Sensitivity analysis and application to trotting of a noninvasive method to calculate flexor tendon forces in the equine forelimb

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Abstract
Objective—To test the sensitivity to measurement and modeling errors of a method for noninvasive calculation of flexor tendon forces in the equine forelimb and to calculate tendon forces for Dutch Warmblood horses during trotting. Sample Population—A normative set of kinematic and ground-reaction force (GRF) data obtained from horses during trotting in another study. Procedure—Forces in the flexor tendons were calculated from the data set before and after addition of fixed relative and absolute errors. Amount of error was based on normal accuracy of the variables. A similar analysis was performed for a measure of strain of the accessory ligament of the deep digital flexor tendon. Results—The only errors that had a substantial influence on accuracy were modeling errors in the mechanical properties of the suspensory ligament and measurement errors in the point of application of the GRF and position of the marker on the distal interphalangeal joint. Influence of the measurement errors could be minimized by applying usual correction methods. Conclusion and Clinical Relevance—After correction of measurement errors, the method can be used to calculate mean tendon forces for a group of horses and to evaluate the influence of factors such as surface properties, type of shoe, speed, and fatigue on tendon forces. The method could become an important tool for use in research on the cause, prevention, and treatment of tendon injuries in horses. (Am J Vet Res 2001;62:1594–1598)