title: Low BMD affects initial stability and delays stem osseointegration in cementless total hip arthroplasty in women: a 2-year RSA study of 39 patients.
abstract: OBJECTIVE
  Immediate implant stability is a key factor for success in cementless total hip arthroplasty (THA). Low bone mineral density (BMD) and age-related geometric changes of the proximal femur may jeopardize initial stability and osseointegration. We compared migration of hydroxyapatite-coated femoral stems in women with or without low systemic BMD.
  
  
  METHODS
  61 female patients with hip osteoarthritis were treated with cementless THA with anatomically designed hydroxyapatite-coated femoral stems and ceramic-ceramic bearing surfaces (ABG-II). Of the 39 eligible patients between the ages of 41 and 78 years, 12 had normal systemic BMD and 27 had osteopenia or osteoporosis. According to the Dorr classification, 21 had type A bone and 18 had type B. Translational and rotational migration of the stems was evaluated with radiostereometric analysis (RSA) up to 2 years after surgery.
  
  
  RESULTS
  Patients with low systemic BMD showed higher subsidence of the femoral stem during the first 3 months after surgery than did those with normal BMD (difference = 0.6, 95% CI: 0.1-1.1; p = 0.03). Low systemic BMD (odds ratio (OR) = 0.1, CI: 0.006-1.0; p = 0.02), low local hip BMD (OR = 0.3, CI: 0.1-0.7; p = 0.005) and ageing (OR = 1.1, CI: 1.0-1.2; p = 0.02) were risk factors for delayed translational stability. Ageing and low canal flare index were risk factors for delayed rotational stabilization (OR = 3, CI: 1.1-9; p = 0.04 and OR = 1.1, CI: 1.0-1.2; p = 0.02, respectively). Harris hip score and WOMAC score were similar in patients with normal systemic BMD and low systemic BMD.
  
  
  CONCLUSIONS
  Low BMD, changes in intraosseous dimensions of the proximal femur, and ageing adversely affected initial stability and delayed osseointegration of cementless stems in women.
authors.affiliation: Orthopaedic Research Unit, Department of Orthopaedic Surgery and Traumatology, Turku University Hospital and University of Turku, Finland. hannu.aro@utu.fi
authors.forename: Hannu T
authors.initials: HT
authors.lastname: Aro
authors.forename: Jessica J
authors.initials: JJ
authors.lastname: Alm
authors.forename: Niko
authors.initials: N
authors.lastname: Moritz
authors.forename: Tatu J
authors.initials: TJ
authors.lastname: Mäkinen
authors.forename: Petteri
authors.initials: P
authors.lastname: Lankinen
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology; D019644:Arthroplasty, Replacement, Hip / Q000295:instrumentation; D015519:Bone Density / Q000502:physiology*; D001851:Bone Diseases, Metabolic / Q000150:complications* / Q000503:physiopathology; D005260:Female; D006621:Hip Joint / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D006622:Hip Prosthesis; D006801:Humans; D007593:Joint Instability / Q000000981:diagnostic imaging / Q000453:epidemiology* / Q000503:physiopathology; D016015:Logistic Models; D008137:Longitudinal Studies; D008875:Middle Aged; D016348:Osseointegration / Q000502:physiology*; D015207:Osteoarthritis, Hip / Q000601:surgery; D010024:Osteoporosis / Q000150:complications* / Q000503:physiopathology; D011475:Prosthesis Failure / Q000009:adverse effects; D059869:Radiostereometric Analysis; D012189:Retrospective Studies; D012307:Risk Factors