Evaluating MRI predictors for surgical outcomes in selective laminoplasty for OPLL-Induced cervical myelopathy: A comparative analysis of mKappa-line and mK-line.

Abstract

To investigate the effectiveness of the Modified Kappa-line (mKappa-line) and Modified K-line (mK-line) as prognostic tools in managing ossification of the posterior longitudinal ligament (OPLL)-induced cervical myelopathy, especially in selective laminoplasty (LMP) cases. This retrospective study analyzed 78 patients who underwent LMP for OPLL-induced cervical myelopathy between September 2012 and April 2017. Patients were categorized based on their mKappa-line and mK-line statuses. Radiographic measurements, Japanese Orthopaedic Association (JOA) scores, and Neck Disability Index (NDI) were comprehensively analyzed. Patients in the mKappa-line (-) group exhibited significantly higher OPLL thickness (6.4 ± 1.7 mm; P < 0.01) and canal occupying ratio (64.4 %; P < 0.01) compared to the mKappa-line (+) group. The mKappa-line (-) group also reported lower postoperative JOA scores at 6 months (11.2 ± 4.1 vs. 14.5 ± 2.5; P = 0.01) and at the final follow-up (11.3 ± 4.0 vs. 14.4 ± 2.5; P = 0.01). Multivariate analysis highlighted the interval (INT) of mKappa-line as the sole significant predictor of JOA recovery rate (P = 0.037). Receiver operating characteristic (ROC) curve analysis revealed an area under the curve (AUC) of 0.792 for the mKappa-line (P < 0.01) and 0.675 for the mK-line (P < 0.01), with a critical cut-off value of 1.88 mm for the mKappa-line (INT), below which an inferior outcome (JOA RR < 40 %) is associated. The mKappa-line serves as a superior prognostic tool compared to the mK-line, providing enhanced guidance for surgical planning in selective LMP cases. Further research is warranted to confirm these findings and assess their clinical implications.