title: Cervical laminoplasty construct stability: an experimental and finite element investigation.
abstract: METHODS
  Experimental and finite element investigation of cervical laminoplasty.
  
  
  OBJECTIVE
  To determine the stability of the construct post cervical laminoplasty.
  
  
  BACKGROUND
  Cervical laminoplasty is a widely used technique to widen the spinal canal dimensions without permanently removing the dorsal elements of the cervical spine. Although various laminoplasty procedures have been developed recently, the use of mini-plates to hold the lamina open and prevent restenosis of the spinal cord is a fairly new method and has not been thoroughly investigated.
  
  
  METHODS
  Biomechanical compression tests and finite element analyses were performed in this study. Sixteen cervical vertebrae (C3 - C6) were isolated from six cadaveric cervical spines (age at death 68 to 91 years; mean 85 years) and were used for compression tests. Out of the 16 vertebrae, four were without any surgical intervention and the remaining 12 were implanted with one of the two laminoplasty plates: open door (OD) graft. Each vertebra was randomly assigned to one of the three groups: OD plate (6), graft plate (6) or intact vertebrae (4). The intact and implanted vertebrae were potted and loaded to failure. Cross-head displacements and the corresponding reaction force throughout the test were recorded to determine the failure loads. A finite element model of the C5 cervical vertebra was created to accommodate the laminoplasty implants. Experimental loading and boundary conditions were simulated and the stress distribution in the lamina was predicted in response to the compressive loads.
  
  
  RESULTS
  A substantial increase in the sagittal canal diameter (27%-33%) and the spinal canal area (31.2%-47%) was observed at all levels. The strength of the implanted specimens was considerably decreased (by six to eight times) as compared to the intact specimens.
  
  
  CONCLUSIONS
  Experimentally obtained data can be combined with mathematical models, such as finite element models, to accurately predict the biomechanical behavior (stresses and strains) of implants and the posterior bone which may not be possible by the use of any other method.
authors.affiliation: Department of Biomedical Engineering, The University of Iowa, Iowa City, USA.
authors.forename: Srinivas C
authors.initials: SC
authors.lastname: Tadepalli
authors.forename: Anup A
authors.initials: AA
authors.lastname: Gandhi
authors.forename: Douglas C
authors.initials: DC
authors.lastname: Fredericks
authors.forename: Nicole M
authors.initials: NM
authors.lastname: Grosland
authors.forename: Joseph
authors.initials: J
authors.lastname: Smucker
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001860:Bone Plates; D002102:Cadaver; D002574:Cervical Vertebrae / Q000502:physiology* / Q000601:surgery*; D019245:Compressive Strength / Q000502:physiology; D019299:Decompression, Surgical / Q000379:methods / Q000592:standards; D020342:Finite Element Analysis; D006801:Humans; D007796:Laminectomy / Q000295:instrumentation / Q000379:methods* / Q000592:standards; D008954:Models, Biological; D011237:Predictive Value of Tests; D019736:Prostheses and Implants; D012015:Reference Standards; D013115:Spinal Canal / Q000502:physiology / Q000601:surgery; D016474:Weight-Bearing / Q000502:physiology
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