spine. Phase-contrast magnetic resonance images (PC-MRI), retrospectively cardiac gated, were acquired for fourteen laterally recumbent, anaesthetised and ventilated, female domestic pigs (22–29 kg). Axial images were obtained at C2/C3, T8/T9, T11/T12 and L1/L2. Dorsal and ventral SAS regions of interest (ROI) were manually segmented. CSF flow and velocity were determined throughout a cardiac cycle. Linear mixed-effects models, with post-hoc comparisons, were used to identify differences in peak systolic/diastolic flow, and maximum velocity (cranial/caudal), across spinal levels and dorsal/ventral SAS. Velocity wave speed from C2/C3 to L1/L2 was calculated. PC-MRI data were obtained for 11/14 animals. Pulsatile CSF flow was observed at all spinal levels. Peak systolic flow was greater at C2/C3 (dorsal: − 0.32 ± 0.14 mL/s, ventral: − 0.15 ± 0.13 mL/s) than T8/T9 dorsally (− 0.04 ± 0.03 mL/s p 0.001), but not different ventrally (− 0.08 ± 0.08 mL/s p = 0.275), and no difference between thoracolumbar levels (p 0.05). Peak diastolic flow was greater at C2/C3 (0.29 ± 0.08 mL/s) compared to T8/T9 (0.03 ± 0.03 mL/s, p 0.001) dorsally, but not different ventrally (p = 1.000). Cranial and caudal maximum velocity at C2/C3 were greater than thoracolumbar levels dorsally (p 0.001), and T8/T9 and L1/L2 ventrally (p = 0.022). Diastolic velocity wave speed was 1.41 ± 0.39 m/s dorsally and 1.22 ± 0.21 m/s ventrally, and systolic velocity wave speed was 1.02 ± 0.25 m/s dorsally and 0.91 ± 0.22 m/s ventrally. In anaesthetised and ventilated domestic pigs, spinal CSF has lower pulsatile flow and slower velocity wave propagation, compared to humans. This study provides baseline CSF flow at spinal levels relevant for future SCI research in this animal model.
Publisher: The University of Adelaide
Date: 2022
DOI: 10.25909/20544666
Publisher: The University of Adelaide
Date: 2022
DOI: 10.25909/20544603
Publisher: Public Library of Science (PLoS)
Date: 14-01-2021
DOI: 10.1371/JOURNAL.PONE.0244503
Abstract: Adhesions are often considered to be an inevitable consequence of abdominal and pelvic surgery, jeopardizing the medium and long-term success of these procedures. Numerous strategies have been tested to reduce adhesion formation, however, to date, no surgical or medical therapeutic approaches have been successful in its prevention. This study demonstrates the safety and efficacy of Chitogel with Deferiprone and/or antibacterial Gallium Protoporphyrin in different concentrations in preventing adhesion formation after abdominal surgery. 112 adult (8–10 week old) male Wistar albino rats were subjected to midline laparotomy and caecal abrasion, with 48 rats having an additional enterotomy and suturing. Kaolin (0.005g/ml) was applied to further accelerate adhesion formation. The abrasion model rats were randomized to receive saline, Chitogel, or Chitogel plus Deferiprone (5, 10 or 20 mM), together with Gallium Protoporphyrin (250μg/mL). The abrasion with enterotomy rats were randomised to receive saline, Chitogel or Chitogel with Deferiprone (1 or 5 mM). At day 21, rats were euthanised, and adhesions graded macroscopically and microscopically the tensile strength of the repaired caecum was determined by an investigator blinded to the treatment groups. Chitogel with Deferiprone 5 mM significantly reduced adhesion formation (p .01) when pathologically assessed in a rat abrasion model. Chitogel with Deferiprone 5 mM and 1 mM also significantly reduced adhesions (p .05) after abrasion with enterotomy. Def-Chitogel 1mM treatment did not weaken the enterotomy site with treated sites having significantly better tensile strength compared to control saline treated enterotomy rats. Chitogel with Deferiprone 1 mM constitutes an effective preventative anti-adhesion barrier after abdominal surgery in a rat model. Moreover, this therapeutic combination of agents is safe and does not weaken the healing of the sutured enterotomy site.
Publisher: The University of Adelaide
Date: 2022
DOI: 10.25909/20544627
Publisher: The University of Adelaide
Date: 2022
DOI: 10.25909/20544648
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 24-08-2022
DOI: 10.1097/CORR.0000000000002327
Abstract: A nanostructured titanium surface that promotes antimicrobial activity and osseointegration would provide the opportunity to create medical implants that can prevent orthopaedic infection and improve bone integration. Although nanostructured surfaces can exhibit antimicrobial activity, it is not known whether these surfaces are safe and conducive to osseointegration. Using a sheep animal model, we sought to determine whether the bony integration of medical-grade, titanium, porous-coated implants with a unique nanostructured surface modification (alkaline heat treatment [AHT]) previously shown to kill bacteria was better than that for a clinically accepted control surface of porous-coated titanium covered with hydroxyapatite (PCHA) after 12 weeks in vivo. The null hypothesis was that there would be no difference between implants with respect to the primary outcomes: interfacial shear strength and percent intersection surface (the percentage of implant surface with bone contact, as defined by a micro-CT protocol), and the secondary outcomes: stiffness, peak load, energy to failure, and micro-CT (bone volume/total volume [BV/TV], trabecular thickness [Tb.Th], and trabecular number [Tb.N]) and histomorphometric (bone-implant contact [BIC]) parameters. Implants of each material (alkaline heat-treated and hydroxyapatite-coated titanium) were surgically inserted into femoral and tibial metaphyseal cancellous bone (16 per implant type interference fit) and in tibial cortices at three diaphyseal locations (24 per implant type line-to-line fit) in eight skeletally mature sheep. At 12 weeks postoperatively, bones were excised to assess osseointegration of AHT and PCHA implants via biomechanical push-through tests, micro-CT, and histomorphometry. Bone composition and remodeling patterns in adult sheep are similar to that of humans, and this model enables comparison of implants with ex vivo outcomes that are not permissible with humans. Comparisons of primary and secondary outcomes were undertaken with linear mixed-effects models that were developed for the cortical and cancellous groups separately and that included a random effect of animals, covariates to adjust for preoperative bodyweight, and implant location (left/right limb, femoral/tibial cancellous, cortical diaphyseal region, and medial/lateral cortex) as appropriate. Significance was set at an alpha of 0.05. The estimated marginal mean interfacial shear strength for cancellous bone, adjusted for covariates, was 1.6 MPa greater for AHT implants (9.3 MPa) than for PCHA implants (7.7 MPa) (95% CI 0.5 to 2.8 p = 0.006). Similarly, the estimated marginal mean interfacial shear strength for cortical bone, adjusted for covariates, was 6.6 MPa greater for AHT implants (25.5 MPa) than for PCHA implants (18.9 MPa) (95% CI 5.0 to 8.1 p 0.001). No difference in the implant-bone percent intersection surface was detected for cancellous sites (cancellous AHT 55.1% and PCHA 58.7% adjusted difference of estimated marginal mean -3.6% [95% CI -8.1% to 0.9%] p = 0.11). In cortical bone, the estimated marginal mean percent intersection surface at the medial site, adjusted for covariates, was 11.8% higher for AHT implants (58.1%) than for PCHA (46.2% [95% CI 7.1% to 16.6%] p 0.001) and was not different at the lateral site (AHT 75.8% and PCHA 74.9% adjusted difference of estimated marginal mean 0.9% [95% CI -3.8% to 5.7%] p = 0.70). These data suggest there is stronger integration of bone on the AHT surface than on the PCHA surface at 12 weeks postimplantation in this sheep model. Given that the AHT implants formed a more robust interface with cortical and cancellous bone than the PCHA implants, a clinical noninferiority study using hip stems with identical geometries can now be performed to compare the same surfaces used in this study. The results of this preclinical study provide an ethical baseline to proceed with such a clinical study given the potential of the alkaline heat-treated surface to reduce periprosthetic joint infection and enhance implant osseointegration.
Publisher: Elsevier BV
Date: 08-2014
Publisher: Wiley
Date: 07-10-2015
DOI: 10.1111/GEB.12382
Publisher: Elsevier BV
Date: 02-2021
DOI: 10.1016/J.JMBBM.2021.105056
Abstract: The objective of this study was to characterize and compare the mechanical properties of porcine pericranium and spinal dura mater, to evaluate the mechanical suitability of pericranium as a dural graft. Eighty-eight spinal dura (cervical, thoracic, and lumbar regions, in ventral longitudinal, dorsal longitudinal and circumferential orientations) and eighteen pericranium s les (ventral-dorsal, and lateral orientations) from four pigs, were harvested and subjected to uniaxial loading while hydrated. The stiffness, strain at toe-linear regions transition, strain at linear-yield regions transition and other structural and mechanical properties were measured. Stress-strain curves were fitted to a one-term Ogden model and Ogden parameters were calculated. Linear regression models with cluster-robust standard errors were used to assess the effect of region and orientation on material and structural properties. Both spinal dura and pericranium exhibited distinct anisotropy and were stiffer in the longitudinal direction. The tissues exhibited structural and mechanical similarities especially in terms of stiffness and strains in the linear region. Stiffness ranged from 1.28 to 5.32 N/mm for spinal dura and 2.42-3.90 N/mm for pericranium. In the circumferential and longitudinal directions, the stiffness of spinal dura specimens was statistically similar to that of pericranium in the same orientation. The strain at the upper bound of the linear region of longitudinal pericranium (28.0%) was statistically similar to that of any spinal dura specimens (24.4-32.9%). Autologous pericranium has advantageous physical properties for spinal duraplasty. The present study demonstrated that longitudinally oriented pericranium is mechanically compatible with spinal duraplasty procedures. Autologous pericranium grafts will likely support the mechanical loads transmitted from the spinal dura, but further biomechanical analyses are required to study the effect of the lower yield strain of circumferential pericranium compared to spinal dura. Finally, the Ogden parameters calculated for pericranium, and the spinal dura at each spinal level, will be useful for computational models incorporating these soft tissues.
Publisher: Springer Science and Business Media LLC
Date: 21-09-2023
Publisher: Elsevier BV
Date: 2019
DOI: 10.1016/J.JBIOMECH.2018.11.047
Abstract: The subaxial cervical facets are important load-bearing structures, yet little is known about their mechanical response during physiological or traumatic intervertebral motion. Facet loading likely increases when intervertebral motions are superimposed with axial compression forces, increasing the risk of facet fracture. The aim of this study was to measure the mechanical response of the facets when intervertebral axial compression or distraction is superimposed on constrained, non-destructive shear, bending and rotation motions. Twelve C6/C7 motion segments (70 ± 13 yr, nine male) were subjected to constrained quasi-static anterior shear (1 mm), axial rotation (4°), flexion (10°), and lateral bending (5°) motions. Each motion was superimposed with three axial conditions: (1) 50 N compression (2) 300 N compression (simulating neck muscle contraction) and, (3) 2.5 mm distraction. Angular deflections, and principal and shear surface strains, of the bilateral C6 inferior facets were calculated from motion-capture data and rosette strain gauges, respectively. Linear mixed-effects models (α = 0.05) assessed the effect of axial condition. Minimum principal and maximum shear strains were largest in the compressed condition for all motions except for maximum principal strains during axial rotation. For right axial rotation, maximum principal strains were larger for the contralateral facets, and minimum principal strains were larger for the left facets, regardless of axial condition. Sagittal deflections were largest in the compressed conditions during anterior shear and lateral bending motions, when adjusted for facet side.
Publisher: Springer Science and Business Media LLC
Date: 17-11-2021
DOI: 10.1007/S10439-021-02888-8
Abstract: Computational models of experimental data can provide a noninvasive method to estimate spinal facet joint biomechanics. Existing models typically consider each vertebra as one rigid-body and assume uniform facet cartilage thickness. However, facet deflection occurs during motion, and cervical facet cartilage is nonuniform. Multi rigid-body computational models were used to investigate the effect of specimen-specific cartilage profiles on facet contact area estimates. Twelve C6/C7 segments underwent non-destructive intervertebral motions. Kinematics and facet deflections were measured. Three-dimensional models of the vertebra and cartilage thickness estimates were obtained from pre-test CT data. Motion-capture data was applied to two model types (2RB: C6, C7 vertebrae each one rigid body 3RB: left and right C6 posterior elements, and C7 vertebrae, each one rigid body) and maximum facet mesh penetration was compared. Constant thickness cartilage (CTC) and spatially-varying thickness cartilage (SVTC) profiles were applied to the facet surfaces of the 3RB model. Cartilage apposition area (CAA) was compared. Linear mixed-effects models were used for all quantitative comparisons. The 3RB model significantly reduced penetrating mesh elements by accounting for facet deflections (p = 0.001). The CTC profile resulted in incongruent facet articulation, whereas realistic congruence was observed for the SVTC profile. The SVTC profile demonstrated significantly larger CAA than the CTC model (p < 0.001).
Publisher: The University of Adelaide
Date: 2022
DOI: 10.25909/20544552
Publisher: The University of Adelaide
Date: 2022
DOI: 10.25909/20544579
Publisher: Springer Science and Business Media LLC
Date: 07-03-2022
DOI: 10.1007/S10439-022-02940-1
Abstract: During cervical spine trauma, complex intervertebral motions can cause a reduction in facet joint cartilage apposition area (CAA), leading to cervical facet dislocation (CFD). Intervertebral compression and distraction likely alter the magnitude and location of CAA, and may influence the risk of facet fracture. The aim of this study was to investigate facet joint CAA resulting from intervertebral distraction (2.5 mm) or compression (50, 300 N) superimposed on shear and bending motions. Intervertebral and facet joint kinematics were applied to multi rigid-body kinematic models of twelve C6/C7 motion segments (70 ± 13 year, nine male) with specimen-specific cartilage profiles. CAA was qualitatively and quantitatively compared between distraction and compression conditions for each motion linear mixed-effects models ( α = 0.05) were applied. Distraction significantly decreased CAA throughout all motions, compared to the compressed conditions ( p 0.001), and shifted the apposition region towards the facet tip. These observations were consistent bilaterally for both asymmetric and symmetric motions. The results indicate that axial neck loads, which are altered by muscle activation and head loading, influences facet apposition. Investigating CAA in longer cervical spine segments subjected to quasistatic or dynamic loading may provide insight into dislocation and fracture mechanisms.
Start Date: 2021
End Date: 2022
Funder: Hospital Research Foundation
View Funded Activity