Subject-specific MRI-based gait modelling in recurrent paediatric patellofemoral dislocation

Abstract

Learning Objectives: The main objective was to demonstrate how MRI-informed 3D modelling can provide individualized biomechanical insight into PFJ instability. With technical advancement, subject-specific gait modelling has the potential benefit of predicting, on an individual level, how surgical interventions may impact gait or patellofemoral joint pathology and improve patient outcomes. Background: Patellofemoral joint (PFJ) dislocation is an intricate and incapacitating pathoanatomical problem, notably affecting the paediatric and adolescent population, with an incidence rate of 147.7/100,000 person years. of particular concern is the susceptibility to recurrent dislocations, afflicting up to 71% of afflicted individuals. Recurrent PFJ dislocation can result in pain, reduced joint function and changes to lifestyle. The aetiology of patellar dislocation is marked by multifaceted interactions in the bony and soft tissue anatomy as well as biomechanics. Imaging Findings OR Procedure Details: MRI imaging and gait analysis were obtained for 24 patients with a history of multiple patellar dislocations and 25 age-matched controls. Bony anatomy was segmented (Mimics 25.0) and skeletal models were generated (STAPLE MATLAB toolbox). Models were combined with gait cycle (OpenSim) to obtain kinematic data. Statistical analysis of the gait variables and comparison between each group is performed to identify significant differences which may inform pathoanatomy and mechanics. Preliminary data analysis has focused on three key variables: tibiofemoral joint (TFJ) flexion, hip rotation and hip flexion. Preliminary segmentation and analysis of two controls and two dislocators have shown qualitative differences in joint kinetics. Compared to the controls, dislocators showed reduced TFJ flexion in the heel-strike phase of the gait cycle. Hip rotation produced variable findings across the participants. A dislocator also demonstrated reduced hip flexion, range and magnitude, compared to the controls. There was greater magnitude of hip flexion during the swing phase of the gait cycle for some controls compared to dislocators. The results show greater heterogeneity between the dislocators and greater variability in gait trials. These results will continue to be expanded and validated. Conclusion: This study provides valuable insight into the biomechanical aetiology of PFJ dislocations through comparison of control and dislocator gait cycle variables. Innovatively, the use of subject-specific modelling allows for individualised analysis of pathoanatomyand provides valuable steps towards informing clinicians on subject-specific reparative or corrective surgical decisions. The preliminary results obtained will be enhanced with a broader range of gait cycle variables and will be validated in a larger cohort..