title: The Effect of Screw Design on Union Rates in Scaphoid Nonunions.
abstract: BACKGROUND
  The purpose of this study is to compare the outcome of the conical fully threaded headless screw to that of a smooth shaft headless screw in a series of scaphoid nonunions requiring screw fixation to determine if screw design had an influence on union rates.
  
  
  METHODS
  We retrospectively reviewed 104 cases of surgically treated scaphoid nonunions. After eliminating cases with our exclusion criteria, the study cohort had 40 cases for analysis. A comparison and analysis of union rates was undertaken between the fully threaded Acutrak 2 mini screw and the smooth shaft Herbert screw.
  
  
  RESULTS
  Overall union rate for screw fixation was 88%. The fully threaded conical screw fixation had a significantly lower union rate of 50% compared to 97% for the smooth shaft screws.
  
  
  CONCLUSIONS
  Our data revealed that the fully threaded conical screws were associated with significantly lower union rate compared to the smooth shaft Herbert type screws.
authors.affiliation: † Department of Hand Surgery, Singapore General Hospital, Singapore.
authors.forename: Jiwei
authors.initials: J
authors.lastname: Wu
authors.affiliation: † Department of Hand Surgery, Singapore General Hospital, Singapore.
authors.forename: Shian Chao
authors.initials: SC
authors.lastname: Tay
authors.affiliation: * Division of Hand Surgery, Mayo Clinic, Rochester, Minnesota, USA.
authors.forename: Alexander Y
authors.initials: AY
authors.lastname: Shin
mesh_terms: D000293:Adolescent; D000328:Adult; D001863:Bone Screws; D004867:Equipment Design; D005260:Female; D005500:Follow-Up Studies; D005593:Fracture Fixation, Internal / Q000295:instrumentation*; D005599:Fractures, Ununited / Q000601:surgery*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D021361:Scaphoid Bone / Q000293:injuries* / Q000601:surgery; D014954:Wrist Injuries / Q000601:surgery*; D055815:Young Adult
keywords: Fixation; Nonunion; Scaphoid; Screw