Results of ACL reconstruction with tibial Retroscrew fixation: Comparison of clinical outcomes and tibial tunnel widening

Abstract

Summary. ACL reconstruction with the RetroScrew™ shows superior clinical outcomes compared to historical Achilles allograft studies with antegrade screws. Addition of antegrade screw augmentation to retrograde fixation causes an increase in tibial tunnel widening. Introduction. In traditional antegrade screw fixation of Anterior cruciate ligament (ACL) soft tissue allografts, the screw is secured in the opposite direction of graft tension, potentially altering the appropriate tension on the graft. The RetroScrew (Arthrex) is a bioabsorbable screw placed in a retrograde fashion, potentially improving the tension of the graft by placing the screw in a proximal-to-distal direction. In addition, the RetroScrew theoretically decreases tibial tunnel widening by closing the aperture of the tibial tunnel, which prevents ingress of synovial fluid. Early tunnel expansion has been implicated due to excessive transverse and longitudinal graft motion. The clinical effects of tunnel expansion have yet to be fully understood. The purpose of this study is to assess the clinical results and tunnel width after ACL soft tissue fixation in the tibia with the RetroScrew. Methods. Fifty-nine patients who underwent ACL reconstruction performed by two surgeons using the RetroScrew device returned for postoperative evaluation at an average of 25 months following surgery with a minimum follow-up of 12 months. Clinical evaluation, SF-36, IKDC and KT-1000 scores were recorded, and knee radiographs were used to measure tibial tunnel widening. Thirty-five patients had backup antegrade screw fixation in conjunction with the RetroScrew, and 24 patients had RetroScrew fixation alone. The results were compared to two previously reported studies on ACL reconstruction with Achilles tendon allograft that used antegrade screws. Results. The average IKDC score was 87 (range: 44–100), with mean KT-1000 side-to-side difference of 1.2 mm (range: 0–5 mm). Tibial tunnel widening was 4.93 mm (SD 3.32) on AP radiographs and 4.40 mm (SD 2.72) on lateral radiographs greater than the native tunnel drilling. Patients with additional backup fixation had significantly more tunnel widening than patients without backup fixation (P < 0.05). There was one failure based on KT-1000 measurements. When compared to previous studies using ACL allografts, RetroScrew patients had statistically superior Lachman exams, KT-1000 side-to-side differences and decreased tibial tunnel widening (P < 0.05) when antegrade fixation was excluded. Conclusion. Patients who underwent Achilles allograft ACL reconstruction with the RetroScrew had improved clinical results compared to historical controls using antegrade fixation. Tibial tunnel widening was increased when using additional antegrade screw fixation, suggesting that the amount of bioabsorbable material within the tibial tunnel was related to the degree of tunnel widening.