title: Strontium doping of bone graft extender.
abstract: OBJECTIVE
  Allografts are often used during revision hip replacement surgery for stabilization of the implant. Resorption of the allograft may exceed new bone formation, and instability of the prosthesis can develop. We investigated whether strontium could regulate the imbalance of fast resorption of allograft and slower formation of new bone, because it is both an anabolic and an anticatabolic agent.
  
  
  METHODS
  Strontium was added to the implant interface environment by doping a hydroxyapatite bone graft extender. 10 dogs each received 2 experimental titanium implants. The implants were inserted within a 2.7-mm concentric gap in cancellous bone. The gap was filled with 50% (v/v) allograft mixed with 50% bone graft extender. The extender either had 5% strontium doping (SrHA) or was undoped (HA). After 4 weeks, osseointegration and mechanical fixation were evaluated by histomorphometry and by push-out test.
  
  
  RESULTS
  SrHA bone graft extender induced a 1.2-fold increase in volume of new bone, a 1.2-fold increase in allograft remaining in the gap, and a 1.4-fold increase in surface area of the bone graft extender material in contact with new bone compared to HA bone graft extender. All these increases were statistically significant. SrHA bone graft extender did not significantly improve ongrowth of bone onto the implants or improve any of the mechanical push-out parameters compared to HA bone graft extender.
  
  
  CONCLUSIONS
  Doping of the HA bone graft extender with 5% strontium increased gap healing, preserved more of the allograft in the gap, and increased the ongrowth of bone onto the bone graft extender material, but did not improve mechanical fixation.
authors: Orthopaedic Research Laboratory, Department of Orthopaedic Surgery, Aarhus University Hospital, Aarhus, Denmark. marianne.t@vestermark.dk
authors: Marianne T
authors: MT
authors: Vestermark
authors: Ellen-Margrethe
authors: EM
authors: Hauge
authors: Kjeld
authors: K
authors: Soballe
authors: Joan E
authors: JE
authors: Bechtold
authors: Thomas
authors: T
authors: Jakobsen
authors: Jorgen
authors: J
authors: Baas
mesh_terms: D000818:Animals; D018786:Bone Substitutes / Q000494:pharmacology; D016025:Bone Transplantation / Q000379:methods; D020099:Coated Materials, Biocompatible / Q000494:pharmacology; D004285:Dogs; D017886:Durapatite / Q000494:pharmacology; D005260:Female; D005269:Femur / Q000187:drug effects; D006801:Humans; D006811:Humerus / Q000187:drug effects; D020007:Implants, Experimental; D016348:Osseointegration / Q000187:drug effects / Q000502:physiology; D011475:Prosthesis Failure; D013324:Strontium / Q000494:pharmacology
chemical_list: D018786:Bone Substitutes; D020099:Coated Materials, Biocompatible; D017886:Durapatite; D013324:Strontium