Thoracic myelopathy in the Japanese: epidemiological and clinical observations on the cases in Miyagi Prefecture.

Surgeries for thoracic myelopathy for 7 years in a northeastern prefecture (population, 2.26 million) and surrounding areas were reviewed. Eighty-one residents in the prefecture were operated on. The annual operation rate per one million people was 5.1. The rate corresponded to 9% of that reported for cervical myelopathy in the same prefecture. The mean age at operation was 55 years. Fifty-five patients (68%) were male and 26 (32%), female. Twenty-eight % of the patients had preoperative periods longer than two years, and 23% had severe disabilities. Anterior decompression was performed in 27%, posterior decompression in the others. The postoperative recovery rate averaged 48%. The lowest rate was 31% in patients with a preoperative duration of more than 2 years (p < 0.05). Sixty-four % of the patients had ossification of the ligamentum flavum; 20%, posterior spur; 19%, disc herniation; 16%, ossification of the posterior longitudinal ligament; 1%, calcification of the ligamentum flavum; 1%, degenerative spondylolisthesis. Seventy-nine % had one of the above spinal factors and 21% had two.