Anterior cruciate ligament reconstruction with bioabsorbable polyglycolic acid interference screws:: MR imaging follow-up

PURPOSE: To examine at magnetic resonance (MR) imaging the degradation of an interference screw made of polyglycolic acid (67.5%) and trimethylene carbonate (32.5%) and compare the MR findings with the clinical evaluation results. MATERIALS AND METHODS: Clinical and MR imaging studies were performed concomitantly 6 months (in 20 patients), 1 year (in 10 patients),. and 2 years (in eight patients) after surgery. Screw resorption rate, tibial tunnel appearance and contents, epiphyseal reaction, reconstructed ligament appearances, one plug healing, joint effusion; and synovitis were evaluated. RESULTS: The screw was observed to be partially resorbed (by approximately one-third) at 6 months and totally resorbed at 1 year. Enhancement of the tunnel content, which can be linked to bone healing and screw replacement, was seen without a surrounding inflammatory reaction. Bone tunnel enlargement was observed and remained stable over time; this phenomenon has often been reported with metallic or polylactic acid interference screws and could be due to the position of the screw within the tunnel. The tissue that was seen at MR imaging to be replacing the screw was either fibrous or fatty and fibrous but never bone. CONCLUSION: Resorption of the screw does not appear to be related to clinical results. (C) RSNA, 2002.