Anterior cruciate ligament repairs are performed over 100,000 times annually in the US. A common surgical method is a bone‐patellar tendon‐bone graft, which requires the placement of a tibial tunnel through the proximal tibia. Mismatches between the length of the tibial tunnel and the length of the graft have been reported to occur 26% of the time or more, and require procedural modifications during surgery. Most methods for placing the tibial tunnel rely on consideration of patient height and/or angle of placement. Little is known about the variables that affect mismatches. Better understanding how the shape of the proximal tibia impacts the length of the tibial tunnel will allow for improved surgical technique and could lower the number of mismatches, and perhaps even graft failures. We examined 33 right proximal tibiae from donor cadavers (15 females, 18 males) via three‐dimensional scans that allowed us to take 6 linear measurements to describe the dimensions of the proximal tibia. We also used the directions for a popular tibial tunnel guide to simulate a tibial tunnel length on all individuals. Our analysis found the length of the tibial tunnel is influenced by multiple shape components that vary by sex. Specifically, male tibial measurements were always significantly larger than female measurements (p<0.05), there were a greater number of significant correlations among measurements in the male tibia than the female tibia, and the length of the tibial tunnel is more closely correlated to anterior‐posterior measurements in females in contrast to males, where it is more closely correlated to mediolateral measurements. These findings suggest there are sex‐based differences in the shape of the proximal tibia that may confound tibial tunnel placement. The development of surgical techniques should incorporate knowledge of shape‐based variables, and future research should continue to explore sex‐specific foundations of variable outcomes in clinical treatments.Support or Funding InformationThis project was funded by the Basic Sciences Department, College of Osteopathic Medicine, Touro University NevadaThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.