Comparison of tibial tunnel enlargement after anterior cruciate ligament reconstruction using patellar tendon autograft or allograft.

This retrospective study was designed to compare tibial tunnel enlargement in patients with autograft or allograft anterior cruciate ligament reconstructions. The changes were related to position of the tibial tunnel and clinical outcome. Twenty-six patients with autograft reconstructions and 41 with allograft reconstructions were studied at a mean follow-up of 59 months (range, 41 to 84) after surgery. The average tunnel enlargement on the anteroposterior view was 2.2 mm (SD, 2.5) for autografts and 2.8 mm (SD, 2.1) for allografts. On the lateral view, the tunnel enlargement was 2.6 mm (SD, 2.4) and 3.4 mm (SD, 2.6) for autografts and allografts, respectively. No significant differences were found between the autograft and allograft groups. A trend was found in the correlation between the position of the tibial tunnel and the tunnel enlargement: more anteriorly placed tunnels had more enlargement. The changes in tunnel diameter did not relate to knee functional score or laxity. There was a significant correlation between malposition of the tibial tunnel and poor clinical scores. A significant negative correlation was found between postoperative follow-up time and tunnel enlargement in both groups. We conclude that placement of the tibial tunnel is a determining factor in tibial tunnel enlargement and clinical knee scores after anterior cruciate ligament replacement with an autograft or allograft. Tunnel enlargement tends to be less at a longer postoperative follow-up.