Publications by authors named "Janet L Ronsky"

38 Publications

Vertical Drop Jump Biomechanics of Patients With a 3- to 10-Year History of Youth Sport-Related Anterior Cruciate Ligament Reconstruction.

Orthop J Sports Med 2021 Dec 8;9(12):23259671211058105. Epub 2021 Dec 8.

Sport Injury Prevention Research Centre, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.

Background: A better understanding of movement biomechanics after anterior cruciate ligament reconstruction (ACLR) could inform injury prevention, knee injury rehabilitation, and osteoarthritis prevention strategies.

Purpose: To investigate differences in vertical drop jump (VDJ) biomechanics between patients with a 3- to 10-year history of youth sport-related ACLR and uninjured peers of a similar age, sex, and sport.

Study Design: Cross-sectional study. Level of evidence III.

Methods: Lower limb kinematics and bilateral ground-reaction forces (GRFs) were recorded for participants performing 10 VDJs. Joint angles and GRF data were analyzed, and statistical analysis was performed using 2 multivariate models. Dependent variables included sagittal (ankle, knee, and hip) and coronal (knee and hip) angles at initial contact and maximum knee flexion, the rate of change of coronal knee angles (35%-90% of the support phase; ie, slopes of linear regression lines), and vertical and mediolateral GRFs (normalized to body weight [BW]). Fixed effects included group, sex, and time since injury. Participant clusters, defined by sex and sport, were considered as random effects.

Results: Participants included 48 patients with a history of ACLR and 48 uninjured age-, sex-, and sport-matched controls (median age, 22 years [range, 18-26 years]; 67% female). Patients with ACLR demonstrated steeper negative coronal knee angle slopes (β = -0.04 deg/% [95% CI, -0.07 to -0.00 deg/%]; = .025). A longer time since injury was associated with reduced knee flexion (β = -0.2° [95% CI, -0.3° to -0.0°]; = .014) and hip flexion (β = -0.1° [95% CI, -0.2° to -0.0°]; = .018). Regardless of ACLR history, women displayed greater knee valgus at initial contact (β = 2.1° [95% CI, 0.4° to 3.8°]; = .017), greater coronal knee angle slopes (β = 0.05 deg/% [95% CI, 0.02 to 0.09 deg/%]; = .004), and larger vertical GRFs (landing: β = -0.34 BW [95% CI, -0.61 to -0.07 BW]; = .014) (pushoff: β = -0.20 BW [95% CI, -0.32 to -0.08 BW]; = .001).

Conclusion: Women and patients with a 3- to 10-year history of ACLR demonstrated VDJ biomechanics that may be associated with knee motion control challenges.

Clinical Relevance: It is important to consider knee motion control during activities such as VDJs when developing injury prevention and rehabilitation interventions aimed at improving joint health after youth sport-related ACLR.
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http://dx.doi.org/10.1177/23259671211058105DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8669131PMC
December 2021

Volumetric quantitative measurement of hip effusions by manual versus automated artificial intelligence techniques: An OMERACT preliminary validation study.

Semin Arthritis Rheum 2021 06 17;51(3):623-626. Epub 2021 Mar 17.

Department of Medicine, University of Alberta, Canada.

Objective: Preliminary assessment, via OMERACT filter, of manual and automated MRI hip effusion Volumetric Quantitative Measurement (VQM).

Methods: For 358 hips (93 osteoarthritis subjects, bilateral, 2 time points), 2 radiologists performed manual VQM using custom Matlab software. A Mask R-CNN artificial-intelligence (AI) tool was trained to automatically compute joint fluid volumes.

Results: Manual VQM had excellent inter-observer reliability (ICC 0.96). AI predicted hip fluid volumes with ICC 0.86 (status), 0.58 (change) vs. 2 human readers.

Conclusion: Hip joint fluid volumes are reliably assessed by VQM. It is feasible to automate this approach using AI, with promising initial reliability.
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http://dx.doi.org/10.1016/j.semarthrit.2021.03.009DOI Listing
June 2021

Consequences of Juvenile Idiopathic Arthritis on Single Leg Squat Performance in Youth.

Arthritis Care Res (Hoboken) 2021 08 14;73(8):1187-1193. Epub 2021 Jul 14.

Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.

Objective: Juvenile idiopathic arthritis (JIA) affects body structure and function outcomes that may increase the risk of acute joint injury. The purpose of this study was to examine single leg squat (SLS) biomechanics for youth with JIA and their healthy peers. The study design was a matched pair cohort study.

Methods: Sixty-five youth (JIA n = 30; control n = 35) participated in this ethics-approved study. Participants performed 3 sets of 5 consecutive SLS tasks. Disease activity and functional status were assessed using the Juvenile Arthritis Disease Activity Score and Child Health Assessment Questionnaire. Indexed (most-affected leg [JIA]; dominant leg [control]) and contralateral extremity biomechanics were obtained using a 12-camera system. Outcomes included hip flexion/extension (FE), adduction/abduction (AA), and internal/external (IE) rotation range of motion (ROM). Data were analyzed using a multivariate random coefficient model in R (α⍺ = 0.05).

Results: A total of 29 matched pairs were analyzed. Youth with JIA had low disease activity and performed the SLS with a more internally rotated hip (indexed leg P = 0.023, β = -1.9°). Female participants displayed greater hip FE (indexed leg P = 0.015, β = -4.3°; contralateral leg P = 0.005, β = -4.8°) and IE ROM (indexed leg P = 0.021, β = -2.1°) than male participants. Associations were observed for body mass index and hip IE ROM (contralateral leg P = 0.001, β = -0.4°), knee flexion angle, and hip FE ROM (indexed leg P = 0.001, β = 0.4°; contralateral leg P = 0.001, β = 0.5°) and AA (indexed leg P = 0.010, β = 0.1°; contralateral leg P = 0.002, β = 0.2°).

Conclusion: This study identified functional alterations for an SLS in youth with JIA. These findings support the use of physical therapy as part of a multidisciplinary management approach, to restore normal hip posture and movement.
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http://dx.doi.org/10.1002/acr.24254DOI Listing
August 2021

Vertical Drop Jump Performance in Youth With Juvenile Idiopathic Arthritis.

Arthritis Care Res (Hoboken) 2021 07;73(7):955-963

Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.

Objective: Juvenile idiopathic arthritis (JIA) is associated with altered body structure and function outcomes that may expose youth with JIA to a greater risk of secondary joint injury. This study aimed to examine differences in vertical drop jump (VDJ) biomechanics for youth with JIA and healthy youth (control group).

Methods: The present study was a matched pair cohort study. Youth with JIA (n = 30) and their age- and sex-matched control peers participated in this ethics-approved study. Lower-extremity biomechanics information was obtained using a motion analysis system (Motion Analysis) and 2 force plates (AMTI). Biomechanics outcomes included hip, knee, and ankle joint angles, ground reaction forces (GRF), and VDJ phase durations. Other outcomes included disease activity, physical disability, and sports participation. Matched pairs data (JIA-control) were analyzed using a multivariate random coefficient model (version 3.5.0, R Core Team; joint angles, potential confounders) and paired samples t-tests with Bonferroni correction (α = 0.0125; GRF, VDJ phase durations).

Results: Youth with JIA had low disease activity, pain, and disability scores. Youth with JIA maintained a more erect posture at the hip (β = -4.0°, P = 0.004), knee (β = 7.5°, P = 0.004) and ankle (β = -2.6°, P = 0.001). GRF and phase durations outcomes did not meet criteria for significant differences. Knee extension increased with participant age (β = -1.0°, P = 0.002), while female participants displayed greater hip flexion (β = -6.6°, P = 0.001) and less ankle dorsiflexion (β = 2.3°, P = 0.006).

Conclusion: This study provides evidence for a stiff knee landing strategy by youth with JIA. These findings inform targets for physical therapy management to mitigate the risks of a secondary joint injury in sports participation.
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http://dx.doi.org/10.1002/acr.24219DOI Listing
July 2021

Robust Self-Supervised Learning of Deterministic Errors in Single-Plane (Monoplanar) and Dual-Plane (Biplanar) X-Ray Fluoroscopy.

IEEE Trans Med Imaging 2020 06 1;39(6):2051-2060. Epub 2020 Jan 1.

Fluoroscopic imaging that captures X-ray images at video framerates is advantageous for guiding catheter insertions by vascular surgeons and interventional radiologists. Visualizing the dynamical movements non-invasively allows complex surgical procedures to be performed with less trauma to the patient. To improve surgical precision, endovascular procedures can benefit from more accurate fluoroscopy data via calibration. This paper presents a robust self-calibration algorithm suitable for single-plane and dual-plane fluoroscopy. A three-dimensional (3D) target field was imaged by the fluoroscope in a strong geometric network configuration. The unknown 3D positions of targets and the fluoroscope pose were estimated simultaneously by maximizing the likelihood of the Student-t probability distribution function. A smoothed k-nearest-neighbour (kNN) regression is then used to model the deterministic component of the image reprojection error of the robust bundle adjustment. The Maximum Likelihood Estimation step and the kNN regression step are then repeated iteratively until convergence. Four different error modeling schemes were compared while varying the quantity of training images. It was found that using a smoothed kNN regression can automatically model the systematic errors in fluoroscopy with similar accuracy as a human expert using a small training dataset. When all training images were used, the 3D mapping error was reduced from 0.61-0.83 mm to 0.04 mm post-calibration (94.2-95.7% improvement), and the 2D reprojection error was reduced from 1.17-1.31 to 0.20-0.21 pixels (83.2-83.8% improvement). When using biplanar fluoroscopy, the 3D measurement accuracy of the system improved from 0.60 mm to 0.32 mm (47.2% improvement).
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http://dx.doi.org/10.1109/TMI.2019.2963446DOI Listing
June 2020

Characterizing healthy knee symmetry using the finite helical axis and muscle power during open and closed chain tasks.

J Biomech 2020 01 16;99:109580. Epub 2019 Dec 16.

Department of Mechanical and Manufacturing Engineering, University of Calgary, Calgary, Alberta, Canada; McCaig Institute for Bone and Joint Health, University of Calgary, Calgary, Alberta, Canada.

Understanding healthy joint movement and muscle control, and injurious alterations, is important to determine musculoskeletal contributions to post-injury joint instabilities or altered dynamic joint function. The contralateral limb is often used as a point of reference to determine the effects of knee joint injury. However, it is currently difficult to interpret within subject variability between limbs as this is not well established in the healthy population. There is a continuing need to characterize healthy knee joint mechanics and neuromuscular control to determine the degree of symmetry within healthy individuals. The current study quantified limb symmetry in healthy individuals using the finite helical axis with a unique reference position (rFHA) and electromyography (EMG) approaches, for a closed-chain single leg squat (SLS) and an open-chain seated leg swing. Muscle power and FHA translation, orientation and dispersion were similar between limbs. However, the FHA was located significantly more anterior in the dominant limb relative to the contralateral during both tasks. These between-limb differences in FHA location could be attributed to differences in joint geometry and strength between limbs. This finding provides evidence that healthy knees have asymmetries which have implications for selection of control limbs in studies comparing conditions within and between individuals. Differences identified in dynamic joint function between tasks suggest that the SLS is useful for revealing joint asymmetries due to altered muscular control strategies, while the swing task is expected to highlight asymmetries in joint motion due to altered knee structures following injury.
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http://dx.doi.org/10.1016/j.jbiomech.2019.109580DOI Listing
January 2020

Establishing outcome measures in early knee osteoarthritis.

Nat Rev Rheumatol 2019 07 14;15(7):438-448. Epub 2019 Jun 14.

Oxford University, Oxford, UK.

The classification and monitoring of individuals with early knee osteoarthritis (OA) are important considerations for the design and evaluation of therapeutic interventions and require the identification of appropriate outcome measures. Potential outcome domains to assess for early OA include patient-reported outcomes (such as pain, function and quality of life), features of clinical examination (such as joint line tenderness and crepitus), objective measures of physical function, levels of physical activity, features of imaging modalities (such as of magnetic resonance imaging) and biochemical markers in body fluid. Patient characteristics such as adiposity and biomechanics of the knee could also have relevance to the assessment of early OA. Importantly, research is needed to enable the selection of outcome measures that are feasible, reliable and validated in individuals at risk of knee OA or with early knee OA. In this Perspectives article, potential outcome measures for early symptomatic knee OA are discussed, including those measures that could be of use in clinical practice and/or the research setting.
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http://dx.doi.org/10.1038/s41584-019-0237-3DOI Listing
July 2019

Gait Adaptations in Youth With Juvenile Idiopathic Arthritis.

Arthritis Care Res (Hoboken) 2020 07 11;72(7):917-924. Epub 2020 Jun 11.

University of Calgary, Calgary, Alberta, Canada.

Objective: Juvenile idiopathic arthritis (JIA) affects body structure and function and physical activity outcomes. The present study was undertaken to examine differences in gait kinematics during fixed-speed treadmill walking for youth with JIA and typically developing (TD) youth.

Methods: Sagittal plane gait kinematics were obtained using a 12-camera system (Motion Analysis) for youth with JIA (n = 30) and their age and sex-matched TD peers (n = 30). Outcomes included disease activity, pain, well-being, and peak sagittal hip, knee, and ankle joint angles. Kinematics were analyzed for the indexed leg (IL) (i.e., the affected leg of participants with JIA) compared to the dominant leg of TD participants and for the contralateral leg (CL) (i.e., the less/not affected leg of participants with JIA) compared to the nondominant leg of TD participants. Kinematics differences were investigated using multivariate Hotelling's T statistic (paired samples; α = 0.05) and simultaneous 95% confidence intervals (95% CIs). Potential confounders (age, sex, body mass index) were assessed using linear mixed-effects models with random effect for pairs.

Results: Youth with JIA had low disease activity, pain, and disability scores. Deviations in bilateral joint angles were observed (IL P = 0.015, CL P = 0.009). Youth with JIA walked with greater initial hip flexion (mean difference IL 2.8° [95% CI -0.6, 6.2]; CL 3.0° [-0.9, 6.9]) and lower knee extension (mean difference IL -2.2° [95% CI -4.4, 0.1]; CL -3.3° [-7.4, 0.8]), and lower hip extension during terminal stance (mean difference IL 3.4° [95% CI -0.3, 7.0]; CL 4.0° [1.0, 7.0]).

Conclusion: Despite low disease activity, youth with JIA avoided the close-packed knee position, commonly associated with joint inflammation and pain. These findings highlight secondary consequences of JIA and inform targets for physical therapy management for youth with JIA.
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http://dx.doi.org/10.1002/acr.23919DOI Listing
July 2020

Effect of stochastic resonance on proprioception and kinesthesia in anterior cruciate ligament reconstructed patients.

J Biomech 2019 02 16;84:52-57. Epub 2018 Dec 16.

Department of Mechanical and Manufacturing Engineering, University of Calgary, Canada; McCaig Institute for Bone and Joint Health, University of Calgary, Canada.

Low amplitude mechanical noise vibration has been shown to improve somatosensory acuity in various clinical groups with comparable deficiencies through a phenomenon known as Stochastic Resonance (SR). This technology showed promising outcomes in improving somatosensory acuity in other clinical patients (e.g., Parkinson's disease and osteoarthritis). Some degree of chronic somatosensory deficiency in the knee has been reported following anterior cruciate ligament (ACL) reconstruction surgery. In this study, the effect of the SR phenomenon on improving knee somatosensory acuity (proprioception and kinesthesia) in female ACL reconstructed (ACLR) participants (n = 19) was tested at three months post-surgery, and the results were compared to healthy controls (n = 28). Proprioception was quantified by the measure of joint position sense (JPS) and kinesthesia with the threshold to detection of passive movement (TDPM). The results based on the statistical analysis demonstrated an overall difference between the somatosensory acuity in the ACLR limb compared to healthy controls (p = 0.007). A larger TDPM was observed in the ACLR limb compared to the healthy controls (p = 0.002). However, the JPS between the ACLR and healthy limbs were not statistically significantly different (p = 0.365). SR significantly improved JPS (p = 0.006) while the effect was more pronounced in the ACLR cohort. The effect on the TDPM did not reach statistical significance (p = 0.681) in either group. In conclusion, deficient kinesthesia in the ACLR limb was observed at three months post-surgery. Also, the positive effects of SR on somatosensory acuity in the ACL reconstructed group warrant further investigation into the use of this phenomenon to improve proprioception in ACLR and healthy groups.
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http://dx.doi.org/10.1016/j.jbiomech.2018.12.018DOI Listing
February 2019

Advancing quantitative techniques to improve understanding of the skeletal structure-function relationship.

J Neuroeng Rehabil 2018 03 20;15(1):25. Epub 2018 Mar 20.

University of Calgary, Calgary, AB, Canada.

Although all functional movement arises from the interplay between the neurological, skeletal, and muscular systems, it is the skeletal system that forms the basic framework for functional movement. Central to understanding human neuromuscular development, along with the genesis of musculoskeletal pathologies, is quantifying how the human skeletal system adapts and mal-adapts to its mechanical environment. Advancing this understanding is hampered by an inability to directly and non-invasively measure in vivo strains, stresses, and forces on bone. Thus, we traditionally have turned to animal models to garner such information. These models enable direct in vivo measures that are not available for human subjects, providing information in regards to both skeletal adaptation and the interplay between the skeletal and muscular systems. Recently, there has been an explosion of new imaging and modeling techniques providing non-invasive, in vivo measures and estimates of skeletal form and function that have long been missing. Combining multiple modalities and techniques has proven to be one of our most valuable resources in enhancing our understanding of the form-function relationship of the human skeletal, muscular, and neurological systems. Thus, to continue advancing our knowledge of the structural-functional relationship, validation of current tools is needed, while development is required to limit the deficiencies in these tools and develop new ones.
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http://dx.doi.org/10.1186/s12984-018-0368-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5859431PMC
March 2018

Error reduction in the finite helical axis for knee kinematics.

Comput Methods Biomech Biomed Engin 2018 Feb 15;21(2):186-193. Epub 2018 Feb 15.

a Department of Mechanical and Manufacturing Engineering, Schulich School of Engineering , University of Calgary , Calgary , Canada.

Traditionally the FHA is calculated stepwise between data points (sFHA), requiring down sampling to achieve a sufficiently large step size to minimize error. This paper proposes an alternate FHA calculation approach (rFHA), using a unique reference position to reduce error associated with small rotation angles. This study demonstrated error reduction using the rFHA approach relative to the sFHA approach. Furthermore, the rFHA in the femur is defined at each time point providing a continuous representation of joint motion. These characteristics enable the rFHA to quantify small differences in knee joint motion, providing an excellent measure to quantify knee joint stability.
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http://dx.doi.org/10.1080/10255842.2018.1435780DOI Listing
February 2018

Cross-Modality Validation of Acetabular Surface Models Using 3-D Ultrasound Versus Magnetic Resonance Imaging in Normal and Dysplastic Infant Hips.

Ultrasound Med Biol 2016 09 19;42(9):2308-14. Epub 2016 May 19.

Department of Radiology and Diagnostic Imaging, University of Alberta, Edmonton, Alberta, Canada. Electronic address:

Current imaging diagnosis of developmental dysplasia of the hip (DDH) in infancy relies on 2-D ultrasound (US), which is highly operator-dependent. 3-D US offers more complete, and potentially more reliable, imaging of infant hip geometry. We sought to validate the fidelity of acetabular surface models obtained by 3-D US against those obtained concurrently by magnetic resonance imaging (MRI). 3-D US and MRI scans were performed on the same d in 20 infants with normal to severely dysplastic hips (mean age, 57 d; range 13-181 d). 3-D US was performed by two observers using a Philips VL13-5 probe. Coronal 3-D multi-echo data image combination (MEDIC) magnetic resonance (MR) images (1-mm slice thickness) were obtained, usually without sedation, in a 1.5 T Siemens unit. Acetabular surface models were generated for 40 hips from 3-D US and MRI using semi-automated tracing software, separately by three observers. For each hip, the 3-D US and MRI models were co-registered to overlap as closely as possible using Amira software, and the root mean square (RMS) distances between points on the models were computed. 3-D US scans took 3.2 s each. Inter-modality variability was visually minimal. Mean RMS distance between corresponding points on the acetabular surface at 3-D US and MRI was 0.4 ± 0.3 mm, with 95% confidence interval <1 mm. Mean RMS errors for inter-observer and intra-observer comparisons were significantly less for 3-D US than for MRI, while inter-scan and inter-modality comparisons showed no significant difference. Acetabular geometry was reproduced by 3-D US surface models within 1 mm of the corresponding 3-D MRI surface model, and the 3-D US models were more reliable. This validates the fidelity of 3-D US modeling and encourages future use of 3-D US in assessing infant acetabulum anatomy, which may be useful to detect and monitor treatment of hip dysplasia.
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http://dx.doi.org/10.1016/j.ultrasmedbio.2016.04.006DOI Listing
September 2016

Biomechanical Analysis of a Dynamic Stability Test System to Evoke Sway and Step Recovery.

J Biomech Eng 2015 Oct;137(10):104501

This paper reports on the dynamic analysis and experimental validation of a method to perturb the balance of subjects in quiet standing. Electronically released weights pull the subject's waist through a specified displacement sensed by a photoelectric sensor. A dynamic model is derived that computes the force applied to the subject as a function of waist acceleration. This model accurately predicts the acceleration of mock subjects (suspended masses) with high repeatability. The validity and simplicity of this model suggest that this method can provide a standard for provocation testing on stable surfaces. Proof-of-concept trials on human subjects demonstrate that the device can be used with a force platform and motion tracking and that the device can induce both sway and step recoveries in healthy male adults.
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http://dx.doi.org/10.1115/1.4031329DOI Listing
October 2015

Validating Dual Fluoroscopy System Capabilities for Determining In-Vivo Knee Joint Soft Tissue Deformation: A Strategy for Registration Error Management.

J Biomech 2015 Jul 9;48(10):2181-5. Epub 2015 May 9.

University of Calgary, Department of Mechanical and Manufacturing Engineering, Calgary, Alberta, Canada; McCaig Institute for Bone and Joint Health, University of Calgary, Calgary, Alberta, Canada.

Knee osteoarthritis (OA) causes structural and mechanical changes within tibiofemoral (TF) cartilage affecting tissue load deformation behavior. Quantifying in-vivo TF soft tissue deformations in healthy and early OA may provide a novel biomechanical marker, sensitive to alterations occurring prior to radiographic change. Dual Fluoroscopy (DF) allows accurate in-vivo TF soft tissue deformation assessment but requires validation. In-vivo healthy and early OA TF cartilage deforms 0.3-1.2mm during static standing full body-weight loading. Our aim was to establish minimum detectable displacement (MDD) for femoral translation in a DF system using a marker-based and markerless approach with variable image intensifier magnifications. An instrumented frame allowed controlled femur specimen translations. Bone positions were reconstructed from DF data using centroids of affixed steel beads (marker-based) and 2D-3D bone feature registration (markerless). Statistical analyses included independent samples t-tests and reliability analysis. Markerless measurements by three trained operators had large variations making it prudent to have an appropriate error management strategy when performing 2D-3D registration. Marker-based MDD improved with image resolution and was 0.05 mm at 3.2 LP/mm (LP: line pairs). Markerless MDD at 3.2 LP/mm was 0.08 mm. Average femur and tibia 2D-3D registrations yielded excellent reliability (84.4%). Therefore, DF images acquired at resolution greater than 3.2 LP/mm would be capable for determining accurate and reliable in-vivo healthy and early OA TF soft tissue deformation. This study provides a registration error management strategy for in-vivo TF soft tissue deformation assessment that could be applied for future clinical applications to establish non-invasive biomechanical markers for early OA diagnosis.
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http://dx.doi.org/10.1016/j.jbiomech.2015.04.045DOI Listing
July 2015

Swelling significantly affects the material properties of the menisci in compression.

J Biomech 2015 Jun 7;48(8):1485-9. Epub 2015 Feb 7.

McCaig Institute for Bone and Joint Health, Faculty of Medicine, University of Calgary and Department of Mechanical and Manufacturing Engineering, Schulich School of Engineering, University of Calgary, Canada.

This study has evaluated the swelling of meniscal test samples associated with altered osmotic environments. Meniscal samples were cut and weighed, then placed in one of 3 solutions: deionized water, phosphate buffered saline (PBS) or 2× concentration PBS. The amount of swelling in meniscal samples was solution independent with average swelling greater than 20%. The effect of this swelling on the mechanical properties of the samples was evaluated under confined compression testing. Samples were measured using a photogrammetric technique at the time of sample preparation and again after 1h in PBS. Meniscal samples used for mechanical testing swelled on average 18% in thickness after 1h in isotonic PBS. Free-swollen tissue was 1/3 as stiff at equilibrium as those that were recompressed to their original thickness prior to testing. Secant moduli at peak stress were nine times greater in the recompressed samples than the free-swollen samples. Relaxation times were faster in swollen samples, indicating increased permeability compared to recompressed specimen. Swelling pressure in the tissue averaged 14.4kPa in isotonic PBS, identifying that the menisci are pre-stressed structures within the knee joint. Histological analysis identified that the quantity of swelling is related to both the osmotic pressure generated by proteoglycans and the local collagen architecture in the sample. This is the first study to quantify the amount and swelling in meniscal test samples. This swelling behavior significantly influences the properties of the tissue in compression and should be addressed in future mechanical testing and protocol development for the menisci.
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http://dx.doi.org/10.1016/j.jbiomech.2015.02.001DOI Listing
June 2015

Rigorous geometric self-calibrating bundle adjustment for a dual fluoroscopic imaging system.

IEEE Trans Med Imaging 2015 Feb 14;34(2):589-98. Epub 2014 Oct 14.

High-speed dual fluoroscopy is a noninvasive imaging technology for three-dimensional skeletal kinematics analysis that finds numerous biomechanical applications. Accurate reconstruction of bone translations and rotations from dual-fluoroscopic data requires accurate calibration of the imaging geometry and the many imaging distortions that corrupt the data. Direct linear transformation methods are commonly applied for performing calibration using a two-step process that suffers from a number of potential shortcomings including that each X-ray source and corresponding camera must be calibrated separately. Consequently, the true imaging set-up and the constraints it presents are not incorporated during calibration. A method to overcome such drawbacks is the single-step self-calibrating bundle adjustment method. This procedure, based on the collinearity principle augmented with imaging distortion models and geometric constraints, has been developed and is reported herein. Its efficacy is shown with a carefully controlled experiment comprising 300 image pairs with 48 507 image points. Application of all geometric constraints and a 31 parameter distortion model resulted in up to 91% improvement in terms of precision (model fit) and up to 71% improvement in terms of 3-D point reconstruction accuracy (0.3-0.4 mm). The accuracy of distance reconstruction was improved from 0.3±2.0 mm to 0.2 ±1.1 mm and angle reconstruction accuracy was improved from -0.03±0.55(°) to 0.01±0.06(°). Such positioning accuracy will allow for the accurate quantification of in vivo arthrokinematics crucial for skeletal biomechanics investigations.
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http://dx.doi.org/10.1109/TMI.2014.2362993DOI Listing
February 2015

Tie-fibre structure and organization in the knee menisci.

J Anat 2014 May 12;224(5):531-7. Epub 2014 Mar 12.

Department of Surgery, Faculty of Medicine, University of Alberta, Calgary, AB, Canada.

The collagenous structure of the knee menisci is integral to the mechanical integrity of the tissue and the knee joint. The tie-fibre structure of the tissue has largely been neglected, despite previous studies demonstrating its correlation with radial stiffness. This study has evaluated the structure of the tie-fibres of bovine menisci using 2D and 3D microscopy techniques. Standard collagen and proteoglycan (PG) staining and 2D light microscopy techniques were conducted. For the first time, the collagenous structure of the menisci was evaluated using 3D, second harmonic generation (SHG) microscopy. This technique facilitated the imaging of collagen structure in thick sections (50-100 μm). Imaging identified that tie-fibres of the menisci arborize from the outer margin of the meniscus toward the inner tip. This arborization is associated with the structural arrangement of the circumferential fibres. SHG microscopy has definitively demonstrated the 3D organization of tie-fibres in both sheets and bundles. The hierarchy of the structure is related to the organization of circumferential fascicles. Large tie-fibre sheets bifurcate into smaller sheets to surround circumferential fascicles of decreasing size. The tie-fibres emanate from the lamellar layer that appears to surround the entire meniscus. At the tibial and femoral surfaces these tie-fibre sheets branch perpendicularly into the meniscal body. The relationship between tie-fibres and blood vessels in the menisci was also observed in this study. Tie-fibre sheets surround the blood vessels and an associated PG-rich region. This subunit of the menisci has not previously been described. The size of tie-fibre sheets surrounding the vessels appeared to be associated with the size of blood vessel. These structural findings have implications in understanding the mechanics of the menisci. Further, refinement of the complex structure of the tie-fibres is important in understanding the consequences of injury and disease in the menisci. The framework of meniscus architecture also defines benchmarks for the development of tissue-engineered replacements in the future.
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http://dx.doi.org/10.1111/joa.12170DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3981495PMC
May 2014

Ankle kinematics and muscle activity in functional ankle instability.

Clin J Sport Med 2014 Jan;24(1):62-8

*McCaig Center for Joint Injury and Arthritis Research, University of Calgary, Calgary, Alberta, Canada; †LifeMark Health Sport Medicine Centre, Kelowna, British Columbia, Canada; ‡Faculty of Medicine, School of Health and Exercise Sciences, University of British Columbia, Kelowna, British Columbia, Canada; and §Departments of Orthopaedic Surgery and Biomedical Engineering and School of Kinesiology, University of Michigan, Ann Arbor, Michigan.

Objective: Following an ankle injury, many patients have functional ankle instability (FAI) with an increased predisposition to reinjury. The purpose of this study was to assess the effects of FAI on ankle kinematics and muscle activity during a lateral hop movement.

Design: Cross-sectional and observational study; all data collection for each subject was performed on 1 day.

Setting: Clinical biomechanics laboratory.

Patients: Two groups were studied: (1) Control group-no ankle injury (n = 12), and (2) FAI group (n = 12).

Interventions: The lateral hop movement consisted of multiple lateral and medial 1-legged hops over an obstacle (width, 72.5 cm; depth, 25.5 cm; height, 14.3 cm) onto adjacent force platforms. Each subject was instructed to perform as many lateral hops as possible during the 6-second trial. Means, SDs, 95% confidence intervals of the differences, and P-values were calculated.

Main Outcome Measures: Ankle kinematics and muscle activity throughout the lateral hop movement.

Results: Significant differences existed between groups for mean (SD) dorsiflexion ankle positions--FAI 82.4 degrees (6.4) versus normal 75.2 degrees (10.1) and tibialis anterior normalized muscle activity--FAI 0.27 (0.21) versus normal 0.16 (0.13) at ground contact.

Conclusions: The FAI group revealed greater tibialis anterior muscle activity and dorsiflexion ankle position at contact moving in the lateral direction. These differences between groups may have been related to an inherent predisposition to ankle injuries, a preexisting difference in task performance, a consequence of injuries, or a compensatory adaptation to previous injuries.
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http://dx.doi.org/10.1097/01.jsm.0000432858.86929.80DOI Listing
January 2014

A geometric approach to study the contact mechanisms in the patellofemoral joint of normal versus patellofemoral pain syndrome subjects.

Comput Methods Biomech Biomed Engin 2015 19;18(4):391-400. Epub 2013 Aug 19.

a Department of Civil and Environmental Engineering , University of Alberta , Edmonton , AB , Canada.

The biomechanics of the patellofemoral (PF) joint is complex in nature, and the aetiology of such manifestations of PF instability as patellofemoral pain syndrome (PFPS) is still unclear. At this point, the particular factors affecting PFPS have not yet been determined. This study has two objectives: (1) The first is to develop an alternative geometric method using a three-dimensional (3D) registration technique and linear mapping to investigate the PF joint contact stress using an indirect measure: the depth of virtual penetration (PD) of the patellar cartilage surface into the femoral cartilage surface. (2) The second is to develop 3D PF joint models using the finite element analysis (FEA) to quantify in vivo cartilage contact stress and to compare the peak contact stress location obtained from the FE models with the location of the maximum PD. Magnetic resonance images of healthy and PFPS subjects at knee flexion angles of 15°, 30° and 45° during isometric loading have been used to develop the geometric models. The results obtained from both approaches demonstrated that the subjects with PFPS show higher PD and contact stresses than the normal subjects. Maximum stress and PD increase with flexion angle, and occur on the lateral side in healthy and on the medial side in PFPS subjects. It has been concluded that the alternative geometric method is reliable in addition to being computationally efficient compared with FEA, and has the potential to assess the mechanics of PFPS with an accuracy similar to the FEA.
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http://dx.doi.org/10.1080/10255842.2013.803082DOI Listing
December 2015

An evaluation of meniscal collagenous structure using optical projection tomography.

BMC Med Imaging 2013 Jul 23;13:21. Epub 2013 Jul 23.

Background: The collagenous structure of menisci is a complex network of circumferentially oriented fascicles and interwoven radially oriented tie-fibres. To date, examination of this micro- architecture has been limited to two-dimensional imaging techniques. The purpose of this study was to evaluate the ability of the three-dimensional imaging technique; optical projection tomography (OPT), to visualize the collagenous structure of the meniscus. If successful, this technique would be the first to visualize the macroscopic orientation of collagen fascicles in 3-D in the meniscus and could further refine load bearing mechanisms in the tissue. OPT is an imaging technique capable of imaging samples on the meso-scale (1-10 mm) at a micro-scale resolution. The technique, similar to computed tomography, takes two-dimensional images of objects from incremental angles around the object and reconstructs them using a back projection algorithm to determine three-dimensional structure.

Methods: Bovine meniscal samples were imaged from four locations (outer main body, femoral surface, tibial surface and inner main body) to determine the variation in collagen orientation throughout the tissue. Bovine stifles (n = 2) were obtained from a local abattoir and the menisci carefully dissected. Menisci were fixed in methanol and subsequently cut using a custom cutting jig (n = 4 samples per meniscus). Samples were then mounted in agarose, dehydrated in methanol and subsequently cleared using benzyl alcohol benzyl benzoate (BABB) and imaged using OPT.

Results: Results indicate circumferential, radial and oblique collagenous orientations at the contact surfaces and in the inner third of the main body of the meniscus. Imaging identified fascicles ranging from 80-420 μm in diameter. Transition zones where fascicles were found to have a woven or braided appearance were also identified. The outer-third of the main body was composed of fascicles oriented predominantly in the circumferential direction. Blood vessels were also visualized using this technique, as their elastin content fluoresces more brightly than collagen at the 425 nm wavelength used by the OPT scanner.

Conclusions: OPT was capable of imaging the collagenous structure, as well as blood vessels in the bovine meniscus. Collagenous structure variability, including transition zones between structural regions not previously described in the meniscus, was identified using this novel technique.
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http://dx.doi.org/10.1186/1471-2342-13-21DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3726444PMC
July 2013

Lateral hop movement assesses ankle dynamics and muscle activity.

J Appl Biomech 2012 May 14;28(2):215-21. Epub 2011 Nov 14.

McCaig Centre for Joint Injury and Arthritis Research, University of Calgary, Calgary, Alberta, Canada.

Ankle function is frequently measured using static or dynamic tasks in normal and injured patients. The purpose of this study was to develop a novel task to quantify ankle dynamics and muscle activity in normal subjects. Twelve subjects with no prior ankle injuries participated. Video motion analysis cameras, force platforms, and an EMG system were used to collect data during a lateral hop movement task that consisted of multiple lateral-medial hops over an obstacle. Mean (SD) inversion ankle position at contact was 4.4° (4.0) in the medial direction and -3.5° (4.4) in the lateral direction; mean (SD) tibialis anterior normalized muscle activity was 0.11 (0.08) in the medial direction and 0.16 (0.13) in the lateral direction. The lateral hop movement was shown to be an effective task for quantifying ankle kinematics, forces, moments, and muscle activities in normal subjects. Future applications will use the lateral hop movement to assess subjects with previous ankle injuries in laboratory and clinical settings.
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http://dx.doi.org/10.1123/jab.28.2.215DOI Listing
May 2012

Computer-aided optimal design of custom scoliosis braces considering clinical and patient evaluations.

Comput Methods Programs Biomed 2012 Sep 22;107(3):478-89. Epub 2011 Jan 22.

Department of Mechanical and Manufacturing Engineering, University of Calgary, 2500 University Drive N.W., Calgary, AB, Canada.

Scoliosis causes an abnormal three dimensional curvature of the spine that is often treated by an orthotic device called brace. The objective of this research was to develop a new approach to automatically identify the optimal design of custom-built brace, based on clinical and patient evaluations. In this approach, torso geometry of the scoliosis patient was achieved using a 3-D imaging system that generated a 3-D torso surface model, which was modified using a custom CAD system to design the 3-D brace surface model. Two design parameters, a translational correction factor and a rotational correction factor, were selected to design the brace geometry from the torso geometry. The 3-D digital brace was evaluated by three clinical evaluation measures (imbalance, rib hump and principal axis angle reduction) and one patient evaluation measure (discomfort). A multi-objective optimization method was employed to identify the optimal design parameters considering both clinical and patient evaluations.
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http://dx.doi.org/10.1016/j.cmpb.2010.12.017DOI Listing
September 2012

Time series spinal radiographs as prognostic factors for scoliosis and progression of spinal deformities.

Eur Spine J 2011 Jan 27;20(1):112-7. Epub 2010 Jul 27.

Department of Mechanical and Manufacturing Engineering, Schulich School of Engineering, Faculty of Kinesiology, University of Calgary, 2500 University Drive NW, Calgary, Alberta, Canada.

The effectiveness of clinical measures to predict scoliotic progression is unclear. The objective of this study was to identify potential prognostic factors affecting scoliosis progression. Consecutive measurements (181) from 35 non-instrumented adolescent idiopathic scoliosis patients with at least two follow-up assessments were studied. Potential prognostic factors of gender, curve pattern, age, curve magnitude, apex location and lateral deviation and spinal growth were analyzed. Stable and progressed groups were compared (threshold: Cobb angle ≥5° or 10°) with sequential clinical data collected in 6-month intervals. Double curves progressed simultaneously or alternatively on curve regions. Age was not significantly different prior to and at maximal Cobb angle. Maximal Cobb angles were significantly correlated to initial Cobb angles (r = 0.81-0.98). Progressed males had larger initial Cobb angles than progressed females. Apex locations were higher in progressed than stable groups, and at least a half vertebra level higher in females than males. Maximal apex lateral deviations correlated significantly with the initial ones (r = 0.73-0.97) and moderately with maximal Cobb angles (r = 0.33-0.85). In the progressed groups, males had larger apex lateral deviations than females. Spinal growth did not relate to curve progression (r = -0.64 to +0.59) and was not significantly different between groups and genders. Scoliosis may dynamically progress between major and minor curves. Gender, curve magnitude, apex location and lateral deviation have stronger effects on scoliosis progression than age or spinal growth. Females with high apex locations may be expected to progress.
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http://dx.doi.org/10.1007/s00586-010-1512-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3036030PMC
January 2011

Prediction of scoliosis progression with serial three-dimensional spinal curves and the artificial progression surface technique.

Med Biol Eng Comput 2010 Nov 9;48(11):1065-75. Epub 2010 Jul 9.

Department of Mechanical and Manufacturing Engineering, Schulich School of Engineering, University of Calgary, 2500 University Drive NW, Calgary, AB, T2N 1N4, Canada.

Adolescent idiopathic scoliosis (AIS) progression is clinically monitored by a series of full spinal X-rays. To decrease radiation exposure, an artificial progression surface (APS) is proposed to predict progression. Fifty-six acquisitions (posteroanterior radiographs, 0° and 20°) were obtained from 11 AIS patients (29.8 ± 9.6° Cobb angle). Three-dimensional curves were constructed through vertebral pedicle centers. Three previous serial spinal curves (6-month intervals) were used to construct an APS with a Non-uniform Rational B-Spline surfacing technique. Future progression was achieved by aligning the curves on the APS using the generalized cross-validation extrapolation technique. With three and four previous serial spinal curves, the prediction accuracies of future progression at the next 6-month interval were 4.1 ± 3.3° for Cobb angles and 3.6 ± 3.5 mm for apex lateral deviations. Apex locations and Cobb regions varied within one vertebral level. The proposed technique shows potential as an accurate three-dimensional prediction method for AIS progression and could help pediatricians make decisions about treatment. However, it could only be applied once before more radiographic data would be needed.
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http://dx.doi.org/10.1007/s11517-010-0654-6DOI Listing
November 2010

ACL/MCL transection affects knee ligament insertion distance of healing and intact ligaments during gait in the Ovine model.

J Biomech 2009 Aug 29;42(12):1825-33. Epub 2009 Jul 29.

Department of Mechanical and Manufacturing Engineering, University of Calgary, Calgary, Alberta, Canada.

The objective of this study was to assess the impact of combined transection of the anterior cruciate and medial collateral ligaments on the intact and healing ligaments in the ovine stifle joint. In vivo 3D stifle joint kinematics were measured in eight sheep during treadmill walking (accuracy: 0.4+/-0.4mm, 0.4+/-0.4 degrees ). Kinematics were measured with the joint intact and at 2, 4, 8, 12, 16 and 20 weeks after either surgical ligament transection (n=5) or sham surgery without transection (n=3). After sacrifice at 20 weeks, the 3D subject-specific bone and ligament geometry were digitized, and the 3D distances between insertions (DBI) of ligaments during the dynamic in vivo motion were calculated. Anterior cruciate ligament/medial collateral ligament (ACL/MCL) transection resulted in changes in the DBI of not only the transected ACL, but also the intact lateral collateral ligament (LCL) and posterior cruciate ligament (PCL), while the DBI of the transected MCL was not significantly changed. Increases in the maximal ACL DBI (2 week: +4.2mm, 20 week: +5.7mm) caused increases in the range of ACL DBI (2 week: 3.6mm, 20 week: +3.8mm) and the ACL apparent strain (2 week: +18.9%, 20 week: +24.0%). Decreases in the minimal PCL DBI (2 week: -3.2mm, 20 week: -4.3mm) resulted in increases in the range of PCL DBI (2 week: +2.7mm, 20 week: +3.2mm). Decreases in the maximal LCL DBI (2 week: -1.0mm, 20 week: -2.0mm) caused decreased LCL apparent strain (2 week: -3.4%, 20 week: -6.9%). Changes in the mechanical environment of these ligaments may play a significant role in the biological changes observed in these ligaments.
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http://dx.doi.org/10.1016/j.jbiomech.2009.05.034DOI Listing
August 2009

Alterations in knee joint laxity during the menstrual cycle in healthy women leads to increases in joint loads during selected athletic movements.

Am J Sports Med 2009 Jun 16;37(6):1169-77. Epub 2009 Mar 16.

Human Performance Laboratory, University of Calgary, Calgary, Alberta T2N 1N4, Canada.

Background: It has been speculated that the hormonal cycle may be correlated with higher incidence of ACL injury in female athletes, but results have been very contradictory.

Hypothesis: Knee joint loads are influenced by knee joint laxity (KJL) during the menstrual cycle.

Study Design: Controlled laboratory study.

Methods: Serum samples and KJL were assessed at the follicular, ovulation, and luteal phases in 26 women. Knee joint mechanics (angle, moment, and impulse) were measured and compared at the same intervals. Each of the 26 subjects had a value for knee laxity at each of the 3 phases of their cycle, and these were ordered and designated low, medium, and high for that subject. Knee joint mechanics were then compared between low, medium, and high laxity.

Results: No significant differences in knee joint mechanics were found across the menstrual cycle (no phase effect). However, an increase in KJL was associated with higher knee joint loads during movement (laxity effect). A 1.3-mm increase in KJL resulted in an increase of approximately 30% in adduction impulse in a cutting maneuver, an increase of approximately 20% in knee adduction moment, and a 20% to 45% increase in external rotation loads during a jumping and stopping task (P < .05).

Conclusion: Changes in KJL during the menstrual cycle do change knee joint loading during movements. Clinical Relevance Our findings will be beneficial for researchers in the development of more effective ACL injury prevention programs.
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http://dx.doi.org/10.1177/0363546508330146DOI Listing
June 2009

Changing hormone levels during the menstrual cycle affect knee laxity and stiffness in healthy female subjects.

Am J Sports Med 2009 Mar 27;37(3):588-98. Epub 2009 Jan 27.

Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.

Background: Whether knee laxity varies throughout the menstrual cycle remains controversial. As increased laxity may be a risk factor for anterior cruciate ligament (ACL) injury, further research is warranted.

Hypothesis: Variation in estradiol and progesterone levels during the menstrual cycle influences knee laxity and stiffness.

Study Design: Case control study; Level of evidence, 3.

Methods: The serum estradiol and progesterone levels of 26 healthy female subjects were recorded in the follicular phase, ovulation, and the luteal phase. Knee joint laxity was assessed using a standard knee arthrometer at the same intervals. Stiffness changes in the load-displacement curve were determined. Hormone levels across the cycle were compared between responders and nonresponders, defined by whether changes in knee laxity at 89 N occurred.

Results: Greater laxity at 89 N during ovulation was observed (ovulation: 5.13 +/- 1.70 mm vs luteal: 4.55 +/- 1.54 mm, P = .012). In knee laxity testing at manual maximum load, greater laxity was noticed during ovulation (14.43 +/- 2.60 mm, P = .018), as compared with the follicular phase (13.35 +/- 2.53 mm). A reduction in knee stiffness of approximately 17% (ovulation: 12.48 +/- 5.46 N/mm vs luteal: 15.02 +/- 7.71 N/mm, P = .042) during ovulation was observed. However, there were no differences in hormone levels between responders and nonresponders at 89 N.

Conclusion: Female hormone levels are related to increased knee joint laxity and decreased stiffness at ovulation. To understand subject variations in knee joint laxity during the menstrual cycle in female athletes, further investigation is warranted.
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http://dx.doi.org/10.1177/0363546508326713DOI Listing
March 2009

Biomechanics of volunteers subject to loading by a motorized shoulder belt tensioner.

Spine (Phila Pa 1976) 2008 Apr;33(8):E225-35

Department of Mechanical and Manufacturing Engineering, University of Calgary, Calgary, Alberta, Canada.

Study Design: A biomechanical study using human volunteers.

Objective: Motorized shoulder belt tensioning is a new seatbelt technology that is likely to be incorporated into future vehicles. The objective of this study was to characterize the upper torso biomechanics of 3 sizes of adult volunteers (5th percentile female, 50th percentile male, and 95th percentile male) subjected to motorized shoulder belt tensioning in the static environment.

Summary Of Background Data: There is a lack of volunteer data concerning the biomechanics of occupants subject to motorized precrash shoulder belt tensioning. Studies of torso repositioning by the air force for ejection seats are much too aggressive to be relevant to motorized systems. Low-level motorized shoulder belt tensioning is well tolerated by vehicle occupants but optimized performance by occupant size is unknown.

Methods: Nineteen male and 6 female subjects were instrumented in a fixture designed to support the occupant leaning forward and apply seatbelt tension. The subjects were 5th percentile females, 50th percentile males, and 95th percentile males. Reflective markers were placed on the subjects to monitor torso kinematics during tensioning.

Results: Changes in spinal curvature were small during shoulder belt tensioning and the angular motion of the torso originated within 4.2 cm of the pelvis-femur junction or H-point. Torso repositioning and retraction timing was found to be: 54.3 degrees in 0.78 seconds for the 5th percentile female, 57.6 degrees in 0.95 seconds for the 50th percentile male, and 42.2 degrees in 0.92 seconds for the 95th percentile male.

Conclusion: Occupant size has a significant effect on retraction time to reposition the torso during shoulder belt tensioning. Larger vehicle occupants require more time because of a slower retraction velocity. The results are sufficiently simple that a lumped-mass model can predict tensioning kinetics.
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http://dx.doi.org/10.1097/BRS.0b013e31816b87d2DOI Listing
April 2008

Dynamic in vivo three-dimensional (3D) kinematics of the anterior cruciate ligament/medial collateral ligament transected ovine stifle joint.

J Orthop Res 2008 May;26(5):660-72

Department of Mechanical and Manufacturing Engineering, University of Calgary, c/o Joint Injury and Arthritis Research Group, 3330 Hospital Drive, Calgary, Alberta, Canada.

The objective of this study was to use an ovine stifle joint model to assess the impact of combined transection of the anterior cruciate and medial collateral ligaments on three-dimensional (3D) joint motion serially over 20 weeks after transection. In vivo 3D kinematics were measured in the right hind limb of eight sheep while walking on a treadmill (accuracy, 0.4 mm +/- 0.4 mm, 0.4 degrees +/- 0.4 degrees ). Five sheep received surgical ligament transection and three sheep received sham surgery without transection. At 2 weeks after transection, average joint flexion at hoof strike was significantly increased (8.9 degrees +/- 3.0 degrees ), and the tibial position was significantly shifted in the anterior direction relative to the femur during midstance (4.9 mm +/- 0.9 mm). By 20 weeks after transection, joint flexion had normalized, but the tibial position was significantly adducted (0.5 degrees +/- 0.7 degrees ) and shifted in the medial (2.5 mm +/- 1.2 mm), anterior (5.8 mm +/- 1.9 mm), and superior directions (1.6 mm +/- 0.4 mm). At 2 and 20 weeks after surgical intervention, the maximal anterior tibial position was significantly increased during mid-stance in the transected group (4.9 mm +/- 0. 9 mm and 5.8 mm +/- 1.9 mm) compared to the sham operated group (0.2 mm +/- 0.2 mm and -0.1 +/- 0.1 mm). Although the anterior tibial shift was observed in all transected sheep, a high degree of variability existed between sheep, in the initial joint position, the magnitude of the early change, the change over time, and the change at 20 weeks. In this situation statistics must be interpreted carefully, and in future studies, individual changes should be assessed in the context of individual pathological changes in order to investigate potential clinical significance.
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http://dx.doi.org/10.1002/jor.20557DOI Listing
May 2008

Accuracy and reliability of MRI vs. laboratory measurements in an ex vivo porcine model of arthritic cartilage loss.

J Magn Reson Imaging 2007 Oct;26(4):992-1000

Department of Radiology and Diagnostic Imaging, Faculty of Medicine, University of Alberta, Edmonton, Alberta, Canada.

Purpose: To quantify the accuracy of magnetic resonance imaging (MRI) measurement of change in cartilage volume due to thin linear excisions, simulating arthritic cartilage losses, by comparison with laboratory volume measurements in an ex vivo porcine model.

Materials And Methods: We scanned 15 porcine patellae by T1-weighted spoiled gradient echo (SPGR) MRI at baseline and after excision of up to three thin layers of articular cartilage. Excised fragment volume was determined from density and weight. Postexcision scans were "fused" to the baseline scan by three-dimensional (3D) registration. This allowed automated recalculation of the remaining cartilage volume within a baseline region of interest (ROI) following each excision. We compared MRI estimates of change in cartilage volume to direct laboratory measurement of fragment volume.

Results: Our 38 excised fragments averaged 0.16 mL, or approximately 7% of cartilage volume. MRI and laboratory estimates of total cartilage volume loss differed by 1.6% +/- 13.2% (mean, coefficient of variation [CV]). Accuracy was +/-0.1 mL for 95% of scans.

Conclusion: MRI estimates of small changes in porcine patellar cartilage volume were unbiased, reliable, and accurate to 0.1 mL. Despite a proportionately high error in the very thin fragments tested, achievement of similar accuracy in vivo would be adequate to detect approximately two years of osteoarthritic cartilage loss.
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http://dx.doi.org/10.1002/jmri.21107DOI Listing
October 2007
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