Body Weight and Range of Motion as Predictors of Trunk Asymmetry in Children With Spinal Muscular Atrophy: A Prospective Functional Assessment

BACKGROUND Spinal muscular atrophy (SMA) is a lower motor neuron disease characterized primarily by motor function impairment, as well as the development of contractures and scoliosis. MATERIAL AND METHODS A prospective study was conducted involving 38 children with SMA, including 8 with type 1, 20 with type 2, and 10 with type 3 SMA. Patients were categorized based on motor function into non-sitters (n=9), sitters (n=23), and walkers (n=6). Anthropometric measurements, including body mass index (BMI) and BMI z-scores, were recorded according to World Health Organization standards. Structural trunk parameters, the presence of contractures, and joint range of motion were assessed in all participants. RESULTS Changes in trunk parameters in all 3 groups showed no deterioration of structural elements. There was an increase in lower limb contractures measured at all 3 joints in the non-sitters and sitters groups. As BMI increased, the range of motion of the hips and right knee increased, while the left knee and feet remain unchanged. As body weight increased, the risk of trunk asymmetry increased in all patients. In the non-sitters group, there was an increase in hip and knee contractures regardless of BMI category. CONCLUSIONS As body weight increased, the risk of trunk asymmetry increased. As BMI increased, the neutral position of the hips changed (contracture increased), and the position of the knees did not change, while the neutral position of the feet improved. The measurement of contractures and range of motion should be introduced as a standard of practice in the evaluation of children with SMA.