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

Abstract

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.

Keywords: Cervical spondylotic myelopathy; Degenerative cervical kyphosis; Magnetic resonance imaging; Muscles; Radiography.