Postoperative Paralysis From Thoracic Ossification of Posterior Longitudinal Ligament Surgery Risk Factor of Neurologic Injury: Nationwide Multiinstitution Survey.

STUDY DESIGN: Retrospective case-control study. OBJECTIVE: The purpose of this study was to examine the factors of postoperative paralysis in patients who have undergone thoracic ossification of posterior longitudinal ligament (OPLL) surgery. SUMMARY OF BACKGROUND DATA: A higher percentage of thoracic OPLL patients experience postoperative aggravation of paralysis than cervical OPLL patients, including patients that presented great difficulties in treatment. However, there were a few reports to prevent paralysis thoracic OPLL. METHODS: The 156 patients who had received thoracic OPLL surgery were selected as the subjects of this study. The items for review were the duration of disease; the preoperative muscle strength (Muscle Manual Testing); OPLL levels (T1/2-4/5: high, T5/6-8/9: middle, and T9/10-11/12: low); the spinal canal occupancy ratio; the ratio of yellow ligament ossification as a complication; the ratio of transcranial-motor evoked potential (Tc-MEP) derivation; the preoperative/postoperative kyphotic angles in the thoracic vertebrae; the correction angle of kyphosis; the duration of surgery; and the amount of bleeding. The subjects were divided into two groups based on the absence or presence of postoperative paralysis to determine the factors of postoperative paralysis. RESULTS: Twenty-three patients (14.7%) exhibited postoperative paralysis. Multivariate analysis identified factors associated with postoperative paralysis: the duration of disease (odds ratio, OR = 3.3); the correction angle of kyphosis (OR = 2.4); and the ratio of Tc-MEP derivation (OR = 2.2). CONCLUSION: The risk factors of postoperative paralysis are a short duration of disease and a small correction angle of kyphosis. In addition, ratios of Tc-MEP derivation below 50% may anticipate paralysis. LEVEL OF EVIDENCE: 4.