Congenital vertebral displacement.

We defined congenital vertebral displacement as displacement at a single vertebral level that results in an abrupt displacement of the neural canal. We reviewed the data on 642 patients who had congenital vertebral abnormalities and identified ten who had congenital vertebral displacement. There were two patterns of deformity: Type A (eight patients) consisted of displacement in the sagittal plane only, and Type B (two patients), rotatory, transverse, and sagittal displacement. The spinal deformity was usually noted in infancy. Neurological deficits were identified at the time of presentation or developed later in six patients. Two patients had a sudden onset of paraplegia after slight trauma, two had a gradual onset of neurological abnormalities, and two had neurological abnormalities when they were first seen. Three patients had congenital anomalies of the spinal cord. We found marked mechanical instability intraoperatively in five patients, and we believe that the instability in combination with compression of the spinal cord resulted in myelopathy. We recommend combined anterior and posterior arthrodesis of the spine for the treatment of this disorder. We believe that decompression of the spinal cord is indicated for patients who have a neurological deficit of recent onset or a progressive neurological deficit. Decompression of the spinal cord may also be indicated for the treatment of long-standing deficits after spinal stability has been obtained.