title: Bone regeneration 6 years after impaction bone grafting: a PET analysis.
abstract: BACKGROUND
  Impacted morselized bone allograft in revision total hip arthroplasty for prosthetic loosening has gained widespread clinical use during the last decades. The clinical results are good but little is known about the bone regeneration in the graft.
  
  
  METHODS
  5 patients were revised with impaction of morselized frozen allograft and a cemented total hip arthroplasty (THA) due to loosening and osteolysis of a primary THA. We used positron emission tomography ([18F]-fluoride PET) to produce quantitative images of new bone formation in the allograft surrounding the femur stem 6 years after surgery.
  
  
  RESULTS
  The 5 patients had previously been analyzed by [18F]-fluoride PET during the first year after surgery (Sörensen et al. 2003). During the first year, bone formation proceeded through the graft layer and reached the cement layer surrounding the femoral stems. The clinical and radiographic results were excellent at 6 years. PET analyses at 6 years showed that the bone metabolism was significantly reduced in most areas of the proximal femur, compared to the elevated activity during the first year after surgery, and also normalized compared to the contralateral healthy femur. Graft bone metabolism distal to the stem tip remained slightly increased. Small patchy areas of increased uptake remained along the proximal femoral stem, probably reflecting small volumes of fibrous healing.
  
  
  CONCLUSIONS
  The metabolism of the allografted bone had normalized compared to native bone, indicating full regeneration throughout the graft--and a good long-term prognosis for implant fixation.
authors.affiliation: Department of Orthopedics, Länssjukhuset, SE-801 87, Gävle, Sweden.
authors.forename: Gösta
authors.initials: G
authors.lastname: Ullmark
authors.forename: Jens
authors.initials: J
authors.lastname: Sörensen
authors.forename: Bengt
authors.initials: B
authors.lastname: Långström
authors.forename: Olle
authors.initials: O
authors.lastname: Nilsson
mesh_terms: D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects*; D001861:Bone Regeneration; D016025:Bone Transplantation / Q000379:methods; D005260:Female; D005270:Femur Head / Q000000981:diagnostic imaging / Q000637:transplantation; D006801:Humans; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography; D011379:Prognosis; D011475:Prosthesis Failure; D012086:Reoperation; D013997:Time Factors; D014182:Transplantation, Autologous; D016896:Treatment Outcome