Prospective comparisons of femoral tunnel enlargement with 3 different postoperative immobilization periods after double-bundle anterior cruciate ligament reconstruction with hamstring grafts

Abstract

Purpose: To determine the effect of differing postoperative immobilization periods on femoral bone tunnel enlargement and clinical outcome after double-bundle anterior cruciate ligament (ACL) reconstruction with hamstring grafts.

Methods: Fifty-one patients undergoing primary double-bundle ACL reconstruction with hamstring grafts were divided into 3 postoperative immobilization protocol groups: 2-day immobilization with the knee in 20° of flexion postoperatively (group A, n = 18); 1-week immobilization (group B, n = 17); and 2-week immobilization (group C, n = 16). Bone tunnel enlargement was determined by computed digital radiographs taken on the first postoperative day and at 24 months in the anteroposterior (AP) and lateral views. Each tunnel diameter was shown as a percentage of the maximum joint width of the proximal tibia on the AP view or a percentage of the maximum diameter of the patella on the lateral view. To determine the incidence of tunnel enlargement, a percentage diameter change of more than 10% was defined as an enlarged tunnel. The standard clinical evaluation was also performed. This study used nonrandomized procedures.

Results: In each group there were no significant differences in the incidence and magnitude of anteromedial and posterolateral bone tunnel enlargement on both the AP and lateral views (1-factor analysis of variance). Group C showed significantly less muscle strength in knee extension compared with the contralateral knee (85.3% ± 18.4%) than group A (93.7% ± 13.1%, P = .049) and group B (96.8% ± 12.9%, P = .044).

Conclusions: This prospective radiographic study showed that femoral bone tunnel enlargement, in both the anteromedial and posterolateral tunnels, may occur after double-bundle ACL reconstruction with hamstring grafts despite different postoperative immobilization periods, with no significant difference in the incidence and magnitude among groups with differing postoperative immobilization periods. In addition, a 2-week immobilization period after surgery showed harmful effects, such as significantly less quadriceps muscle strength.

Level of evidence: Level II, prospective comparative study.