Motor-evoked potentials in the intraoperative decision-making of circumferential decompression via posterior approach for treating thoracic posterior longitudinal ligament ossification

Abstract

Background context: Surgical treatment is indicated for symptomatic thoracic ossification of posterior longitudinal ligament (OPLL), and circumferential decompression (CD) is a promising option. However, the risk of postoperative paralysis in ventral decompression of CD is as high as 30%. Therefore, it is important to balance surgical outcomes and safety of ventral decompression.

Purpose: To investigate the role of intraoperative motor-evoked potential (MEP) changes in decision-making of one-staged CD via posterior approach for treating thoracic OPLL.

Study design: A retrospective cohort analysis PATIENT SAMPLE: Twenty-five thoracic OPLL patients in this study underwent posterior decompression (PD) alone, and the other 21 patients accepted CD.

Outcome measures: Intraoperative MEP monitoring from both abductor hallucis and tibialis anterior, and modified Japanese Orthopaedic Association (mJOA) scores.

Methods: MEPs were recorded in all patients before and after PD, and patients accepting CD underwent further MEP recordings after ventral decompression. According to MEP changes after PD, patients were divided into MEP improvement, MEP deterioration and no MEP change. Postoperative MEP improvement rates were measured in all tested muscles. Additionally, all patients accepted mJOA scores before and 2 years after operation.

Results: Patients in both CD and PD groups exhibited improved mJOA scores after operation (p<.05), and both mJOA and MEP improvement rates were similar between these two groups (p>.05). In no MEP change group, patients accepting CD exhibited increased mJOA improvement rates compared with those accepting PD (p<.05). In MEP deterioration group, higher mJOA improvement rates were observed in PD group than in CD group (p<.05). In MEP improvement group, mJOA improvement rates were similar between CD and PD groups (p>.05).

Conclusions: Both CD and PD can effectively treat thoracic OPLL, and which of these two strategies can achieve better functional recovery may be related to different MEP changes after PD. Therefore, monitoring MEP changes may provide additional references in decision-making of one-staged CD for treating thoracic OPLL.

Keywords: Circumferential decompression; Complication; Intraoperative monitoring; Motor-evoked potentials; Posterior decompression; Thoracic ossification of the posterior longitudinal ligament.