Femoral and Tibial Tunnel Diameter and Bioabsorbable Screw Findings After Double-Bundle ACL Reconstruction in 5-Year Clinical and MRI Follow-up

BACKGROUND: Tunnel enlargement is frequently seen in short-term follow-up after anterior cruciate ligament reconstruction (ACLR). According to new evidence, tunnel enlargement may be followed by tunnel narrowing, but the long-term evolution of the tunnels is currently unknown. HYPOTHESIS/PURPOSE: The hypothesis was that tunnel enlargement is followed by tunnel narrowing caused by ossification as seen in follow-up using magnetic resonance imaging (MRI). The purpose of this study was to evaluate the ossification pattern of the tunnels, the communication of the 2 femoral and 2 tibial tunnels, and screw absorption findings in MRI. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: Thirty-one patients underwent anatomic double-bundle ACLR with hamstring grafts and bioabsorbable interference screw fixation and were followed with MRI and clinical evaluation at 2 and 5 years postoperatively. RESULTS: The mean tunnel enlargement at 2 years was 58% and reduced to 46% at 5 years. Tunnel ossification resulted in evenly narrowed tunnels in 44%, in conical tunnels in 48%, and fully ossified tunnels in 8%. Tunnel communication increased from 13% to 23% in the femur and from 19% to 23% in the tibia between 2 and 5 years and was not associated with knee laxity. At 5 years, 54% of the screws were not visible, with 35% of the screws replaced by a cyst and 19% fully ossified. Tunnel cysts were not associated with worse patient-reported outcomes or knee laxity. Patients with a tibial anteromedial tunnel cyst had higher Lysholm scores than patients without a cyst (93 and 84, P = .03). CONCLUSION: Tunnel enlargement was followed by tunnel narrowing in 5-year follow-up after double-bundle ACLR. Tunnel communication and tunnel cysts were frequent MRI findings and not associated with adverse clinical evaluation results.