Graft-Tunnel Mismatch in Endoscopic ACL Reconstruction: Reliability of Measuring Tunnel Lengths and Intra-articular Distance

BACKGROUND: A continued technical challenge for surgeons performing bone–patellar tendon–bone anterior cruciate ligament (ACL) reconstruction with endoscopic techniques is graft-tunnel mismatch. If tibial tunnel and intra-articular distances could be reliably estimated, surgeons could adjust the length of the femoral tunnel to minimize graft-tunnel mismatch. PURPOSE/HYPOTHESIS: To determine whether arthroscopic measurement of the following was reliable: femoral tunnel distance (FTD), tibial tunnel distance (TTD), intra-articular distance (IAD), and total distance (TD; sum of these 3 measurements). It was hypothesized that intraoperative measurement of these distances would be reliable. STUDY DESIGN: Controlled laboratory study. METHODS: Eight sports fellowship–trained orthopedic surgeons independently performed arthroscopic measurements of the FTD, TTD, IAD, and TD in 7 cadaveric knees in which femoral and tibial tunnels had been drilled. Each surgeon performed the measurements twice using an EndoButton depth gauge. Following this, each parameter was measured open with a medial parapatellar approach. Finally, a computed tomography (CT) scan of each knee was performed, with the FTD, TTD, and IAD measured by a musculoskeletal radiologist. Inter- and intrarater reliability of the arthroscopic measurements was calculated, as well as the correlation between arthroscopic measurements and open and CT measurements. RESULTS: Interrater reliability for the arthroscopic measurements was 0.8 for FTD, 0.89 for TTD, 0.61 for IAD, and 0.76 (range, 0.54-0.93) for TD. Intrarater reliability was 0.94 for FTD, 0.97 for TTD, 0.83 for IAD, and 0.93 for TD. The correlation between arthroscopic and open measurements was 0.9 for FTD, 0.94 for TTD, 0.4 for IAD, and 0.84 for TD. The correlation between arthroscopic and CT measurements was 0.85 for FTD, 0.92 for TTD, and 0.71 for IAD. CONCLUSION: The results of this study show that arthroscopic measurement of FTD and TTD has a high degree of intra- and interrater reliability, while that of IAD and TD demonstrates high intrarater reliability but moderate interrater reliability. CLINICAL RELEVANCE: Reliable measurement of the TTD and IAD can potentially allow adjustment of the FTD, minimizing graft-tunnel mismatch in endoscopic ACL reconstruction.