The relationship between surface contour and vertebral body measures of upper spine curvature.

Abstract

In this study, parameters of sagittal cervical posture obtained from surface markers and from vertebral body locations were compared. Several postural parameters were examined to establish the degree to which surface measures of cervical alignment reflect the underlying vertebral body alignment. Previous studies of the relation between surface and vertebral alignment in the thoracic and lumbar regions have shown conflicting results. Some data suggest a connection between surface cervical posture and head and neck pain, but the relation between surface and vertebral posture in the cervical region has not been reported. Lateral view radiographs of 24 healthy volunteers were used to give the surface alignment of skin markers and the locations of the geometric centers of vertebral bodies. Three angles describing sagittal alignment were investigated: 1) forward inclination of C2 relative to C7 (cervical inclination); 2) cervicothoracic kyphosis; and 3) cervical lordosis. A strong relationship between surface and vertebral data was not established. Two factors were identified as contributing to the observed differences: length of spinous processes and depth of soft tissue overlying the spinous processes at each spinal level. The assumption that the surface curve is the same as the vertebral curve is not supported by these results, suggesting caution is needed in inferring vertebral alignment from observed surface contours.