Anterior Cruciate Ligament Femoral Tunnel Length: Cadaveric Analysis Comparing Anteromedial Portal Versus Outside-In Technique

PurposeThe purpose was to measure anterior cruciate ligament (ACL) femoral tunnel lengths comparing anteromedial (AM) portal and outside-in techniques.MethodsACL femoral guide pins were drilled into 12 cadaveric knees through the AM portal technique and then the outside-in technique in each specimen. Pin intraosseous distance was measured in millimeters by a MicroScribe 3-dimensional digitizer (Immersion, San Jose, CA).ResultsWith the AM portal technique, the mean ACL femoral tunnel distance was 30.5 mm. With the outside-in technique, the mean ACL femoral tunnel distance was 34.1 mm. The difference was statistically significant (P = .04).ConclusionsOur results show that the outside-in technique for creating the ACL femoral tunnel results in a longer mean tunnel length than the AM portal technique for creating the ACL femoral tunnel. The outside-in technique best prevents excessively short tunnels.Clinical RelevanceOur results have clinical relevance for surgeons who desire to perform independent, rather than transtibial, drilling of the ACL femoral tunnel and desire adequate length of tendon graft within the femoral bone tunnel.