Maximal facet tropism of 10.8° as a quantitative cutoff for predicting lumbar disk herniation in young elite athletes: a retrospective case-control study in Japan

Study Design: Retrospective case-control study. Purpose: To determine whether maximal facet tropism (FT) is an independent risk factor for lumbar disk herniation (LDH) in young athletes and establish a data-driven, quantitative cutoff value. Overview of Literature: The role of FT in LDH remains debated because previous studies have focused on level-specific prevalence without defining a clinically significant threshold for maximal asymmetry, particularly in athletes. Methods: Axial magnetic resonance images from L3 to S1 in 43 athletes were compared with LDH and 11 symptomatic nonherniated athletes. The primary variable was maximal FT, the single greatest asymmetry across the measured levels. Risk was assessed using multivariable logistic regression, and a cutoff was determined by receiver-operating characteristic (ROC) curve analysis. Results: The LDH group exhibited significantly greater maximal FT (11.8°±5.9° vs. 7.6°±3.0°, p=0.028) and was confirmed to be an independent predictor of LDH (with odds ratio of 1.23 per increment of 1°; p=0.041). ROC curve analysis identified an optimal 10.8° cutoff (area under the ROC curve, 0.727), yielding 55.8% sensitivity and 90.9% specificity. Although severe FT (>10°) was most prevalent at L5/S1 in the LDH group (p=0.024), maximal FT values were not significantly different between the L4/5 and L5/S1 groups (p=0.353) in an analysis stratified by herniation level. Conclusions: Maximal FT is an independent risk factor for LDH in young athletes. The magnitude of maximal asymmetry in the lower lumbar spine, rather than its specific spinal level, appears to be the primary contributor to this risk, and an angle >10.8° serves as a preliminary threshold for identifying high-risk athletes.