Effect and evaluation of MRI-based prediction of decompression outcomes before posterior cervical expansive open-door laminoplasty

English Keywords:Cervical spondylotic myelopathy  Cervical expansive open-door laminoplasty  MRI prediction  Clinical efficacy

English Abstract:

  【Abstract】 Objectives: To explore and evaluate the efficacy of preoperative MRI in predicting decompression outcomes in expansive open-door laminoplasty for cervical spondylosis. Methods: The clinical data of 48 patients with cervical spondylotic myelopathy(CSM) who underwent cervical expansive open-door laminoplasty in our hospital from January 2020 to October 2022 were retrospectively analyzed. There were 35 males and 13 females, aged from 41 to 78 years old(59.9±9.1 years). The midsagittal diameter of the dural sac of the compressed segment was measured on the midsagittal view of MRI T2WI before operation. The line between the anterior inferior edge of the superior lamina and the anterior superior edge of the inferior lamina was set as the lamina line(LL). The measurement of the midsagittal diameter from the anterior dural margin to the LL was the LL simulated decompression midsagittal diameter. The spinal cord′s actual decompression midsagittal diameter was measured as the dural sac midsagittal diameter at the decompressed level on the MRI T2WI mid-sagittal plane one month postoperatively. The correlation between the actual postoperative midsagittal diameter of spinal cord decompression at 1 month and the simulated decompression midsagittal diameter using LL was analyzed. The prediction was defined as accurate when there was no statistically significant difference(P>0.05) between the preoperative simulated decompression midsagittal diameter using LL and the actual postoperative decompression midsagittal diameter according to paired t test analysis. For cases predicted accurately, the effect of C2-C7 Cobb angle on the predictive value of the LL simulated decompression was assessed. The postoperative efficacy was evaluated using the modified Japanese Orthopaedic Association(mJOA) score at 12-month follow-up. Results: The spinal cord′s actual decompression midsagittal diameter after the operation was 14.1±1.4mm and the midsagittal diameter in the preoperative LL simulated decompression was 14.3±1.6mm, which were both significantly increased compared with the preoperative midsagittal diameter of the dural sac at the compressed level of 10.1±1.5mm(P<0.05). Correlation analysis showed that the predictive accuracy rate of the midsagittal diameter in LL simulated decompression was 93.8%(45/48). The preoperative C2-C7 Cobb angle of the 45 patients with accurate prediction were 24.2°±6.7°, and the postoperative C2-C7 Cobb angle was 24.2°±6.3°, and there was no statistically significant difference(P>0.05). The 45 patients with accurate predictions were grouped with preoperative C2-C7 Cobb angles into 16 patients with Cobb<20° and 29 patients with Cobb≥20°. The mean midsagittal diameter of LL simulated and actual decompression in patients with Cobb≥20° was significantly greater than that in patients with Cobb<20°(P<0.05). In the three patients with inaccurate prediction, the C2-C7 Cobb angle was significantly reduced postoperatively compared to preoperatively, and the actual midsagittal diameter of the dural sac after the operation was smaller than that in the LL simulated decompression(P<0.05). All the 48 patients were followed up for 12 to 36 months(22.5±7.0 months), and the mJOA score at 12-month postoperative follow-up was 16.5±0.8 points, which was significantly higher than that before operation(P<0.05). Conclusions: The application of MRI T2WI midsagittal LL simulated decompression before operation can well predict the effect of spinal cord decompression in cervical expansive open-door laminoplasty.