title: Risk of acetabular protrusion is low in rheumatoid arthritis patients treated with bipolar hemiarthroplasty for displaced femoral neck fractures without rheumatoid change in hip joints.
abstract: OBJECTIVE
  The aim of this study was to analyze the radiological outcomes of bipolar hemiarthroplasty after displaced femoral neck fractures of non-arthritic hip joints in rheumatoid arthritis patients.
  
  
  METHODS
  We retrospectively investigated 25 hip joints in 23 rheumatoid arthritis patients who underwent bipolar hemiarthroplasty for displaced femoral neck fracture of non-arthritic hip joints. All patients were female with an average age of 69.8 years (range 51-83 years). Mean follow-up duration was 8.4 years (range 5-12 years). Radiographs taken immediately, 1 year after surgery and most recently, were collected for each case. Radiographic measurement of the migration distance of the outer-head prosthesis in the direction of vertical, horizontal and medial to Köhler's line was undertaken at 1 year after surgery and most recently.
  
  
  RESULTS
  No patients had hip-related pain after surgery. No case indicated apparent central migration and >3-mm migration of the hemisphere in each direction. There was no significant change in migration distance between evaluation at 1 year after surgery and most recently.
  
  
  CONCLUSIONS
  We conclude that risk of acetabular protrusion appears to be low in patients of rheumatoid arthritis treated with bipolar hemiarthroplasty for displaced femoral neck fractures of non-arthritic hip joints in the medium term.
authors.affiliation: Department of Orthopaedic Surgery, Tohoku University Graduate School of Medicine, 1-1 Seiryo machi, Aobaku, Sendai, Miyagi, 980-8574, Japan, yu-mori@med.tohoku.ac.jp.
authors.forename: Yu
authors.initials: Y
authors.lastname: Mori
authors.forename: Naoko
authors.initials: N
authors.lastname: Mori
authors.forename: Taketo
authors.initials: T
authors.lastname: Mori
authors.forename: Satoshi
authors.initials: S
authors.lastname: Nakamura
authors.forename: Masato
authors.initials: M
authors.lastname: Ishizuka
authors.forename: Tokuhisa
authors.initials: T
authors.lastname: Sano
authors.forename: Eiji
authors.initials: E
authors.lastname: Itoi
mesh_terms: D000077:Acetabulum / Q000000981:diagnostic imaging*; D000368:Aged; D000369:Aged, 80 and over; D001172:Arthritis, Rheumatoid / Q000150:complications*; D005260:Female; D005265:Femoral Neck Fractures / Q000601:surgery*; D005500:Follow-Up Studies; D062785:Hemiarthroplasty; D006621:Hip Joint / Q000000981:diagnostic imaging; D006622:Hip Prosthesis / Q000009:adverse effects*; D006801:Humans; D008875:Middle Aged; D011475:Prosthesis Failure; D011859:Radiography; D012189:Retrospective Studies; D018570:Risk Assessment