title: The migration pattern of the Charnley femoral stem: a five-year follow-up RSA study in a well-functioning patient group.
abstract: BACKGROUND
  Implant stability is considered vital to long-time implant survival in total hip arthroplasty (THA), since loose implants are reported to be a major cause of hip revision. There is an association between early implant micromotion and increased risk of revision. More implant-specific data are needed to establish acceptable levels of early implant movement.
  
  
  METHODS
  Thirty-five patients (36 hips) undergoing Charnley THA were followed with repeated clinical, radiographic, and radiostereometric analysis (RSA) over 5 years. Twenty-three patients attended 5 years postoperatively.
  
  
  RESULTS
  The patient group was well functioning based on the radiological and clinical evaluations. The stems constantly moved up to 5 years postoperatively, with subsidence, retroversion, and varus tilt, based on the RSA.
  
  
  CONCLUSIONS
  Continuous movement of the Charnley stem was observed up to 5 years postoperatively in a well-functioning patient group. The migration data presented herein could be useful when defining acceptable migration limits for certain types of cemented femoral stems.
authors.affiliation: Orthopaedic Research Centre, Trondheim University Hospital, 7006, Trondheim, Norway. kristin.haugan@ntnu.no
authors.forename: Kristin
authors.initials: K
authors.lastname: Haugan
authors.forename: Otto S
authors.initials: OS
authors.lastname: Husby
authors.forename: Jomar
authors.initials: J
authors.lastname: Klaksvik
authors.forename: Olav A
authors.initials: OA
authors.lastname: Foss
mesh_terms: D000368:Aged; D019644:Arthroplasty, Replacement, Hip; D005260:Female; D005272:Femur Neck / Q000601:surgery*; D005500:Follow-Up Studies; D006621:Hip Joint / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D015207:Osteoarthritis, Hip / Q000000981:diagnostic imaging* / Q000503:physiopathology / Q000601:surgery; D011446:Prospective Studies; D011474:Prosthesis Design; D011475:Prosthesis Failure; D059869:Radiostereometric Analysis / Q000379:methods*; D016059:Range of Motion, Articular; D012720:Severity of Illness Index; D016896:Treatment Outcome