title: Sheep cervical spine biomechanics: a finite element study.
abstract: BACKGROUND
  Animal models are often used to make the transition from scientific concepts to clinical applications. The sheep model has emerged as an important model in spine biomechanics. Although there are several experimental biomechanical studies of the sheep cervical spine, only a limited number of computational models have been developed. Therefore, the objective of this study was to develop and validate a C2-C7 sheep cervical spine finite element (FE) model to study the biomechanics of the normal sheep cervical spine.
  
  
  METHODS
  The model was based on anatomy defined using medical images and included nonlinear material properties to capture the high flexibility and large neutral zone of the sheep cervical spine. The model was validated using comprehensive experimental flexibility testing. Ten adult sheep cervical spines, from C2-C7, were used to experimentally ascertain overall and segmental flexibility to ±2 Nm in flexion-extension, lateral bending, and axial rotation.
  
  
  RESULTS
  The ranges of motion predicted by the computational model were within one standard deviation of the respective experimental motions throughout the load cycle, with the exception of extension and lateral bending. The model over- and under predicted the peak motions in extension and lateral bending, respectively. Nevertheless, the model closely represents the range of motion and flexibility of the sheep cervical spine.
  
  
  CONCLUSIONS
  This is the first multilevel model of the sheep cervical spine. The validated model affords additional biomechanical insight into the intact sheep cervical spine that cannot be easily determined experimentally. The model can be used to study various surgical techniques, instrumentation, and device placement, providing researchers and clinicians insight that is difficult, if not impossible, to gain experimentally.
authors.affiliation: Department of Biomedical Engineering The University of Iowa, Iowa City, IA 52242 ; Center for Computer Aided Design The University of Iowa, Iowa City, IA 52242.
authors.forename: Nicole A
authors.initials: NA
authors.lastname: DeVries Watson
authors.affiliation: Department of Biomedical Engineering The University of Iowa, Iowa City, IA 52242 ; Center for Computer Aided Design The University of Iowa, Iowa City, IA 52242.
authors.forename: Anup A
authors.initials: AA
authors.lastname: Gandhi
authors.affiliation: Department of Orthopaedic Surgery and Rehabilitation The University of Iowa, Iowa City, IA 52242.
authors.forename: Doug C
authors.initials: DC
authors.lastname: Fredericks
authors.affiliation: Department of Orthopaedic Surgery and Rehabilitation The University of Iowa, Iowa City, IA 52242.
authors.forename: Joseph D
authors.initials: JD
authors.lastname: Smucker
authors.affiliation: Department of Biomedical Engineering The University of Iowa, Iowa City, IA 52242 ; Center for Computer Aided Design The University of Iowa, Iowa City, IA 52242 ; Department of Orthopaedic Surgery and Rehabilitation The University of Iowa, Iowa City, IA 52242.
authors.forename: Nicole M
authors.initials: NM
authors.lastname: Grosland
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena / Q000502:physiology; D002574:Cervical Vertebrae / Q000502:physiology*; D020342:Finite Element Analysis; D023421:Models, Animal; D016059:Range of Motion, Articular / Q000502:physiology*; D012399:Rotation; D012756:Sheep