Predictive Model of Cerebrospinal Fluid Leakage After Posterior Circumferential Decompression for Thoracic Ossification of Posterior Longitudinal Ligament
Authors: Zhong Jun , Wen Bingtao , Chen Zhongqiang 
Published: June 2021

Abstract
Background: Cerebrospinal fluid leakage(CSFL) is one of the most common complications after posterior transarticular osteotomy and circumferential decompression for thoracic ossification of posterior longitudinal ligament(OPLL). It is of great usefulness If the cerebrospinal fluid leakage can be predicted preoperatively. These predictors help to attract the attention of the surgeon in advance and warn the patient. Therefore, the aim of this study is to find out the factors that can predict the CSFL prior to operation and try to build a predictive model.Methods: A total of 61 patients with thoracic OPLL underwent posterior transarticular osteotomy and circumferential decompression from August 2015 to June 2020 in our hospital were included in this study, including 29 males and 32 females. The patients were divided into CSLF group and non-CSFL group according to whether they suffered cerebrospinal fluid leakage. Univariate analysis was used to identify possible predictors in Demographic characteristics, clinical and radiological data. A logistic regression model was developed by multivariate analyses to predict probability of CSFL. Model validation was done using the receiver operating characteristic(ROC) curve.Results: The incidence of CSFL was 31.1%, including 7 males and 12 females, with an average age of 49.8 ±11.4 years. The mean drainage indwelling time in CSFL group was 5.6±1.0 days, which was significantly higher than that in non-CSFL group (4.2±1.3 days, P < 0.001). The mean length of hospital stay was 16.3±6.3 days, slightly higher than that of the non-CSF group (15.8±6.7 days), but there was no statistical difference (P=0.77). Among them, 12 patients (63.2%) suffered low intracranial pressure manifested as headache; 1 patient (5.3%) had cerebrospinal fluid outflow from the incision, and the wound healed successfully after debridement.1 patient (5.3%) was re-admitted to the hospital due to fever after 3 weeks, considering deep wound effusion and pleural effusion. The wound effusion was found to be cured after 2 weeks of anti-infective treatment. Univariate regression analysis showed statistical differences (P<0.05) in smoking history, segment of circumferential decompression, combined with ossification of the ligamentum flavum (OLF), number of laminectomy, occupying ratio and OPLL base ratio. Multivariate regression model showed smoking history (OR=30.1, P=0.003), the upper thoracic segment (OR= 188.0, P= 0.002), the middle thoracic segment (OR= 57.4, P= 0.005) and OPLL base ratio (OR=1.3, P=0.007) were the predictors of CSFL. The ROC curve was in the upper left corner (area under the curve = 0.955, 95% CI 0.91-1.00, P< 0.001), indicating good predictability of the model.Conclusion: The predictive model established in this study has a high predictive effect. When the patients with thoracic OPLL have smoking history or the segment of circumferential decompression is located in the upper or middle thoracic spine or the OPLL has a wide base, the operator should be highly alert to the possibility of postoperative CSFL and warn the patient before surgery. Evidence level: level II-2