The correlation between common 2D femoral notch parameters and 3D notch volume: a retrospective MRI study

BACKGROUND: Although the stenotic femoral intercondylar notch was associated with anterior cruciate ligament (ACL) injuries, the parameters for notch assessment were numerous. The present study aimed to compare the 2-dimensional (2D) femoral notch parameters, including the notch width (NW) and notch width index (NWI), with the 3-dimensional (3D) notch volume based on magnetic resonance imaging (MRI), to determine appropriate femoral parameters for ACL injuries. METHODS: Two hundred forty individuals were included in this study, including 120 patients with ACL ruptures and 120 age- and gender-matched individuals without ACL ruptures. The NWs and NWIs were measured at four sites (the popliteal groove, the notch inlet and outlet, and the ACL attachment), and the notch volumes were calculated. The Pearson correlation coefficients between the 2D and 3D parameters were calculated. A multivariate analysis of the ACL injuries was conducted with these parameters and the demographic data. RESULTS: The associations of the NW and NWI with the notch volume at each of the four locations of the femoral notch were poor in the subgroup analysis, with the exception of the NW in the male ACL-intact group (R = 0.307, 0.256, 0.404 and 0.387 at the popliteal groove, notch inlet and outlet, and ACL attachment, respectively). The multivariate analysis revealed that the notch volume (OR = 0.679, P < 0.001) and the NW at the popliteal groove (OR = 0.844, P = 0.004), notch inlet (OR = 0.720, P < 0.001) and ACL attachment (OR = 0.871, P = 0.028) were predictable parameters to the risk of ACL injuries. CONCLUSIONS: The correlations between the 2D parameters and the 3D volumes were weak. The notch volume and the NW at the popliteal groove, notch inlet and ACL attachment were useful parameters for predicting the risk of ACL injuries. LEVEL OF EVIDENCE: Level III, case-control study.