Abstract
Introduction
Compressive thoracic myelopathy caused by combined ossification of the posterior longitudinal ligament (OPLL) and ossification of the ligamentum flavum (OLF) at the same level(s) is a rare condition. Clinical diagnosis is usually delayed because of the vague and nonspecific symptoms at the early stage, particularly to the unwary. While CT and MRI confirm the level of involvement readily, surgical decompression not only is risky but improvement is never guaranteed. Majority of the case reports and case series are from North Eastern Asia with sporadic reports from the Indian subcontinent. We hereby report our case series consisting of four patients, all are ethnic Southern Chinese.
Material and Methods
Four patients, three females and one male, average age 54.3 years (range, 49–63) were treated in our institution between 2004 to 2009. All of them presented with acute paraplegia after very trivial injuries. Two were totally asymptomatic before the injury while the other two were waiting for elective decompressive surgery before their sudden deterioration. Japanese Orthopaedic Association (JOA) score for the thoracic spine (full points = 11), which measures truncal sensory function, lower limb motor, and sensory function and bladder function was used as the evaluation tool throughout the follow-up period.
Results
The mean extend of laminectomy was 3.25 levels (range, 2–5 levels). The average follow-up was 4.5 years. The average JOA score improvement ratio was 36%. In the first case only 5-level laminectomy was performed, there was cerebrospinal fluid (CSF) leakage intraoperatively and she became total paraplegic postoperatively. At final follow-up 7.5 years later the Cobb angle of the operated level remained same as preoperation, and JOA score improved from 0 to 3, constituting an improvement ratio of 27%. In the other three cases pedicle screws and rods were added for dekyphosis and stabilization together with average 3.3 levels of laminectomy (range, 3–4 levels). One case had CSF leakage intraoperatively. Despite all of them had significant neurological deterioration immediately after operation, the recovery was rapid and all could walk with support on discharge 2.3 months (range, 2–3 months) after the index operation. At final follow-up 3.5 years postoperation (range, 2.5–5 years) the kyphotic Cobb angle reduced from 23.80 (range, 140–31.20) to 16.50 (range, 5.80–23.10), and the JOA score improved from 2.7 (0–4) to 8.7 (8–10), constituting an improvement ratio of 72%. There were no implant-related complications. All these four cases had concomitant cervical spine OPLL detected perioperatively with significant cervical spinal canal stenosis on imaging studies. Throughout the follow-up periods none of them developed any clinically significant cervical myelopathic symptoms and signs.
Conclusion
Thoracic myelopathy due to same level compression by OPLL and OLF is rare and challenging to the spine surgeon. From our small case series it is suggestive that the addition of posterior instrumentation on top of the posterior decompression for dekyphosis and stabilization of the thoracic spine apparently give a more certain clinical improvement. Intraoperative CSF leakage and postoperative transient neurological deterioration are the two particular risks that need to be conveyed to the patient before surgery.