Scoliosis in Duchenne muscular dystrophy children is fully reducible in the initial stage, and becomes structural over time

BACKGROUND: Patients with Duchenne muscular dystrophy (DMD) often develop scoliosis that progresses rapidly after loss of ambulation. Management of scoliosis is crucial because it affects both life expectancy and quality of life of patients with DMD. Spinal orthosis attempts to prevent or delay scoliosis using spinal support at three points of the controlling mechanism; the curve should be flattened by the pressure. Therefore, it is assumed that spine flexibility could be a significant influencing factor for the effectiveness of braces. Hence, we attempted to investigate the flexibility of scoliosis in non-ambulant patients with DMD. METHODS: We reviewed the medical records of 273 boys who were genetically identified as having DMD, and finally, 50 boys with serial records of radiographs after loss of ambulation were finally enrolled. And among them, only 31 patients developed scoliosis. Spine radiographs in sitting and supine positions were also reviewed to obtain Cobb angle, curve flexibility, and pelvic obliquity. Flexibilities (%) were calculated by the difference in angles between the sitting and supine positions divided by the angle at the sitting position, multiplied by 100. RESULTS: Among 31 boys who had scoliosis, all but 2 boys with curves went through a sequential course of 1) no scoliosis, 2) nonstructural scoliosis, when scoliosis was only measurable in the sitting position, and 3) structural scoliosis, when scoliosis was also detectable in the supine position. Flexibility decreased each year after detection of scoliosis in those who developed scoliosis the first year, from 75.5 ± 5.0% to 57.1 ± 10.5% and to 49.1 ± 10.0% (mean ± standard deviation). Spinal flexibility was significantly correlated with curve magnitude of scoliosis in both sitting and supine position (p < 0.05, respectively). CONCLUSIONS: There is a period of fully reducible curve in DMD patients at the initial stage of scoliosis. Afterward, as spinal curve progresses, flexibility decreases over time. To detect the scoliosis when the curve is fully reducible, scoliosis curve in DMD patients should be evaluated dynamically, including radiographs of at least in two different positions.