Kinetic analysis of the cervical spinal cord in patients after spinous process-splitting laminoplasty using a kinematic magnetic resonance imaging technique

Study Design. An in vivo flexion-extension magnetic resonance imaging study. Objective. To evaluate the kinetic changes of the cervical spinal cord after laminoplasty in patients with cervical myelopathy. Summary of Background Data. Laminoplasty for cervical myelopathy increases the space occupied by the spinal cord, leading to a decompressive effect on the cord. However, there are few reports on kinetic changes of the spinal cord following this surgical procedure, by which it may contribute to an improvement of clinical symptoms. Methods. Patients who underwent spinous process-splitting laminoplasty (n = 40) and control group (n = 20) were enrolled in the study. Cervical spines of the subjects were examined from maximum extension to maximum flexion using a magnetic resonance imaging scanner. Sagittal T1-weighted images were obtained at 12 different angle positions. Images were analyzed with respect to the distance and alignment disparity between the dorsal edge of the vertebral column and the center of the cord at each disc level using National Institutes of Health Image software. Results. Spinal cords of patients after laminoplasty were dorsally shifted in the enlarged spinal canal at neutral, extension, and flexion positions. Alignment changes of the cord during flexion-extension movements of the cervical spine were dissociated from those of the vertebral column because of smaller changes in the cord alignment. Conclusions. Spinous process-splitting laminoplasty increases the degree of freedom of the spinal cord.