Application of classification of spinal cord line in posterior cervical open-door laminoplasty

English Keywords:Spinal cord line  Classification  Decompression  Cervical vertebra  Laminoplasty

English Abstract:

  【Abstract】 Objectives: To introduce the definition of the spinal cord(SC) line, and its clinical classification and application strategies in posterior cervical open-door laminoplasty, and to examine and analyze the credibility and repeatability of this classification. Methods: The clinical data of a total of 86 patients who underwent cervical open-door laminoplasty via posterior approach in The Second Affiliated Hospital of Wenzhou Medical University from January 2018 to December 2020 were analyzed retrospectively. There were 51 males and 35 females, aged 34-77 years old, with postoperative follow-up period ranging from 12 to 36 months. The patients were classified into three types based on the location relationships between the SC line and compressor in the preoperative MRI: Type Ⅰ, the compressor at compression level did not exceed the SC line; Type Ⅱ, the compressor contacted the SC line; Type Ⅲ, the compressor exceeded the SC line. Five spinal surgeons independently evaluated and classified the MRI images of the patients, and Kappa consistency tests were performed to analyze the credibility and repeatability. 50 patients with multilevelcervical spinal cord compression diseases(cervical spondylotic myelopathy, ossification of the posterior longitudinal ligament, and developmental cervical spinal canal stenosis) were recruited and treated for a prospective study from January 2021 to December 2022, and the range of open-door segments was determined under the principle of improving the SC line classification as much as possible. The patients were followed up for 12 to 34 months. The modified anterior spinal cord compression score, neck pain visual analogue scale(VAS), Japanese Orthopaedic Association(JOA) score and recovery rates of the patients were recorded pre-operatively and at final follow-up in both retrospective and prospective studies. Paired samples t test was used to compare the scores before and after surgery in each type of patients, and one-way ANOVA was used to compare the scores between the three groups, to assess the postoperative spinal cord decompression and clinical outcomes of the different SC line types. Results: Among the 86 patients analyzed retrospectively, 38 were Type Ⅰ, 31 were Type Ⅱ and 17 were Type Ⅲ. The Kappa coefficient was 0.817-0.945 for inter-observer consistency, which was 0.891-0.963 for intra-observer consistency, indicating satisfactory credibility and repeatability. There was no significant difference in modified anterior spinal cord compression score and VAS score between the three types of patients before surgery(P>0.05), and all of them were statistically different at the final follow-up compared with the preoperative period(P<0.05). The modified anterior spinal cord compression score and VAS score were the lowest at the final follow-up in Type Ⅰ, which were the highest in Type Ⅲ(P<0.05). The JOA recovery rate was (73.49±11.26)% in Type Ⅰ, (67.08±9.01)% in Type Ⅱ, and (53.74±7.93)% in Type Ⅲ, with statistically significant differences between the three types(P<0.05). Among the 50 patients analyzed prospectively, 27 were Type Ⅰ, 15 were Type Ⅱ and 8 were Type Ⅲ. The preoperative spinal cord compression score was 3.67±0.47 in Type Ⅰ, 3.84±0.37 in Type Ⅱ, and 4.00±0.00 in Type Ⅲ, which was 1.24±0.62 in Type Ⅰ, 2.60±0.58 in Type Ⅱ, and 3.40±0.52 in Type Ⅲ at the final follow-up, respectively. The VAS score decreased from 6.48±0.85 preoperatively to 1.11±0.51 at final follow-up in Type Ⅰ. Type Ⅱ cases exhibited a decrease in VAS score from 6.67±0.90 preoperatively to 1.73±0.59 at final follow-up. And the VAS score decreased from a preoperative value of 7.13±0.64 to 2.38±0.52 at final follow-up in Type Ⅲ(P<0.05). The modified anterior spinal cord compression score and VAS score were the lowest in Type Ⅰ and the highest in Type Ⅲ at final follow-up(P<0.05). The JOA score improved from 12.07±1.17 preoperatively to 15.59±0.69 at final follow-up in Type Ⅰ. Type Ⅱ cases exhibited an improvement in JOA score from 10.93±0.80 preoperatively to 14.67±0.72 at final follow-up. And the JOA score improved from a preoperative value of 10.13±1.13 to 13.63±0.74 at final follow-up in Type Ⅲ(P<0.05). The JOA recovery rate was (72.50±12.38)% in Type Ⅰ, (61.99±9.78)% in Type Ⅱ, and (51.25±5.19)% in Type Ⅲ, which was statistically different between the three groups(P<0.05). Conclusions: The SC line and its classification are practical and reliable, demonstrating good credibility and repeatability. Suitable open-door segment in posterior open-door laminoplasty in patients of Type Ⅰ SC line can make anterior spinal cord compression relieved; And anterior surgery needs to be considered when anterior compression remained after posterior surgery in patients of Type Ⅲ SC line.