Effects of experimental desmotomy on material properties and histomorphologic and ultrasonographic features of the accessory ligament of the deep digital flexor tendon in clinically normal horses

Abstract

Objective - To evaluate posttrauma biomechanical behavior of the scar attributable to desmotomy of the accessory ligament of the deep digital flexor tendon (AL-DDFT), compared with the histomorphologic and ultrasonographic appearance. Animals - 5 Standardbred trotters. Procedure - Gross appearance, length, cross-sectional area (CSA), in vitro material properties, and ultrasonographic and histomorphologic features were studied 6 months after desmotomy. Tensile tests were conducted, with forces and elongation simultaneously recorded. Surgically treated limbs were compared with nontreated contralateral limbs. Results - The CSA of the treated ligaments was increased threefold, and treated ligaments were 1 cm longer than control ligaments. In the healed AL-DDFT, stress and material stiffness were approximately a third of those values for controls. The functional characteristics force and elongation at failure, reached 80% of control values. Ultrasonographic and the histomorphologic examination of the scar tissue revealed high amounts of randomly oriented collagen. Conclusion - From the ultrasonographic and histomorphologic findings and the material properties, it was concluded that the scar tissue was of inferior quality. However, the functional properties had been restored for the most part by increase of the CSA. The length increase may lead to strain relief in the AL-DDFT after desmotomy. Clinical Relevance - Desmotomy is recommended as treatment for chronic desmitis.