title: Lower periprosthetic bone loss and good fixation of an ultra-short stem compared to a conventional stem in uncemented total hip arthroplasty.
abstract: OBJECTIVE
  We hypothesized that an ultra-short stem would load the proximal femur in a more physiological way and could therefore reduce the adaptive periprosthetic bone loss known as stress shielding.
  
  
  METHODS
  51 patients with primary hip osteoarthritis were randomized to total hip arthroplasty (THA) with either an ultra-short stem or a conventional tapered stem. The primary endpoint was change in periprosthetic bone mineral density (BMD), measured with dual-energy x-ray absorptiometry (DXA), in Gruen zones 1 and 7, two years after surgery. Secondary endpoints were change in periprosthetic BMD in the entire periprosthetic region, i.e. Gruen zones 1 through 7, stem migration measured with radiostereometric analysis (RSA), and function measured with self-administered functional scores.
  
  
  RESULTS
  The periprosthetic decrease in BMD was statistically significantly lower with the ultra-short stem. In Gruen zone 1, the mean difference was 18% (95% CI: -27% to -10%). In zone 7, the difference was 5% (CI: -12% to -3%) and for Gruen zones 1-7 the difference was also 5% (CI: -9% to -2%). During the first 6 weeks postoperatively, the ultra-short stems migrated 0.77 mm more on average than the conventional stems. 3 months after surgery, no further migration was seen. The functional scores improved during the study and were similar in the 2 groups.
  
  
  CONCLUSIONS
  Up to 2 years after total hip arthroplasty, compared to the conventional tapered stem the ultra-short uncemented anatomical stem induced lower periprosthetic bone loss and had equally excellent stem fixation and clinical outcome.
authors.affiliation: a Department of Orthopaedics, Danderyd Hospital and Department of Clinical Sciences at Danderyd Hospital (KIDS), Karolinska Institutet , Stockholm, Sweden.
authors.forename: Mats
authors.initials: M
authors.lastname: Salemyr
authors.affiliation: a Department of Orthopaedics, Danderyd Hospital and Department of Clinical Sciences at Danderyd Hospital (KIDS), Karolinska Institutet , Stockholm, Sweden.
authors.forename: Olle
authors.initials: O
authors.lastname: Muren
authors.affiliation: a Department of Orthopaedics, Danderyd Hospital and Department of Clinical Sciences at Danderyd Hospital (KIDS), Karolinska Institutet , Stockholm, Sweden.
authors.forename: Torbjörn
authors.initials: T
authors.lastname: Ahl
authors.affiliation: a Department of Orthopaedics, Danderyd Hospital and Department of Clinical Sciences at Danderyd Hospital (KIDS), Karolinska Institutet , Stockholm, Sweden.
authors.forename: Henrik
authors.initials: H
authors.lastname: Bodén
authors.affiliation: a Department of Orthopaedics, Danderyd Hospital and Department of Clinical Sciences at Danderyd Hospital (KIDS), Karolinska Institutet , Stockholm, Sweden.
authors.forename: Thomas
authors.initials: T
authors.lastname: Eisler
authors.affiliation: a Department of Orthopaedics, Danderyd Hospital and Department of Clinical Sciences at Danderyd Hospital (KIDS), Karolinska Institutet , Stockholm, Sweden.
authors.forename: André
authors.initials: A
authors.lastname: Stark
authors.affiliation: a Department of Orthopaedics, Danderyd Hospital and Department of Clinical Sciences at Danderyd Hospital (KIDS), Karolinska Institutet , Stockholm, Sweden.
authors.forename: Olof
authors.initials: O
authors.lastname: Sköldenberg
mesh_terms: D015502:Absorptiometry, Photon; D019644:Arthroplasty, Replacement, Hip / Q000295:instrumentation / Q000379:methods*; D015519:Bone Density; D001862:Bone Resorption / Q000517:prevention & control; D005260:Female; D005269:Femur / Q000601:surgery; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D011475:Prosthesis Failure; D059869:Radiostereometric Analysis