Idiopathic clubfoot patients produce less ankle power during hopping when compared to typically developing children

Idiopathic clubfoot patients show deviations in their gait patterns and other motor activities [1–4]. One of the most challenging motor activities for clubfoot patients is hopping on one leg [4–6]. Difficulty with one-leg-hopping might result from limitations in ankle mobility and plantarflexor force production in clubfoot patients [7]. This hypothesis has however not yet been investigated with detailed three-dimensional motion analysis. What are the differences in ankle power and mobility during walking and one-leg-hopping in clubfoot patients and typically developing children of 5-to-9 years old? Motion analysis was performed in 14 typically developing children (TDC) and 15 Ponseti- treated clubfoot patients of 5-to-9-year-old. Motion analysis during walking and one-leg-hopping was performed using an extended Helen-Hayes model. Spatiotemporal, kinematic, and kinetic data was collected using two integrated force plates (AMTI OR6-7) and four cameras (Codamotion CX1). For clubfoot patients, data from the most affected leg and for TDC, data from the preferred leg was used for further processing. Stride and hop length were calculated based on heel marker displacement, which was divided by stride and hop time to provide velocity. Average group data was computed for TDC and clubfoot patients, and compared using Mann-Withney U tests (p<0.05). Data from one clubfoot patient was excluded from the data analysis of one-leg-hopping, as the patient was unable to perform consecutive hops. No differences were found in spatiotemporal, kinematic, and kinetic parameters during walking between TDC and clubfoot patients (Table 1). During one-leg-hopping, however, differences were found between clubfoot patients and TDC (Table 1). Clubfoot patients showed lower peak ankle power generation (4.25 ± 1.46 W/kg) and absorption (4.65 ± 2.47 W/kg). Furthermore, clubfoot patients showed a lower peak ankle moment (1.60 ± 0.49 N/kg) and a lower velocity during one-leg-hopping. Also, a trend where clubfoot patients showed a smaller hop length was observed (p = 0.085). No differences were found in ankle range of motion during hopping.Download : Download high-res image (164KB)Download : Download full-size image During one-leg-hopping, clubfoot patients absorbed and generated less power at the ankle joint when compared to TDC. These results might indicate that clubfoot patients have a less effective stretch-shortening mechanism of the plantarflexor muscles. This could be due to different elastic properties of the muscle complex, inherent to their pathology [8]. Subsequently, there might be less stored energy that contributes to the ankle power generation. Additionally, the lower ankle moment might indicate that the force-generating capacity of clubfoot patients might be lower, resulting in a lower ankle power generation. This might have resulted in the lower hopping velocity that was seen in clubfoot patients. These results provide insight in the problems clubfoot patients have during challenging motor tasks, and thereby aid in personalizing future treatment plans.