Staged spinal cord decompression through posterior approach for thoracic myelopathy caused by ossification of posterior longitudinal ligament

Study Design. Prospective clinical study of the effect of staged eliminatio n of anatomic factors inhibiting posterior shift of the thoracic spinal cor d on the degree of posterior shift of the thoracic spinal cord and its sign ificance in augmenting the safety of ossification of posterior longitudinal ligament (OPLL) manipulation in thoracic OPLL myelopathy. Objectives. To develop a comprehensive method that enables safe and suffici ent decompression of the spinal cord for thoracic OPLL myelopathy. Summary of Background Data. Decompression of the spinal cord by direct mani pulations of thoracic OPLLs, via either anterior or posterior approach, cau sed some iatrogenic catastrophic spinal cord injuries, and methods to preve nt such injuries during surgery have not yet been developed. Methods. Procedures of elimination of anatomic factors inhibiting posterior shift of the thoracic spinal cord were performed in stages at intervals of between 1 month and 11 years depending on patients' neurologic status. The first stage operation consisted of extensive cervicothoracic laminoplastic decompression with or with out posterior longitudinal durotomy, and if the decompression were insufficient, measures for OPLL-spinal cord separation with or without OPLL manipulation were added. Results. All 17 patients with thoracic OPLL myelopathy showed improvements of neurology comparable with those with successful anterior approaches afte r decompression. The mean follow-up period was 42 months (range 6-101 month s). Neurologic improvements persisted for the entire follow-up period in al l patients except one patient who developed arachnoid cyst compressing the dorsum of the once-decompressed spinal cord 30 months after surgery. Conclusions. Staged posterior decompression to eliminate anatomic factors i nhibiting posterior shift of the thoracic spinal cord is the safest and the most reliable method of spinal cord decompression to treat thoracic OPLL m yelopathy, so far. However, long-term results are required before the metho ds can be established.