Tibial fixation in anterior cruciate ligament reconstruction: a prospective randomized study comparing metal interference screw and staples with a centrally placed polyethylene screw and sheath.

Background: The use of hamstring tendons for anterior cruciate ligament reconstruction has increased in popularity over recent years. However, concerns with the stability of graft fixation on the tibial side remain. Centrally placed interference screw/sheath implants have demonstrated promising results in biomechanical studies.

Hypothesis: Centrally placed, polyethylene screw and sheath implants will provide clinically equivalent fixation to the standard metal interference screw and supplemental staple fixation.

Study Design: Randomized controlled trial; Level of evidence, 1.

Methods: A total of 113 consecutive patients undergoing isolated, unilateral, primary anterior cruciate ligament reconstruction with hamstring autografts were randomized to tibial fixation with metal interference screw and staples (RCI) or with a centrally placed polyethylene screw and sheath implant (INTRAFIX). Prospective assessment of subjective outcomes was performed using Lysholm, Mohtadi, and International Knee Documentation Committee (IKDC) scores.

Results: At minimum 2-year follow-up, there were no significant differences between the 2 groups in terms of instrumented stability testing (KT-1000 arthrometer) or subjective assessment of knee outcomes (IKDC, Lysholm, Mohtadi). Both fixation methods demonstrated a significant, but not different, increase in outcomes scores from preoperative to postoperative evaluation. There were 7 failures (5 INTRAFIX, 2 RCI) caused by reinjury, but no statistically significant differences were observed between the 2 fixation methods.

Conclusion: The centrally placed polyethylene screw and sheath provided equivalent clinical outcomes at minimum 2-year follow-up to standard tibial fixation with metal interference screw and staples.