The prognostic factors of cervical spondylotic myelopathy treated with posterior cervical decompression and internal fixation

English Keywords:Cervical posterior decompression and internal fixation  Cervical spondylotic myelopathy  Imaging parameters  Prognostic factors

English Abstract:

  【Abstract】 Objectives: To analyze the imaging related prognostic factors of cervical spondylotic myelopathy treated with posterior cervical decompression and internal fixation. Methods: The clinical data and imaging data of 72 cases of cervical spondylotic myelopathy treated with posterior decompression and internal fixation in the neurosurgery department of Northern Theater Command general hospital from May 2014 to May 2018 were retrospectively analyzed. The patients included 55 males and 17 females, and aged from 21 to 80 years old (average, 56.9±12.0 years old). Data of disease course, compression segment, Japanese Orthopaedic Association (JOA) scores before surgery and one week after surgery, preoperative Cobb angle, maximum diameter of compressed matter in compression segment, effective cervical spinal canal rate, average compression rate, transverse area of spinal cord, spinal canal occupancy rate, spinal cord drift distance after surgery, and improvement rate of JOA were collected. According to the improvement rate of JOA, the patients were divided into the following groups: 58 cases of excellent prognosis(improvement rate ≥50%) and 14 cases of poor prognosis (improvement rate <50%). The prognostic factors were analyzed by single factor and multi-factor binary logistic regression. The receiver operating characteristic curve (ROC) was used to determine the critical value of prognosis related factors. The largest cut of Youden index was selected as the demarcation value and the critical value of prognostic factors. Results: Univariate analysis showed that there werestatistically significant differences (P<0.05) between preoperative Cobb angle of 12.81°±4.27°, effective cervical spinal canal rate of (33.71±9.87)%, spinal cord drift distance of 3.38±0.62mm, maximum diameter of compressed matter of 3.83±0.83mm, and spinal canal occupancy rate of (64.02±7.74)% in excellent prognosis group and preoperative Cobb angle of 9.68°±4.00°, effective cervical spinal canal rate of (22.86±8.78)%, spinal cord drift distance of 2.13±0.75mm, maximum diameter of compressed matter of 5.38±1.01mm, and spinal canal occupancy rate of (69.21±9.28)% in poor prognosis group. Further multivariate analysis of the above relevant factors showed that the maximum diameter of compressed matter and spinal cord drift distance were the main factors affecting the prognosis of cervical spondylotic myelopathy(P<0.05). ROC curve showed that the diagnostic critical value of the maximum diameter of compressed matter was 4.950mm(the area under the curve was 0.875). The diagnostic threshold for drift distance of spinal cord was 2.625mm(the area under curve was 0.897). Conclusions: The maximum diameter compressed matter and the drift distance of the spinal cord are the main factors influencing the prognosis of cervical spondylotic myelopathy treated by posterior decompression and internal fixation, and the prognosis is worse when the maximum diameter of compressed matter exceeds 4.950mm in the compression stage and better when the drift distance of the spinal cord exceeds 2.625mm after this operation.