Transarticular osteotomy and circumferential decompression through a single posterior approach for ossification of thoracic posterior longitudinal ligament: outcomes and risk factors of transient postoperative neurologic deterioration

English Keywords:Ossification of the posterior longitudinal ligament  Thoracic  Transarticular osteotomy  Circumferential decompression  Outcome

English Abstract:

  【Abstract】 Objectives: To retrospectively evaluate the clinical efficacy of posterior transarticular osteotomy and circumferential decompression for thoracic ossification of posterior longitudinal ligament(OPLL), and to explore the risk factors of transient postoperative neurologic deterioration. Methods: A total of 29 patients with thoracic OPLL underwent posterior transarticular osteotomy and circumferential decompression from August 2015 to September 2018, including 18 males and 11 females. The age ranged from 27 to 80 years old, with an average age of 52.8±14.6 years. 20 patients were beaked type OPLL, 5 patients were continuous type and 4 patients were mixed type. All patients underwent 1 level of circumferential decompression and an average of 3 level of laminectomy. The average follow-up time was 30.0±11.7 months(range 13-50 months). A modified Japanese Orthopedic Association(JOA) scale for thoracic spine was used to evaluate neurologic status at pre-operation and post-operation respectively, and final recovery rates were assessed according to Hirabayashi system. The patients were divided into 2 groups based on the absence or presence of transient postoperative paralysis. The following items were compared between two groups: age, sex, body mass index, the duration of disease(from first symptom to operation), the preoperative JOA score, location of the OPLL, type of the OPLL, operation time, the blood loss, mean arterial pressure, difference value of pre-operative and intraoperative mean arterial pressure. And then, items with statistical difference and risk factors reported in the previous literature that may lead to transient postoperative paralysis were selected for binary Logistic regression analysis. Results: All patients underwent surgery. The average operation time was 170.7±74.1min(range 80-354min). The mean blood loss was 1097.9±788.7ml(range 150-3500ml). Surgical complications included dural tear in 6 patients(20.7%), intercostal neuralgia in 1 patient(3.4%), and transient postoperative neurologic deterioration in 6 patients(20.7%). The average JOA score was significantly improved from 5.3±2.1 before surgery to 8.9±1.6 at the final follow-up(P<0.001). The mean recovery rate was (64.2±21.4)%(range 16.7%-100%), and excellent and good rate was 86.2%: 9 patients were excellent, 16 patients were good, 3 patients were fair and 1 patient was poor. None had suffered neurological deterioration at the final follow-up. The blood loss, the difference value of pre-operative and intraoperative mean arterial pressure were significantly different between two groups(P<0.05). When included in a binary Logistic regression model, difference value of pre-operative and intraoperative mean arterial pressure was associated with the transient postoperative neurological deterioration(OR＝1.27, P=0.026, 95%CI 1.01-1.57). For every 1mmHg decrease compared with the preoperative mean arterial pressure, the risk of transient postoperative neurological deterioration increased by 27 percents. Conclusions: Posterior transarticular osteotomy and circumferential decompression seemed to be effective for the thoracic ossification of posterior longitudinal ligament. Maintaining intraoperative mean arterial pressure at a consistent preoperative level can significantly reduce the risk of transient postoperative neurologic deterioration.