title: An ex vivo biomechanical comparison of a novel vertebral compression fracture treatment system to kyphoplasty.
abstract: BACKGROUND
  Vertebral compression fracture repair aims to relieve pain and improve function by restoring vertebral structure and biomechanics, but is still associated with risks arising from polymethylmethacrylate cement extravasation. The Kiva® Vertebral Compression Fracture Treatment System, a stacked coil implant made of polyetheretherketone and delivered over a guide-wire, is a novel device designed to provide height restoration and mechanical stabilization, while improving cement containment and minimizing disruption of cancellous bone. The objective of this study was to determine whether the Kiva system is as effective as balloon kyphoplasty at restoring mechanical properties in osteoporotic vertebral compression fractures.
  
  
  METHODS
  Wedge fractures were created in the middle vertebra of fourteen osteoporotic three-vertebra spine segments and then repaired with either the Kiva or kyphoplasty procedure. Height, stiffness and displacement under compression of the spine segments were measured for four conditions: intact, fractured, augmented, and post-cyclic eccentric loading (50,000cycles, 200-500N, 30mm anterior lever arm).
  
  
  RESULTS
  No significant differences were seen between the two procedures for height restoration, stiffness at high or low loads, or displacement under compression. However, the Kiva System required an average of 66% less cement than kyphoplasty to achieve these outcomes (mean 2.6 (SD 0.4) mL v. mean 7.5 (SD 0.8) mL 0; P<0.01). Extravasations and excessive posterior cement flow were also significantly lower with Kiva (0/7 v. 4/7; P<.05).
  
  
  CONCLUSIONS
  Kiva exhibits similar biomechanical performance to balloon kyphoplasty, but may reduce the risk of extravasation through the containment mechanism of the implant design and by reducing cement volume.
authors.affiliation: Department of Orthopaedics, University of British Columbia & Vancouver Coastal Health Research Institute, Canada. dawilson@interchange.ubc.ca
authors.forename: Derek C
authors.initials: DC
authors.lastname: Wilson
authors.forename: Ryan J
authors.initials: RJ
authors.lastname: Connolly
authors.forename: Qingan
authors.initials: Q
authors.lastname: Zhu
authors.forename: Jeff L
authors.initials: JL
authors.lastname: Emery
authors.forename: Stephen P
authors.initials: SP
authors.lastname: Kingwell
authors.forename: Scott
authors.initials: S
authors.lastname: Kitchel
authors.forename: Peter A
authors.initials: PA
authors.lastname: Cripton
authors.forename: David R
authors.initials: DR
authors.lastname: Wilson
mesh_terms: D019245:Compressive Strength; D003198:Computer Simulation; D019544:Equipment Failure Analysis; D050815:Fractures, Compression / Q000503:physiopathology* / Q000628:therapy*; D006801:Humans; D066298:In Vitro Techniques; D058498:Kyphoplasty / Q000379:methods*; D008954:Models, Biological; D019736:Prostheses and Implants; D011474:Prosthesis Design; D016103:Spinal Fractures / Q000503:physiopathology* / Q000628:therapy*; D016896:Treatment Outcome; D016474:Weight-Bearing