• Michael J Lee, Richard J Bransford, Carlo Bellabarba, Jens R Chapman, Amy M Cohen, Richard M Harrington, and Randal P Ching.
• University of Washington Medical Center, Department of Sports Medicine and Orthopaedic Surgery, Seattle, WA 98195, USA. jihoon2000@hotmail.com
• Spine. 2010 Sep 1; 35 (19): 1789-93.

Study DesignA cadaveric simulation model of the lumbar spine was used to study the intervertebral motion characteristics of the lumbar spine after bilateral laminotomy and facet-sparing laminectomy.ObjectiveTo assess differences in motion patterns and lumbar spine stiffness after bilateral laminotomy versus laminectomy.Summary Of Background DataSpondylolisthesis after facet-sparing laminectomy has been reported with a frequency of 8% to 31%. Bilateral laminotomies have been shown to be effective in decompressing the spine, without resection of the posterior osteo-ligamentous complex. We hypothesize that bilateral laminotomies induce significantly less iatrogenic hypermobility and less stiffness reduction than a traditional facet-sparing laminectomy in the lumbar spine.MethodsSix fresh frozen human cadaveric lumbar spines (L1-L5) were mounted into a spine motion simulator for testing. With physiologic follower preload, flexion/extension, lateral bending, and axial rotation moments were applied to the lumbar spine in 3 trials: (1) Intact lumbar spine-no surgery, (2) Lumbar spine after bilateral lumbar laminotomies at L2-L5, (3) Lumbar spine after full laminectomies at L2-L5. The lumbar spine kinematics were measured using a Vicon motion tracking system. Total and segmental range of motion and spine stiffness were recorded.ResultsIn flexion/extension, bilateral laminotomies resulted in an average increase in L2-L5 range of flexion/extension motion of 14.3%, whereas a full laminectomy resulted in an increase of 32.0% (P<0.05). Analysis per level demonstrated roughly twofold increase in motion with laminectomy compared with bilateral laminotomies (P<0.05, at every treated level). Stiffness was decreased by an average of 11.8% after the 3-level-laminotomies and by 27.2% (P<0.05) after the 3-level-laminectomy.ConclusionThese data demonstrate that bilateral laminotomies induce significantly less hypermobility and less stiffness reduction compared with a full laminectomy. The preservation of the central posterior osteo-ligamentous structures may provide a stabilizing effect in preventing postdecompression spondylolisthesis.

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