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Thoracic and Lumbar Spine in Diastrophic Dysplasia: A Clinical and Magnetic Resonance Imaging Analysis

Study Design. Cross-sectional study to evaluate the thoracic and lumbar spine in patients with diastrophic dysplasia (DD). Objectives. To find the causative factors behind the spinal deformities and restricted mobility of the spine. Summary of Background Data. Typical findings in this skeletal dysplasia are short-limbed stature, multiple joint contractures, early degeneration of joints, and spinal deformities such as cervical kyphosis, scoliosis, and exaggerated lumbar lordosis. The pathogenic mechanism of scoliosis is unknown. Methods. A physical examination was performed on 88 patients (55 females, 33 males) with an average age of 31 years (range, 3–56). Magnetic resonance (MR) images from T2 to S1 and radiographs were obtained. Degree of scoliosis was measured according to Cobb from standing radiographs.The anatomy of the medulla and the size of the spinal canal were assessed. The transverse dural tube area was measured from L2 to S1. Disc space, degeneration, and protrusions were evaluated. Vertebral abnormalities, if any, facet joint degeneration and the state of the spinal muscles were also assessed. Results. Physical examination showed diminished mobility of the spine. Scoliosis was noted in 70 patients with an average of 42° (range, 11–188°). The mean transverse area of the dural tube ranged from 94 mm2 at L2–L3 to 57 mm2 at L5–S1. The area was smaller at all levels compared with reference values (P < 0.001). One patient had severe thoracic and lumbar spinal stenosis. Five patients had compression of neural structures in the lumbar spinal canal in MR images, but had no clinical symptoms. All patients exhibited narrowed disc heights and a decrease in the signal intensity of discs on T2-weighted images. The prevalence of disc protrusions was low; three patients had a prolapse in the lumbar spine. Two patients displayed vertebral anomalies. All patients also had muscular atrophy and degenerative-like facet joint hypertrophy. The severity of these changes increased with age. Conclusions. Abnormal disc structure and rapid degeneration explain the diminished decreased mobility of the spine and may be a causative factor in the development of scoliosis. Muscular atrophy may be caused by reduced physical activity and rigid spinal deformities. The spinal canal is narrowed, but symptomatic lumbar spinal stenosis is uncommon.