Imbalance of Muscles Around the Cervical Spine in Patients with Degenerative Cervical Spondylotic Kyphosis and Myelopathy.

BACKGROUND

To measure the muscle strength around the cervical spine; clarify the relationships among muscles, cervical sagittal alignment, and cervical spondylotic myelopathy (CSM); and understand the process underlying loss of cervical lordosis.

METHODS

Sex, age, course of illness, and radiological data were obtained for patients with CSM and a control group of healthy individuals. C2-7 Cobb angles were measured in cervical radiographs, and the vertebral body areas (VBAs) and cross-sectional areas (CSAs) of the deep flexors, superficial flexors, deep extensors, and superficial extensors were measured from the C3/4 to C6/7 intervertebral levels in T2-weighted axial magnetic resonance images. The CSA/VBA ratio was compared among CSM patients with and without degenerative cervical kyphosis (DCK) and control group.

RESULTS

Patients with CSM, especially those with DCK, showed an imbalance of muscles around the cervical spine. The CSA/VBA ratios of superficial flexor/superficial extensor at the C3/4 level (P = 0.036), total flexors/total extensors at the C6/7 level (P = 0.006), total deep muscles/total superficial muscles at the C4/5 level (P = 0.004), and total deep muscles/total superficial muscles at the C6/7 level (P = 0.031) differed significantly among the 3 groups. The CSM with DCK group tended to show larger CSA/VBA ratios of flexors/extensors and superficial muscles/deep muscles.

CONCLUSIONS

The greater strength of the flexors relative to the extensors and the superficial muscles compared with the deep muscles plays a role in pathogenesis of CSM with DCK, indicating the importance of neck and shoulder muscle-strengthening exercises in patients showing CSM with DCK.