Relationship between hip abductor muscle strength and balance in unilateral spastic cerebral palsy: an observational cross-sectional study

Abstract Background Children with unilateral spastic cerebral palsy display deficits in muscle strength and activation patterns, and the contribution of these deficits to balance requires analysis. Objectives The purpose of the study was to determine the relationship between isometric hip abductor strength and balance in children with unilateral spastic cerebral palsy. Methods Forty-eight children with unilateral spastic cerebral palsy, of both genders, aged four to nine years, with spasticity ranging from grade 1 or 1 + on the Modified Ashworth Scale and classified as levels I, II, or III on the Gross Motor Functional Classification System, participated in this study. Participants’ muscle strength was assessed using a handheld dynamometer, and balance was assessed using the Biodex balance system. Results Relative hip-abductor force demonstrated a weak but statistically significant negative correlation with both the overall stability index (OSI) and mediolateral stability index (MLSI) at stability levels 6, 4, and 2 ( r = -0.31 to -0.36, p < 0.05). No significant correlation was observed at level 8 (OSI: r = -0.25, p = 0.08; MLSI: r = -0.28, p = 0.06). For the anteroposterior stability index (APSI), a significant weak negative correlation was identified only at level 4 ( r = -0.29, p = 0.046), while correlations at levels 8, 6, and 2 remained weak and non-significant ( r = -0.12 to -0.20, p = 0.18–0.41). Conclusion On the more involved side, the relative isometric force of the hip abductor muscles showed a weak, negative, significant association with overall and mediolateral stability indices among children with unilateral spastic cerebral palsy. Stronger abductors were associated with steadier posture, but only when the balance task was moderately to highly demanding.