title: Maintenance of bone mineral density after implantation of a femoral neck hip prosthesis.
abstract: BACKGROUND
  Stress shielding of the proximal femur has been observed in a number of conventional cementless implants used in total hip arthroplasty. Short femoral-neck implants are claiming less interference with the biomechanics of the proximal femur. The goal of this study was to investigate the changes of bone-mineral density in the proximal femur and the clinical outcome after implantation of a short femoral-neck prosthesis.
  
  
  METHODS
  We prospectively assessed the clinical outcome and the changes of bone mineral density of the proximal femur up to one year after implantation of a short femoral neck prosthesis in 20 patients with a mean age of 47 years (range 17 to 65). Clinical outcome was assessed using the Harris Hip Score. The WOMAC was used as a patient-relevant outcome-measure. The bone mineral density was determined using dual energy x-ray absorptiometry, performed 10 days, three months and 12 months after surgery.
  
  
  RESULTS
  The Harris Hip Score improved from an average preoperative score of 46 to a postoperative score at 12 months of 89 points, the global WOMAC index from 5,3 preoperatively to 0,8 at 12 months postoperatively. In contrast to conventional implants, the DEXA-scans overall revealed a slight increase of bone mineral density in the proximal femur in the 12 months following the implantation.
  
  
  CONCLUSIONS
  The short femoral neck stem lead to a distinct bone reaction. This was significantly different when compared to the changes in bone mineral density reported after implantation of conventional implants.
authors.affiliation: Orthopaedic Department, University of Ulm, Oberer Eselsberg 45, 89075 Ulm, Germany. ralf.decking@uni-ulm.de
authors.forename: Ralf
authors.initials: R
authors.lastname: Decking
authors.forename: Christoph
authors.initials: C
authors.lastname: Rokahr
authors.forename: Matthias
authors.initials: M
authors.lastname: Zurstegge
authors.forename: Ulrich
authors.initials: U
authors.lastname: Simon
authors.forename: Jens
authors.initials: J
authors.lastname: Decking
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000295:instrumentation* / Q000592:standards; D015519:Bone Density / Q000502:physiology*; D004867:Equipment Design / Q000379:methods / Q000592:standards; D005260:Female; D005272:Femur Neck / Q000000981:diagnostic imaging* / Q000502:physiology; D006622:Hip Prosthesis / Q000592:standards; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011859:Radiography