Prognostic Factors Of Laminoplasty For Cervical Ossification Of Posterior Longitudinal Ligament With A High Canal Occupying Ratio

Objective:Posterior laminoplasty is a widely used surgical procedure for the treatment of cervical ossification of posterior longitudinal ligament（OPLL）,it can provide posterior decompression by migration of the spinal cord posteriorly.But laminoplasty cannot directly remove the compressed ossified mass in the ventral part of the cervical spinal canal,especially for patients with a canal occupying ratio≥50%.Hence,it remains unclear whether laminoplasty could yield satisfied outcomes for OPLL patients with a high canal occupying ratio.This study aimed to investigate the prognostic factors related to surgical outcomes of laminoplasty for cervical OPLL with an occupying ratio≥50%.Methods:Between January 2013 and January 2019,45 patients with an occupying ratio≥50%undergoing laminoplasty with titanium miniplates in the spine surgery department of the First Affiliated Hospital of Fujian Medical University were retrospectively reviewed.The patients consisted of 35 males and 10 females,with a mean age of 59.3±9.1 years.Clinical data（pre-and postoperative Japanese Orthopaedic Association[JOA]scores,JOA recovery rate,and duration of symptoms）and radiologic parameters(levels of cord compression,K-line,C_2-7 sagittal vertical axis,C_2-7Cobb angle,T₁ slope,type and shape of OPLL,cerebrospinal fluid imaging,and cord compression ratio)were collected,and then univariate and multivariate logistic regression analyses were performed to determine the significant prognostic factors for surgical outcomes.Results:All patients were treated with laminoplasty successfully.The average follow-up period was 27.8±9.2 months（range,10～43 months）.The JOA score was significantly improved from 8.3±2.1 preoperatively to 13.5±2.2 at final follow-up（P<0.01）,with a mean recovery rate of 61.0±23.5%.Final JOA recovery rates including9 excellent,17 good,14 fair,and 5 poor cases.The patients were divided into two groups:26 cases of satisfied outcomes（recovery rate≥50%）and 19 cases of unsatisfied outcomes（recovery rate<50%）.No significant differences were found in terms of age,sex ratio,duration of symptoms,preoperative JOA,and follow-up period（P>0.05）.Univariate analysis demonstrated that unsatisfied group had more K-line（-）patients（11/19 vs 6/26）,lower C_2-7Cobb angle（9.7±7.9°vs 15.6±10.3°）and cord compression ratio（19.0±6.1%vs 23.4±7.2%）compared with satisfied group（P<0.05）.Multivariate logistic regression analysis showed that K-line（-）（OR=9.712,P<0.05）,C_2-7 Cobb angle（OR=0.894,P<0.05）,and cord compression ratio（OR=0.827,P<0.05）were the significant surgical outcomes prognostic factors.Conclusion:Preoperative K-line,C_2-7 Cobb angle and cord compression ratio are the significant factors related to surgical outcomes of laminoplasty for cervical OPLL with a high canal occupying ratio.Laminoplasty might not be a suitable option for patients with preoperative K-line（-）,low cervical lordosis and cord compression ratio.