Radiographic evaluation of the tunnel position in single and double bundle anterior cruciate ligament reconstruction

Aim To evaluate tunnel positioning on radiographs in singlebundle (SB) and double-bundle (DB) anterior cruciate ligament (ACL) reconstruction, to evaluate if measurement is accurate and reproducible. Methods Radiographs of 30 SB and 30 DB ACL reconstruction were reviewed by two examiners who measured tunnel positioning with the quadrant method on the femur (a=depth, b=height) and the Amis and Jakob method on the tibia. Intra- and inter-observer reliability were evaluated with intra-class correlation coefficient (ICC). Results A radiographic analysis was completed in all patients in a SB-group and in 27 in a DB-group (p>0.05). Intra-observer reliability was almost perfect on femoral (ICC: a=0.85, b=0.83) and tibial (ICC=0.87) side in the SB-group. In the DB-group, it was almost perfect for tibial anteromedial (AM) and posterolateral (PL) bundles (ICC: AM=0.84, PL=0.81) and for femoral PL bundle (ICC: a=0.83, b=0.82), and substantial for femoral AM bundle (ICC: a=0.78, b=0.74). Inter-observer reliability was almost perfect on tibial (ICC=0.81) and femoral (ICC: a=0.81, b=0.87) side in the SB-group, and substantial on tibial (ICC: AM=0.71, PL=0.77) and femoral (ICC: AM a=0.73, b=0.78; PL a=0.74, b=0.76) side in the DB-group. Standard deviation (SD) was low (±9%) with respect to the centre of tunnel(s). Conclusion The quadrant method and the Amis and Jakob method are accurate and reproducible measurement methods. Also, as SD was low, an outside-in approach with a front-entry guide, which is free-hand positioned, can be postulated as a reliable method to locate the femoral tunnel in SB reconstruction and the AM bundle in DB reconstruction.