Abstract
Introduction
Surgical advances attempt to alleviate lumbar spinal stenosis, which burdens many people in our aging population. One goal of pedicle screw and spinous process distraction is to decompress the neural foramina of the affected segment. The objective of this study is to evaluate the change in the foraminal size adjacent to the distracted level.
Materials and Methods
The lumbar spine of a prone cadaveric specimen was exposed. Titanium pedicle screws were placed from L1-L5. A titanium rod spanning only two levels on either side of the spine was fastened down at the caudal end and secured at the cephalad end. The screws were distracted until maximal resistance on the left side was reached and then the cephalad set screw was secured. The same amount of distraction was applied to the right side and secured in the same fashion.
A second prone cadaveric specimen was exposed. Titanium screws were instead inserted into the spinous processes at levels L1-L4. The distraction technique described above was used with two predetermined distances (3 mm and 6 mm).
A CT scan was obtained before and after distraction at each level. Foraminal openings at the level of distraction as well as the adjacent above and below foramina were measured and analyzed.
Results
In the pedicle-distraction specimen, there was an overall positive percent change at the level of distraction and an overall negative percent change in the levels above and below. The level of L3-L4 on the right revealed the largest percent change (11.09%) in foramen distraction. The foramen superior to the L2-L3 distraction demonstrated the least amount of change (−9.71%).
The spinous process-distraction specimen demonstrated an overall positive percent change at the level of the distraction but not an overall negative change at the adjacent levels. The L1-L2 superior adjacent foramina had negative percent changes at the 3 mm and 6 mm of −2.80% R, −12.52% L and −4.20% R,−15.46% L, respectively. Only the right, 3 mm distraction of the inferior adjacent of L1-L2 showed a negative percent change, the rest were positive changes. The L3-L4 distractions including above and below foramina were positive percent changes. The greatest percent change at L3-L4 for the 6 mm distraction was 43.1% at the level of distraction and 6.35% at the above adjacent level.
Conclusion
Distraction of the lumbar spine at any level does increase foramen size at that level, but adjacent levels are affected differently depending on the type of distraction. Distraction at the spinous process may be more beneficial particularly in the lower lumbar area. Further studies are necessary to reproduce these results to provide a basis for determining an optimal method for foraminal distraction which minimizes adjacent level stenosis.
None declared