Effect of Botulinum Toxin Injection in Hip Adductor Muscles on Gross Motor Function in Low-Functioning Children with Spastic Cerebral Palsy

Abstract

Purpose: Botulinum toxin type A (BoNT-A) injections are used to manage spasticity in children with low-functioning cerebral palsy (CP), particularly in cases involving the hip adductor muscles. Despite their widespread use, research on the impact of BoNT-A injections on gross motor function in children with CP within Gross Motor Function Classification System (GMFCS) levels III-V remains limited, prompting us to evaluate their effectiveness in this population. Materials and Methods: This retrospective study included 100 preschool children (mean age, 3.9 years) with CP (GMFCS levels III-V) who received BoNT-A injections targeting the adductor muscles at a tertiary hospital (2006-2024). Gross motor function was assessed using the Gross Motor Function Measure (GMFM) within 1 month before injection and between 3 weeks and 4 months post-injection. Subgroup analyses were conducted by GMFCS level and by injection site. Pre- and post-injection assessments were compared using the Wilcoxon signed-rank test. Results: GMFM scores improved significantly across all GMFCS levels (p<0.05). Children at GMFCS levels III and IV demonstrated improvements across all domains (A-E), whereas those at GMFCS level V showed significant gains in domains A, B, and C (p<0.05). Further analyses showed significant improvements in all three groups: adductors alone, adductors and hamstrings, and adductors and distal muscles (p<0.05). Conclusion: BoNT-A injections into hip adductor muscles improved gross motor function in children with low-functioning CP, affecting both overall and specific functional domains. This effect was observed in children who received injections into the adductors alone, as well as in combination with injections into the hamstrings or distal muscles.