The Tibial Tunnel Size Relative to the Proximal Tibia Affects the Tibial Tunnel Widening in Anatomical Anterior Cruciate Ligament Reconstruction

The impact of the bone tunnel size relative to body size on clinical results in anterior cruciate ligament (ACL) reconstruction remains unclear. This study aimed to assess the morphological alteration of the tibial tunnel aperture and relationship between the tibial tunnel size relative to the proximal tibia among the tibial tunnel widening (TW) and clinical results following ACL reconstruction. This study comprised 131 patients who had undergone anatomical ACL reconstruction utilizing bone-patellar tendon-bone autografts. The morphology and enlargement of the tibial tunnel were examined via three-dimensional computed tomography 1 week and 1 year postoperatively. The anteroposterior (AP) and mediolateral (ML) positions were determined as a percentage relative to the proximal AP and ML tibial dimensions, respectively. Clinical assessment was conducted 2 years postoperatively. The association between the primary tibial tunnel size among TW and clinical outcomes was examined. The tibial tunnel significantly migrated posterolaterally. The ML diameter significantly widened; however, the AP diameter did not exhibit widening. AP widening was associated with the AP diameter of the primary tibial tunnel (<i>r</i> = -0.482, <i>p</i> < 0.01), and ML widening correlated with the ML diameter of that tunnel (<i>r</i> = -0.478, <i>p</i> < 0.01). However, there was no significant correlation observed between the primary tibial tunnel size and clinical outcomes. The tibial tunnel migrated and enlarged laterally in the ML plane, but did not enlarge in the AP plane. The primary tibial tunnel diameter relative to the proximal tibia negatively correlated with the tibial TW in the AP and ML planes. Level of evidence: level IV.