Higher Posterior Tibial Slope and Lower Medial Proximal Tibial Angle of the Knee Are Associated With Delayed Graft Maturation After Anterior Cruciate Ligament Reconstruction Surgery With Hamstring Autograft.

Purpose: To relate bone shape with anterior cruciate ligament (ACL) graft maturation, as evaluated by quantitative magnetic resonance imaging.

Methods: We retrospectively evaluated patients aged 18 to 60 years who underwent ACL reconstruction with a hamstring autograft with doubled semitendinosus and gracilis at our institution between 2018 and 2020 with isolated ACL injuries. All patients had a minimum follow-up period of 2 years. To evaluate alignment, radiographs of the knee were taken preoperatively. Postoperative 3T magnetic resonance imaging and patient-reported outcome scores were acquired at 2 years after surgery. A combined T1ρ/T2 quantification sequence and a 3-dimensional multiecho ultrashort echo time (UTE) cone sequence were obtained in a sagittal-oblique plane for better assessment of the ACL graft. After acquiring images, a manual segmentation for the ACL graft was performed to assess T1ρ, T2, and UTE T2∗ relaxation times. Correlations between radiographic parameters or patient-reported outcome scores and T1ρ, T2, and UTE T2∗ values were tested with Pearson correlation coefficients. Significance was defined as P < .05.

Results: Participants were 28 patients (12 men and 16 women) who had a mean (SD) age of 34.3 (8.5) years and body mass index of 24.4 (4.5). A significant correlation was found between the preoperative posterior tibial slope (PTS) and the T1ρ, T2, and UTE T2∗ relaxation times (r = 0.41, P = .033; r = 0.47, P = .014; and r = 0.41, P = .030), indicating inferior graft maturation in patients with a higher PTS. Furthermore, a negative correlation was identified between the preoperative medial proximal tibial angle and the T1ρ, T2, and UTE T2∗ relaxation times (r = -0.39, P = .039; r = -0.46, P = .018; and r = -0.43, P = .024), indicating inferior graft maturation in patients with greater varus knee alignment.

Conclusions: The study findings suggest that an increased PTS and a lower medial proximal tibial angle are associated with inferior graft maturation as per T1ρ, T2, and UTE T2∗ imaging at 2 years post-ACL reconstruction.

Level Of Evidence: Level IV, retrospective case series.