Identifying biomechanical and neurophysiological risk factors for postoperative neurologic deterioration in OPLL surgery: A study using ROC curve and path analysis

Abstract

Objective Ossification of the posterior longitudinal ligament (OPLL) can lead to compressive myelopathy, which requires surgical intervention. This study aimed to evaluate biomechanical and neurophysiological predictors of postoperative motor (PMD) and sensory deterioration (PSD) in cervical OPLL surgery, with the goal of improving patient prognosis and surgical outcomes. Methods A retrospective cohort study was conducted on 111 patients with cervical OPLL who underwent surgery with intraoperative neurophysiological monitoring during 5 years in a single institute. The axial size of OPLL, intraoperative motor evoked potential (MEP) changes, and somatosensory evoked potential (SEP) latency prolongation were analyzed using ROC curve and linear path analysis to assess their predictive value for PMD and PSD. Results The axial size of the OPLL at each level demonstrates no significant difference, regardless of changes in SEPs or MEPs, or the presence of postoperative sensory or motor deterioration. Differences in the OPLL occupying area ratio between the C5 and C6 levels (triangle OPLLC5-C6 occupying area ratio) was significantly greater in patients with SEP latency prolongation (P = 0.04) or MEP amplitude reduction (P = 0.002). The ratio difference was also identified as a critical predictor for PMD and PSD. Receiver operating characteristic (ROC) analysis shows that triangle OPLLC5-C6 occupying area ratio had the highest area under the curve (AUC) for predicting significant MEP amplitude (AUC = 0.837, p < 0.001) and SEP latency (AUC = 0.712, p = 0.015) changes. Path analysis revealed that the triangle OPLLC5-C6 occupying area ratio had a significant indirect effect on PMD (B = 0.561, p = 0.002) and PSD (B = 0.305, p = 0.034), mediated by MEP and SEP changes, respectively. Conclusion The triangle OPLLC5-C6 occupying area ratio appears to be a strong predictor of PMD and PSD in cervical OPLL surgery, potentially influencing outcomes primarily through neurophysiological changes. To help mitigate postoperative neurological complications, continuous neurophysiological monitoring and targeted biomechanical assessments may be beneficial components of the surgical planning process.