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The application of the axial view projection of the S1 pedicel for sacroiliac screw.

BACKGROUND
The objective of this study was to position the iliosacral screws speedily, easily, and safely, we sought to delineate readily reproducible radiographic anatomic clues of the pedicel of S1 for the iliosacral screw placement.


METHODS
We used eight normal adult pelvic specimens lying on the operation table in the prone position. First, the C-arm fluoroscope unit is positioned for the lateral view of the body of S1. We gradually changed the angle of the C-arm to ventral and cephalad. When a clear oval track image appears, we fix the angle of the C-arm. With the assistance of the C-arm projection, the starting point for the guide pin is centered on the oval track, and the orientation is adjusted. When the projection of the guide pin became a point inside of the oval track, the guide pin is inserted using battery-powered equipment. The accuracy and angle of pin placement is assessed using computed tomography scans in all cases.


RESULTS
In all the pelves, the oval track has been successfully found, and the guide pins are accurately inserted using the sacral pedicel axial view. In the angular orientations by the computed tomography scan, the transverse plane inclination to the ventral of the guide pin is approximately 38.3 degrees +/- 1.9 degrees, and the frontal plane inclination to the cephalad is approximately 29.6 degrees +/- 2.0 degrees.


CONCLUSION
The sacral pedicel axial view projection is a optimal radiographic technique for percutaneous placement of iliosacral screws in clinical practice. We can get the limpid axial view of pedicel of S1 to applicate this project method, which provides a speedier method with less radiation exposure for percutaneous placement of iliosacral screws.