Musculoskeletal Modeling and Dynamic Simulation of the Thoroughbred Equine Forelimb During Stance Phase of the Gallop

Abstract

Because thoroughbred racehorses have a high incidence of forelimb musculoskeletal injuries, a model was desired to screen potential risk factors for injuries. This paper describes the development of a musculoskeletal model of the thoroughbred forelimb and a dynamic simulation of the motion of the distal segments during the stance phase of high-speed (18 m/s) gallop. The musculoskeletal model is comprised of segment, joint, muscle-tendon, and ligament information. The dynamic simulation incorporates a proximal forward-driving force, a distal ground reaction force model, muscle activations, and initial positions and velocities. A simulation of the gallop after transection of an accessory ligament demonstrated increased soft tissue strains in the remaining support structures of the distal forelimb. These data were consistent with those previously reported from in vitro experimental data and supported usefulness of the model for the study of distal forelimb soft tissue mechanics during the stance phase of the gallop.

Relationship between muscle forces, joint loading and utilization of elastic strain energy in equine locomotion

“…The results showed that the strain in the DDF tendon was larger than that in the SDF tendon, contrary to findings obtained from in vivo strain gauge measurements (Butcher et al, 2009;Riemersma et al, 1996). Other modeling studies have produced results that agree more closely with strain gauge measurements by analyzing the torques developed about the MCP and distal interphalangeal (DIP) joints (Meershoek et al, 2001;Swanstrom et al, 2005a;Wilson et al, 2001) rather than the carpal joint, but these studies have focused only on the portion of the limb below the carpus without considering the important actions of the carpal and digital extensor muscles.…”

“…The ligaments were represented as passive elastic structures. The force-length curve of each tendon and ligament was modeled by fitting a third-order polynomial function to experimental data reported in the literature (Jansen et al, 1993a;Jansen et al, 1998;Kostyuk et al, 2004;Lochner et al, 1980;Meershoek et al, 2001;Swanstrom et al, 2004;Swanstrom et al, 2005a;Swanstrom et al, 2005b;Weller, 2006). The lengths, moment arms and tendon wrapping directions of each muscle and ligament were calculated using a software program called OpenSim (Delp et al, 2007).…”

“…These ligaments insert near to the musculotendinous junction and connect the tendon to the palmar aspect of the carpus (from the DDF) or the caudal radius (from the SDF). Very few studies have considered the function of these structures (Meershoek et al, 2001;Swanstrom et al, 2005a), and a detailed mathematical model of the mechanical interactions between muscle belly, AL and the distal tendon has yet to be presented. Such a model is needed for accurate determination of the forces generated by the muscles, tendons and ligaments and for a thorough analysis of the work done by each of these structures.…”

“…This approach has been used extensively to determine musculoskeletal function in human movement (Pandy and Zajac, 1991;van Soest et al, 1993;Zajac, 1993;Pandy, 2001;Shelburne et al, 2004;Shelburne et al, 2006;Pandy and Andriacchi, 2010); however, relatively few studies have applied this approach to the study of equine locomotion (Biewener, 1998;Meershoek et al, 2001;Merritt et al, 2008;Swanstrom et al, 2005a;Wilson et al, 2001). Detailed models of isolated muscle-tendon preparations have been used to study the interactions between the active and passive properties of an actuator (Swanstrom et al, 2005b), but few studies have used models of the musculoskeletal system to evaluate muscle and joint loading during gait.…”

An Investigation of Humeral Stress Fractures in Racing Thoroughbreds using a 3D Finite Element Model in Conjunction with a Bone Remodeling Algorithm

“…In this model, a slow gallop was defined as a velocity of 10m/s at 2.8 times walking force with a peak vertical force of 1.8 times body weight. A fast gallop was defined as a velocity of 17m/s (Swanstrom et al, 2005) at 3.5 times walking force with a peak vertical force of 2.3 times body weight. All contact and muscle forces were assumed to be proportional to walking forces, and were based on muscle MVC and equine EMG data for walking.…”