Recurrence of ossification of ligamentum flavum at the same intervertebral level in the thoracic spine: a report of two cases and review of the literature

Purpose: Ossification of the ligamentum flavum (OLF) is a possible cause of thoracic myelopathy. We report two rare cases with recurrent thoracic myelopathy caused by OLF markedly re-extended at the same intervertebral level after the primary surgery. Methods: Both patients had thoracic myelopathy caused by OLF and underwent decompressive laminectomy and resection of the OLF in the primary surgery. However, the neurological conditions gradually deteriorated following recovery after the primary surgery due to the recurrent OLF at the same intervertebral level. Results: These patients were successfully treated by revision surgery via resection of the recurrent OLF and posterior spinal fusion with instrumentation. Two years after the second surgery, the neurological disturbance was resolved satisfactorily, and re-growth of the resected ossified lesion was not observed. Conclusions: The recurrence of OLF following resection of the ossified lesions is exceedingly rare but should be noted in patients treated surgically for thoracic myelopathy due to OLF.