The Function of the Short Medial Collateral Ligaments of the Canine Tarsus: A Cadaveric Study

Abstract

ABSTRACT Information on the clinical behavior of cases with an isolated rupture of the short collateral ligaments of the canine tarsus is sparse. Our objective was to evaluate the function of the short medial collateral ligaments (SMCLs) in 90° flexion. Eight cadaveric limbs were tested for internal/external rotation and valgus/varus before and after transection of one or both SMCLs. In one group, the tibiocentral ligament was transected first, followed by the tibiotalar. In the second group, the order of transection was reversed. Angular changes between two k-wires were measured and compared. Internal rotation increased significantly after transection of one or both SMCLs (P = .015 and P = .004), with higher angular changes in the group in which the tibiotalar ligament was transected first (P = .003). Transection of this ligament alone was sufficient to cause caudomedial subluxation upon internal rotation. Valgus angulation increased after transection of one ligament (P = .022), but there was also an increase in varus angulation after transection of both ligaments (P = .027). Unlike the long medial collateral ligament, which stabilizes against deviation toward lateral, the SMCL stabilizes against subluxation toward medial, with the tibiotalar ligament being the major stabilizer in flexion. Findings can be used as diagnostic guidance for isolated tarsal short collateral ligament injuries.