Anatomical rectangular tunnel (ART) anterior cruciate ligament (ACL) reconstruction using bone-patellar tendon-bone (BPTB) autografts can place the tunnel aperture within the ACL footprint and is expected to achieve good clinical outcomes. However, the morphological change of the tibial tunnel after ART ACL reconstruction using BPTB autografts is unclear. This study aimed to investigate this morphological change, and to evaluate the correlation between tunnel size relative to the proximal tibia and tunnel enlargement.
This study included 156 patients (102 female and 54 male; mean age, 29.0 ± 11.6 years) who underwent ART ACL reconstruction using BPTB grafts. The femoral and tibial tunnel apertures were rectangular (6 × 10 mm) in all cases. Using three-dimensional computed tomography 1 week and 1 year postoperatively, four edge points of the tibial tunnel were evaluated. These points were the most anterior, most posterior, most medial, and most lateral points in the tibial tunnel. For each point, the anteroposterior (AP) position was calculated as a percentage relative to the proximal AP tibial dimension, and the mediolateral (ML) position was calculated as a percentage relative to the proximal ML tibial dimension. Each point was measured 1 week postoperatively (baseline) and 1 year postoperatively, and the findings were compared. For the tibial tunnel, the AP diameter was the distance between the AP positions of the most anterior and posterior points of the tunnel, and the ML diameter was the distance between the ML positions of the most medial and lateral points of the tunnel. The relationship between tibial tunnel diameter and tunnel enlargement was evaluated.
The AP diameter of the tibial tunnel was 20.9% relative to the AP diameter of the tibia at 1 week postoperatively and 20.5% at 1 year postoperatively (p > 0.05). The ML diameter of the tibial tunnel was 9.8% relative to the ML diameter of the tibia at 1 week postoperatively and showed significant enlargement to 10.2% at 1 year postoperatively (p = 0.01). The most anterior point migrated 3.2% posteriorly and 0.9% laterally, the most posterior point migrated 2.9% posteriorly and 0.8% laterally, the most medial point migrated 3.4% posteriorly and 0.9% laterally, and the most lateral point migrated 2.2% posteriorly and 1.3% laterally. All points significantly migrated posteriorly and laterally at 1 year postoperatively compared with 1 week postoperatively (p < 0.01). AP enlargement (difference in AP migration between the most anterior and posterior points) correlated with the AP diameter of the tibial tunnel 1 week postoperatively (r = -0.536, p < 0.01). ML enlargement (difference in ML migration between the most medial and lateral points) correlated with the ML diameter of the tibial tunnel 1 week postoperatively (r = -0.612, p < 0.01).
In ART ACL reconstruction using BPTB autografts, the tibial tunnel migrated laterally and enlarged in the ML plane, while it migrated posteriorly but did not enlarge in the AP plane. Negative correlations were found between tunnel enlargement and tunnel diameter relative to the tibia in both the AP and ML planes, suggesting that a smaller tibial tunnel size relative to the proximal tibia resulted in tunnel enlargement.