title: Migration of the lag screw within the femoral head: a comparison of the intramedullary hip screw and the Gamma Asia-Pacific nail.
abstract: OBJECTIVE
  To study the functional difference in the performances of sliding femoral head screws by comparing the displacement of the screw in relation to the femoral head in hips treated with the Gamma Asia-Pacific nail (GN) and hips treated with the intramedullary hip screw (IMHS).
  
  
  METHODS
  Retrospective review of prospectively collected data.
  
  
  METHODS
  Displacement of the femoral head screw in relation to the femoral head was measured in fifty-six elderly patients with intertrochanteric fractures who were treated with an IMHS or GN. Displacement of the femoral head screw was determined by comparing screw position in the immediate postoperative radiograph with a film taken 3 months after surgery.
  
  
  RESULTS
  In the GN group, significant displacement of the screw was observed with 3.8 +/- 3.8 percent translation in the horizontal axis (P < 0.005) and 4.3 +/- 5.1 percent displacement in the vertical axis (P < 0.05) in comparison with the diameter of the femoral head. In comparison, displacement of the femoral head screw was not observed with the IMHS (P = 0.48 for horizontal, P = 0.18 for vertical). Total displacement of the femoral head screw in relation to the femoral head in the GN was twice that observed in the IMHS (P < 0.001).
  
  
  CONCLUSIONS
  These results indicate that the displacement of the femoral head screw of the IMHS was less than the lag screw of the GN. However, it is still unknown whether this smaller displacement of the IMHS is clinically significant for reducing the rate of screw cut-out after surgery.
authors.affiliation: Department of Orthopaedic Surgery, Kyoto Prefectural University of Medicine, Kyoto, Japan.
authors.forename: Yoshinobu
authors.initials: Y
authors.lastname: Watanabe
authors.forename: Ginjiro
authors.initials: G
authors.lastname: Minami
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Takeshita
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Fujii
authors.forename: Shinro
authors.initials: S
authors.lastname: Takai
authors.forename: Yasusuke
authors.initials: Y
authors.lastname: Hirasawa
mesh_terms: D000368:Aged; D001858:Bone Nails; D001863:Bone Screws; D005260:Female; D005270:Femur Head; D005548:Foreign-Body Migration; D005593:Fracture Fixation, Internal; D006620:Hip Fractures / Q000601:surgery*; D006801:Humans; D008297:Male; D012189:Retrospective Studies