Repeatability of Clinical, Biomechanical, and Motor Control Profiles in People with and without Standing-Induced Low Back Pain

A major research focus is optimization of interventions for low back pain (LBP). Predisposing factors for LBP development have been previously identified. To differentiate changes in these factors with intervention, factor stability over time must be determined. Twenty-three volunteers without LBP participated in a LBP-inducing standing protocol on two separate days. Outcome measures included visual analog scale (VAS) for LBP and trunk/hip muscle coactivation patterns. Intraclass correlation coefficients (ICCs) were used to examine repeatability. Between-day repeatability of outcome measures was excellent (ICCs >0.80). Individuals were consistent in subjective LBP, with 83% reporting similar day-to-day VAS levels. Muscle co-activation patterns and LBP reports are stable measures over time for this LBP-inducing protocol. Changes in these measures following intervention can be considered to be treatment effects and are not due to natural variability. This provides support for use of this protocol in studying interventions for standing-induced LBP

Effect of obesity on knee joint biomechanics during gait in young adults

This article is MacLean, K. F. E., Callaghan, J. P., & Maly, M. R. (2016). Effect of obesity on knee joint biomechanics during gait in young adults. Cogent Medicine, 3(1). https://doi.org/10.1080/2331205X.2016.1173778While there are many comorbidities associated with obesity, one of the more poorly understood is knee osteoarthritis through obesity. The purpose of this study was to compare the kinematics and kinetics of gait and cumulative knee adductor load, which represents the sum of repetitive exposures to medial knee loading during daily activity, between young obese adults with young, healthy-weight adults. Eight obese and eight healthy-weight young adults participated. Data from a three-dimensional motion capture system and a synchronized floor-mounted force plate were collected during gait trials. Participants wore accelerometers to determine step counts for seven consecutive days. Dependent t-tests were used to identify differences in gait kinematics, kinetics and cumulative knee adductor load between groups. Compared to the healthy-weight participants, obese young adults demonstrated a slower walking speed, greater stance duration, less knee flexion at heel contact, greater knee adduction in early stance and less knee abduction at terminal stance (p < 0.05). The obese young adults had a greater external knee extension moment (p < 0.05) and external rotation moment (p < 0.05) in early stance. The obese group had a greater cumulative knee adductor load. These results provide insight into a potential pathway by which obesity predisposes a healthy young adult for knee osteoarthritis.This research is supported by Canada Research Chairs, Canadian Institutes of Health Research, and Natural Sciences and Engineering Research Council of Canad

Automated Histological Analysis System for Quantifying Microstructural Damage Accumulation to the Annulus Fibrosus

Ben Daya, I., Noguchi, M., Callaghan, J. P., & Wong, A. (2016). Automated Histological Analysis System for Quantifying Microstructural Damage Accumulation to the Annulus Fibrosus. Journal of Computational Vision and Imaging Systems, 2(1). Retrieved from http://openjournals.uwaterloo.ca/index.php/vsl/article/view/100In this paper, we proposed an automated histological analysis system for quantifying microstructural damage accumulation to the annulus fibrosus. This system takes in a digital histology image and uses Gaussian mixture model based segmentation, followed by connected components analysis to extract and label possible clefts. The image is then refined through spatial and size constraints. Finally, the required statistics for quantifying microstructural damage are calculated.This research was funded by the Natural Sciences and Engineering Research Council of Canada, the Canada Research Chairs Program, and the Ontario Ministry of Research and Innovation

A procedure for determining parameters of a simplified ligament model

The final publication is available at Elsevier via http://dx.doi.org/10.1016/j.jbiomech.2017.10.037 © 2017. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/A previous mathematical model of ligament force-generation treated their behavior as a population of collagen fibres arranged in parallel. When damage was ignored in this model, an expression for ligament force in terms of the deflection, x, effective stiffness, k, mean collagen slack length, μ, and the standard deviation of slack lengths, σ, was obtained. We present a simple three-step method for determining the three model parameters (k, μ, and σ) from force-deflection data: (1) determine the equation of the line in the linear region of this curve, its slope is k and its x -intercept is -μ; (2) interpolate the force-deflection data when x is -μ to obtain F0; (3) calculate σ with the equation σ=2πF0/k. Results from this method were in good agreement to those obtained from a least-squares procedure on experimental data – all falling within 6%. Therefore, parameters obtained using the proposed method provide a systematic way of reporting ligament parameters, or for obtaining an initial guess for nonlinear least-squares.Jack P. Callaghan is supported by the Tier 1 Canada Research Chair in Spine Biomechanics Jeff M. Barrett is supported by an NSERC PGS-D Scholarshi

The impact of compressive force magnitude on the in vitro neutral zone range and passive stiffness during a flexion–extension range of motion test

Noguchi, M., Gooyers, C. E., Holmes, M. W. R., & Callaghan, J. P. (2015). The impact of compressive force magnitude on the in vitro neutral zone range and passive stiffness during a flexion-extension range of motion test. Cogent Engineering, 2(1). https://doi.org/10.1080/23311916.2015.1014253The objective of this work was to examine the influence of compressive force magnitude on a functional spinal unit’s (FSU) flexion–extension neutral zone measured during pure moment (PM) tests. Each porcine cervical FSU received four repeats of a PM test with 10, 300, 900 and 1,800 N of compressive force, in a randomized order. Increasing the magnitude of compression significantly decreased the neutral zone range (p < 0.001), while increasing passive stiffness (p < 0.001). The flexion limit at 10 N was significantly lower (p < 0.05) than the other loading conditions. Reporting the compressive force magnitude is important when posture is a standardized experimental factor considered in the design of in vitro spine biomechanics studies.The authors acknowledge partial funding from the Natural Science and Engineering Research Council of Canada (NSERC). Dr. Jack Callaghan is supported by the Canada Research Chair in Spine Biomechanics and Injury Preventio

Knee power is an important parameter in understanding medial knee joint load in knee osteoarthritis.

Calder, K. M., Acker, S. M., Arora, N., Beattie, K. A., Callaghan, J. P., Adachi, J. D., & Maly, M. R. (2014). Knee Power Is an Important Parameter in Understanding Medial Knee Joint Load in Knee Osteoarthritis: Knee Power and OA. Arthritis Care & Research, 66(5), 687–694. https://doi.org/10.1002/acr.22223Objective To determine the extent to which knee extensor strength and power explain variance in knee adduction moment (KAM) peak and impulse in clinical knee osteoarthritis (OA). Methods Fifty-three adults (mean ± SD age 61.6 ± 6.3 years, 11 men) with clinical knee OA participated. The KAM waveform was calculated from motion and force data and ensemble averaged from 5 walking trials. The KAM peak was normalized to body mass (Nm/kg). The mean KAM impulse reflected the mean total medial knee load during stride (Nm × seconds). For strength, the maximum knee extensor moment attained from maximal voluntary isometric contractions (MVIC) was normalized to body mass (Nm/kg). For power, the maximum knee extensor power during isotonic contractions, with the resistance set at 25% of MVIC, was normalized to body mass (W/kg). Covariates included age, sex, knee pain on the Knee Injury and Osteoarthritis Outcome Score, gait speed, and body mass index (BMI). Relationships of the KAM peak and impulse with strength and power were examined using sequential stepwise forward linear regressions. Results Covariates did not explain variance in the KAM peak. While extensor strength did not, peak knee extensor power explained 8% of the variance in the KAM peak (P = 0.02). Sex and BMI explained 24% of the variance in the KAM impulse (P < 0.05). Sex, BMI, and knee extensor power explained 31% of the variance in the KAM impulse (P = 0.02), with power contributing 7% (P < 0.05). Conclusion Knee extensor power was more important than isometric knee strength in understanding medial knee loads during gait.Canadian Institutes of Health Research. Grant Number: 102643Canadian Institutes of Health Research Joint Motion Program Postdoctoral FellowshipNetwork Scholar Award through The Arthritis Society/Canadian Arthritis NetworkTier I Canada Research Chair in Spine Biomechanics and Injury PreventionAlliance for Better Bone Health Chair in RheumatologyNew Investigator Award from the Canadian Institutes of Health Researc

Low back pain development differentially influences centre of pressure regularity following prolonged standing

The final publication is available at Elsevier via http://dx.doi.org/10.1016/j.gaitpost.2017.06.005 © 2017. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/Occupations requiring prolonged periods of static standing are associated with the development of low back pain (LBP). Certain individuals are susceptible to LBP development during prolonged standing (pain developers, PDs) while others are not (non-pain developers, NPDs). Linear centre of pressure (COP) measures suggest that standing balance control is negatively influenced following prolonged standing, and that PDs and NPDs may be differentially affected. The objective of this study was to determine if nonlinear standing balance control, quantified on COP, using sample entropy, is altered after 2-h of standing. Thirty two participants stood for 2-h. Separate 2-min standing trials, performed with eyes open and eyes closed, were collected before and after the 2-h standing protocol. Sample entropy, median power frequency and RMS amplitude of the COP time-series, was calculated from the 2-min standing trials for all participants. For comparison, participants were classified, post hoc, as PDs or NPDs according to visual analog scale pain scores. Sample entropy decreased after 2-h of standing for both PDs and NPDs, however, the decrease for NPDs was only 21% of the decrease observed in PDs. This study demonstrated that nonlinear control of upright standing changes after 2- hours of standing, resulting in an increase in COP regularity post 2- hours of standing for both PDs and NPDs. PDs displayed a greater change in COP regularity, which is supported by the theory that increased COP regularity occurs with pain/pathologyNatural Sciences and Engineering Research Council (NSERC)Discovery grant and the Ontario Graduate Scholarship (OGS

MRI-guided histology of TDP-43 knock-in mice implicates parvalbumin interneuron loss, impaired neurogenesis and aberrant neurodevelopment in amyotrophic lateral sclerosis-frontotemporal dementia.

Amyotrophic lateral sclerosis and frontotemporal dementia are overlapping diseases in which MRI reveals brain structural changes in advance of symptom onset. Recapitulating these changes in preclinical models would help to improve our understanding of the molecular causes underlying regionally selective brain atrophy in early disease. We therefore investigated the translational potential of the TDP-43Q331K knock-in mouse model of amyotrophic lateral sclerosis-frontotemporal dementia using MRI. We performed in vivo MRI of TDP-43Q331K knock-in mice. Regions of significant volume change were chosen for post-mortem brain tissue analyses. Ex vivo computed tomography was performed to investigate skull shape. Parvalbumin neuron density was quantified in post-mortem amyotrophic lateral sclerosis frontal cortex. Adult mutants demonstrated parenchymal volume reductions affecting the frontal lobe and entorhinal cortex in a manner reminiscent of amyotrophic lateral sclerosis-frontotemporal dementia. Subcortical, cerebellar and brain stem regions were also affected in line with observations in pre-symptomatic carriers of mutations in C9orf72, the commonest genetic cause of both amyotrophic lateral sclerosis and frontotemporal dementia. Volume loss was also observed in the dentate gyrus of the hippocampus, along with ventricular enlargement. Immunohistochemistry revealed reduced parvalbumin interneurons as a potential cellular correlate of MRI changes in mutant mice. By contrast, microglia was in a disease activated state even in the absence of brain volume loss. A reduction in immature neurons was found in the dentate gyrus, indicative of impaired adult neurogenesis, while a paucity of parvalbumin interneurons in P14 mutant mice suggests that TDP-43Q331K disrupts neurodevelopment. Computerized tomography imaging showed altered skull morphology in mutants, further suggesting a role for TDP-43Q331K in development. Finally, analysis of human post-mortem brains confirmed a paucity of parvalbumin interneurons in the prefrontal cortex in sporadic amyotrophic lateral sclerosis and amyotrophic lateral sclerosis linked to C9orf72 mutations. Regional brain MRI changes seen in human amyotrophic lateral sclerosis-frontotemporal dementia are recapitulated in TDP-43Q331K knock-in mice. By marrying in vivo imaging with targeted histology, we can unravel cellular and molecular processes underlying selective brain vulnerability in human disease. As well as helping to understand the earliest causes of disease, our MRI and histological markers will be valuable in assessing the efficacy of putative therapeutics in TDP-43Q331K knock-in mice