title: Steady state acetabular cartilage wear after bipolar hemiarthroplasty: a case series of 10 patients with radiostereometric analysis.
abstract: BACKGROUND
  Cartilage wear is a concern after hemiarthroplasty. The precise pattern of the progression of wear has not been evaluated. We previously reported the application of radiostereonetric analysis (RSA) for the measurement of cartilage wear in patients. The purpose of this study was to report the amount and the orientation of the steady state wear of cartilage between 1 and 3 years after bipolar hemiarthroplasty.
  
  
  METHODS
  22 patients with a bipolar hemiarthroplasty for displaced femoral neck fracture were included. 10 patients completed the mean follow up of 37 months. The cartilage wear was evaluated by calculating the migration of the bipolar head in reference to the markers in the acetabulum using RSA.
  
  
  RESULTS
  The mean age of the patients at the final follow-up was 80 (range 67-91) years. The 3-D migration was -0.02 mm (SD 0.30) between 1 and 3 years. The migration in each direction was 0.03 mm (SD 0.49) in medial, 0.03 mm (SD 0.14) in proximal and 0.11 mm (SD 0.29) in posterior directions. 2 patients showed migration of more than 0.2 mm. The large initial migration seen in some patients up to 1 year did not progress further. Total wear after 37 months was 0.43 mm (SD 0.17).
  
  
  CONCLUSIONS
  Cartilage wear progressed slowly in 2 of 10 patients from 1 to 3 years. No pelvic penetration was seen. We believe that RSA will give a basic knowledge about the development and the progression of cartilage wear after hemiarthroplasty.
authors.affiliation: Department of Orthopaedic Surgery, Oslo University Hospital, Oslo - Norway.
authors.forename: Masako
authors.initials: M
authors.lastname: Tsukanaka
authors.affiliation: Department of Orthopaedic Surgery, Oslo University Hospital, Oslo - Norway.
authors.forename: Ragnhild Ø
authors.initials: RØ
authors.lastname: Støen
authors.affiliation: Department of Orthopaedic Surgery, Vestre Viken Hospital Trust, Baerum Hospital, Gjettum - Norway.
authors.forename: Wender
authors.initials: W
authors.lastname: Figved
authors.affiliation: Department of Orthopaedic Surgery, Oslo University Hospital, Oslo - Norway.
authors.forename: Frede
authors.initials: F
authors.lastname: Frihagen
authors.affiliation: Department of Orthopaedic Surgery, Oslo University Hospital, Oslo - Norway.
authors.forename: Lars
authors.initials: L
authors.lastname: Nordsletten
authors.affiliation: Department of Orthopaedic Surgery, Oslo University Hospital, Oslo - Norway.
authors.forename: Stephan M
authors.initials: SM
authors.lastname: Röhrl
mesh_terms: D000077:Acetabulum / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D000368:Aged; D000369:Aged, 80 and over; D002358:Cartilage, Articular / Q000473:pathology* / Q000503:physiopathology; D015331:Cohort Studies; D005260:Female; D005265:Femoral Neck Fractures / Q000000981:diagnostic imaging / Q000601:surgery; D005500:Follow-Up Studies; D062785:Hemiarthroplasty / Q000009:adverse effects / Q000379:methods*; D006620:Hip Fractures / Q000000981:diagnostic imaging* / Q000601:surgery*; D006801:Humans; D015601:Injury Severity Score; D008297:Male; D011475:Prosthesis Failure / Q000639:trends; D059869:Radiostereometric Analysis; D012189:Retrospective Studies; D018570:Risk Assessment; D013997:Time Factors; D016896:Treatment Outcome