Dorsiflexor muscle-group thickness in children with cerebral palsy: Relation to cross-sectional area

Abstract

If the thickness and cross-sectional area of the dorsiflexor muscle group are related in children with cerebral palsy, measurements of muscle thickness may be used to monitor changes in muscle size due to training or immobilisation in these patients. We assessed the validity and reliability of measurements of dorsiflexor muscle-thickness using the cross-sectional area of the muscle group as the criterion-related muscle-size variable. Muscle thickness was measured using ultrasound, and cross-sectional area using MRI in nine children with spastic cerebral palsy (eight with hemiplegia). Test-retest reliability of the muscle-thickness measurements was assessed in six healthy subjects. All measurements were made on both legs at 35% lower leg length. In the children with cerebral palsy, dorsiflexor muscle-thickness and cross-sectional area were well correlated (r(2) = 0.778, P < 0.001), and the reliability of the muscle-thickness measurements was high in the healthy subjects (ICC(2.1) = 0.94, standard error of measurement = 0.04 cm). The dorsiflexor muscle-thickness was 22% less in the affected compared to the non-affected leg in children with hemiplegic cerebral palsy (P < 0.001). Accordingly, the dorsiflexor cross-sectional area was 32% less in the affected compared to the non-affected leg (P = 0.002). Measurements of dorsiflexor muscle-thickness can be reliably obtained, and they reflect dorsiflexor cross-sectional area in children with cerebral palsy.