Sagittal alignment changes after thoracic laminectomy in adults.

Object: The increased kyphosis after thoracic laminectomy in adult patients was retrospectively evaluated and various factors affecting this spinal deformity were analyzed.

Methods: The authors conducted a retrospective study of 58 cases in which laminectomy was performed and more than half of the facet joints were left intact. The study group included 44 men (mean age 59 years) and 14 women (mean age 61 years) with thoracic myelopathy due to ossifications of the ligamentum flavum and/or the posterior longitudinal ligament or due to posterior bone spurs. Patients were followed up for a minimum of 2 years. Their neurological condition was evaluated using the Japanese Orthopaedic Association (JOA) scale (a full score is 11), and the magnitude of local kyphosis in the laminectomized area was determined using the Cobb angle method.

Results: The mean preoperative JOA score was 5.4; the mean postoperative score was 8.3. No relationship was found between postoperative JOA score and increased kyphotic angle. The mean preoperative kyphotic angle was 7.0 degrees . The mean postoperative kyphotic angle was 10.8 degrees . Thus local kyphosis in the treated area increased by only 3.8 degrees . The mean increase in kyphosis per spinal segment, calculated by dividing the kyphotic angle of the surgically decompressed area by the number of resected laminae, was 1.9 degrees . Female patients with >or= 3-level laminectomies showed a significant increase of kyphosis in both the laminectomized area and each spinal segment.

Conclusions: The increase in kyphosis after thoracic laminectomy is not large and thus spinal fusion is usually not necessary. In cases involving female patients who undergo long-segment laminectomies, however, careful radiographic follow-up is recommended.