Potential risk factors for poor outcome after anterior surgery for patients with cervical ossification of the posterior longitudinal ligament

Objective Our purpose here was to identify risk factors of poor outcome after anterior operation in patients with cervical ossification of the posterior longitudinal ligament (OPLL). Methods This study retrospectively reviewed 98 patients who underwent anterior surgery for improving neurological symptoms. The Japanese Orthopedic Association (JOA) recovery rate <50% was defined as poor surgical outcome. We investigated the relationship between various predictors and outcome by logistic regression analysis and receiver operating characteristic curves. To explore the cause of cerebrospinal fluid (CSF) leakage, we used the Mann-Whitney U-test, χ2 test, or independent t-test. Results Multivariate logistic regression analysis showed that age (odds ratio [OR] =1.1, 95% confidence interval [CI] =1.03-1.18, P=0.005), occupying ratio of OPLL (OR =1.08, 95% CI =1.03-1.12, P=0.001), and residual ratio of OPLL (OR =1.07, 95% CI =1.02-1.13, P=0.008) were independently associated with poor outcome. The cutoffs of the above risk factors were set at 63.5 years, 39.65%, and 25.165%, respectively. Predictors for CSF leakage were occupying ratio of OPLL, the K-line, and shape of the ossified lesion (P<0.001, P=0.019, and P=0.003). Conclusion These findings suggest that advanced age, high occupying ratio of OPLL, and high residual ratio of OPLL were risk factors for postoperative poor outcome in patients with OPLL. In addition, the high occupying ratio of OPLL, the K-line (-), and hill-shape ossification were potential causes of CSF leakage.