title: [Analysis of the periprosthetic femoral bone reaction after uncemented total hip arthroplasty with computertomography assisted osteodensitometry in vivo: 6-year follow-up].
abstract: OBJECTIVE
  We prospectively analyzed the cancellous and cortical periprosthetic femoral bone reaction after implantation of a cementless total hip arthroplasty with computertomography assisted osteodensitometry after a mean of 1 and 6 years.
  
  
  METHODS
  Twenty-one patients (Ø age at implantation: 52 years) with osteoarthrits of the hip joint received 21 cementless hip prostheses with a three-dimensionally tapered design. All patients were analyzed clinically, with CT-osteodensitometry and plain radiography after a mean of 10 days, at 1 and 6 years postoperatively. Cancellous and cortical bone density was evaluated automatically using a special software tool.
  
  
  RESULTS
  The proximal region of the stem showed progessive cortical (Ø -15% 1 year, -25% 6 years post-OP) and cancellous (Ø -26% 1 year, -49% 6 years post-OP) bone density loss. Cortical bone density loss was lower and non-progressive at the diaphysis (Ø -7% 1 year, -9% 6 years post-OP) and the distal region (Ø -6% 1 year, -4% 6 years post-OP) of the stem. All stems showed no signs of loosening on plain radiography and good clinical results according to the Harris hip score.
  
  
  CONCLUSIONS
  Computertomography assisted osteodensitometry is the only method which allows discrimination between periprosthetic cortical and cancellous bone density changes in vivo. The analyzed uncemented stem fixates at the diaphysis and distal region. Due to the changed biomechanical loading after stem implantation, progressive proximal cancellous bone density loss was measured for the first time in vivo. Its role in the pathogenesis of implant loosening is still unknown and needs to be further elucidated.
authors.affiliation: Orthopädische Klinik mit Poliklinik der Friedrich-Alexander-Universität Erlangen-Nürnberg am Waldkrankenhaus St. Marien, Rathsberger Str. 57, 91054 Erlangen, Deutschland. LTZMLL@aol.com
authors.forename: Lutz A
authors.initials: LA
authors.lastname: Müller
authors.forename: Tobias E
authors.initials: TE
authors.lastname: Nowak
authors.forename: Michael
authors.initials: M
authors.lastname: Völk
authors.forename: Rocco P
authors.initials: RP
authors.lastname: Pitto
authors.forename: David
authors.initials: D
authors.lastname: Pfander
authors.forename: Raimund
authors.initials: R
authors.lastname: Forst
authors.forename: Rainer
authors.initials: R
authors.lastname: Schmidt
authors.forename: Stephan
authors.initials: S
authors.lastname: Eichinger
mesh_terms: D015502:Absorptiometry, Photon / Q000379:methods*; D000328:Adult; D000368:Aged; D019644:Arthroplasty, Replacement, Hip; D002113:Calcification, Physiologic; D002484:Cementation; D003936:Diagnosis, Computer-Assisted / Q000379:methods*; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control*; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D015207:Osteoarthritis, Hip / Q000150:complications / Q000175:diagnosis* / Q000503:physiopathology / Q000601:surgery*; D014054:Tomography / Q000379:methods; D016896:Treatment Outcome