title: Cup press fit in uncemented THA depends on sex, acetabular shape, and surgical technique.
abstract: BACKGROUND
  Uncemented press-fit cups provide bone fixation in primary THA, but the use of screws is sometimes necessary to achieve primary stability of the socket. However, it is unclear whether and when screws should be used.
  
  
  OBJECTIVE
  We analyzed the factors related to screw use with a press-fit uncemented cup and assessed whether screw use is associated with the same rates of loosening and revision as a press-fit technique.
  
  
  METHODS
  We retrospectively reviewed 248 patients who underwent THA using the same prosthetic design. Eighty-eight hips had screws to achieve primary cup fixation (Group 1), and 189 did not (Group 2). Mean age was 50 years (range, 14-73 years). We analyzed factors related to the patient, acetabular type, and reconstruction of the rotation center of the hip. Minimum followup was 5 years (mean, 8.9 years; range, 5-12 years).
  
  
  RESULTS
  We found higher screw use in women, patients with less physical activity, Acetabular Types A or C, and a distance from the center of the prosthetic femoral head to the normal center of rotation of more than 3 mm. There were four revisions in Group 1 and five in Group 2. Eight hips had radiographic loosening in Group 1 and nine in Group 2. Cups with a postoperative abduction angle of more than 50° had a higher risk for loosening.
  
  
  CONCLUSIONS
  Press fit was achieved less frequently in women and patients with Acetabular Types A or C and less physical activity; a closer distance to the normal center of rotation decreased screw use. Screw use to augment fixation achieved survival similar to that of a press-fit cup.
  
  
  METHODS
  Level II, prognostic study. See Instructions for Authors for a complete description of levels of evidence.
authors.affiliation: Department of Orthopaedics, Hospital La Paz-Idi Paz, Pº Castellana 261, 28046 Madrid, Spain. edugrey@yahoo.es
authors.forename: Eduardo
authors.initials: E
authors.lastname: García-Rey
authors.forename: Eduardo
authors.initials: E
authors.lastname: García-Cimbrelo
authors.forename: Ana
authors.initials: A
authors.lastname: Cruz-Pardos
mesh_terms: D000077:Acetabulum / Q000000981:diagnostic imaging*; D000293:Adolescent; D000328:Adult; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000379:methods*; D001672:Biocompatible Materials; D001843:Bone Cements; D001863:Bone Screws; D017886:Durapatite; D005260:Female; D006621:Hip Joint / Q000000981:diagnostic imaging / Q000601:surgery*; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D011475:Prosthesis Failure; D011859:Radiography; D012189:Retrospective Studies; D012737:Sex Factors; D055815:Young Adult
chemical_list: D001672:Biocompatible Materials; D001843:Bone Cements; D017886:Durapatite