Validation of a simplified modeling approach to predict strain in the cartilage and labrum of the hip with application to femoroacetabular impingement syndrome.

Subject-specific finite element (FE) modeling enables detailed evaluation of cartilage and labral contact mechanics in the hip; however, the computational demands of this approach limit its use in large cohorts. Soft tissue overlap (STO) modeling is a simplified alternative that estimates strain from geometric overlap between articulating surfaces; however, its predictive accuracy remains unclear. The objective of this study was to evaluate the accuracy of STO models for predicting acetabular cartilage and labral strains during simulated walking by direct comparison with subject-specific FE models. Eight individuals with radiographically normal hips and eight patients with cam-type femoroacetabular impingement syndrome were evaluated using subject-specific anatomy, kinematics, and joint reaction forces. STO-predicted strains were compared with FE-predicted compressive strains using correspondence-based Network Analysis and Bland-Altman analyses at heel-strike and heel-off. No group-dependent differences in agreement were observed, so the results for the two cohorts were pooled. STO models captured the general spatial patterns and locations of peak strain in both cartilage and labrum. However, significant differences between STO and FE predictions were present across 1% to 75% of the gait cycle, particularly during higher magnitudes of joint loading. STO systematically underpredicted strain at higher magnitudes, with disagreement increasing as strain magnitude increased. Discrepancies were most pronounced in the anterosuperior cartilage and labrum near heel-off, where FE models predicted higher, more localized strains. These findings indicate that while STO modeling provides qualitative insight into strain patterns and contact locations, its ability to quantify strain magnitude, particularly under higher loading conditions and in the labrum, is limited.