Biomechanical analysis of an isolated fibular (lateral) collateral ligament reconstruction using an autogenous semitendinosus graft.

BACKGROUND The fibular collateral ligament is the primary stabilizer to varus instability of the knee. Untreated fibular collateral ligament injuries can lead to residual knee instability and can increase the risk of concurrent cruciate ligament reconstruction graft failures. Anatomic reconstructions of the fibular collateral ligament have not been biomechanically validated. PURPOSE To describe an anatomic fibular collateral ligament reconstruction using an autogenous semitendinosus graft and to test the hypothesis that using this reconstruction technique to treat an isolated fibular collateral ligament injury will restore the knee to near normal stability. STUDY DESIGN Controlled laboratory study. METHODS Ten nonpaired, fresh-frozen cadaveric knees were biomechanically subjected to a 10 N.m varus moment and 5 N.m external and internal rotation torques at 0 degrees, 15 degrees, 30 degrees, 60 degrees, and 90 degrees of knee flexion. Testing was performed with an intact and sectioned fibular collateral ligament, and also after an anatomic reconstruction of the fibular collateral ligament with an autogenous semitendinosus graft. Motion changes were assessed with a 6 degree of freedom electromagnetic motion analysis system. RESULTS After sectioning, we found significant increases in varus rotation at 0 degrees, 15 degrees, 30 degrees, 60 degrees, and 90 degrees, external rotation at 60 degrees and 90 degrees, and internal rotation at 0 degrees, 15 degrees, 30 degrees, 60 degrees, and 90 degrees of knee flexion. After reconstruction, there were significant decreases in motion in varus rotation at 0 degrees, 15 degrees, 30 degrees, 60 degrees, and 90 degrees, external rotation at 60 degrees and 90 degrees, and internal rotation at 0 degrees, 15 degrees, and 30 degrees of knee flexion. In addition, we observed a full recovery of knee stability in varus rotation at 0 degrees, 60 degrees, and 90 degrees, external rotation at 60 degrees and 90 degrees, and internal rotation at 0 degrees and 30 degrees of knee flexion. CONCLUSION An anatomic fibular collateral ligament reconstruction restores varus, external, and internal rotation to near normal stability in a knee with an isolated fibular collateral ligament injury. CLINICAL SIGNIFICANCE An anatomic reconstruction of the fibular collateral ligament with an autogenous semitendinosus graft is a viable option to treat nonrepairable acute or chronic fibular collateral ligament tears in patients with varus instability.