Variation in the length of the tibial tunnel in anterior cruciate ligament reconstruction: is it safe to use a 35-mm screw?

Tibial fixation is the key to success in anterior cruciate ligament (ACL) surgery using the hamstring tendon technique. Interference screws are popular intratunnel fixation devices not exceeding 35 mm in length. A mismatch between the lengths of the tibial tunnel and the interference screw can cause protrusion of the screw inside the knee or outside the anterior tibia, with a poor postoperative outcome. Our objective was to evaluate the safety length that exists with the use of a 35-mm screw in the tibial tunnel. For this purpose, 27 patients with ACL reconstruction were included. All measurements were performed directly during surgery. The lengths were recorded along with the patients' data. Our study group included 16 male and 11 female patients with an average age of 30.9 years. The average tibial tunnel length was 43.4 mm (range, 40 to 48 mm). This means that for a tibial tunnel drilled at a 55 degrees angle, its length will be at least 5 mm longer than the 35-mm screw. In the same way, the distance between the graft fixation and the articular surface will not exceed 13 mm if the screw is completely inside the tunnel.