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The effect of posterior cervical distraction on foraminal dimensions utilizing a screw-rod system
Louis G Jenis1, Steven Banco, John J Jacquemin
1The Boston Spine Group, Boston, MA 02120, USA. ljenis@caregroup.harvard.edu
Study Design:
Cadaveric human cervical spine anatomic study using posterior lateral mass screw-rod instrumentation to assess foraminal enlargement via distraction techniques.
Objectives:
To determine the role of posterior cervical distraction on foraminal dimensions and to ascertain the impact of this technique on segmental kyphosis.
Summary Of Background Data:
Management of cervical spondylotic radiculopathy includes removal of offending compressive structures and enlarging the neuroforamen via anterior discectomy with interbody fusion or posterior laminoforaminotomy.
Methods:
Six human cervical spines were prepared and posterior exposure performed. Lateral mass screws were inserted from C5 to C7 and a longitudinal rod attached. Distraction was applied between the screw heads at 2 mm intervals and accuracy confirmed with digitized calipers. Pre- and postdistraction computed tomography was performed including axial and reformatted images. Foraminal area, height, and width and sagittal alignment and disc heights were evaluated.
Results:
The results suggest that minimal posterior distraction of 4 to 6 mm at C5-C6 and C6-C7 may enlarge the neuroforamen by 10 to 18 mm. Foraminal height and width increased minimally from baseline to maximum distraction; however, these measurements did not reach statistical significance at either level. A decrease of segmental lordosis at C5-C6 was noted from baseline to 8 mm of distraction. Statistically significant kyphosis from baseline was present at 6 mm of distraction leading to overall 5.2 +/- 1.4degrees change in alignment. At C6-C7, statistically significant kyphosis was not present until 8 mm of distraction (4.62 +/- 2.23degrees).
Conclusions:
This study suggests that posterior cervical instrumented distraction in the setting of foraminal stenosis is a reasonable supplement to direct laminoforaminotomy and nerve root decompression. Distraction leads to minimal segmental kyphosis, allowing this technique to serve as an adjunct for additional foraminal enlargement.