Knee joint contact forces to assess the effect of single event multi level surgery over time in crouch gait

Effective treatment planning for crouch gait (CG) in cerebral palsy (CP) patients requires a thorough understanding of multiple factors. Single Event Multi Level Surgery (SEMLS) is often used, with emphasis on the knee joint. Clinical examination (CE) and instrumented gait analysis (IGA) are valuable tools for evaluating the outcomes of these procedures. However, since these exams do not measure knee joint contact loading, musculoskeletal modelling approaches must be included to estimate these variables. The aim of this study was to estimate knee joint contact forces (JCF) in a child with CG and assess its ability as an evaluation parameter following SEMLS. This work was a longitudinal study of a child with spastic bilateral diplegic CP, Gross Motor Function Classification System (GMFCS) level III, Functional Mobility Scale (FMS) 5-1-1, CG, who underwent SEMLS. Biomechanical data was collected at pre- op, 1-year post-op, and 2-years post-op (age (years):13, 14, 15; height (cm):169.7, 170.8, 171.5; mass (Kg): 60.6, 62.8, 68). Data collection was performed with 14 optoelectronic cameras at 100 Hz and 2 force plates, in three one-day sessions, where the participant walked in a 10 m corridor. In these sessions, CE was also assessed. Muscle and knee JCF were attained through OpenSim, using scaled musculoskeletal models1. Peak force values are presented for midstance and terminal stance, during the single support phase of gait, given in terms of bodyweight (Fig. 1). Along the anterior/posterior (A/P) direction, peak forces decreased through sessions (5.02; 4.41; 3.33), albeit they are still higher than unimpaired gait values (0.89). Concerning the vertical direction, during midstance, CG simulations showed higher peak compressive forces (-4.27; -4.58; -5.59) than in unimpaired gait (-2.88). During terminal stance, a peak is observed in unimpaired gait (-5.76), and only 2 years after surgery (-4.49). Regarding the mediolateral direction, no noticeable changes were found. Knee JCFDownload : Download high-res image (218KB)Download : Download full-size image CE and IGA showed improvements in knee flexion during stance throughout the sessions, albeit it is still different from unimpaired gait. These observations are corroborated by the decrease in peak knee JCF along the A/P direction. Yet, despite the observed improvements, the A/P peak knee JCF 2-years post-op is still 4 times higher than in unimpaired gait, which may be a potential risk factor for knee osteoarthritis (KOA)2. Additionally, there are differences in compressive knee JCF profile and magnitude. It is known that joint contact loading is influenced by muscle forces, with quadriceps and gastrocnemii being the main contributors to the compressive tibiofemoral contact forces during stance in CG3.This could clarify the above-mentioned results, as the muscle forces obtained by musculoskeletal modelling match these disparities. In summary, the successful treatment of CG in CP patients entails a multifaceted approach, incorporating various techniques such as SEMLS, CE, IGA, and musculoskeletal modelling.