title: Variables Affecting Fusion Rates in the Rat Posterolateral Spinal Fusion Model with Autogenic/Allogenic Bone Grafts: A Meta-analysis.
abstract: The rat posterolateral spinal fusion model with autogenic/allogenic bone graft (rat PFABG) has been increasingly utilized as an experimental model to assess the efficacy of novel fusion treatments. The objective of this study was to investigate the reliability of the rat PFABG model and examine the effects of different variables on spinal fusion. A web-based literature search from January, 1970 to September, 2015, yielded 26 studies, which included 40 rat PFABG control groups and 449 rats. Data regarding age, weight, sex, and strain of rats, graft volume, graft type, decorticated levels, surgical approach, institution, the number of control rats, fusion rate, methods of fusion assessment, and timing of fusion assessment were collected and analyzed. The primary outcome variable of interest was fusion rate, as evaluated by manual palpation. Fusion rates varied widely, from 0 to 96%. The calculated overall fusion rate was 46.1% with an I2value of 62.4, which indicated moderate heterogeneity. Weight >300 g, age >14 weeks, male rat, Sprague-Dawley strain, and autogenic coccyx grafts increased fusion rates with statistical significance. Additionally, an assessment time-point ≥8 weeks had a trend towards statistical significance (p = 0.070). Multi-regression analysis demonstrated that timing of assessment and age as continuous variables, as well as sex as a categorical variable, can predict the fusion rate with R2= 0.82. In an inter-institution reliability analysis, the pooled overall fusion rate was 50.0% [44.8, 55.3%], with statistically significant differences among fusion outcomes at different institutions (p < 0.001 and I2of 72.2). Due to the heterogeneity of fusion outcomes, the reliability of the rat PFABG model was relatively limited. However, selection of adequate variables can optimize its use as a control group in studies evaluating the efficacy of novel fusion therapies.
authors.affiliation: Department of Neurosurgery, The Johns Hopkins University School of Medicine, 1800 Orleans St., Room 6007, Baltimore, MD, 21287, USA.
authors.forename: Wataru
authors.initials: W
authors.lastname: Ishida
authors.affiliation: Department of Neurosurgery, The Johns Hopkins University School of Medicine, 1800 Orleans St., Room 6007, Baltimore, MD, 21287, USA. belder4@jhmi.edu.
authors.forename: Benjamin D
authors.initials: BD
authors.lastname: Elder
authors.affiliation: Department of Neurosurgery, The Johns Hopkins University School of Medicine, 1800 Orleans St., Room 6007, Baltimore, MD, 21287, USA.
authors.forename: Christina
authors.initials: C
authors.lastname: Holmes
authors.affiliation: Department of Neurosurgery, The Johns Hopkins University School of Medicine, 1800 Orleans St., Room 6007, Baltimore, MD, 21287, USA.
authors.forename: Sheng-Fu L
authors.initials: SL
authors.lastname: Lo
authors.affiliation: Department of Neurosurgery, The Johns Hopkins University School of Medicine, 1800 Orleans St., Room 6007, Baltimore, MD, 21287, USA.
authors.forename: Timothy F
authors.initials: TF
authors.lastname: Witham
mesh_terms: D064591:Allografts; D000818:Animals; D016025:Bone Transplantation / Q000379:methods*; D008297:Male; D008954:Models, Biological; D051381:Rats; D017207:Rats, Sprague-Dawley; D013123:Spinal Fusion / Q000379:methods*
keywords: Allograft; Autograft; Manual palpation; Osteogenic scaffold; Posterolateral fusion; Rat; Spinal fusion; Stem-cell therapy