Selecting a Surgical Method for Thoracic Myelopathy Caused by Ossification of the Posterior Longitudinal Ligament

STUDY DESIGN: The authors classified typical distributional patterns of ossification of the posterior longitudinal ligament of the thoracic spine in 1) central part of S-curve, 2) just above apical vertebra, and 3) combined with ossification of ligamentum flavum below apical vertebra. The results of the surgical methods selected according to the authors' classification were compared with those of previous reports. OBJECTIVES: To establish the criteria for selecting an appropriate surgical method for ossification of the posterior longitudinal ligament of the thoracic spine. SUMMARY OF BACKGROUND DATA: Poor surgical results for ossification of the posterior longitudinal ligament of "middle or lower thoracic spine" have been reported, but the unsuccessful location and curve has not been strictly defined. METHODS: The authors studied postsurgical results in 26 cases of thoracic myelopathy caused by ossification of the posterior longitudinal ligament. They also investigated radiographs of 111 cases, including 85 patients under observation, and examined the relationships between thoracic spine alignment and ossification of the posterior longitudinal ligament distribution. RESULTS: Twenty-three patients treated with methods conforming to the authors' criteria achieved satisfactory recovery in walking ability except for one patient. The results of the other three patients who underwent surgery with nonconforming methods were uneven. CONCLUSION: Posterior decompression, as well as anterior decompression, is effective in the first pattern in the cervicothoracic region. In case of the second pattern, the responsible ossification of the posterior longitudinal ligament always lies one or two levels above the apical vertebra and should be removed by anterior approach, regardless of the extent of kyphosis. Transthoracic anterior decompression surgery is considered the best method for most patients under the second and third patterns.