The predictive value of multi-segment foot kinetics in the development of foot deformities in cerebral palsy

Foot deformities are common in children with cerebral palsy (CP)1, but it is hard to predict how they develop. They are likely caused by a disturbed interplay of forces within the foot during gait, which can be quantified with multi-segment foot kinetics. Differences in foot joint kinetics have been shown between several foot deformity types and typically-developed feet2. These differences seem to indicate that mainly the misalignment of the foot causes further deterioration of the deformity rather than muscle actions2. Altered joint moments due to this malalignment are expected to lead to more deformation, which again results in more affected joint moments, entering a negative vicious circle. Assessing the relation between foot deformity severity and joint moments might provide support for this theory and it will allow to identify whether specific kinetic variables could serve as predictors. Is there an association between foot deformity severity and multi-segment foot kinetics in children with CP? 31 children (48 feet) with a spastic paresis (27 CP, 4 hereditary spastic paresis) were included, with a total of 6 equinovarus, 8 cavovarus, 16 planovalgus and 18 neutral feet. Additionally, 13 typically-developed (TD) feet with a normal foot posture were included. All children performed a gait analysis with the Amsterdam Foot Model3 marker set attached, while walking over a pressure plate on top of a force plate to be able to calculate the multi-segment foot kinetics4. The CP and TD children walked at 100% and 75% of comfortable speed respectively, to match their speed for further analyses. Peak foot joint moments were associated to a static measure (the foot posture index5) and a dynamic measure (the foot profile score6) of foot deformity severity, using Pearson correlations. Moderate significant correlations (r=0.60-0.65) were found between the static foot deformity score and the internal plantar flexion peak moment in the Lisfranc joint and the frontal plane peak moment in the ankle and Chopart joints (Fig. 1). For the dynamic foot deformity score, strong significant correlations (r>0.8) were present with peak plantar flexion moment for the equinovarus deformity in all joints. Low to moderate correlations (r=0.4-0.6) were found in the Chopart and Lisfranc joints for the cavovarus deformity in the sagittal and frontal plane and for the planovalgus deformity in the transverse plane. Fig. 1.Download : Download high-res image (154KB)Download : Download full-size image The significant associations between foot deformity severity and specific peak joint moments suggests that foot joint moments may play a role in the deterioration of foot deformities. Furthermore, specific joint moments per foot deformity group were identified which might have a predictive value for the progression of the deformation. However, longitudinal data is required to actually establish this predictive value. Identifying foot deformity predictors will allow for early interventions thereby reducing the need for invasive surgery.