title: Bone remodelling around the Metha short stem in total hip arthroplasty: a prospective dual-energy X-ray absorptiometry study.
abstract: OBJECTIVE
  On the basis of positive clinical results with mid- and long-term follow-up using the Mayo short stem, the Metha neck-preserving stem (BBraun, Aesculap, Tuttlingen, Germany) was introduced. The purpose of this study was to validate the implant design by direct acquisition of bone remodelling data from total hip arthroplasty (THA) recipients using dual-energy X-ray absorptiometry (DEXA).
  
  
  METHODS
  After power analysis, 25 patients were included in this prospective study. Patients were examined clinically and underwent DEXA examinations preoperatively and postoperatively at one week, six months and one and two years after THA. Gruen zones were adapted to the short stem design (R1-R7).
  
  
  RESULTS
  The Harris Hip Score (HHS) increased significantly by 31 points. No stem had to be revised. Bone mineral density (BMD) in the greater trochanter decreased significantly from 0.78 g/cm(2) postoperatively to 0.72 g/cm(2) two years after surgery. Marginal changes were seen in the lateral distal regions (R4-R5). In the minor trochanter region, BMD increased significantly after two years by 12.9%. In the calcar region, BMD exceeded the baseline value by 6.1% two years after implantation.
  
  
  CONCLUSIONS
  Stress shielding seems to occur at the greater trochanter due to the vast cross-section of the implant. However, the aim of proximal load transfer of the Metha stem seems to be partially achieved. DEXA analysis revealed a concentrated load distribution on the medial portion of the femur, which is an important region to guarantee long-term implant survival.
authors.affiliation: Department of Orthopaedic Surgery, Hannover Medical School, Anna-von-Borries Str. 1-7, 30625, Hannover, Germany. matthias.lerch@ddh-gruppe.de
authors.forename: Matthias
authors.initials: M
authors.lastname: Lerch
authors.forename: Annelene
authors.initials: A
authors.lastname: von der Haar-Tran
authors.forename: Henning
authors.initials: H
authors.lastname: Windhagen
authors.forename: Bernd A
authors.initials: BA
authors.lastname: Behrens
authors.forename: Patrick
authors.initials: P
authors.lastname: Wefstaedt
authors.forename: Christina M
authors.initials: CM
authors.lastname: Stukenborg-Colsman
mesh_terms: D015502:Absorptiometry, Photon; D000328:Adult; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects / Q000295:instrumentation* / Q000379:methods*; D015519:Bone Density / Q000502:physiology; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging / Q000378:metabolism; D006304:Health Status; D006621:Hip Joint / Q000503:physiopathology / Q000601:surgery; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D016348:Osseointegration; D015207:Osteoarthritis, Hip / Q000000981:diagnostic imaging / Q000378:metabolism / Q000601:surgery; D011183:Postoperative Complications; D011446:Prospective Studies; D011474:Prosthesis Design; D011788:Quality of Life; D020127:Recovery of Function; D016474:Weight-Bearing / Q000502:physiology