Reliability of measuring femoral tunnel aperture location after anterior cruciate ligament reconstruction: quadrant method versus anatomical coordinate axes method

Background: The purpose was to quantitatively compare the reliability of the quadrant and ACA methods in identifying the position of the femoral tunnel aperture after ACL reconstruction (ACLR) using 3D-CT. Methods: This study included 90 patients (90 knees) who underwent primary single-bundle ACLR. 3D-CT was performed on each knee, and the femoral tunnels were evaluated twice each by two observers using both the quadrant and anatomical coordinate axes (ACA) methods. The data were analyzed statistically to determine the inter and intraobserver reliabilities using an intraclass correlation coefficient [ICC, excellent (>0.9), good (0.75–0.9), moderate (0.5–0.75), poor (<0.5)]. Results: Regarding intraobserver comparisons, the ICCs of quadrant method (1st observer: excellent, 2nd observer: excellent) were better than ACA method (1st observer: good, 2nd observer: good) on Y-axis. Both methods showed good ICCs on X-axis. Regarding interobserver comparisons, the ICCs of the ACA method were better than those of the quadrant method on the X-axis. (1st measurement: moderate, 2nd measurement: good vs. 1st measurement: good, 2nd measurement: good) However, ICCs of quadrant method were better on the Y-axis. (1st measurement: excellent, 2nd measurement: excellent vs. 1st measurement: excellent, 2nd measurement: good). Conclusion: For measuring the femoral tunnel aperture on 3D-CT after ACLR, the quadrant method showed better intraobserver and interobserver reliability on Y-axis, whereas the ACA method showed better interobserver reliability on the X-axis.