Modulating tibiofemoral contact force in the sheep hind limb via treadmill walking: Predictions from an opensim musculoskeletal model

Abstract

Sheep are a predominant animal model used to study a variety of orthopedic conditions. Understanding and controlling the in-vivo loading environment in the sheep hind limb is often necessary for investigations relating to bone and joint mechanics. The purpose of this study was to develop a musculoskeletal model of an adult sheep hind limb and investigate the effects of treadmill walking speed on muscle and joint contact forces. We constructed the skeletal geometry of the model from computed topography images. Dual-energy x-ray absorptiometry was utilized to establish the inertial properties of each model segment. Detailed dissection and tendon excursion experiments established the requisite muscle lines of actions. We used OpenSim and experimentally-collected marker trajectories and ground reaction forces to quantify muscle and joint contact forces during treadmill walking at 0. 5 Since mechanical stimuli affect the biosynthesis, remodeling, and degradation of biological tissues, proper investigation of many such orthopedic conditions requires knowledge, and standardization of the loading environment in the sheep hind limb.6-9 The combination of treadmill locomotion and musculoskeletal modeling may allow researchers to modulate and quantify muscle and joint contact forces in-vivoIn humans, peak compressive and anterior-posterior tibiofemoral contact forces are proportional to walking speed. 10 This suggests that treadmill walking at set speeds may be a way to manipulate in-vivo loading in the sheep hind limb. However, it is unknown how walking speed alters sheep hind limb loading. Joint contact forces have only been reported for self-selected over-ground walking speeds in sheep and are therefore highly variable with standard deviations of AE50% of body weight (BW) at peak loading.11,12 Furthermore, sheep may be noncompliant and erratic during treadmill walking, and since quadrupeds have the ability to unweight and vary loading within individual limbs to a greater extent than bipeds, 13 the variability of loading during treadmill locomotion at set speeds in sheep is unknown.Musculoskeletal models and analysis software offer a method to non-invasively estimate the mechanical loads (i.e., muscle and joint contact forces) in weightbearing limbs during locomotor activites.14-16 However, while there are many open-source musculoskeletal models available to estimate muscle and joint contact forces in humans, 17 we are not aware of a freelyavailable model of the sheep hind limb.This study had two aims. The first aim was to develop a freely-available musculoskeletal model of the sheep hind limb for use in OpenSim. 16 The second aim was to determine how treadmill walking speed alters estimates of in-vivo joint loading in the sheep hind limb. This was accomplished by quantifying tibiofemoral contact forces from the musculoskeletal model while the animal walked on a treadmill at 0.25m• s À1 and 0.75m• s À1. The tibiofemoral joint was identified as the focus of this study due to the ease of translation between sheep...

Muscle moment arm analyses applied to vertebrate paleontology: a case study usingStegosaurus stenopsMarsh, 1887

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Sheep Gait Biomechanics and the Assessment of Musculoskeletal Conditions: A Systematic Review

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Computational characterization of fracture healing under reduced gravity loading conditions

“…Hindlimb muscles were created in both ExFix and Control FE models using a constraint between a single reference node and a node set on the surface on the bone corresponding to the known muscle cross‐sectional area. The muscle forces utilized for the FE analysis were predicted by a previously developed seven‐segment musculoskeletal model of the ovine hindlimb . The latter model, with 13 degrees of freedom and 31 muscle‐tendon units was used to predict the muscle and stifle joint contact forces utilized in the FE analysis during standing with vertical GRFs of 100, 200, and 300 N .…”