title: The influence of alendronate treatment and bone graft volume on posterior lateral spine fusion in a porcine model.
abstract: METHODS
  An experimental animal study with randomized, paired control design was conducted using a porcine model.
  
  
  OBJECTIVE
  The aim of this study was to evaluate the influence of alendronate treatment and the significance of different amounts of bone graft on posterior lateral spine fusion.
  
  
  BACKGROUND
  Treatment with bisphosphonates inhibits osteoclast-induced bone resorption and increases bone quality and density. It has been widely used clinically for treatment of osteoporosis. Bisphosphonates have been reported to elongate the callus remodeling process during fracture healing. Bisphosphonate treatment may modify bone graft healing and the remodeling process in spine fusion. The bone resorption phase exists during the healing process. Extensive bone graft resorption could reduce the basis for new bone formation, which could be an important factor for failure of spine fusion. Furthermore, different amounts of initially applied bone graft may influence spine fusion rate and bone graft incorporation process.
  
  
  METHODS
  Twenty-two pigs were included in the study. Eleven pigs in the treatment group received alendronate 10 mg/day p.o. for 3 months after surgery. The other 11 pigs received no bisphosphonate and served as control group. Posterior lateral fusion with the CD Horizon system was performed on the lumbar spine using different amounts of autograft (4 g on one side and 8 g on the other side) in all animals. The fusion was evaluated using radiograph, CT scan, and histomorphometry at 3 months after operation.
  
  
  RESULTS
  There was no statistical difference in either fusion rate or fusion mass volume between the two groups. The fusion rate based on radiograph was 75% on the 8-g autograft side and 45% on the 4-g side (P < 0.05). The mean volume of fusion mass was 2.36 cm3 on the 4-g side and 3.29 cm3 on the 8-g side (P < 0.01). No difference was found in either trabecular bone volume or fusion rate between treatment and control groups using histologic evaluation.The treatment group showed a higher fibrous tissue volume(P < 0.05), higher proportion of woven bone structure(P < 0.001), and lower bone marrow volume (P = 0.088) in the fusion mass. Different amounts of bone graft did not change the tissue composition of the fusion mass.
  
  
  CONCLUSIONS
  Alendronate treatment in this study decreased fusion mass remodeling without inhibiting fusion rate. Increased amounts of autologous bone graft could improve the fusion rate in this experimental spine fusion study.
authors.affiliation: Orthopedic Department, Institute for Experimental Clinical Research, Aarhus, Denmark. xueqingyun@hotmail.com
authors.forename: Qingyun
authors.initials: Q
authors.lastname: Xue
authors.forename: Haisheng
authors.initials: H
authors.lastname: Li
authors.forename: Xuenong
authors.initials: X
authors.lastname: Zou
authors.forename: Mathias
authors.initials: M
authors.lastname: Bünger
authors.forename: Niels
authors.initials: N
authors.lastname: Egund
authors.forename: Martin
authors.initials: M
authors.lastname: Lind
authors.forename: Finn B
authors.initials: FB
authors.lastname: Christensen
authors.forename: Cody
authors.initials: C
authors.lastname: Bünger
mesh_terms: D000284:Administration, Oral; D019386:Alendronate / Q000494:pharmacology*; D000818:Animals; D050071:Bone Density Conservation Agents / Q000494:pharmacology*; D016025:Bone Transplantation; D004195:Disease Models, Animal; D005260:Female; D006085:Graft Survival / Q000187:drug effects; D008159:Lumbar Vertebrae / Q000187:drug effects / Q000473:pathology / Q000601:surgery*; D016348:Osseointegration / Q000187:drug effects* / Q000502:physiology; D010012:Osteogenesis / Q000187:drug effects*; D013123:Spinal Fusion; D013552:Swine
chemical_list: D050071:Bone Density Conservation Agents; D019386:Alendronate