Abstract:

Objective　To identify the safe zone for screws to fix fractures of acetabular quadrilateral plateby anatomical parameter measurement and virtual screws insertion at upper boundary of three-dimensional reconstruction quadrilateral plate model.　Methods　50 pelves(100 sides) including 25 females and 25 males were reconstructed in three-dimensional form and cut by Mimics software. The quadrilateral plate anatomical parameters were measured and the dangerous zone of screw insertion was determined；then the virtual screws were placed in the quadrilateral plate through different entry points at upper boundary,and the safe ranges of the screws were calculated.　Results　The maximum backward incline angles of screw P1 were （7.63±5.47）° in male and（6.18±5.16）° in female, and the maximum forward incline angles of screw P5 were（7.50±6.09）° in male and（7.30±6.54）° in female, both of them had no significant difference between genders. The inward and outward incline safe ranges of screw P2 and P4 were（7.60±2.93）° and （16.88±5.61）° in male and（7.96±2.98）° and（15.82±5.94）° in female, respectively. There were 13 sides in male and 28 sides in female whose safe range of screw P3 was extremely narrow that they have to be inserted at given angles, which were（-0.22±2.87）°in male and （-5.62±4.48）°in female, and the difference between male and female had statistical significance. The safe ranges of screw P3 of the remaining 59 sides were （5.39±2.60）° in male and（4.06±2.58）°  in female, with no significant difference between genders.　Conclusions　Point P3 is the most dangerous zone of the upper boundary of the quadrilateral plate, which is about 27 mm from point P3 to point P1. If the thickness of the thinnest portion of quadrilateral plate is less than 4.47 mm in male or 3.56 mm in female by Mimics measurement, then no screw or short screw with length shorter than 14 mm in male or 12 mm in female is recommended to be inserted at point P3.

Key words: Quadrilateral plate, Safe zone, Applied anatomy