A biomechanical digital twin of Legg-Calvé-Perthes disease deformity

The dynamic stress environment in the hip joint is thought to contribute to pain and osteoarthritis (OA) in people with Legg-Calvé-Perthes disease (LCPD) deformity, but is poorly understood, limiting clinical management options. The objective of this study was to develop and evaluate a patient-specific biomechanical "digital twin" model of LCPD to predict chondrolabral shear stress in dynamic and static loading scenarios.

We produced a digital twin model of both hips in a patient with unilateral LCPD deformity using anatomical magnetic resonance imaging (MRI) and the ArtiSynth modeling platform. We evaluated the model's sensitivity to changes in material properties and joint angles during a typical gait cycle, and verified its stress and femoral translation predictions against upright open MRI of the hip in high-flexion postures.

The model's prediction of the highest chondrolabral shear stress during a gait cycle was 22-93% greater in the LCPD hip than in the unaffected hip. The model was sensitive to changes in material parameters and joint angles, but could accurately reproduce femoral translation and expected stress distribution in extreme static postures.

This study demonstrates the importance of both dynamic motion and morphology in the stress environment of highly aspherical hip joints. Although some challenges remain, digital twin models are a promising tool to study the long-term outcomes of LCPD, and could be applied in future to aid clinical management.