title: [Computer-assisted navigated cup placement of different cup types in hip arthroplasty--a randomised controlled trial].
abstract: OBJECTIVE
  The position of the acetabular implant has a great influence on the outcome of total hip arthroplasty. The acetabular implants differ in their characteristics during insertion. In order to control the influence of the implant in different axes, 80 implantations of acetabular component were performed under computer-assisted control by a surogate navigation system.
  
  
  METHODS
  Within a prospective randomised study, 70 total hip replacements were performed by one surgeon using two different uncemented implants (PPF screw cup/Hedrocel pressfit cup). The position of the cup was measured at different times during surgery and was compared to 10 cemented PE cup placements.
  
  
  RESULTS
  During the milling procedure the anteversion of the two uncemented cups differed significantly (p = 0.026). The standard deviation of anteversion during implantation different significantly relating to the cup type: press-fit cup 3.86 degrees, screw cup 2.1 degrees and cemented PE cups 0,84 degrees. The inclination was less susceptible.
  
  
  CONCLUSIONS
  The cup design of uncemented acetabular implants influences the outcome of surgery. In our trial a spherical press-fit cup showed a greater variability than the screw-cup. The CAS system can be used as a tool to minimise these effects.
authors.affiliation: Girardet Clinic Essen, Germany. Kai.Bernsmann@ruhr-uni-bochum.de
authors.forename: K
authors.initials: K
authors.lastname: Bernsmann
authors.forename: U
authors.initials: U
authors.lastname: Langlotz
authors.forename: B
authors.initials: B
authors.lastname: Ansari
authors.forename: M
authors.initials: M
authors.lastname: Wiese
mesh_terms: D000077:Acetabulum / Q000601:surgery*; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000295:instrumentation*; D005260:Female; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D015207:Osteoarthritis, Hip / Q000601:surgery*; D010043:Outcome and Process Assessment, Health Care; D011474:Prosthesis Design; D025321:Surgery, Computer-Assisted / Q000295:instrumentation*