title: Remodeling of bone tissue around the distal part of Zweymüller stem.
abstract: BACKGROUND
  The Zweymüller stem is well-known in Europe and widely used for total hip replacement since 1980. Few authors have noted the presence of increased bone density below the tip of the stem; however, the underlying mechanism is still unknown. The aim of this study was to reveal factors influencing bone remodeling around the tip of the Zweymüller stem.
  
  
  METHODS
  102 consecutive patients (69 women and 33 men) who received a second generation Zweymüller type stem (123 prostheses) were included. Mean follow-up was 9.2 years (6 - 15 years). A Cortical Index (CI) was defined as the ratio between stem width and external cortical diameter in Gruen zones 3 and 5.
  
  
  RESULTS
  Patients with a wide femoral canal and thin cortical bone (CI ≥0.4) demonstrated a positive correlation with the presence of increased bone density (IBD) below the stem (p<0.0001, r=0.6028). During follow-up, the mean Cortical Index decreased by 0.02 points and mean thickness of cortical bone in zone 3 and 5 increased by 2.0 millimeters. Cortical thickening was more pronounced in cases without IBD (1.5 vs. 2.4 mm, p=0.0172).
  
  
  CONCLUSIONS
  1. Thin cortical layers and a wide femoral canal (CI ≥0.4) can result in the presence of IBD below the stem. 2. IBDs probably appear due to mechanical stress transferred by the tip of stem to cancellous bone in Gruen zone 4. 3. Based on clinical symptoms, we conclude that the presence of IBD is not associated with increased aseptic loosening or stem instability.
authors.affiliation: Department of General Orthopedics, Musculoskeletal Oncology and Trauma Surgery, Poznań University of Medical Sciences, Poland.
authors.forename: Paweł
authors.initials: P
authors.lastname: Kokoszka
authors.affiliation: Department of General Orthopedics, Musculoskeletal Oncology and Trauma Surgery, Poznań University of Medical Sciences, Poland.
authors.forename: Jacek
authors.initials: J
authors.lastname: Markuszewski
authors.affiliation: Department of General Orthopedics, Musculoskeletal Oncology and Trauma Surgery, Poznań University of Medical Sciences, Poland.
authors.forename: Łukasz
authors.initials: Ł
authors.lastname: Łapaj
authors.affiliation: Department of General Orthopedics, Musculoskeletal Oncology and Trauma Surgery, Poznań University of Medical Sciences, Poland.
authors.forename: Małgorzata
authors.initials: M
authors.lastname: Wierusz-Kozłowska
mesh_terms: D000328:Adult; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000379:methods*; D016723:Bone Remodeling / Q000502:physiology*; D005260:Female; D005500:Follow-Up Studies; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D011474:Prosthesis Design; D014025:Titanium
chemical_list: D014025:Titanium