Tibial tunnel area changes following arthroscopic anterior cruciate ligament reconstructions with autogenous patellar tendon graft

We investigated radiographic changes in tibial tunnel area after ACL reconstructions with autogenous patellar tendon grafts on anteroposterior and lateral radiographs over 3 years. Fifty patients followed up for at least 1 year were included in the study. Radiographs were taken on the day of surgery and 3, 6, 9, 12, 24, and 36 months postoperatively. Tibial tunnels on both radiographs were divided into proximal, middle, and distal one-third. The area of each one-third and the greatest diameter of the tibial tunnel on both radiographs was measured using an image-processing software. According to the tunnel area changes, the shape of tibial tunnel was classified into one of four shapes; cylinder, mallet, reverse bottle, and reverse triangle. The correlations between area, diameter and shape of the tunnel, and clinical variables including arthrometer measurement and clinical score were determined. The areas of each one-third of the tibial tunnels on lateral radiographs was always greater than that on anteroposterior radiographs, although the diameters on the two radiographs did not differ significantly. The area of proximal one-third largest and that of distal one-third smallest on both radiographs at any time point. The enlargement and reduction occurred within 3 months and tended to continue for 9 months. Thereafter the tunnel change stabilized on both radiographs. The most common shape of the enlarged tunnels was cylindrical on anteroposterior radiographs reverse triangle on lateral radiographs. No negative effects of enlarged area, diameter, or tunnel shape on clinical results were found in our study.