Biomechanical comparison of four isometric prosthetic ligament repair techniques for tarsal medial collateral ligament injury.

Objective: To compare the stability, ultimate strength, and isometry of 4 prosthetic ligament repairs for canine tarsal medial collateral ligament injury.

Methods: 24 cadaveric canine distal hind limbs with induced medial tarsal instability were randomly divided into 4 groups. Simulated medial shearing injury of the collateral and medial malleolus were repaired using 1 of 4 isometric suture techniques: bone tunnels with nylon suture (TN), ultrahigh-molecular-weight polyethylene (UHMWPE) suture (TU), tibial bone anchor with nylon suture (AN), or talar bone anchor with UHMWPE suture (AU). Each repair was evaluated for medial stability before and after cyclic range of motion. 3 of 4 repair configurations allowed string potentiometer isometry data collection during cyclic range of motion. Each construct was subsequently tested to failure; the strength and failure mode were recorded.

Results: All repair groups showed statistically increased laxity compared to intact ligament. There was no difference in joint laxity between repair techniques. Cyclic range-of-motion testing did not increase joint laxity at any tested joint angle. Strength to failure was no different between repair groups. Isometry was achieved in the TU and TN groups.

Conclusions: All 4 techniques improved medial stability compared to that medial collateral ligament injury; however, no technique returned stability to the tarsal of the intact ligament. All 4 techniques maintained stability after range-of-motion testing. Isometric placement of the prosthetic suture was achievable. The constructs did not provide sufficient resistance to physiologic valgus stress.

Clinical relevance: Isometric placement of a prosthetic ligament is possible; secondary stabilization appears necessary to support the repair postoperatively.