title: The effect of bilateral laminotomy versus laminectomy on the motion and stiffness of the human lumbar spine: a biomechanical comparison.
abstract: METHODS
  A 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.
  
  
  OBJECTIVE
  To assess differences in motion patterns and lumbar spine stiffness after bilateral laminotomy versus laminectomy.
  
  
  BACKGROUND
  Spondylolisthesis 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.
  
  
  METHODS
  Six 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.
  
  
  RESULTS
  In 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.
  
  
  CONCLUSIONS
  These 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.
authors.affiliation: University of Washington Medical Center, Department of Sports Medicine and Orthopaedic Surgery, Seattle, WA 98195, USA. jihoon2000@hotmail.com
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Lee
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Bransford
authors.forename: Carlo
authors.initials: C
authors.lastname: Bellabarba
authors.forename: Jens R
authors.initials: JR
authors.lastname: Chapman
authors.forename: Amy M
authors.initials: AM
authors.lastname: Cohen
authors.forename: Richard M
authors.initials: RM
authors.lastname: Harrington
authors.forename: Randal P
authors.initials: RP
authors.lastname: Ching
mesh_terms: D000368:Aged; D001696:Biomechanical Phenomena; D002102:Cadaver; D019299:Decompression, Surgical / Q000009:adverse effects / Q000379:methods*; D006801:Humans; D007593:Joint Instability / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control; D007796:Laminectomy / Q000009:adverse effects / Q000379:methods*; D008159:Lumbar Vertebrae / Q000503:physiopathology / Q000601:surgery*; D016059:Range of Motion, Articular; D013168:Spondylolisthesis / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control