title: The cementless Bicontact stem in a prospective dual-energy X-ray absorptiometry study.
abstract: OBJECTIVE
  The cementless Bicontact total hip arthroplasty (THA) system (AESCULAP AG, Tuttlingen, Germany) was introduced in 1986/1987 and has been in successful clinical use in an unaltered form up to today. Although good long-term results with the Bicontact stem have been published, it is questionable whether the implant provides the criteria for a state-of-the-art stem regarding proximal bone stock preservation. The purpose of the study was to monitor the periprosthetic bone mineral density (BMD) in a prospective two-year follow-up dual-energy X-ray absorptiometry (DEXA) study.
  
  
  METHODS
  After power analysis, a consecutive series of 25 patients with unilateral Bicontact stem implantation was examined clinically and underwent DEXA examinations. Scans of seven regions of interest were taken preoperatively and at one week, six months, and one and two years.
  
  
  RESULTS
  One patient required stem revision due to a deep infection. The Harris Hip Score increased significantly by 44 points. The most significant bone loss was observed in the calcar region (R7) in the first six months (-19.2 %). It recovered in the following 18 months to -8.5 %. The BMD in the greater trochanter dropped significantly after six months and remained stable at this level. BMD exceeded baseline values in distal regions and even more in the lesser trochanter region after two years.
  
  
  CONCLUSIONS
  We conclude that the Bicontact stem provides adequate proximal bone stock preservation. We observed some signs of stress shielding at the tip of the stem, which is inevitable to some degree in THA with cementless straight stems. However, in this prospective DEXA investigation, we showed that proximal off-loading does not occur after THA with the Bicontact system. Thus, we believe that this stem is still a state-of-the-art implant.
authors.affiliation: Department of Orthopaedic Surgery, Hannover Medical School, Anna-von-Borries Str. 1-7, 30625 Hannover, Germany. matthias.lerch@ddh-gruppe.de
authors.forename: Matthias
authors.initials: M
authors.lastname: Lerch
authors.forename: Agnes
authors.initials: A
authors.lastname: Kurtz
authors.forename: Henning
authors.initials: H
authors.lastname: Windhagen
authors.forename: Anas
authors.initials: A
authors.lastname: Bouguecha
authors.forename: Bernd A
authors.initials: BA
authors.lastname: Behrens
authors.forename: Patrick
authors.initials: P
authors.lastname: Wefstaedt
authors.forename: Christina M
authors.initials: CM
authors.lastname: Stukenborg-Colsman
mesh_terms: D015502:Absorptiometry, Photon / Q000379:methods*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects / Q000295:instrumentation* / Q000379:methods; D015519:Bone Density / Q000502:physiology*; D001862:Bone Resorption; D002484:Cementation; D005260:Female; D005500:Follow-Up Studies; D006304:Health Status; D006621:Hip Joint / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D016348:Osseointegration / Q000502:physiology*; D011183:Postoperative Complications / Q000209:etiology; D011446:Prospective Studies; D011474:Prosthesis Design; D016059:Range of Motion, Articular; D020127:Recovery of Function; D012086:Reoperation; D016896:Treatment Outcome