The intercarpal ligaments of the equine midcarpal joint, Part 2: The role of the palmar intercarpal ligaments in the restraint of dorsal displacement of the proximal row of carpal bones.

Abstract

To determine the relative contributions of the palmar intercarpal ligaments in the midcarpal joint to the restraint of dorsal displacement of the proximal row of carpal bones. A biomechanical study of cadaver equine carpi. Eight equine forelimbs from six thoroughbred horses. With joints in full extension, the radius was dorsally displaced while midcarpal joint displacement was measured. The restraining force at a joint displacement of 1.5 mm was determined from the load-displacement curve. A ligament or pair of ligaments was then cut and the testing procedure repeated. Their contribution to restraining force was calculated as the percentage change in restraining force after the ligament was sectioned. Relative cross-sectional areas of the ligaments tested were measured at the level of the midcarpal joint. The collateral ligaments were the major contributors to the restraint of dorsal displacement (P < .001). In all joints, the palmar intercarpal ligaments contributed a greater proportion than the palmar carpal ligament (PCL) (P < .05). The mean percentage (+/-SEM) contributions to the restraint of dorsal displacement were 62.8 +/- 3.4 for the collateral ligaments, 14.5 +/- 1.4 for the PCL, and 22.7 +/- 2.2 for the palmar intercarpal ligaments. Mean cross-sectional area expressed as a percentage (+/-SEM) of the total ligamentous area were 9.0 +/- 0.3 for the palmar intercarpal ligaments, 27.1 +/- 3.0 for the PCL, and 63.8 +/- 2.8 for the collateral ligaments. Despite the small size of the palmar intercarpal ligaments, they play an important role in the restraint of dorsal displacement of the proximal row of carpal bones. Interpretation, as well as prevention and treatment of intercarpal ligament tearing requires an understanding of their function.