OBJECTIVETo radiographically analyze the osseous fixation zone for the iliac crest external fixation with Schanz screws and in order to guide their placement.

METHODSNine adults with 2.0-mm-slice continuous pelvic axial CT scans were selected as research subjects. Each CT scan data was imported into MIMICS 10.0. The osseous fixation zone the upper portion of the anterior column of the acetabulum which is located between the anterior superior iliac spine and the gluteal medius pillar and between the iliac crest and the acetabulum-for the iliac crest external fixation with Schanz screws was reconstructed into true sagittal and true coronal planes by using the software. Then the measurements were taken on the reconstructed planes with measuring tools. Finally, the measured data was analyzed.

RESULTSThe palpable iliac crest segment, which was of 49.6 mm width and located 16.5 mm posterior to the anterior superior iliac spine could be used to locate the start points of the Schanz screws. Under the above-mentioned iliac crest segment, the osseous zone was deep, got ample bony materials and could intraosseously contain Schanz screws with 5.0 mm diameter. The screws could be safely inserted to a minimal depth of 71.7 mm towards the acetabular dome and to a maximal depth of 143.5 mm posterior to the acetabulum.

CONCLUSIONThe study can guide the effective insertion of the iliac crest Schanz screws. By setting a suitable start point in the above-mentioned iliac crest region and angling correctly relative to the acetabulum,the Schanz screw can be inserted into the relative strong cancellous bone above or posterior to the acetabulum with a considerable depth, to getting more bone engagement.