Biceps tendon tenodesis for posterolateral instability of the knee. An in vitro study.

The effects of biceps tendon tenodesis on internal-external and varus-valgus laxity were measured using fresh-frozen cadaveric specimens that had undergone sequential sectioning of the posterolateral structures and of the fibular collateral ligament. Tenodesis (using 89 N graft tension and a fixation point located 1 cm anterior to the fibular collateral ligament's insertion on the femur) was effective in restoring external rotation and varus laxity; the procedure actually overconstrained external tibial rotation at all flexion positions and varus angulation at 60 degrees and 90 degrees of flexion. Internal rotation and valgus laxity were unaffected by the tenodesis procedure. The anterior fixation point was more effective in reducing laxity than a fixation point located 1 cm proximal to the fibular collateral ligament insertion. Tenodesis using the proximal fixation point, which was nonisometric, did not restore external rotation and varus laxities to intact values at 60 degrees and 90 degrees of knee flexion. Graft tension (45 or 89 N) had no measurable effect on the results of the tenodesis. This study has demonstrated that the biceps tenodesis procedure is effective for reducing static laxity in the knee with posterolateral instability.