title: Osteogenic protein-1 delivered by hydroxyapatite-coated implants improves bone ingrowth in extracortical bone bridging.
abstract: BACKGROUND
  Extracortical bone bridging for treatment of massive bone loss can improve stability and longevity of massive endoprostheses. Osteogenic protein-1 (OP-1), when used with allograft bone, reportedly improves extracortical bone bridging and bone ingrowth.
  
  
  OBJECTIVE
  We asked whether OP-1 delivered by hydroxyapatite (HA) without bone grafting could improve bone ingrowth and bone formation in the context of extracortical bone bridging.
  
  
  METHODS
  We implanted unilateral segmental femoral diaphyseal replacement prostheses in 18 dogs (three groups of six dogs). The groups consisted of an HA-coated group augmented with OP-1, an HA-coated group, and a plain porous group. Bone grafting techniques were not used to augment bone formation. The implants were retrieved at 12 weeks for histologic assessment.
  
  
  RESULTS
  After removing one specimen owing to a complication, 17 femora were analyzed (six HA-coated augmented with OP-1, five HA-coated, and six plain). We observed better bone ingrowth in the HA-coated OP-1 group than in the plain porous and HA-coated groups, with no difference between the latter two groups. There also was better bone apposition and callus height in the HA-coated OP-1 group than in the plain group but no differences between the HA-coated OP-1 and HA-coated groups or between the HA-coated and plain groups.
  
  
  CONCLUSIONS
  OP-1 (2.9 mg) delivered by HA-coated segmental replacement prostheses in this canine extracortical bone bridging model revealed improved bone ingrowth over HA-coated implants without OP-1 or plain porous-coated prostheses.
authors.affiliation: Division of Orthopaedic Surgery, McGill University Health Centre, Montreal General Hospital, 1650 Cedar Avenue, Room B5.159.6, Montreal, QC H3G 1A4, Canada. nsaran77@hotmail.com
authors.forename: Neil
authors.initials: N
authors.lastname: Saran
authors.forename: Renwen
authors.initials: R
authors.lastname: Zhang
authors.forename: Robert E
authors.initials: RE
authors.lastname: Turcotte
mesh_terms: D000818:Animals; D019644:Arthroplasty, Replacement, Hip / Q000379:methods*; D055419:Bone Morphogenetic Protein 7 / Q000008:administration & dosage*; D020099:Coated Materials, Biocompatible; D004285:Dogs; D017886:Durapatite / Q000737:chemistry*; D005269:Femur / Q000000981:diagnostic imaging / Q000187:drug effects* / Q000473:pathology / Q000503:physiopathology / Q000601:surgery*; D006622:Hip Prosthesis; D016348:Osseointegration / Q000187:drug effects*; D016062:Porosity; D011474:Prosthesis Design; D011859:Radiography; D013997:Time Factors
chemical_list: D055419:Bone Morphogenetic Protein 7; D020099:Coated Materials, Biocompatible; D017886:Durapatite