Arthroscopic Viewing Position Affects Anterior Cruciate Ligament Reconstruction Femoral Tunnel Length Measurements

Purpose To purpose of this study was to compare arthroscopic anterior cruciate ligament (ACL) reconstruction femoral tunnel length measurements from the anterolateral portal between the standard notch view using a 30° arthroscope versus a "top-down" view utilizing a 70° arthroscope to visual the far side of the femoral tunnel aperture. Methods Arthroscopic femoral tunnel length measurements using calibrated reamers from the standard notch versus the "top-down" view were obtained and reviewed in 54 skeletally mature patients undergoing ACL reconstruction with no prior bony knee surgery. Patient age, height, weight, sex, and surgery laterality were also recorded. Measurements of femoral tunnel length were repeated using both views for inter-observer and intra-observer correlation. Results Inter-observer and intra-observer intra-class correlation coefficients for the standard notch view and "top-down" views were excellent, with higher reliability values appreciated using the "top down" view. Mean overall femoral tunnel length measurements obtained using the standard notch view were significantly longer than measurements from the "top-down" view (p < 0.001). Conclusions The standard notch view provides significantly longer femoral tunnel length measurements in comparison to the "top-down" view.