Anterior versus Posterior Tibial Tunnel Placement in ACL Reconstruction

OBJECTIVES: Previously, we reported that the use of the posterior border of the anterior horn of the lateral meniscus as a landmark for tibial tunnel placement during anatomic ACL reconstruction resulted in a wide variation of tunnel location in the sagittal plane. The effects of such tibial tunnel variations on functional outcomes have not been previously reported. HYPOTHESIS: Anteriorly placed tibial tunnels lead to better anterior knee stability than posteriorly placed tunnels. STUDY DESIGN: Cohort study, Level of evidence 3. METHODS: 71 patients (aged 18-55) underwent isolated unilateral anatomic single bundle primary ACL reconstruction with quadrupled hamstring tendons or bone patellar tendon bone autografts between March 2013 and June 2014 by the same surgeon using an accessory medial portal technique. All guide pins for the tibial tunnel were placed using a 55-degree guide using the posterior border of the anterior horn of the lateral meniscus as a landmark. Following pin placement, a true lateral fluoroscopic image was obtained and these were digitally analyzed to measure the location of the pin along the length of the tibial plateau using the method described by Amis and Jakob. The patients were divided into two groups—one anterior and the other posterior to 40% of the tibial plateau length. Side-to-side difference in anterior knee translation (KT-1000), thigh circumference, range of motion, IKDC and Marx activity scale were evaluated and compared between the groups at a minimum of 2 years following ACL reconstructive surgery. RESULTS: 50 patients (26 in the anterior group and 24 in the posterior group) were avaliable for follow-up at a mean of 2.5 years. There was no difference in the terms of age, sex, BMI, loss of extension, graft type (Hams-BPTB) and size (mm) between the groups (p>.05). In terms of stability, the mean side-to-side difference was 0.19±1.3 mm for anterior group and 1.27 ±1.3 mm for posterior group based on KT-1000 measurements (P<.005). The IKDC (75.1±4.1 vs 79.2±2.8) and Marx activity (6.6±1.05 vs 8.3±1.04) scores were similar in both groups. No difference in thigh circumference was found between the involved and uninvolved extremities of the both groups (-1.48±1.41 vs -1.52±1.17). CONCLUSION: Using the posterior border of the anterior horn of the lateral meniscus as a landmark yields a wide range of tibial tunnel locations along the tibial plateau. Anterior placement of the tibial tunnel leads to better anterior knee stability than posterior placement does.