Impact of Femoral Derotation Osteotomy on Patellofemoral Loading in Patients With Patellofemoral Instability:...

Increased femoral version is linked to patellofemoral instability, increased lateral loading of the patella and might be treated with femoral derotation osteotomy (FDO) in excessive cases. However, the effects of FDO on patellofemoral stability and loading while walking are not fully understood and not measurable in vivo. This study used personalized in-silico musculoskeletal modeling to investigate the impact of FDO on medio-lateral patellofemoral joint loading in individuals with patellofemoral instability. We analyzed retrospective data from 16 participants with recurrent patellofemoral instability and femoral version ≥ 30° using musculoskeletal simulations. We prepared two models per participant based on gait analysis and magnetic resonance data: (i) a model with personalized femoral version and tibial torsion and (ii) a post-surgery model with femoral version adjusted to 12° to simulate the derotation osteotomy. We assessed joint angles, joint moments, muscle moments, muscle forces, and patellofemoral joint contact forces. Simulated FDO significantly altered superior-inferior and anterior-posterior patellofemoral joint contact forces but did not significantly change medio-lateral patellofemoral joint loading at the group level. Six participants (37.5%) demonstrated a reduction in lateralizing patellofemoral joint contact forces, three (18.8%) showed no relevant change, and seven (43.7%) exhibited increased lateralizing forces. Changes in rectus femoris muscle force correlated with changes in medio-lateral patellofemoral joint loading. Participants with worsening patellofemoral loading had greater tibial torsion and exhibited distinct gait characteristics. These findings suggest that patient-specific functional and anatomical characteristics should be considered when selecting candidates for FDO and planning surgical treatment.