Reference values for the cross-sectional area of the lumbar multifidus muscle in children

BACKGROUND: The multifidus muscle plays a major role in the growth and postural control of children. Therefore, the reference values of the cross-sectional area (CSA) of the lumbar multifidus muscle represent an important tool for assessing muscle development and the early monitoring of musculoskeletal disorders. OBJECTIVE: The aim of this study was to provide percentile scores for the CSA of the lumbar multifidus muscle in eutrophic children aged 5 to 10 years. METHODS: This was a cross-sectional, observational study, involving 736 children. An anthropometric assessment was conducted and ultrasound (US) imaging was used to assess the CSA of the lumbar (vertebral level L5) multifidus muscle. The CSA was expressed as percentile scores. RESULTS: The CSA in the boys ranged from 1.8 cm(2) to 5.3 cm(2) and in girls from 1.9 cm(2) to 5.9 cm. The CSA in the 50th percentile scores of both sexes was 3.4 cm(2). There was an increase in the CSA between 5 and 7 years old in both sexes. The CSA presented a greater variance in girls than in boys. After 8 years of age, the multifidus CSA increased in girls and decreased in boys. CONCLUSION: The present study has provided percentile scores for the CSA of the lumbar multifidus muscle for eutrophic children aged 5 to 10 years. An increase was observed of the CSA of the multifidus muscle between the ages of 5 and 7 years and there were no differences in the CSA percentiles in relation to sex. An increase in the CSA after 8 years of age was only observed in the girls.