Association of Thigh Thickness and Femoral Notch Width with Anterior Cruciate Ligament Attachment Size and Tear Risk

Background/Objectives: An accurate understanding of anterior cruciate ligament (ACL) morphology is essential for individualized surgical planning in ACL reconstruction. Morphometric parameters of the knee, including the femoral notch width and surrounding soft tissue characteristics, may influence native ACL dimensions and potentially assist in preoperative graft sizing. Methods: This retrospective case-control study analyzed medical records, radiographs, and knee magnetic resonance imaging (MRI) performed at a tertiary academic medical center. Variables collected included femoral notch width, thigh thickness, and ACL attachment dimensions at the femoral and tibial insertions. Comparisons between patients with ACL tears and those with intact ACLs were also performed. Correlation analyses were performed to evaluate associations between morphometric parameters and ACL attachment size. Multivariable linear regression models were constructed to identify independent predictors after adjusting for age, sex, body mass index (BMI), limb side (left or right leg), and ACL status. Results: A total of 600 participants were included. The mean femoral notch width was 21.55 ± 6.15 mm, and the mean thigh thickness was 53.05 ± 11.66 mm. The mean ACL femoral and tibial attachment sizes were 8.12 ± 2.57 mm and 11.79 ± 3.89 mm, respectively. Thigh thickness demonstrated weak but significant positive correlations with both ACL femoral (r = 0.168, p = 0.001) and tibial attachment sizes (r = 0.236, p < 0.001). Femoral notch width showed a borderline association with ACL femoral attachment size (r = 0.092, p = 0.068) and a weak but significant correlation with ACL tibial attachment size (r = 0.095, p = 0.039). ACL tear group exhibited smaller thigh thickness measurements compared with controls (49.80 ± 12.00 mm vs. 55.65 ± 14.80 mm, p < 0.001) and smaller femoral notch width measurements compared with controls (21.20 ± 3.40 mm vs. 22.50 ± 3.18 mm, p = 0.001). Moreover, further analysis demonstrated that ACL tear status was associated with smaller measured ACL attachment sizes (p < 0.001). Conclusions: Thigh thickness and femoral notch width demonstrate measurable association with ACL attachment dimensions and differ between patients with ACL tears and those with intact ligaments. These findings indicate that both osseous and soft-tissue morphometric characteristics may influence ACL morphology and susceptibility to injury. Comprehensive preoperative imaging assessment of these anatomical parameters may help to optimize individualized surgical planning in ACL reconstruction.