Postoperative changes at the lower end of cervical laminoplasty: for preservation of the C7 spinous process in laminoplasty.

Introduction: C3-C7 laminoplasty has been the standard treatment for cervical myelopathy, although several recent reports described C3-C6 laminoplasty for preserving the muscles inserting in C7 and reducing postoperative axial symptoms. However, postoperative changes at C6/C7 of the lower end of C3-C6 laminoplasty, especially regarding a possibility of postoperative spinal canal narrowing have not been measured. The purpose of this study was to clarify postoperative changes at the lower end of laminoplasty.

Methods: Pre and postoperative spinal dura diameter at the lower end of conventional C3-C7 laminoplasty using MRI, and the related factors for spinal dura diameter and the causes of postoperative dura narrowing were investigated.

Results: At the last follow-up after C3-C7 laminoplasty, dura diameter at C7/T1 was significantly wider after operation than before operation, and postoperative narrowing of dura diameter, which was found in 20% of patients, was a maximum amount of one millimeter. No pre and postoperative factor significantly correlated with dura diameter at C7/T1. The causes of postoperative narrowing at the lower end of laminoplasty were disc protrusion and/or posterior scar, or segmental angulation of the spinal cord.

Conclusion: In conclusion, the presence of preoperative subarachnoid space over one millimeter at C6/C7 may be able to be one of the radiological indications for C3-C6 laminoplasty.