Bone morphology and morphometry of the lateral femoral condyle is a risk factor for ACL injury.

PURPOSE: The purpose of this study was to investigate the influence of the knee lateral compartment bony morphology and morphometry on risk of sustaining an anterior cruciate ligament (ACL) injury.
METHODS: A total of 400 age and sex-matched patients (200 ACL-ruptured and 200 ACL-intact) were included. The lateral femoral and tibial bone morphology and morphometric parameters were measured on knee lateral radiographs, taken at 30° of knee flexion with overlapping of the femoral condyles. Radiographic measurements included: anteroposterior-flattened surface of the femur's lateral condyle (XY); femur's diaphysis anteroposterior distance (A); anteroposterior distance of the femur's lateral condyle (B); height of the femur's lateral condyle (C); anteroposterior distance of the tibial plateaus (AB); tibial slope. In addition, three morphological ratios were calculated: B/AB; B/XY; XY/AB (Porto ratio).
RESULTS: Most of bone morphological parameters were different between genders (P < 0.05). ACL-ruptured female subjects showed statistical significant smaller condyle heights (C), smaller distances of the flattened surface of the distal femoral condyle (XY), smaller tibial plateau anteroposterior distances (AB), and higher XY/AB ratio (P < 0.05). ACL-ruptured male subjects had statistical significant smaller condyle height (C), anteroposterior distance of the femur's lateral condyle (B), tibial plateau anteroposterior distances (AB), and tibial slope (P < 0.05). Multivariate logistic regression model showed that five morphological parameters (A, XW, XY, XZ, and AB) were significantly associated with ACL rupture (AUC = 0.967, P < 0.001). Calculated ratios (XY/AB; B/AB; B/XY) showed a significant accuracy in identifying individuals with ACL injury (P < 0.001).
CONCLUSIONS: The most important finding of this study was that the calculated ratios (XY/AB; B/AB; B/XY) showed a significant accuracy in identifying the individuals with and without an ACL injury. Within this line, a longer flat surface of the lateral femoral condyle or higher Porto ratio (XY/AB) is associated with a lower the risk of ACL injury. Moreover, when considering the combination of five primary bone morphology and morphometric parameters (A, XW, XY, XZ, and AB), the accuracy in identifying these individuals was excellent (AUC = 0.967). These findings may contribute to injury risk assessment, sports participation, and injury prevention counseling and surgical planning refining by identifying high-risk patients who would benefit from the addition of associated procedures to the anatomic ACL reconstruction aiming the improvement of knee stability and decrease the risk of further injuries. LEVEL OF EVIDENCE: III, case-control study.