Summary

Tibio-femoral bone morphology seems to play a role in ACL rupture and its measurements allows to identify individuals at high risk of sustaining an injury.

Abstract

Background

Tibiofemoral bone morphology has been proposed as a potential risk factor for anterior cruciate ligament (ACL) rupture, with recent increasing interest in the lateral femoral condyle. This work aims to investigate several tibiofemoral bone morphology measurements on lateral radiographs as potential risk factors for rupturing the ACL.

Methods

Retrospective case–control study, including 400 sex-matched patients (mean 24 years old), 200 subjects with an ACL rupture and 200 subjects without history of previous knee injuries. Lateral radiographs of each subject knee were taken at 30° of knee flexion with overlapping of the femoral condyles. Radiographic measurements of the distal epiphysis/diaphysis of the femur and proximal epiphysis of the tibia were performed, including: 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: XY/AB; B/AB; B/XY.
To assess the differences between control and ACL-ruptured subjects, and between genders, it was performed an unpaired t-student test with two tailed hypothesis. After univariate analysis, the stepwise binary logistic multivariate regression model (Wald backward stepwise method, P=0.05 for covariate inclusion and 0.2 for exclusion) has been performed to identify independent factors associated with ACL outcome. The models validity has been evaluated through the determination coefficients of Cox and Snell, NagelKerke, and the Hosmer and Lemeshow test. Furthermore, it has been assessed using the area under the receiver operating characteristic (ROC) curve (AUC).

Results

All the bone morphological parameters were different between genders (P<0.05), with the exception of tibial slope and AB distance (for both conditions), and XY and XY/AB for the ACL-ruptured subjects. When compared to normal subjects, the ACL-ruptured female subjects showed statistical significant smaller condyle heights, smaller XY and AB distances, and higher XY/AB ratio (P<0.05). The ACL-ruptured male subjects had statistical significant smaller height and AP distance of the femur’s lateral condyle, AB distance and tibial slope (P<0.05).
Logistic regression model showed that 5 bone morphological parameters were significantly associated with ACL rupture (AUC=0.967, P<0.001). The calculated ratios (XY/AB; B/AB; B/XY) showed significant accuracy in identifying individuals with higher risk of sustaining an ACL injury (P<0.001).

Conclusions

Several tibiofemoral bone morphology radiographic measurements are associated with an ACL rupture. Morphological ratios based on these measurements seem to identify individuals at higher risk of sustaining an ACL rupture. These findings might contribute to health counselling on level of sports participation. Moreover, it may help to identify individuals who may benefit the most from secondary prevention programs, where the risk of new injury is highly probable.