Individuals with bilateral cerebral palsy rely on excessive hip extension to complete a step-up task

Research Objectives: To investigate the hip, knee, and ankle joint moments of individuals with bilateral cerebral palsy (CP) during a step-up task. Due to distal joint impairment, we hypothesized that individuals with bilateral CP would generate less knee and ankle moments and more hip moments when stepping up than individuals without CP.

Design: In this cross-sectional study, participants were instructed to step up onto a 10.2-cm platform 5-15 times with the same leading limb.

Setting: University gait laboratory

Participants: We recruited from convenience samples of individuals with and without bilateral CP between 5-19 years of age. Individuals without bilateral CP (n=11, 6 females, mean age=12.8 years) were included if they had no known neurological conditions. Individuals with bilateral CP (n=5, 1 female, mean age=10.6 years) were included if they had some ambulatory function without assistive devices or orthotics, no botulinum toxin injections in the past 6 months, no lower limb surgeries in the past year, and no serious co-morbidities.

Interventions: N/A

Main Outcome Measures: Extensor support moments were calculated by summing normalized hip, knee, and ankle sagittal plane moments. Peak support moments were identified in the push-off and pull-up stance phases, where typically the ankle and knee joints generate the highest moments, respectively. Individual joint contributions to peak support moments were averaged and compared between groups using a Welch’s t-test.

Results: For the push-off phase, the difference in hip extension moments was significant between groups, where individuals with bilateral CP generated larger hip moments during peak support moments compared to individuals without bilateral CP (p < 0.001, CI: [0.445 0.798] Nm/kg). For the pull-up phase, differences in hip and knee extension moments were significant between groups. Individuals with bilateral CP generated larger hip moments (p < 0.001, CI: [0.364 0.911] Nm/kg) and smaller knee moments (p=0.007, CI: [-0.729 -0.161] Nm/kg) during peak support moments compared to individuals without bilateral CP.

Conclusions: Increased generation of hip extension moments during a step-up task is likely a neural and biomechanical compensation for distal joint impairment in individuals with bilateral CP.

Author(s) Disclosures: None