Effect of K-line (-) or (+) on surgical outcomes in cervical ossification of the posterior longitudinal ligament: A systematic and meta-analysis.

Background: To conduct a systematic review and meta-analysis assessing the influence of K-line status on postoperative clinical outcomes in patients with cervical posterior longitudinal ligament ossification (OPLL).

Methods: We searched PubMed, Embase, OVID, Cochrane Library, and Web of Science databases for English-language literature related to K-line and OPLL up to June 7, 2024. The study underwent rigorous selection, quality assessment, and data extraction, followed by meta-analysis using Review Manager 5.3 and Stata 17.0 software. This study has been registered with the international PROSPERO registry (registration number: CRD42024558578).

Results: Seventeen articles encompassing 1247 patients were included. The meta-analysis revealed that patients with a positive K-line (K-line (+)) exhibited significantly enhanced Japanese Orthopaedic Association score recovery rate (mean differences [MD] = 19.28, 95% confidence interval [CI]: 12.28-26.28, P < .00001), Japanese Orthopaedic Association score (MD = 1.51, 95% CI: 0.64-2.37, P = .0007), C2-C7 Cobb angle (MD = 6.45, 95% CI: 3.73-9.17, P < .00001), alongside reduced occupation ratio (MD = -7.67, 95% CI: -10.86 to -4.49, P < .00001), C2-C7 sagittal vertical axis (MD = -6.18, 95% CI: -8.36 to -3.99, P < .00001), and neck disability index (MD = -1.85, 95% CI: -3.18 to -0.52, P = .006) at final follow-up compared to those with a negative K-line (K-line (-)). No significant differences were observed in postoperative complication rates (odds ratio = 1.15, 95% CI: 0.41-3.20, P = .79), final follow-up visual analog scale scores (MD = -0.10, 95% CI: -0.80 to 0.59, P = .77), or T1 slope (MD = 2.66, 95% CI: -0.20 to 5.52, P = .07) between the 2 groups.

Conclusion: A positive preoperative K-line (K-line (+)) is a better predictor of prognosis and is associated with improved clinical outcomes in patients with multi-segmental cervical OPLL compared to a negative K-line (K-line (-)).