The length of the cervical cord: Effects of postural changes in healthy volunteers using positional magnetic resonance imaging

Study Design. The length of the cervical cord in healthy volunteers was measured in the supine and erect position using positional magnetic resonance imaging (MRI). Objective. To assess the relationship between the length of the cervical cord and cervical posture in healthy volunteers. Summary of Background Data. A number of detailed descriptions of the normal morphologic features of the cervical cord have been published. However, to our knowledge, there is no report to compare the relationship between the length of the cervical cord and cervical posture in healthy volunteers using positional MRI. Methods. This study was performed on 20 healthy volunteers using positional MRI. The subjects were studied in the supine and erect positions. The recumbent series consisted of 3 positions: neutral, flexion, and extension. The erect series consisted of 3 positions: neutral, flexion, and extension. On the midsagittal image, the length of the cervical cord from C1 to C7 was measured at the anterior, middle, and posterior line. The angle of the lower-endplate of C2 and C7 was measured. The results were compared with each series. Results. In the recumbent and erect series, the mean length of the cervical cord in flexion was longer than in neutral and extension at the anterior, middle, and posterior line. There were significant differences between the length of the cervical cord in flexion, neutral, and extension. The mean length of the cervical cord in extension was shorter than in neutral and flexion at the anterior, middle, and posterior line. There were significant differences between length of the cervical cord in extension, neutral, and flexion. Conclusions. We found posture-dependent differences of the length of the cervical cord in the recumbent and erect series. These results may be important when assessing the dynamic factor in cervical spondylotic myelopathy.