Biomechanical aspects of the cervical cord: effects of postural changes in healthy volunteers using positional magnetic resonance imaging.

STUDY DESIGN: The area in cross-sectional view of the cervical cord (ACSCC) at each disc levels was measured in supine and erect positions using positional magnetic resonance imaging (pMRI). OBJECTIVES: To assess the relationship between ACSCC and cervical posture in healthy volunteers using pMRI. SUMMARY OF BACKGROUND DATA: There have been few detailed descriptions of the normal morphologic features of the cervical cord. However, there is no report to compare the relationship between ACSCC and cervical posture in healthy volunteers. METHODS: The study was performed on 20 healthy volunteers. The subjects were studied with pMRI in the supine and erect positions. The recumbent series and the erect series consist of 3 positions each: neutral, flexion and extension. On axial images, ACSCC was measured at the C2/3, C3/4, C4/5, C5/6, and C6/7 disc levels. On midsagittal image, the angle of the lower-endplate of C2 and C7 was measured. The results were compared between each series. RESULTS: In the recumbent and erect series, ACSCC was larger in extension than in neutral and flexion at all levels. There were significant differences between ACSCC in extension, neutral and flexion. ACSCC was smaller in flexion than in neutral and extension at all levels. There were significant differences between ACSCC in flexion, neutral and extension. CONCLUSIONS: We found posture-dependent differences of ACSCC in the recumbent and erect series. These results may be valuable for identifying a dynamic factor in patients with cervical spondylotic myelopathy.