title: The femoral neck safe zone: a radiographic simulation study to prevent cortical perforation with multiple screw insertion.
abstract: OBJECTIVE
  To calculate the probability of iatrogenic perforation when screws seem to be safe on radiographs. A risk zone (RZ) gradient is mapped to help surgeons determine the suitable screw positions.
  
  
  METHODS
  Using computed tomography data and image-processing software, 24 proximal femurs were reconstructed. The anteroposterior, lateral, and axial views were then simulated, and the safe zone and RZ were identified and calculated on the axial graphs. Each original axial graph was zoomed and compiled to match a calculated average image, and a gradient figure of the RZs was visualized.
  
  
  RESULTS
  All 24 femoral necks had cortical perforation RZs. The average risk percentage was 23.7%. The individual risk per quadrant was as follows: anterosuperior 2.5%, posteroinferior 3.8%, posterosuperior 6.7%, and anteroinferior 10.7%. Four safe and cortex-touching zones and a safe region were identified in femoral neck for 6.5-mm screws.
  
  
  CONCLUSIONS
  Surgeons should be wary of screws that appear close to the cortex on both radiographs, especially in the posterosuperior and anteroinferior quadrants, because such screws probably perforate the cortex. To minimize iatrogenic perforation, screw position should be assessed using a gradient figure of the RZs.
authors.affiliation: Department of Orthopaedic Surgery, Yangpu Hospital and Tongji Hospital, Tongji University School of Medicine, Shanghai, China.
authors.forename: Ying Qi
authors.initials: YQ
authors.lastname: Zhang
authors.forename: Shi Min
authors.initials: SM
authors.lastname: Chang
authors.forename: Yi Gang
authors.initials: YG
authors.lastname: Huang
authors.forename: Xin
authors.initials: X
authors.lastname: Wang
mesh_terms: D000328:Adult; D001863:Bone Screws / Q000009:adverse effects*; D003198:Computer Simulation; D005260:Female; D005265:Femoral Neck Fractures / Q000601:surgery*; D005272:Femur Neck / Q000000981:diagnostic imaging* / Q000293:injuries / Q000601:surgery; D005593:Fracture Fixation, Internal / Q000009:adverse effects / Q000379:methods*; D006801:Humans; D007049:Iatrogenic Disease / Q000517:prevention & control*; D021621:Imaging, Three-Dimensional; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D014057:Tomography, X-Ray Computed; D055815:Young Adult