title: Incorporation of raloxifene-impregnated allograft around orthopedic titanium implants impairs early fixation but improves new bone formation.
abstract: BACKGROUND
  The anti-osteoporotic drug raloxifene reduces the risk of vertebral fractures by increasing bone mass density. We investigated whether raloxifene offers any benefits in augmenting early fixation of orthopedic implants in the setting of impaction bone grafting.
  
  
  METHODS
  24 non-weight-bearing grafted gap implants were inserted bilaterally into the tibia of 12 dogs. The 2.5-mm peri-implant gap was filled with either raloxifene-impregnated or untreated bone allograft. Implants were harvested after 28 days. Implant fixation was assessed by mechanical testing and histomorphometric evaluation.
  
  
  RESULTS
  Raloxifene-treated allograft reduced early implant fixation compared to untreated allograft, as measured by inferior maximum shear strength (p < 0.001) and apparent shear stiffness (p = 0.001). We found that the raloxifene group had more newly formed bone in the gap around the implant (p = 0.02), but also less allograft (p = 0.03).
  
  
  CONCLUSIONS
  The accelerated allograft resorption in the raloxifene group explained the impaired early fixation, despite its stimulation of new bone formation. Our results with local and possible high-dose treatment are not consistent with current theory regarding the mechanism of how systemic raloxifene administration counteracts the decrease in BMD in postmenopausal women. Instead of being solely anti-resorptive as generally held, our results indicate a possible anabolic side of raloxifene.
authors.affiliation: Othopedic Research Laboratory , Aarhus University Hospital, Aarhus , Denmark.
authors.forename: Lars L
authors.initials: LL
authors.lastname: Hermansen
authors.forename: Mette
authors.initials: M
authors.lastname: Sørensen
authors.forename: Jeppe
authors.initials: J
authors.lastname: Barckman
authors.forename: Joan E
authors.initials: JE
authors.lastname: Bechtold
authors.forename: Kjeld
authors.initials: K
authors.lastname: Søballe
authors.forename: Jørgen
authors.initials: J
authors.lastname: Baas
mesh_terms: D064591:Allografts / Q000187:drug effects*; D000818:Animals; D050071:Bone Density Conservation Agents / Q000494:pharmacology*; D001862:Bone Resorption; D016025:Bone Transplantation / Q000379:methods*; D004285:Dogs; D016348:Osseointegration / Q000187:drug effects*; D010012:Osteogenesis / Q000187:drug effects; D019736:Prostheses and Implants; D020849:Raloxifene Hydrochloride / Q000494:pharmacology*; D013977:Tibia / Q000601:surgery*; D014025:Titanium
chemical_list: D050071:Bone Density Conservation Agents; D020849:Raloxifene Hydrochloride; D014025:Titanium