LAUSR

BACKGROUND We examined the association of sagittal spinal alignment in the sitting position with the trunk and lower extremity muscle masses in children and adults with cerebral palsy (CP). We also compared muscle masses between children and adults with CP who could and could not sit without the support of their upper extremities. METHODS The subjects were 34 children and adults with CP. Sagittal spinal alignment in the sitting position, such as thoracic kyphosis, lumbar lordosis, and sacral anterior inclination angles were measured using a Spinal Mouse. The thicknesses of the trunk and lower extremity muscles were measured using an ultrasound imaging device. Furthermore, the subjects were classified into the sitting-possible group (n = 18), who could sit without the support of the upper extremities, or a sitting-impossible group (n = 16), who could not sit without the support of the upper extremities. FINDINGS Stepwise regression analysis revealed that the lumbar multifidus muscle thickness and body weight were significant and independent factors of the lumbar lordosis angle in the sitting position. The thicknesses of the thoracic erector spinae, gluteus maximus and minimus, long head of the biceps femoris, semitendinosus, and rectus femoris muscles were significantly lower in the sitting-impossible group than those in the sitting-possible group. INTERPRETATION Decreased lumbar lordosis angle in the sitting position was associated with decreased lumbar multifidus muscle mass in children and adults with CP. Furthermore, not only trunk extensor but also hip joint muscles may contribute to sitting without upper extremity support.