Objective:To explore the accuracy and clinical effect of computer navigation system in locating the tunnel position in anterior cruciate ligament (ACL) reconstruction.Methods:A retrospective case-control study was conducted to analyze clinical data of 60 patients with ACL rupture treated in Daping Hospital of Army Military Medical University from March 2017 to March 2018, including 44 males and 16 females, aged 15-48 years (mean, 26.3 years). Computer navigation system was used to locate the internal orifice of intra-articular femoral and tibial tunnel in 30 patients (navigation group), and artificial location of intra-articular femoral and tibial tunnel in 30 patients (control group). The operation time and complications of two groups were recorded after operation. The tunnel position was evaluated by CT three-dimensional reconstruction, and the ratio of the tunnel position on the lateral surface of the femoral condyle to the tibial platform was evaluated by the grid method. The proportion sites from the deep posterior edge of lateral intercondylar surface of the femur to the shallow anterior edge (DS) and from the upper edge to the lower edge (HL) were used to represent the position of the femoral tunnel, and the proportion sites of the line connecting the anterior and posterior edge of the tibial plateau were used to represent the tibial tunnel position. The postoperative tunnel position was compared between the two groups. The knee joint stability (Lachman test, pivot shift test) and knee joint function score (Lysholm score, Tegner score) were compared between the two groups before operation and 12 months after operation.Results:All patients were followed up for 12-24 months (mean, 15 months). The operation time was (56.1±8.1)minutes in control group versus (76.0±6.7)minutes in navigation group ( P<0.05). In navigation group, 2 patients had skin edge necrosis at the place where the navigation needle was installed. The proportion of DS in femoral tunnel was (27.2±3.7)% in navigation group versus (33.9±4.4)% in control group ( P<0.05). HL proportion site was (36.6±4.8)% in navigation group versus (38.9±4.9)% in control group ( P<0.05). Proportion of the tibial tunnel at the anterior and posterior edge of the tibial plateau was (44.9±1.8)% in navigation group and (44.7±3.0)% in control group ( P>0.05). Both groups showed significant improvements in Lysholm score, Tegner score, Lachman test and pivot shift test 12 months after operation compared to the preoperative levels ( P<0.05), but the knee joint function score and knee joint stability score had no significant difference between the two groups 12 months after operation ( P>0.05). Conclusions:No significant differences are found between computer navigated and manually navigated ACL reconstruction with regards to knee joint stability, knee joint function, and tibial tunnel localization. However, computer assisted navigation enables the location of the lateral femoral tunnel closer to the anatomical position.