Bioabsorbable Versus Titanium Screws in Anterior Cruciate Ligament Reconstruction Using Hamstring Autograft: A Prospective, Blinded, Randomized Controlled Trial With 5-Year Follow-up

Abstract

Background: Longer-term results of bioabsorbable screws for anterior cruciate ligament reconstruction (ACLR) have been reported, but results are specific to the exact screw material and design. Titanium and poly-L-lactic acid with hydroxyapatite (PLLA-HA) screw outcomes have been compared only to 2 years.

Purpose/hypothesis: The purpose of this study was to compare the clinical and radiologic outcomes of the PLLA-HA screw versus titanium screw for hamstring tendon ACLR over a 5-year follow-up period. The hypothesis was that there are no differences in clinical scores or tunnel widening between the PLLA-HA and the titanium screws and that the PLLA-HA screw as seen on magnetic resonance imaging (MRI) should show high-grade resorption and ossification response over 5 years.

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

Methods: A total of 40 patients undergoing ACLR were randomized to receive either a PLLA-HA screw (PLLA-HA group) or a titanium screw (titanium group) for ACL fixation. Blinded evaluation was performed at 2 and 5 years with the International Knee Documentation Committee and Lysholm knee score, KT-1000 arthrometer, single-legged hop test, and MRI to evaluate tunnel and screw volumes, periscrew ossification, graft integration, and cyst formation.

Results: There was no difference in any clinical outcome measure at 2- or 5-year follow-up between the 2 groups. At 2 years, the femoral tunnel in the PLLA-HA group was smaller than that in the titanium group (P = .02); at 5 years, there was no difference. At 2 years, the femoral PLLA-HA screw was a mean 76% of its original volume, and by 5 years, it was 36%. At 2 years, the tibial PLLA-HA screw mean volume was 68% of its original volume, and by 5 years, it was 46%. At 5 years in the PLLA-HA group, 88% of femoral tunnels and 56% of tibial tunnels demonstrated a significant ossification response. There was no increase in cyst formation in the PLLA-HA group and no screw breakages.

Conclusion: There were equivalent clinical results between the PLLA-HA and titanium groups at 2- and 5-year follow-ups. The PLLA-HA screw was not associated with increased tunnel widening or cyst formation when compared with the titanium screw. The PLLA-HA screw demonstrated progressive screw resorption and gradual but incomplete ossification over 5 years.

Keywords: ACL; bioabsorbable; clinical; fixation.