title: An analysis of spine fusion outcomes in sheep pre-clinical models.
abstract: The ovine model is often used to evaluate new spine fusion technologies prior to clinical testing. An important aspect of designing sheep surgery protocols is to select the appropriate postoperative time period for comparing fusion outcomes. Unfortunately, determining the ideal study endpoint is complicated by the fact that prior published studies have not used consistent timeframes. Thus, the primary aim of this study was to provide a reference for investigators as to the expected fusion outcomes of control groups at varying timepoints in sheep spine surgery models.
  
  
  
  We identified published sheep fusion studies using autograft, interbody cages, and/or instrumentation. Fusion data were extracted, converted to a common scale, and analyzed across studied timepoints.
  
  
  
  Overall, 29 studies of 360 fusion levels were identified: 11 ALIF (158 levels), 3 PLIF/TLIF (28 levels), 8 PLF (90 levels), and 7 ACDF (84 levels). Studied timepoints ranged from 4 to 48 weeks postoperative. In general, fusion rates varied across techniques and instrumentation. The time to reach solid fusion differed by as many as 20 weeks between control groups.
  
  
  
  Recommended timeframes for future studies designed to show either superiority over controls or equivalent outcomes with controls were developed based on aggregate results. Designating ideal study endpoints for sheep fusion models has both ethical implications associated with responsible use of animals in research, and economic implications given the cost of animal research. The current results can guide the development of future research methods and help investigators choose appropriate study timelines for various control groups.
authors.affiliation: Department of Orthopedics, University of Colorado, Anschutz Medical Campus, 13001 E. 17th Place, Mail Stop F432, Aurora, CO, 80045, USA. emily.lindley@ucdenver.edu.
authors.forename: Emily M
authors.initials: EM
authors.lastname: Lindley
authors.affiliation: Department of Orthopedics, University of Colorado, Anschutz Medical Campus, 13001 E. 17th Place, Mail Stop F432, Aurora, CO, 80045, USA.
authors.forename: Cameron
authors.initials: C
authors.lastname: Barton
authors.affiliation: Department of Orthopedics, University of Colorado, Anschutz Medical Campus, 13001 E. 17th Place, Mail Stop F432, Aurora, CO, 80045, USA.
authors.forename: Thomas
authors.initials: T
authors.lastname: Blount
authors.affiliation: Department of Orthopedics, University of Colorado, Anschutz Medical Campus, 13001 E. 17th Place, Mail Stop F432, Aurora, CO, 80045, USA.
authors.forename: Evalina L
authors.initials: EL
authors.lastname: Burger
authors.affiliation: Department of Orthopedics, University of Colorado, Anschutz Medical Campus, 13001 E. 17th Place, Mail Stop F432, Aurora, CO, 80045, USA.
authors.forename: Christopher M J
authors.initials: CM
authors.lastname: Cain
authors.affiliation: Department of Clinical Sciences, Colorado State University, College of Veterinary Medicine & Biomedical Sciences, Ft. Collins, CO, USA.
authors.forename: Howard B
authors.initials: HB
authors.lastname: Seim
authors.affiliation: Department of Clinical Sciences, Colorado State University, College of Veterinary Medicine & Biomedical Sciences, Ft. Collins, CO, USA.
authors.forename: A Simon
authors.initials: AS
authors.lastname: Turner
authors.affiliation: Department of Orthopedics, University of Colorado, Anschutz Medical Campus, 13001 E. 17th Place, Mail Stop F432, Aurora, CO, 80045, USA.
authors.forename: Vikas V
authors.initials: VV
authors.lastname: Patel
mesh_terms: D000818:Animals; D023421:Models, Animal; D016348:Osseointegration; D012756:Sheep; D013123:Spinal Fusion / Q000295:instrumentation* / Q000379:methods*; D013997:Time Factors
keywords: Fusion; Lumbar; Ovine; Sheep; Spine