title: Long-term results of bipolar hemiarthroplasty for osteoarthritis of the hip and idiopathic osteonecrosis of the femoral head.
abstract: BACKGROUND
  Satisfactory results have been reported from long-term studies on bipolar hemiarthroplasty for femoral neck fracture. However, long-term results of this procedure for osteoarthritis of the hip (OA) and idiopathic necrosis of the femoral head (ION) have given rise to pessimism. These poor results have often reported migration of the bipolar head, but few had described the direction of this migration. The purpose of the present study was to conduct a long-term follow-up analysis of bipolar hemiarthroplasty for OA and ION, including the direction of migration.
  
  
  METHODS
  We retrospectively reviewed a consecutive series of 64 patients (76 hips) who underwent primary bipolar hemiarthroplasty for symptomatic OA and ION with a cementless femoral component between 1976 and 1995. Of these 64 patients, 35 patients (40 hips) were available for clinical and radiographic review at a minimum follow-up duration of 10 years.
  
  
  RESULTS
  The Japanese Orthopaedic Association score significantly improved and pain relief was high following surgery; however, preservation of acetabular bone stock could not be achieved because of migration. The survival rate declined 10 years after surgery. Superomedial migration was found to be a risk factor for revision, and one factor affecting superomedial migration was the postoperative center edge angle.
  
  
  CONCLUSIONS
  The long-term results of bipolar hemiarthroplasty for OA and ION are not favorable. If a sufficient centripetal position is obtained with reaming, the bipolar head tends to migrate superomedially, subsequently requiring revision.
authors.affiliation: Department of Orthopaedic Surgery, Mie University Graduate School of Medicine, 2-174 Edobashi, Tsu, Mie, 514-8507, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Muraki
authors.forename: Akihiro
authors.initials: A
authors.lastname: Sudo
authors.forename: Masahiro
authors.initials: M
authors.lastname: Hasegawa
authors.forename: Aki
authors.initials: A
authors.lastname: Fukuda
authors.forename: Atsumasa
authors.initials: A
authors.lastname: Uchida
mesh_terms: D000328:Adult; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects* / Q000295:instrumentation* / Q000379:methods; D004868:Equipment Failure; D005260:Female; D005271:Femur Head Necrosis / Q000601:surgery*; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D015207:Osteoarthritis, Hip / Q000601:surgery*; D011474:Prosthesis Design; D012189:Retrospective Studies