Impact of gait patterns, bony morphology, and derotation osteotomy on knee joint loads in patients with patellofemoral instability

Abstract

The patella plays a critical role in enhancing power transmission within the extensor system of the lower extremity. Best possible functionality necessitates precise alignment of the patella within the trochlear groove. Patellofemoral stability is supported by ligaments, bony structures and neuromuscular factors. Instability in this system can lead to dislocations and impairments, particularly affecting young, active individuals. The complex etiology of patellofemoral instability complicates the in vivo assessment of confounding factors affecting joint stability. Recent advancements in computational models have facilitated the study of these factors through musculoskeletal simulations. Although the impact of several morphological parameters on the stability of the patellofemoral joint has been explored, substantial gaps remain in understanding the specific influences of altered gait patterns and other morphological variations, such as lower limb torsion. This thesis aims to address these gaps. Three studies were conducted to examine the impacts of (i) gait pattern, (ii) lower limb torsion and (iii) femoral derotation osteotomies on patellofemoral joint loading. The first study addressed the impact of patient-specific gait patterns on joint loading in individuals with patellofemoral instability. Utilizing a model with twelve degrees of freedom in the knee joint, musculoskeletal simulations based on three-dimensional motion capture data from 21 individuals with patellofemoral instability and 17 healthy controls were performed. Findings indicated that the patellofemoral instability group walked with a less flexed knee joint, exhibiting reduced knee flexion and abduction moments compared to the control group despite similar gait velocity. This altered gait pattern required less quadriceps muscle force, which in turn resulted in lower tibiofemoral and patellofemoral joint contact forces. The second study examined the influence of lower limb torsion on patellofemoral joint loading. Musculoskeletal simulations were conducted using data from 40 individuals with patellofemoral instability. Three models for each participant were created: one with generic lower limb torsion, one with personalized torsion of both the femur and tibia, and one with isolated personalization of femoral version. The analysis revealed that tibial torsion was significantly correlated with differences in medio-lateral patellofemoral forces, whereas the femoral version showed no significant correlation to these forces. However, when individual tibial torsion was neglected, as usually practiced in studies, femoral version exhibited a moderate correlation with lateralizing forces on the patella. This underlines the relevance of evaluating tibial torsion and femoral torsion conjointly. The third study investigated the effects of femoral derotation osteotomy on patellofemoral stability and loading. Retrospective data from 16 participants with recurrent patellofemoral instability and femoral version higher than 30 degrees, were used to personalize in-silico musculoskeletal models based on gait analysis and magnetic resonance data. Two models were prepared for each participant: one with the pre-surgery femoral version and tibial torsion, and another simulating post-surgery conditions with an adjusted femoral version to 12 degrees. The results showed that the derotation osteotomy significantly shifted the medio-lateral patellofemoral joint contact force to the medial side in 14 of 16 participants, which potentially leads to increased patellofemoral stability. However, two cases showed no improvement, which was attributed to specific gait patterns that avoided dynamic patella loading. In conclusion, these studies collectively advance our understanding of patellofemoral instability by highlighting the significance of patient-specific factors such as gait patterns and lower limb torsion. They demonstrated that a comprehensive biomechanical analysis, which includes both static morphological factors and dynamic aspects of movement, is essential for accurately assessing the biomechanical environment of the patellofemoral joint and for devising effective treatment strategies. The use of personalized musculoskeletal modelling is a promising approach to better understand the causes of patellofemoral instability and optimize treatment outcomes.

Date of Award	2025
Original language	English
Awarding Institution	Medical University Graz
Supervisor	Tanja Kraus (Supervisor) & Martin Svehlik (Supervisor)