Stem anteversion affects periprosthetic bone mineral density after total hip arthroplasty.
OBJECTIVE
The present study aimed to evaluate periprosthetic bone mineral density (BMD) changes around a cementless short tapered-wedge stem used for total hip arthroplasty (THA) and to determine the correlation between BMD changes and stem alignment after THA.


METHODS
The study included 21 patients (21 joints) who underwent THA with a TriLock stem. At baseline and 6, 12, 18, and 24 months postoperatively, the BMDs in the 7 Gruen zones were evaluated using dual-energy X-ray absorptiometry. BMD changes and stem alignment, that is, anteversion, varus, and anterior tilt, were correlated.


RESULTS
Minimal BMD changes were found in the distal femur (Gruen zones 3, 4, and 5), but significant BMD loss was noted in zone 7. BMD loss was also noted in zone 1 at 6 and 12 months postoperatively, but it recovered after 18 months. No correlation was found between BMD changes and anterior tilt. However, significant negative correlations were found between BMD changes and anteversion. Furthermore, significant negative correlations were found between BMD changes and varus in Gruen zone 1, while positive correlations were found between BMD changes and varus in Gruen zone 7.


CONCLUSIONS
We demonstrated that periprosthetic BMD was well maintained in the proximal femur after THA with a short tapered-wedge stem and that stem anteversion affects periprosthetic BMD after THA.
Department of Orthopaedic Surgery, Kobe University Graduate School of Medicine, Kobe - Japan.
Shinya
S
Hayashi
Department of Orthopaedic Surgery, Kobe University Graduate School of Medicine, Kobe - Japan.
Shingo
S
Hashimoto
Department of Orthopaedic Surgery, Kobe University Graduate School of Medicine, Kobe - Japan.
Noriyuki
N
Kanzaki
Department of Orthopaedic Surgery, Kobe University Graduate School of Medicine, Kobe - Japan.
Ryosuke
R
Kuroda
Department of Orthopaedic Surgery, Kobe University Graduate School of Medicine, Kobe - Japan.
Masahiro
M
Kurosaka
D015502:Absorptiometry, Photon / Q000379:methods; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects / Q000379:methods*; D015519:Bone Density; D016723:Bone Remodeling / Q000502:physiology*; D016009:Chi-Square Distribution; D015331:Cohort Studies; D005260:Female; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000379:methods; D057068:Periprosthetic Fractures / Q000209:etiology / Q000517:prevention & control; D011182:Postoperative Care; D011379:Prognosis; D011446:Prospective Studies; D011474:Prosthesis Design; D018570:Risk Assessment; D016896:Treatment Outcome