title: Daily activity and initial bone mineral density are associated with periprosthetic bone mineral density after total hip arthroplasty.
abstract: OBJECTIVE
  To evaluate periprosthetic bone mineral density (BMD) changes around a cementless short tapered-wedge stem and determine correlations between BMD changes and various clinical factors, including daily activity, after total hip arthroplasty (THA) with a tapered-wedge stem.
  
  
  METHODS
  65 patients underwent THA with a TriLock BPS stem. At baseline and at 6, 12, and 24 months postoperatively the BMD of the 7 Gruen zones were evaluated using dual-energy x-ray absorptiometry. Correlations were determined between BMD changes and clinical factors, including the Harris Hip Score, body mass index, University of California at Los Angeles (UCLA) activity rating score, age at surgery, and initial spine BMD. Radiographic parameters, including the proximal femoral geometry (Dorr Classification), canal filling ratio, canal flare index, and calcar-to-canal ratio were also assessed.
  
  
  RESULTS
  Minimal BMD changes were noted in the distal femur. However, significant BMD loss was noted in zone 7 at each time point. BMD loss was also noted in zone 1 at 6 and 12 months postoperatively, but BMD recovered after 18 months. Significant positive correlations were noted between BMD changes and the UCLA activity score in zones 1, 6, and 7. Additionally, negative correlations were noted between BMD changes and the preoperative lumbar BMD in zones 2 and 3. No correlations were noted between BMD changes and the radiographic parameters. Periprosthetic BMD was was virtually unchanged in the proximal femur, especially Gruen zone 1.
  
  
  CONCLUSIONS
  Daily activity may reflect improvements in periprosthetic bone quality after THA; however, the use of this tapered-wedge stem is not recommended in patients with poor bone quality.
authors.affiliation: Department of Orthopedic Surgery, Kobe University Graduate School of Medicine, Kobe - Japan.
authors.forename: Shinya
authors.initials: S
authors.lastname: Hayashi
authors.affiliation: Department of Orthopedic Surgery, Kobe University Graduate School of Medicine, Kobe - Japan.
authors.forename: Shingo
authors.initials: S
authors.lastname: Hashimoto
authors.affiliation: Department of Orthopedic Surgery, Kobe University Graduate School of Medicine, Kobe - Japan.
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Kanzaki
authors.affiliation: Department of Orthopedic Surgery, Kobe University Graduate School of Medicine, Kobe - Japan.
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Kuroda
authors.affiliation: Department of Orthopedic Surgery, Kobe University Graduate School of Medicine, Kobe - Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Kurosaka
mesh_terms: D015502:Absorptiometry, Photon; D000203:Activities of Daily Living; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects*; D015519:Bone Density; D016723:Bone Remodeling / Q000502:physiology*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D057068:Periprosthetic Fractures / Q000209:etiology / Q000378:metabolism / Q000503:physiopathology*; D011446:Prospective Studies; D011475:Prosthesis Failure; D013997:Time Factors