Differences in the Placement of the Tibial Tunnel During Reconstruction of the Anterior Cruciate Ligament With and Without Computer-Assisted Navigation

Background: Next to graft fixation, correct positioning of the tibial and femoral tunnel is a deciding factor for the clinical result of anterior cruciate ligament reconstruction surgery. Computer-assisted navigation has been proposed as a method to improve tunnel positioning. Purpose: To examine the differences in tibial tunnel placement between cruciate ligament operations using manual and computer-assisted navigation. Study Design: Randomized controlled trial; Level of evidence, 1. Methods: Between December 2003 and April 2004, 53 athletes underwent anterior cruciate ligament reconstruction surgery with arthroscopic press-fit technique. The first group (group N; 24 athletes) were operated on with the aid of a navigation system (OrthoPilot, Aesculap AG & Co. KG, Braun), and the second group (group M; 29 athletes) were “manually” operated on. A lateral radiograph of the knee at maximum extension was used to determine the exact position of the tibial tunnel four days postoperatively. In the measurements, the anterior and posterior boundaries of the tibial tunnel, as well as the center of the tibial tunnel in relation to the maximum tibia anteroposterior diameter were evaluated (indicated in percent). An analysis of the tibial tunnel position proportional to the slope of the intercondylar roof was done to determine intercondylar impingement (method according to Howell). The centers of the tibial tunnels were compared with the “optimal” position noted in previous studies. The standard deviation was determined for both groups to determine the variance of placement. Results: The anterior tibial tunnel border was 19.4 mm in group M (29.7%) and 21.2 mm in group N (32.2%) ( P = .18). The center of the tibial tunnel was located at 24.6 mm in group M (35.6%) and at 26.6 mm in group N (40.3%) ( P = .19). In group M, the posterior tibial tunnel position was located at 30.2 mm (46.2%), and in group N at 32.2 mm (49.1%) ( P = .21). When comparing the centers of the tibial tunnels with the optimal 44% found in previous studies, the value for group M (37.6%) varied significantly, while group N (40.5%) did not. However, there was no significant difference in the range variance for either group; the standard deviation was 6.9% (4.3 mm) for group M and 5.9% (3.5 mm) for group N. One athlete showed moderate impingement in group N, and two athletes in group M. Conclusion: Assisted navigation offers good support for correct placement of the tibial tunnel, although expe