• Peter Grunert, Phillip M Reyes, Anna G U S Newcomb, Sara B Towne, Brian P Kelly, Nicholas Theodore, and Roger Härtl.
• *Weill Cornell Brain and Spine Center, Department of Neurological Surgery, Weill Cornell Medical College, New York, New York; ‡Spinal Biomechanics Research Laboratory, Barrow Neurological Institute, Phoenix, Arizona.
• Neurosurgery. 2016 Dec 1; 79 (6): 895-904.

BackgroundMultilevel lumbar stenosis, in which 1 level requires stabilization due to spondylolisthesis, is routinely treated with multilevel open laminectomy and fusion. We hypothesized that a minimally invasive (MI) decompression is biomechanically superior to open laminectomy and may allow decompression of the level adjacent the spondylolisthesis without additional fusion.ObjectiveTo study the mechanical effect of various decompression procedures adjacent to instrumented segments in cadaver lumbar spines.MethodsConditions tested were (1) L4-L5 instrumentation, (2) L3-L4 MI decompression, (3) addition of partial facetectomy at L3-L4, and (4) addition of laminectomy at L3-L4. Flexibility tests were performed for range of motion (ROM) analysis by applying nonconstraining, pure moment loading during flexion-extension, lateral bending, and axial rotation. Compression flexion tests were performed for motion distribution analysis.ResultsAfter instrumentation, MI decompression increased flexion-extension ROM at L3-L4 by 13% (P = .03) and axial rotation by 23% (P = .003). Partial facetectomy further increased axial rotation by 15% (P = .03). After laminectomy, flexion-extension ROM further increased by 12% (P = .05), a 38% increase from baseline, and axial rotation by 17% (P = .02), a 58% increase from baseline. MI decompression yielded no significant increase in segmental contribution of motion at L3-L4, in contrast to partial facetectomy and laminectomy (<.05).ConclusionMI tubular decompression is biomechanically superior to open laminectomy adjacent to instrumented segments. These results lend support to the concept that in patients in whom a multilevel MI decompression is performed, the fusion might be limited to the segments with actual instability.AbbreviationMI, minimally invasive.

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