Model formulation and determination of in vitro parameters of a noninvasive method to calculate flexor tendon forces in the equine forelimb

Objective-To describe a method to calculate flexor tendon forces on the bas is of inverse dynamic analysis and an In vitro model of the equine forelimb and to quantify parameters for the model. Sample Population-36 forelimbs of 23 horses that each had an estimated body mass of greater than or equal to 500 kg. Procedure-Longitudinal Imb sections were used to determine the lines of act ion of the tendons. Additionally, limb and tendon loading experiments were performed to determine mechanical properties of the flexor tendons. Results-The study quantified the parameters for a pulley model to describe the lines of action. Furthermore, relationships between force and strain of the flexor tendons and between fetlock joint angle and suspensory ligament strain were determined, and the ultimate strength of the tendons was measu red. Conclusion and Clinical Relevance-The model enables noninvasive determinati on of forces in the suspensory ligament, superficial digital flexor tendon, and distal part of the deep digital flexor (DDF) tendon In addition, it pr ovides a noninvasive measure of loading of the accessory ligament of the DD F tendon for within-subject comparisons. However, before application, the m ethod should be validated. The model could become an important tool for use In research of the cause, prevention, and treatment of tendon injuries in horses.