Management of thoracic myelopathy caused by ossification of the posterior longitudinal ligament combined with ossification of the ligamentum flavum-a retrospective study.

BACKGROUND CONTEXT

Ossification of the posterior longitudinal ligament (OPLL) or ossification of the ligamentum flavum (OLF) is being increasingly recognized as a cause of thoracic myelopathy and is relatively common in the Japanese population and literature. However, no series of OPLL combined with OLF has been previously published. Many different surgical procedures have been used for the treatment of thoracic OPLL or OLF. However, the possibility of postoperative paraplegia remains a major risk, and consistent protocols and procedures for surgical treatment of thoracic OPLL combined with OLF have also not been established.

PURPOSE

To compare the effect of thoracic myelopathy treatment and safety of posterior decompression with or without instrumented fusion and circumferential spinal cord decompression via a posterior approach in Chinese patients of OPLL combined with OLF at a single institution.

STUDY DESIGN

This retrospective clinical study of 31 cases was conducted to investigate the clinical outcomes of three kinds of surgical procedures for thoracic myelopathy caused by OPLL combined with OLF in Chinese population.

PATIENT SAMPLE

Procedure was performed in 31 patients.

OUTCOME MEASURES

Neurologic status was evaluated using the Japanese Orthopaedic Association (JOA) score and Hirabayashi recovery rate before and after surgery.

METHODS

A total of 31 patients who underwent surgery for thoracic OPLL combined with OLF were classified into three groups: posterior decompression group (13 patients); circumferential decompression group (seven patients), which included four who underwent extirpation and the other three underwent the floating procedure; and posterior decompression and fusion group (11 patients), all of whom underwent laminectomy with posterior instrumented fusion. In each group, JOA score was used to evaluate thoracic myelopathy, and Hirabayashi recovery rate was calculated 1 year after surgery and at final examination.

RESULTS

Mean recovery rate at the final follow-up was 46.5% in the posterior decompression group, 65.1% in the circumferential decompression group, and 62.7% in the posterior decompression and fusion group. Postoperative paralysis occurred in three patients in the posterior decompression group, one in the circumferential decompression group, and one in the posterior decompression and fusion group. In the circumferential decompression group, leakage of cerebrospinal fluid occurred in four patients. Urinary tract infection occurred in two patients, and superficial wound disruption occurred in one patient. Late neurologic deterioration occurred in four patients in the posterior decompression group. There were no cases of postoperative paralysis or late neurologic deterioration in the posterior decompression and fusion group.

CONCLUSIONS

Thoracic OPLL combined with OLF is an uncommon cause of myelopathy in the Chinese population. It can present acutely after minor trauma. A considerable degree of neurologic recovery was obtained by posterior decompression with instrumented fusion, despite the anterior impingement of the spinal cord by the remaining OPLL. In addition, the rate of postoperative complications was low with this procedure. We consider that one-stage posterior decompression and instrumented fusion be selected for patients in whom the spinal cord is severely damaged before surgery and/or when circumferential decompression is associated with an increased risk.