DEVELOPMENT OF A DYNAMIC ORTHOSIS FOR STABILIZATION AND CORRECTION OF CARPAL DEVELOPMENTAL DISORDERS IN FOALS

Introduction: Incomplete ossification of the carpal bones and flexural/angular carpal deformities are among the most common orthopedic conditions affecting young foals. Conservative treatment includes medical therapy combined with cast/splints or static/dynamic orthoses. Currently, there are few orthoses available for foals. The aim of this study was to develop an innovative dynamic orthosis to stabilize the carpus and to correct carpal deformities while maintaining functionality. Materials and Methods: First, we determined in 112 foals (from premature up to 5 months old) the growth rate of selected forelimb regions using morphometric measurements (length, circumference, diameter) to identify the need for different orthosis sizes. Next, cadaveric foal limbs for those orthosis sizes were CT scanned to reconstruct their 3D geometry and a virtual prototype was created using CAD software. Finally, the orthosis was built using 3D-printing technology and preliminarily validated. Results: The concept of the orthosis was successful from the original idea, through production, and eventually validation of a prototype. The orthosis consisted of 5 or 6 pieces, 4 of which are made of polyolefin filament and articulate with 1 or 2 adjustable metallic polycentric joints to assist and control carpal movements. Based on preliminary testing, the new prototype was satisfactory in terms of functionality and animal comfort. Discussion/Conclusion: The adjustable orthosis prototype has the potential to assist and correct carpal developmental disorders by taking advantage of the young foal’s limb plasticity. Its anatomical design with different sizes may avoid complications associated with conventional external coaptation methods and allow early minimally invasive treatment.