Independently ambulatory children with spina bifida experience near-typical joint moments and forces during walking

Abstract

Background: Spina bifida, a neurological defect, can result in lower-limb muscle weakness. Altered ambulation and reduced musculoskeletal loading can yield decreased bone strength in individuals with spina bifida, yet individuals who remain ambulatory can exhibit normal bone outcomes. Research question: During walking, how do lower-limb joint kinematics, moments, and forces in independently ambulatory children with spina bifida differ from those of children with typical development? Methods: We retrospectively analyzed data from 16 independently ambulatory children with spina bifida and 16 children with typical development and confirmed that bone strength was similar between the two groups. Plantar flexor muscle strength was measured by manual muscle testing, and 14 of the children with spina bifida wore activity monitors for one week. We estimated joint forces using motion capture data and musculoskeletal simulations. We used Statistical Parametric Mapping t-tests to compare lower-limb joint kinematic and kinetic waveforms between the groups with spina bifida and typical development. Within the group with spina bifida, we examined relationships between plantar flexor muscle strength and peak tibial forces by calculating Spearman correlations. Results: Activity monitors from the children with spina bifida reported typical daily steps (9656 [SD 3095]). Despite slower walking speeds (p=0.004) and altered lower-body kinematics (p<0.0001), children with spina bifida had joint moments and forces similar to those of children with typical development, with no detectable differences during stance. Plantar flexor muscle weakness was associated with increased compressive knee force (p=0.001) and shear ankle force (p=0.006). Significance: High-functioning, independently ambulatory children with spina bifida exhibited near-typical bone strength and near-typical step counts and load magnitudes. Our results suggest that maintaining ambulation and muscle strength can promote bone health in this population.