Background: This retrospective study aimed to investigate the difference of the intra-dural reserving space for spinal cord in magnetic resonance imaging (MRI) between patients with and without developmental cervical stenosis and its clinical significance.
Methods: A total of 264 patients with cervical spondylotic myelopathy who had decompression surgeries were recruited. The average follow-up was 29 months. Based on their lateral radiographs, they were divided into stenosis group and non-stenosis group. On the magnetic resonance images, the ratio of the sagittal diameter of the dural sac to that of the vertebral body was measured and calculated as MRI Pavlov ratio at the mid-vertebral level on T2-weighted sagittal images from C3 to C7. The ratio of the transverse area of the spinal cord to that of the dural sac was measured and calculated as occupation ratio on T2-weighted axial images at the same levels. The MRI Pavlov ratio and occupation ratio were compared between the two groups. The stenosis group was further divided into space-reserving and non-space-reserving subgroups based on the occupation ratios; then clinical parameters were compared between the two subgroups to determine the clinical significance of the reserving space.
Results: The MRI Pavlov ratio of the stenosis group was significantly smaller than that of the non-stenosis group at C3-C7 (P < 0.01), while the occupation ratio was significantly larger only at C7 (P < 0.05). For the space-reserving subgroup, the postoperative recovery rate was lower (P < 0.05). The postoperative recovery rate was (23 ± 6)% in anterior approach, larger than (-23±15)% in posterior approach (P < 0.05).
Conclusions: Developmental cervical stenosis is associated with a smaller sagittal diameter of the dural sac, but does not lead to a significant decrease in intra-dural space available for the cord. For patients with normal intra-dural space, the recovery after anterior decompression surgery was better than posterior approach.