Optimizing Femoral Tunnel Placement in ACL Reconstruction: Effect of a 70-degree Arthroscope and Portal Position

Abstract

The aim of this study was to assess the accuracy of femoral tunnel placement for anterior cruciate ligament reconstruction (ACLR) using either an accessory medial portal or a 70-degree arthroscope compared with the standard 2-portal technique. A computerized 3D model of the femur was obtained with 4 reference points marked around the LFC. Using the simulator, 2 surgeons marked 5 consecutive femoral tunnel points with a 30-degree arthroscope in the lateral portal (30AL), then with a 30-degree arthroscope in an accessory medial portal (30AM), and next with a 70-degree arthroscope in the lateral portal (70AL). This was repeated after one week. Subjects then marked their target femoral tunnel positions (T) on the free femur sawbone model. After each episode, the distances from the marked tunnel point to the 4 reference points (d1, d2, d3, d4) were measured. After mapping to the 3D femur model, the co-ordinates of each marked tunnel position were determined. The distance (r) from T was calculated for each episode. The median value of r was 1.27 mm(SE 0.15 mm) using 30AL, 0.54 mm (SE 0.12 mm) using the 30AM portal, and 0.20 mm (SE 0.047 mm) with 70AL. r was significantly smaller with 70AL (P<0.0001). The difference in r between 30AM and 30AL was also statistically significant (P=0.019). A 70-degree arthroscope in the lateral portal allows greater accuracy in femoral tunnel placement compared with a 30-degree arthroscope in either the lateral or an accessory medial portal.