Dimensional changes of the neuroforamina in subaxial cervical spine during in vivo dynamic flexion-extension

Neuroforaminal stenosis is one of the key factors causing clinical symptoms in patients with cervical radiculopathy. Previous quantitative studies on the neuroforaminal dimensions have focused on measurements in a static position. Little is known about dimensional changes of the neuroforamina in the cervical spine during functional dynamic neck motion under physiological loading conditions.

This study aimed to investigate the in vivo dimensional changes of the neuroforamina in human cervical spine (C3-C7) during dynamic flexion-extension neck motion.

A case-control study was carried out.

Ten asymptomatic subjects were recruited for this study. The cervical spine of each subject underwent magnetic resonance image scanning for construction of three-dimensional (3-D) vertebrae models from C3 to C7. The cervical spine was then imaged using a dual fluoroscopic system while the subject performed a dynamic flexion-extension neck motion in a sitting position. The 3-D vertebral models and the fluoroscopic images were used to reproduce the in vivo vertebral motion. The dimensions (area, height, and width) were measured for each cervical neuroforamen (C3/C4, C4/C5, C5/C6, and C6/C7) in the following functional positions: neutral position, maximal flexion, and maximal extension. Repeated measures analysis of variance and post hoc analysis were used to examine the differences between levels and positions.

Compared with the neutral position, almost all dimensional parameters (area, height, and width) of the subaxial cervical neuroforamina decreased in extension and increased in flexion, except the neuroforaminal area at C5/C6 (p=.07), and the neuroforaminal height at C6/C7 (p=.05) remained relatively constant from neutral to extension. When comparisons of the overall change fromextension to flexion were made between segments, the overall changes of the neuroforaminal area and height revealed no significant differences between segments, and the width overall change of the upper levels (C3/C4 and C4/C5) was significantly greater than the lower levels (C5/C6 and C6/C7) (p<.01).

The dimensional changes of the cervical neuroforamina showed segment-dependent characteristics during the dynamic flexion-extension. These data may have implications for diagnosis and treatment of patients with cervical radiculopathy.