Anterior direct decompression significantly relieves spinal cord high signal in patients with ossification of the posterior longitudinal ligament: a case-control study

Abstract

BackgroundIn patients with cervical spondylotic myelopathy caused by ossification of the posterior longitudinal ligament, high cord signal (HCS) is frequently observed. However, limited research has investigated the variations in HCS improvement resulting from different surgical approaches. This study aims to explore the potential relationship between the choice of surgical approach and the postoperative improvement of intramedullary high signal in ossification of the posterior longitudinal ligament (OPLL) patients.MethodsWe extensively reviewed the patients' medical records, based on which demographic information such as gender, age, and body mass index (BMI) were recorded, and assessed the severity of the patients' neurological status preoperatively and postoperatively by using the Japanese Orthopedic Association score (JOAs), focusing on consecutive preoperative and postoperative Magnetic resonance imaging (MRI) T2WI measurements, to study the statistical correlation between the improvement of HCS and the choice of surgical approach.ResultsThere were no significant differences in demographic, imaging parameters, and clinical symptoms between patients undergoing anterior and posterior surgery (p > 0.05, Table 1). However, both improvement in JOAs (Recovery2) and improvement in HCS (CR2) were significantly better in the anterior surgery group two years after surgery (p < 0.05, Table 1). Multifactorial logistic regression analysis revealed that posterior surgery and higher preoperative signal change ratio (SCR) were identified as risk factors for poor HCS improvement at the two-year postoperative period (p < 0.05, Table 2).Table 1Differences in demographic, imaging parameters, and clinical symptoms in patients with anterior and posterior approachAnterior approachPosterior approachP-ValuesDemographic data Sex (male/female)10/126/170.175 Age58.59 ± 5.6861.43 ± 9.040.215 Hypertension14/814/90.848 Diabetes16/619/40.425 BMI25.58 ± 4.7226.95 ± 4.580.331 Smoking history19/316/70.175Preoperative measured imaging parameters Preoperative SCR1.615 ± 0.3691.668 ± 0.3560.623 CR10.106 ± 0.1250.011 ± 0.2460.08 CNR0.33 ± 0.0730.368 ± 0.0960.15 C2–7 Cobb angle8.977 ± 10.81813.862 ± 13.1910.182 SVA15.212 ± 8.02417.46 ± 8.910.38 mK-line INT3.694 ± 3.2914.527 ± 2.2270.323Imaging follow-up 6 months postoperative SCR1.45 ± 0.441.63 ± 0.3970.149 2 years postoperative SCR1.26 ± 0.191.65 ± 0.350.000** CR20.219 ± 0.14− 0.012 ± 0.2370.000**Clinical symptoms Preoperative JOAs10.64 ± 1.5910.83 ± 1.470.679 6 months postoperative JOAs11.82 ± 1.3711.65 ± 1.40.69 2 years postoperative JOAs14.18 ± 1.0112.52 ± 2.060.001** Recovery10.181 ± 0.1090.128 ± 0.1540.189 Recovery20.536 ± 0.1780.278 ± 0.3070.001***, statistical significance (p < 0.05). **, statistical significance (p < 0.01)BMI = body mass index. SCR = the signal change ratio between the localized high signal and normal spinal cord signal at the C7-T1 levels. CR1 = the regression of high cord signals at 6 months postoperatively (i.e., CR1 = (Preoperative SCR—SCR at 6 months postoperatively)/ Preoperative SCR). CR2 = the regression of high cord signal at 2 years postoperatively (i.e., CR2 = (Preoperative SCR—SCR at 2 years postoperatively)/ Preoperative SCR). CNR = canal narrowing ratio. SVA = sagittal vertical axis. mK-line INT = modified K-line interval. JOAs = Japanese Orthopedic Association score. Recovery1 = degree of JOAs recovery at 6 months postoperatively (i.e., Recover1 = (JOAs at 6 months postoperatively—Preoperative JOAs)/ (17- Preoperative JOAs)). Recovery2 = degree of JOAs recovery at 2 years postoperatively (i.e., Recover2 = (JOAs at 2 years postoperatively−Preoperative JOAs)/ (17−Preoperative JOAs))Table 2Linear regression analyses for lower CR2 values95% CIP valueUni-variable analysesDemographic data Sex (male/female)− 0.010.2210.924 Age− 0.0150.0030.195 Hypertension− 0.0710.2040.334 Diabetes− 0.1950.1350.716 BMI− 0.3750.4220.905 Smoking history− 0.2490.0770.295 Surgical approach− 0.349− 0.1130.000#Preoperative measured imaging parameters C2–7 Cobb angle− 0.0090.0020.185 SVA− 0.0080.0080.995 mK-line INT− 0.0430.0050.122 Preoperative SCR0.0920.4450.004# CR10.1560.7840.004# CNR− 0.760.8440.918Multi-variable analyses Surgical approach− 0.321− 0.1180.000** Preoperative SCR0.1270.410.000** CR1− 0.0180.5010.067#, variables that achieved a significance level of p < 0.1 in the univariate analysis*statistical significance (p < 0.05). **statistical significance (p < 0.01)BMI = body mass index. SCR = the signal change ratio between the localized high signal and normal spinal cord signal at the C7-T1 levels. CR1 = the regression of high cord signals at 6 months postoperatively (i.e., CR1 = (Preoperative SCR—SCR at 6 months postoperatively)/ Preoperative SCR). CR2 = the regression of high cord signal at 2 years postoperatively (i.e., CR2 = (Preoperative SCR—SCR at 2 years postoperatively)/ Preoperative SCR). CNR = canal narrowing ratio. SVA = sagittal vertical axis. mK-line INT = modified K-line intervalConclusionsFor patients with OPLL-induced cervical spondylotic myelopathy and intramedullary high signal, anterior removal of the ossified posterior longitudinal ligament and direct decompression offer a greater potential for regression of intramedullary high signal. At the same time, this anterior surgical strategy improves clinical neurologic function better than indirect decompression in the posterior approach.