title: Osteonecrosis following resurfacing arthroplasty.
abstract: OBJECTIVE
  One of the main concerns regarding resurfacing arthroplasty is the viability of the remaining part of the femoral head, and the postoperative risk of a femoral neck fracture or collapse. In contrast to radiographic methods, positron emission tomography using the radiotracer [18F]-fluoride (Fluoride-PET) enables us to visualize the viability of bone in the remaining part of the head, despite the presence of the covering metal component.
  
  
  METHODS
  This is preliminary prospective study of 14 patients who underwent an ASR resurfacing arthroplasty. Apart from clinical and radiographic analyses, all patients were analyzed by PET scan 1 week, 4 months, and 1 year after surgery.
  
  
  RESULTS
  1 patient had a minor region of osteonecrosis on PET scan at 1 week and at 4 months. After 1 year, the necrosis had increased to include most of the head. 2 other patients, normal at 4 months, had developed equally large osteonecrosis at 1 year. A fourth patient had a minor osteonecrosis at 1 year. None of the patients had clinical symptoms, and the necrotic areas were not visible on plain radiographs.
  
  
  CONCLUSIONS
  We found Fluoride PET to be a sensitive and useful method for evaluation of bone metabolism at resurfacing arthroplasty. 3 of the 14 patients had developed osteonecrosis, involving most of the head at 1 year. The late onset of the phenomenon does not support the hypothesis of surgically damaged vascularity. The presence of this complication together with the lack of visibility on plain radiographs gives reason for concern.
authors.affiliation: Department of Orthopedics, Gävle Hospital and Center for Research and Development, Uppsala University/County Council of Gävleborg, Gävle, Sweden. gosta.ullmark@lg.se
authors.forename: Gösta
authors.initials: G
authors.lastname: Ullmark
authors.forename: Kent
authors.initials: K
authors.lastname: Sundgren
authors.forename: Jan
authors.initials: J
authors.lastname: Milbrink
authors.forename: Olle
authors.initials: O
authors.lastname: Nilsson
authors.forename: Jens
authors.initials: J
authors.lastname: Sörensen
mesh_terms: D000328:Adult; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects*; D005260:Female; D005270:Femur Head / Q000378:metabolism; D005271:Femur Head Necrosis / Q000000981:diagnostic imaging / Q000209:etiology* / Q000378:metabolism; D006622:Hip Prosthesis / Q000009:adverse effects; D006801:Humans; D008297:Male; D008875:Middle Aged; D010865:Pilot Projects; D049268:Positron-Emission Tomography / Q000379:methods; D011446:Prospective Studies; D012307:Risk Factors; D013997:Time Factors