Healing of the medial collateral ligament after a combined medial collateral and anterior cruciate ligament injury and reconstruction of the anterior cruciate ligament: Comparison of repair and nonrepair of medial collateral ligament tears in rabbits

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Abstract
The optimal treatment for a combined injury of the medial collateral and anterior cruciate ligaments is controversial, and the question remains as to whether repair of the medial collateral ligament and reconstruction of the anterior cruciate ligament improves healing of the medial collateral ligament. We compared reconstruction of the anterior cruciate ligament with and without repair of the medial collateral ligament in a rabbit model of a combined injury of these two ligaments. The anterior‐posterior translation and varus‐valgus rotation of the knee, the structural properties of the femur‐medial collateral ligament‐tibia complex, and the mechanical properties of the midsubstance of the medial collateral ligament were evaluated immediately after surgery and at 6 and 12 weeks postoperatively. Repair of the medial collateral ligament led to significantly less varus‐valgus rotation of the knee than did no repair, but the anterior‐posterior translation of the knees in the repair and nonrepair groups were not significantly different at any study time. At 12 weeks, the cross‐sectional area and ultimate load in the repair group were 60 and 53% greater, respectively, than in the nonrepair group. Among 12 specimens that were repaired (six specimens at 6 weeks and six specimens at 12 weeks), failure occurred within the midsubstance in four (two at each time period); in all of the specimens that were not repaired, failure occurred at the tibial insertion site. There was no significant difference between the modulus of the midsubstance in the repaired and the nonrepaired medial collateral ligaments. Thus, the improved structural properties of the femur‐medial collateral ligament‐tibia complexes that were repaired resulted from an increase in cross‐sectional area of the repaired medial collateral ligament and healing of the tibial insertion site. Postoperative healing time had little effect on the tensile properties. In this rabbit model, repair of the medial collateral ligament with reconstruction of the anterior cruciate ligament may lead to better healing of the medial collateral ligament in the early phase than does reconstruction of the anterior cruciate ligament alone.