title: The dual radius hemispherical 'Trident" cup: results based on 150 consecutive cases.
abstract: BACKGROUND
  Initial stability with press-fit cups can be achieved in a number of ways based on the design of the cup. With line-to-line fit, screws fixation, press-fit of 1 to 2 mm which is obtained by an oversized hemispherical cup, initial stability can be achieved with the dual-radius press-fit cups, which have an equatorial diameter 1 to 2 mm greater than that of the polar diameter, to ensure a good press-fit and to provide adequate initial stability for bone ingrowth to occur reliably.
  
  
  METHODS
  Between January 2002 and January 2008, 400 total hip replacements (THRs) were carried out. We examined the first 150 consecutive primary THRs. In all hips, the acetabular component was the dual radius Trident AD shell (Stryker Orthopaedics, Mahwah, New Jersey).
  
  
  RESULTS
  The median duration of follow-up was 6,2 yrs (range, 5 to 7 yrs). The median post-operative Harris Hip Score for 150 hips was 90.5 (range, 51 to 98). At the time of the latest follow-up, there was a bony incorporation of all components; we found no definite evidence of radiographic loosening and no signs of radiolucency.
  
  
  CONCLUSIONS
  According to the encouraging results of the present study we conclude that the Trident cup is a valid choice for acetabular replacement.
authors.affiliation: First Department of Orthopaedics, University of Pisa, Italy.
authors.forename: Enrico
authors.initials: E
authors.lastname: Bonicoli
authors.forename: Alessandro
authors.initials: A
authors.lastname: Baluganti
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Andreani
authors.forename: Nicola
authors.initials: N
authors.lastname: Piolanti
authors.forename: Michele
authors.initials: M
authors.lastname: Lisanti
mesh_terms: D000077:Acetabulum / Q000601:surgery*; D000368:Aged; D000369:Aged, 80 and over; D015897:Comorbidity; D005260:Female; D006621:Hip Joint / Q000601:surgery*; D006622:Hip Prosthesis / Q000706:statistics & numerical data*; D006801:Humans; D007593:Joint Instability / Q000000981:diagnostic imaging / Q000453:epidemiology* / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications / Q000453:epidemiology*; D015995:Prevalence; D011474:Prosthesis Design; D011859:Radiography; D012307:Risk Factors; D016896:Treatment Outcome