Background : At present, in patients with degenerative cervical spondylosis, anterior decompression or laminoplasty is performed according to the extent of the lesion and the extent of spinal cord compression. Cervical laminoplasty is a useful surgical technique for multi-level disease, but problems have been identified with this procedure, such as postoperative axial pain, atrophy of the paraspinal muscles and postoperative kyphotic deformity.

  Purpose of the study : The evaluation of the postoperative changes in the nuchal muscles.

  Patient selection : Since December 2006, 65 patients with CSM have undergone the procedure, of whom 60 (35 men and 25 women) were selected for this study. Follow-up periods ranged from 12 to 18 months, with an average of 14 months. Average age at operation was 69 years (range, 37 to 82 years).

  Outcome measures : For quantitative analysis of the damage to the posterior cervical muscles, atrophy rates were calculated using Image J software from cross-sectional areas of the paraspinal muscles on the pre-and postoperative axial MRI. In addition, Serum creatine kinase was measured in preoperatve and postoperative day 1 and 7 to further assesstbe the muscle damage. To evaluate clinical outcomes, the Japanese Orthopaedic Association scoring system for cervical myelopathy (JOA scores) was used. The change of alignment was calculated by subtracting the preoperative C2-7 angle from the postoperative C2-7 angle. Statistical analysis was performed using these parameters.

  Results : No significant difference was found in the volume of all cross-sectional area. However, the volume of the deep muscle layer which is composed of muscles multifidus and rotatores muscles was significantly decreased post-operatively. The mean changes of alignment were 5.4 degree in our study Group, showing a trend toward improvement of alignment. The JOA score showed a significant improvement from 13 to 16.5. The improvement rate was 77.4%.

  Conclusion : Although the slight muscle atrophy was confirmed in the deep layer, no significant difference was found in the other layers. Therefore, it is suggested that this surgical technique not only provide sufficient expansion of the spinal canal, but also prevents postoperative kyphotic deformity.