title: Comparison of Two Synthetic Bone Graft Products in a Rabbit Posterolateral Fusion Model.
abstract: The drawbacks of iliac crest autograft as graft material for spine fusion are well reported. Despite continued modifications to improve bone healing capacity, the efficacy of synthetic graft materials as stand-alone replacements remains uncertain. The rabbit posterolateral fusion model is an established environment for testing of fusion concepts. It offers the opportunity to obtain radiographic, biomechanical and histological data on novel fusion materials. The objective of this study was to compare the spine fusion capability of two synthetic bone graft products in an established rabbit posterolateral spine fusion (PLF) model: Signafuse® Bioactive Bone Graft Putty and Actifuse® ABX.
  
  
  
  Bilateral intertransverse spine fusion was performed at the L5-L6 transverse processes (TPs) of New Zealand White rabbits using either Signafuse or Actifuse ABX as the bone graft material. Bone remodeling and spine fusion were assessed at 6 and 12 weeks using radiographic, biomechanical and histological endpoints.
  
  
  
  Fusion rate by manual palpation at 6 weeks was greater for Signafuse (33%) compared to Actifuse ABX (0%), and equivalent in both groups at 12 weeks (50%). Biomechanical fusion rate based on flexion-extension data was 80% in Signafuse group and 44% for Actifuse ABX. Histology revealed a normal healing response in both groups. MicroCT and histomorphometric data at 6 weeks showed greater new bone formation in the Signafuse group compared to Actifuse ABX (p <0.05), with no differences detected at 12 weeks. Histological fusion scores were greater in the Signafuse group at 6 and 12 weeks, indicated by higher degree structural remodeling and tendency towards complete bridging of the fusion bed compared to the Actifuse ABX group.
  
  
  
  Confirmed by several metrics, Signafuse outperformed Actifuse ABX as a standalone synthetic bone graft in an established PLF model, demonstrating greater rates of bone remodeling and spine fusion. The combination of 45S5 bioactive glass and biphasic HA/βTCP granules of Signafuse appear to provide greater bone healing capability in comparison to the 0.8% silicate-substituted hydroxyapatite material of Actifuse ABX.
authors.affiliation: Bone Healing Research Lab, Iowa Spine Research Lab Orthopedic Surgery, University of Iowa Carver College of Medicine, Iowa City, IA.
authors.forename: Douglas
authors.initials: D
authors.lastname: Fredericks
authors.affiliation: Bone Healing Research Lab, Iowa Spine Research Lab Orthopedic Surgery, University of Iowa Carver College of Medicine, Iowa City, IA.
authors.forename: Emily B
authors.initials: EB
authors.lastname: Petersen
authors.affiliation: MIMX, College of Engineering, University of Iowa, Iowa City, IA.
authors.forename: Nicole
authors.initials: N
authors.lastname: Watson
authors.affiliation: MIMX, College of Engineering, University of Iowa, Iowa City, IA.
authors.forename: Nicole
authors.initials: N
authors.lastname: Grosland
authors.affiliation: Comparative Pathology Lab, University of Iowa Carver College of Medicine, Iowa City, I.
authors.forename: Katherine
authors.initials: K
authors.lastname: Gibson-Corley
authors.affiliation: Bone Healing Research Lab, Iowa Spine Research Lab Orthopedic Surgery, University of Iowa Carver College of Medicine, Iowa City, IA.
authors.forename: Joseph
authors.initials: J
authors.lastname: Smucker
mesh_terms: D000818:Animals; D018786:Bone Substitutes / Q000008:administration & dosage / Q000627:therapeutic use*; D016025:Bone Transplantation / Q000379:methods*; D002130:Calcium Phosphates / Q000008:administration & dosage / Q000627:therapeutic use*; D023421:Models, Animal; D010012:Osteogenesis / Q000187:drug effects*; D011817:Rabbits; D017640:Silicates / Q000008:administration & dosage / Q000627:therapeutic use*; D013123:Spinal Fusion / Q000379:methods*; D013131:Spine / Q000000981:diagnostic imaging / Q000601:surgery; D055114:X-Ray Microtomography
chemical_list: D018786:Bone Substitutes; D002130:Calcium Phosphates; D017640:Silicates; C519529:actifuse synthetic bone graft