Biomechanical comparison of medial collateral ligament reconstructions using computer-assisted navigation.

BACKGROUND

The medial collateral ligament is a broad ligament that functions as the primary stabilizer against valgus knee stress, particularly at 30 degrees of flexion.

HYPOTHESIS: A double-bundle reconstruction technique that better restores the native medial collateral ligament anatomy will restore valgus and external rotation stability to a medial collateral ligament-deficient knee.

STUDY

DESIGN

Controlled laboratory study.

METHODS

Seven fresh-frozen cadaveric knees were studied. A surgical navigation system was used to determine valgus opening and external rotation at 0 degrees and 30 degrees with a 9.8-N.m valgus stress applied to the tibia graft isometry at multiple points on the tibia and femur. Intact and disrupted medial collateral ligament knees were used as controls. Four repair techniques were tested: Bosworth, modified Bosworth, anatomical single bundle, and anatomical double bundle.

RESULTS

Complete sectioning of the medial collateral ligament resulted in an increase in valgus opening of 5 degrees at 0 degrees and 7.7 degrees at 30 degrees . External rotation increased 4.6 degrees at 0 degrees and 9.7 degrees at 30 degrees . Single-bundle techniques (Bosworth, anatomical single bundle) did not restore valgus laxity at 0 degrees or 30 degrees ; the anatomical single bundle did not restore external rotation at 0 degrees . Double-bundle techniques (modified Bosworth, anatomical double bundle) restored valgus laxity and external rotation to the native knee conditions at 0 degrees and 30 degrees . At 30 degrees , the modified Bosworth was 0.3 degrees tighter and the anatomical double bundle 0.2 degrees tighter than was the intact knee. The center of the medial collateral ligament origin on the femur to the proximal insertion of the superficial medial collateral ligament resulted in the most isometric graft position.

CONCLUSION

Medial collateral ligament reconstruction configurations that use a double-bundle reconstruction better resist valgus and external rotations in response to valgus stress than do single-bundle techniques.

CLINICAL RELEVANCE: Although the medial collateral ligament often heals without surgical intervention, surgical reconstruction is occasionally necessary in grade III medial collateral ligament and combined ligamentous injuries to the knee. Double-bundle reconstruction of the medial collateral ligament better resists valgus forces across the knee and may allow for better surgical outcome after medial collateral ligament reconstruction.