Article
Minimally invasive laminotomy preserves a higher spine stability with respect to conventional laminotomy in the treatment of spinal stenosis
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Published: | October 10, 2016 |
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Objectives: The treatment of lumbar stenosis is based on the relief of pressure on the pinched nerve roots by means of surgical decompression, often resulting in a destabilization of the spine which may progress in a spinal deformity. Despite the extent of the decompression has been identified as a risk factor for postoperative deformities, biomechanical data about the actual destabilization due to the tissue removal is scarce, especially regarding recent minimally invasive techniques which are assumed to allow for a better preservation of the native spine stiffness. The aim of the present study is therefore to compare the flexibility of the intact lumbar spine to that after a minimally invasive decompression, a conventional laminotomy and after subsequent posterior fixation.
Methods: A 6-degrees-of-freedom spine tester able to apply pure moments in the three anatomical planes has been used to measure the range of motion of six intact L2-L5 human spine specimens showing negligible signs of degeneration. An incremental damage protocol was then applied: (1) unilateral minimally invasive decompression at L3-L4; (2) on three specimens, the unilateral laminotomy was extended to L4-L5; (3) bilateral minimally invasive laminotomy (at L3-L4 in the first three specimens and at L4-L5 in the rest); (4) conventional laminotomy at the same levels; (5) posterior fixation at the involved levels. After each step, the segmental flexibility of the specimens in flexion-extension, lateral bending and axial rotation was measured by means of an optoelectronic system.
Results and Conclusion: Minimally invasive laminotomy induced a significant increase of the spine flexibility in flexion-extension (18% for the bilateral case) and in axial rotation (7%), whereas lateral bending was negligibly affected. Laminotomy performed with a conventional technique induced a significantly higher destabilization, also in lateral bending (8%). With respect to single level decompression, double level laminotomy approximately induced a twofold destabilization. Posterior fixation always reduced the spine flexibility to values lower than in the intact case. Despite surgical decompression systematically induces a significant destabilization of the lumbar spine, a minimally invasive approach in which portions of the laminae and of the facet joints are preserved allowed for a lower increase of the ranges of motion, thus presumably reducing the risk of postoperative deformities.