Three-dimensional Reconstruction Model For Simulation Of Percutaneous Lag Screw Internal Fixation For Acetabulum Posterior Column Fracture

Objective To provide anatomical basis for lag screw internal fixation for acetabular posteriorcolumn fracture via the lesser sciatic notch.Methods Pelvic CT scanning data from60adults（30males and30females）wereimported into Mimics14.1for3D image reconstruction. The direction of longitudinal axis of theacetabular posterior column was observed in the three-dimensional pelvic model, screw placementwas simulated, and the point where the screw runs out was determined. Measured were the lengthof longitudinal axis, α angle between the longitudinal axis and the frontal plane, and β anglebetween that and the sagittal plane.Results The point where the longitudinal axis of the acetabular posterior column runsdownward out is located at midpoint of the sciatic notch, and the point where it runs upward out atthe midpoint between the rear end of arcuate line and anterior superior spine. The length oflongitudinal axis is (105.04±4.29) mm (male) and （101.80±3.20）mm (female), α angle33.41°±2.18°(male) and31.56°±2.71°(female), β angle21.74°±1.19°(male) and19.15°±1.24°(female). The bone cortex thickness at the screw entrance point is﹙5.54±0.46﹚mm,and that of lateral pelvic and of acetabular side is﹙1.45±0.13﹚mm and (1.04±0.10﹚mm,respectively.Conclusions The three-dimensional reconstruction model for simulation of lag screwinternal fixation via the lesser sciatic notch is able to simulate and measure the screw pathparameters with speed and accuracy, and effective for preoperative evaluation. Using the model toplace screws for fixation of posterior column fracture proves easy and safe.