The purpose of this line of research was to develop a computer mathematical model that reproduces the three-dimensional anatomy and simulates the movements of the equine forelimb. With this model, we were able to estimate the joint movements and the forces involved in the muscle-tendon units, and ligaments in horses during a simulation of the stance phase at high speeds. We are currently working on expanding our model to the foal.

One reason for the development of such a model is to broaden our knowledge of the dynamics of the locomotor system in the horse. Our objectives are (a) to obtain an estimate of the biomechanical forces involved in horses with the most common clinical anomalies affecting the muscle-tendon and ligamentous structures of the equine forelimb and (b) to better assess the repercussions of any conservative treatments (i.e., corrective shoeing) and / or surgical (i.e., tenotomy, desmotomy) on joint movements and teno-desmic forces.

This model will allow us to improve our insights into the problems associated with conformational changes in the equine forelimb. By deepening our basic understanding of the pathophysiology beyond some of the clinical problems, we can facilitate the development of new treatment options and preventive strategies against growth and exercise pathologies and determine how biomechanical forces in the limb can be optimally distributed through specific treatments and/or orthoses. The model is also of important educational value as it helps students learning the anatomy and understanding the etiopathogenesis of numerous musculoskeletal pathologies in foals and adult horses.

In our investigations, we used various approaches that in combination helped us with:

• The quantification of the muscle-tendon and teno-desmic parameters of the equine forelimb to create a database and to estimate and measure the muscle forces required for creating the model.
• The generation of a 3-D model of the equine forelimb using CT / MRI acquisitions and anatomical samples in the adult horse and foal.
• The creation of a dynamic simulation of the stance phase of the equine forelimb at high speed and under particular conditions (i.e., post desmotomy of the accessory ligaments of the superficial flexor).

• Stover SM, Zarucco L, Swanstrom MD, Hubbard M, Clifford L “Computer Modeling of the Front Limb of the Thoroughbred Horse”. Center for Equine Health, University of California, Davis, CA
• Stover SM, Zarucco L, Swanstrom MD, Hubbard M. “Computer Simulation of the Musculoskeletal Structures of the Equine Distal Forelimb”. Marcia MacDonald Riva Grant Proposal, University of California, Davis, CA.
• Stover SM, Zarucco L, Swanstrom MD, Hubbard M, Hawkins D “In vivo study on forelimb superficial and deep digital flexor muscle isometric force characteristics in Thoroughbred horses”. Center for Equine Health, University of California, Davis, CA.

• Zarucco L, Wisner E, Swanstrom MD, Stover SM (2006) Image fusion of computed tomographic and magnetic resonance images for the development of a three-dimensional musculoskeletal model of the equine forelimb. Vet Radiol & Ultrasound. 47(6):553-62.12.
• Swanstrom, MD, Zarucco L, Hubbard M, Stover SM, Hawkins DA (2005) Musculoskeletal modeling and dynamic simulation of the Thoroughbred equine forelimb during stance phase of the gallop. J Biomech Engineering: 127(2):318-28.
• Swanstrom MD, Zarucco L, Stover SM, Hubbard M, Hawkins DA, Driessen B, Steffey EP (2005) Passive and active mechanical properties of the superficial and deep digital flexor muscles in the forelimbs of anesthetized Thoroughbred horses. J Biomech: 38 (3) pp 579-586.7.
• Zarucco L, Swanstrom MD, Driessen B, Hawkins D, Hubbard M, Steffey EP, Stover SM (2003) An in-vivo equine forelimb model for short-term recording of peak isometric force in the superficial and deep digital flexor muscles. Vet Surg: 32 (5), 439-450.
• Swanstrom M, Zarucco L, Stover S, Hubbard M, Hawkins D, Driessen B, Steffey E (2001) In vivo equine flexor muscle force-length properties suggest fibers act in series. Abstracts of the International Society of Biomechanics XVIIIth Congress, Zurich, Switzerland, July 8-13, 2001; Meeting abstracts online at http://congress.akm.ch/abstract/abstract P633
• Zarucco L, Swanstrom MD, Hubbard M, Hawkins D, Driessen B, Steffey EP, Stover SM (2000) In-vivo study on forelimb superficial and deep digital flexor muscle isometric force characteristics in Thoroughbred horses. Abstracts of the American College of Veterinary Surgeons’ Annual Symposium, Arlington, VA, September 21-24, 2000; Vet Surg 29 (5):484
• Zarucco L, Swanstrom MD, Stover SM, Hubbard M, Wisner E (1997) In vitro assessment of the instant centers and angle of rotation of the equine Thoroughbred forelimb joints. Abstracts of 24th Annual Conference Veterinary Orthopedic Society, Big Sky, Montana, March 1-8, 1997; Vet Comp Orthop Traumatol 10:72

• Prof. Susan M.Stover, JD Wheat Veterinary Orthopedic Research Laboratory, School of Veterinary Medicine, University of California - Davis, One Shields Avenue, Davis, CA 95616
• Michael D. Swanstrom, MS,PhD Mont Hubbard Biomedical Engineering Graduate Group, University of California - Davis, One Shields Avenue, Davis, CA 95616