Reliability of quantifying foot and ankle muscle strength in very young children

Abstract

Preschool-age children with neuromuscular disorders are often excluded from clinical trials due to the lack of reliable and objective strength measures. We evaluated the reliability of measuring foot and ankle muscle strength in 60 healthy children age 2-4 years. The strength of foot inversion and eversion, ankle plantarflexion, and dorsiflexion was measured using a hand-held dynamometer. Intrarater and interrater reliability of two assessors was determined for each muscle group using intraclass correlation coefficients (ICCs), 95% confidence intervals (CIs), and standard error of measurement (SEM). For all muscle groups intrarater (ICC(2,2) = 0.85-0.94, 95% CI = 0.75-0.96, SEM = 1.5-4.7 N) and interrater (ICC(2,1) = 0.88-0.96, 95% CI = 0.81-0.98, SEM = 1.2-4.6 N) reliability was high for all children. As expected, reliability was generally highest in 3- and 4-year-old children and lowest in 2-year-old children. Hand-held dynamometry can reliably measure foot and ankle strength in very young children and may help aid in diagnosis and in characterizing disease progression in disorders affecting the foot and ankle.