Femoral Tunnel Length: Accessory Anteromedial Portal Drilling Versus Transtibial Drilling

Purpose: To determine whether drilling using an anteromedial portal technique during single-bundle anterior cruciate ligament (ACL) reconstruction risks creating femoral tunnels less than 25 mm long in the clinical setting. Methods: Intraoperative measurements of femoral tunnel length in a group of 35 consecutive patients undergoing single-bundle primary ACL reconstruction with transtibial (TT) femoral drilling were compared with a subsequent group of 80 consecutive patients undergoing the same procedure with accessory anteromedial portal (AAMP) femoral drilling. The length of femoral tunnels created through the AAMP in male patients was compared with that in female patients, and the expected likelihood of obtaining tunnels shorter than 25 mm was determined for either gender. Results: The mean femoral tunnel length in the AAMP group was significantly shorter than that in the TT group (35.6 mm and 40.7 mm, respectively; P < .0001). In male patients in the AAMP group, the femoral tunnel length was significantly greater on average than that in female patients in the same group (36.8 mm and 33.5 mm, respectively; P = .0001). The shortest measured femoral tunnel was 28 mm long. The statistical likelihood of femoral tunnels created by AAMP drilling being less than 25 mm in length was 0.47% for female patients and 0.1% for male patients. Conclusions: Although femoral tunnel length with AAMP drilling is, on average, approximately 5 mm (12.5%) shorter than with TT drilling, the likelihood of the tunnel being too short to allow for suspensory fixation with adequate graft placed within the femoral tunnel is very low. Female patients undergoing single-bundle ACL reconstruction with AAMP drilling have a femoral tunnel length that is approximately 3 mm (9%) shorter than that in male patients on average, but the expected likelihood of obtaining a tunnel shorter than 25 mm in female patients is still less than 1:200, compared with 1:1,000 for male patients. Level of Evidence: Level III, retrospective comparative study.