Morphological changes in the cervical intervertebral foramen dimensions with unilateral facet joint dislocation

Background: Many investigators have conducted Studies to determine the biomechanics, causes, complications and treatment of unilateral facet joint dislocation in the cervical pine However, there is no quantitative data available on morphological changes in the intervertebral foramen of the cervical spine following unilateral facet joint dislocation These data are important to understand the cause of neurological compromise following unilateral facet joint dislocation. Methods Eight embalmed human cadaver cervical spine specimens ranging from level C1-T1 were used The nerve roots of these specimens at C5-C6 level were marked by wrapping a 0 12 mm diameter wire around them. Unilateral facet dislocation at C5-C6 level was Simulated by serially sectioning the corresponding ligamentous structures A CT scan of the specimens was obtained before and after the dislocation was simulated A sagittal plane through the centre of the pedicle and facet joint was constructed and used for measurement. The height and area of the intervertebral foramen, the facet joint space, nerve root diameter and area, and vertebral alignment both before and after dislocation were evaluated Results The intervertebral foramen area changed from 50 72 +/- 0 88 mm(2) to 67 82 +/- 4 77 mm(2) on the non-dislocated side and from 41 39 +/- 1.11 mm(2) to 113 77 +/- 5.65 mm(2) on the dislocated side The foraminal heights changed from 9 02 +/- 0 30 mm to 10.52 +/- 0 50 mm on the non-dislocated side and 10 43 +/- 0 50 mm to 17 04 +/- 0 96 mm on the dislocated side The facet space area in the sagittal plane changed from 6 80 +/- 0.80 mm(2) to 40 02 +/- 1 40 mm(2) on the non-dislocated side The C-5 anterior displacement showed a great change from 0 mm to 5 40 +/- 0 24 mm on the non-dislocated side and from 0 mm to 3 42 +/- 0 20 mm on the dislocated side. Neither of the nerve roots on either side showed a significant change in size Conclusions: The lack of change in nerve root area indicates that the associated nerve injury with unilateral facet joint dislocation is probably due to distraction rather than clue to direct nerve root: compression. Published by Elsevier Ltd