title: Biomechanical Evaluation of the CD HORIZON Spire Z Spinal System With Pedicle and Facet Fixation.
abstract: METHODS
  Human cadaveric biomechanical study.
  
  
  OBJECTIVE
  The aim of this study was to evaluate the biomechanics of lumbar motion segments instrumented with the CD HORIZON Spire Z plate system (Spire Z), a posterior supplemental fixation spinous process plate, alone and with additional fixation systems.
  
  
  BACKGROUND
  Plates and pedicle screw/rod and facet screw implants are adjuncts to fusion. The plate limits motion, improving segmental stability and the fusion microenvironment. However, the degree to which the plate contributes to overall stability when used alone or in conjunction with additional instrumentation has not been described.
  
  
  METHODS
  Standard nondestructive flexibility tests were performed in 7 L2-L5 human cadaveric spines. Spinal stability was determined as mean range of motion (ROM) in flexion/extension, lateral bending, and axial rotation. Paired comparisons were made between five conditions: (1) intact/control; (2) Spire Z; (3) Spire Z with unilateral pedicle screw/rod system (Spire Z+UPS); (4) Spire Z with unilateral facet screw system (Spire Z+UFS); and (5) Spire Z with bilateral facet screw system (Spire Z+BFS). Stiffness and ROM data were compared using one-way analysis of variance, followed by repeated-measures Holm-Šidák tests.
  
  
  RESULTS
  Spire Z was most effective in limiting flexion (20% of normal) and extension (24% of normal), but less effective in reducing lateral bending and axial rotation. In lateral bending, Spire Z+BFS and Spire Z+UPS constructs were not significantly different and demonstrated greater ROM reduction compared with Spire Z+UFS and Spire Z (P < 0.001). Spire Z+BFS demonstrated greatest stiffness in axial rotation compared with Spire Z+UPS (P = 0.025), Spire Z+UFS (P = 0.001), and Spire Z (P < 0.001). Spire Z+UPS was not significantly different from Spire Z+UFS (P = 0.21), and superior to Spire Z (P = 0.013).
  
  
  CONCLUSIONS
  The Spire Z spinous process plate provides excellent immediate fixation, particularly for flexion and extension. While the hybrid Spire Z+BFS screw construct afforded the greatest stability, Spire Z+UPS demonstrated considerable promise.
  
  
  METHODS
  N/A.
authors.affiliation: Department of Neurosurgery, Barrow Neurological Institute.
authors.forename: Jakub
authors.initials: J
authors.lastname: Godzik
authors.affiliation: Department of Neurosurgery, Barrow Neurological Institute.
authors.forename: Samuel
authors.initials: S
authors.lastname: Kalb
authors.affiliation: Spinal Biomechanics Laboratory, Department of Neurosurgery Research, St. Joseph's Hospital and Medical Center, Phoenix, AZ.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Martinez-Del-Campo
authors.affiliation: Spinal Biomechanics Laboratory, Department of Neurosurgery Research, St. Joseph's Hospital and Medical Center, Phoenix, AZ.
authors.forename: Anna G U S
authors.initials: AGUS
authors.lastname: Newcomb
authors.affiliation: Medtronic, Inc., Memphis, TN.
authors.forename: Vaneet
authors.initials: V
authors.lastname: Singh
authors.affiliation: Department of Neurosurgery, Barrow Neurological Institute.
authors.forename: Corey T
authors.initials: CT
authors.lastname: Walker
authors.affiliation: Department of Neurosurgery, Barrow Neurological Institute.
authors.forename: Steve W
authors.initials: SW
authors.lastname: Chang
authors.affiliation: Spinal Biomechanics Laboratory, Department of Neurosurgery Research, St. Joseph's Hospital and Medical Center, Phoenix, AZ.
authors.forename: Brian P
authors.initials: BP
authors.lastname: Kelly
authors.affiliation: Spinal Biomechanics Laboratory, Department of Neurosurgery Research, St. Joseph's Hospital and Medical Center, Phoenix, AZ.
authors.forename: Neil R
authors.initials: NR
authors.lastname: Crawford
mesh_terms: D001696:Biomechanical Phenomena / Q000502:physiology*; D001863:Bone Screws; D002102:Cadaver; D006801:Humans; D016268:Internal Fixators; D007596:Joints / Q000601:surgery*; D008159:Lumbar Vertebrae / Q000601:surgery*; D008875:Middle Aged; D065289:Pedicle Screws; D018583:Pliability / Q000502:physiology; D016059:Range of Motion, Articular / Q000502:physiology*; D013123:Spinal Fusion / Q000379:methods
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