EFFECT OF CERVICAL-SPINE MOTION ON THE NEUROFORAMINAL DIMENSIONS OF HUMAN CERVICAL-SPINE

A nerve root impingement within a stenotic neuroforamen is a common sequela of cervical degenerative arthritis and herniated nucleus pulposus. Understanding of the effects of cervical position on foraminal size is important in the assessment of pathology and injury, for selection of a provocative maneuver to elicit symptoms and in selecting a position of immobilization for the management of nerve root impingement syndrome. This biomechanical study of human cadaver cervical spines reports the measured variations in the sizes of neuroforamina as a function of cervical positioning. Five fresh frozen adult human cadaver cervical spines (C2-T1) were tested with combinations of flexion-extension and rotational position. Ten pounds of axial load was applied to simulate a normal loading of a cervical spine. The foramina of C5, C6, and C7 were directly measured using a set of finely graded circular probes. Compared to the foraminal diameter at the neutral position, there were statistically significant reductions in the foramen diameter of 10% and 13%, at 20-degrees and 30-degrees of extension respectively (P < 0.01). Conversely, in flexion, there were statistically significant increase of 8% and 10% at 20-degrees and 30-degrees of flexion respectively (P < 0.01). Though there was a reduction in the foraminal size with ipsilateral 20-degrees rotation, and an increase with contralateral 20-degrees rotation, these changes were not significantly different from the mean of the control. Combinations of flexion or extension position with axial rotation did not significantly change the foraminal size compared to the respective sagittal position with no axial rotation. From 30-degrees extension to 30-degrees flexion, the mean change of foraminal diameter was 1.4mm. This anatomical study shows that extension and ipsilateral rotation reduces the forminal area which contributes to pain, nerve root compression, and neural injury. Flexion, extension, and rotational maneuvers may therefore afford a provocative test for establishing the diagnosis of spinal stenosis. Furthermore, the study suggests that patients managed conservatively should be immobilized in their orthoses in a flexed rather than an extended position, to decrease nerve root impingement by maximizing the diameter of the neural foramina.