title: Increased migration of uncemented acetabular cups in female total hip arthroplasty patients with low systemic bone mineral density. A 2-year RSA and 8-year radiographic follow-up study of 34 patients.
abstract: OBJECTIVE
  Low bone mineral density (BMD) may jeopardize the initial component stability and delay osseointegration of uncemented acetabular cups in total hip arthroplasty (THA). We measured the migration of uncemented cups in women with low or normal BMD.
  
  
  METHODS
  We used radiostereometric analysis (RSA) to measure the migration of hydroxyapatite-coated titanium alloy cups with alumina-on-alumina bearings in THA of 34 female patients with a median age of 64 (41-78) years. 10 patients had normal BMD and 24 patients had low systemic BMD (T-score ≤ -1) based on dual-energy X-ray absorptiometry (DXA). Cup migration was followed with RSA for 2 years. Radiographic follow-up was done at a median of 8 (2-10) years.
  
  
  RESULTS
  Patients with normal BMD did not show a statistically significant cup migration after the settling period of 3 months, while patients with low BMD had a continuous proximal migration between 3 and 12 months (p = 0.03). These differences in cup migration persisted at 24 months. Based on the perceived risk of cup revision, 14 of the 24 cases were "at risk" (proximal translation of 0.2 to 1.0 mm) in the low-BMD group and 2 of the 10 cases were "at risk" in the normal-BMD group (odds ratio (OR) = 8.0, 95% CI: 1.3-48). The radiographic follow-up showed no radiolucent lines or osteolysis. 2 cups have been revised for fractures of the ceramic bearings, but none for loosening.
  
  
  CONCLUSIONS
  Low BMD contributed to cup migration beyond the settling period of 3 months, but the migrating cups appeared to osseointegrate eventually.
authors.affiliation: a Orthopaedic Research Unit , Turku University Hospital and University of Turku.
authors.forename: Sami
authors.initials: S
authors.lastname: Finnilä
authors.affiliation: a Orthopaedic Research Unit , Turku University Hospital and University of Turku.
authors.forename: Niko
authors.initials: N
authors.lastname: Moritz
authors.affiliation: b Department of Diagnostic Radiology , Turku University Hospital , Turku , Finland .
authors.forename: Erkki
authors.initials: E
authors.lastname: SvedströM
authors.affiliation: a Orthopaedic Research Unit , Turku University Hospital and University of Turku.
authors.forename: Jessica J
authors.initials: JJ
authors.lastname: Alm
authors.affiliation: a Orthopaedic Research Unit , Turku University Hospital and University of Turku.
authors.forename: Hannu T
authors.initials: HT
authors.lastname: Aro
mesh_terms: D015502:Absorptiometry, Photon / Q000379:methods; D000077:Acetabulum; D000328:Adult; D000367:Age Factors; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects* / Q000379:methods; D001843:Bone Cements; D015519:Bone Density / Q000502:physiology*; D016022:Case-Control Studies; D002484:Cementation; D005260:Female; D005500:Follow-Up Studies; D005548:Foreign-Body Migration / Q000000981:diagnostic imaging* / Q000453:epidemiology; D006622:Hip Prosthesis / Q000009:adverse effects; D006801:Humans; D006882:Hydroxyapatites / Q000737:chemistry; D015994:Incidence; D016014:Linear Models; D008875:Middle Aged; D015999:Multivariate Analysis; D016348:Osseointegration / Q000502:physiology*; D010024:Osteoporosis / Q000150:complications* / Q000000981:diagnostic imaging; D011474:Prosthesis Design; D011475:Prosthesis Failure; D059869:Radiostereometric Analysis / Q000379:methods; D012189:Retrospective Studies; D018570:Risk Assessment; D018709:Statistics, Nonparametric; D013997:Time Factors; D014025:Titanium / Q000737:chemistry
chemical_list: D001843:Bone Cements; D006882:Hydroxyapatites; C098170:hydroxyapatite-titanium alloy; D014025:Titanium