title: Design modifications of the uncemented Furlong hip stem result in minor early subsidence but do not affect further stability: a randomized controlled RSA study with 5-year follow-up.
abstract: OBJECTIVE
  Even small design modifications of uncemented hip stems may alter the postoperative 3-D migration pattern. The Furlong Active is an uncemented femoral stem which, in terms of design, is based on its precursor-the well-proven Furlong HAC-but has undergone several design changes. The collar has been removed on the Active stem along with the lateral fin; it is shorter and has more rounded edges in the proximal part. We compared the migration patterns of the uncemented Furlong HAC stem and the modified Furlong Active stem in a randomized, controlled trial over 5 years using radiostereometry (RSA).
  
  
  METHODS
  50 patients with primary osteoarthritis were randomized to receive either the HAC stem or the Active stem. The patients underwent repeated RSA examinations (postoperatively, at 3 months, and after 1, 2, and 5 years) and conventional radiography, and they also filled out hip-specific questionnaires.
  
  
  RESULTS
  During the first 3 months, the collarless Active stem subsided to a greater extent than the collar-fitted HAC stem (0.99 mm vs. 0.31 mm, p=0.05). There were, however, no other differences in movement measured by RSA or in clinical outcome between the 2 stems. After 3 months, both stem types had stabilized and almost no further migration was seen.
  
  
  CONCLUSIONS
  The Active stem showed no signs of unfavorable migration. Our results suggest that the osseointegration is not compromised by the new design features.
authors.affiliation: Department of Orthopedics , Lund University and Skåne University Hospital, Lund , Sweden.
authors.forename: Erik
authors.initials: E
authors.lastname: Weber
authors.forename: Martin
authors.initials: M
authors.lastname: Sundberg
authors.forename: Gunnar
authors.initials: G
authors.lastname: Flivik
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects* / Q000295:instrumentation* / Q000379:methods; D002484:Cementation; D005260:Female; D005500:Follow-Up Studies; D006622:Hip Prosthesis / Q000009:adverse effects*; D006801:Humans; D008297:Male; D008875:Middle Aged; D016348:Osseointegration; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging / Q000601:surgery*; D011474:Prosthesis Design; D011475:Prosthesis Failure; D059869:Radiostereometric Analysis; D016896:Treatment Outcome