| Objective: To analysis the clinic anatomy, biomechanics, clinic indication and effective about the external fixation combined posterior plate reconstruction the pelvic fracture. Discussion this fixation can be used in the unstable pelvic fracture, the technical details and the clinical indications. The conclusion can offer theoretical support and referring to reconstruct unstable pelvic reconstruction.Methods:1. Anatomy research: To measured the cadaver sample get the anterior inferior iliac spine morphologic, location, and the supraacetabular external fixation pin tract in pelvic bone.2. Biomechanical experiment: Six cadaveric specimens axial loading from the proximal lumbar was applied by electronic universal test machine in the gradient of 100N to 500N, which simulated the double feet standing state. After experiment data acquisition, the mark point was used to analyze the displacement change by Digital Speckle Correlation Method; the strain gauge was used to analyze the strain change by Strain Gauge Method; and the load-displacement data was used to analyze axial stiffness of pelvis under different operating conditions.3. Finite element analysis: The CT images is supplied to established the 3D solid models of intact pelvis and four reconstructed pelvis assembled by different fixations; And after imported into FEA software Abaqus 6.7.2, the models will be executed the preprocessing and finite element calculation to analysis the displacement change and stress distribution.4. Clinic research: Retrospective research the patient who used external fixation combined posterior plate. To conclusion the clinic indication and the operation technical.Results:1. Anatomy research: The transverse diameter of AIIS was 12.23±1.91mm in male, and 11.05±1.56mm in female. In coronal plane the male AIIS down of ASIS 29.49±7.66mm, inner 21.79±6.48mm; the AIIS superior pubic tuberosity 51.70±9.31mm, outer 67.74±5.36mm. In coronal plane the female AIIS down of ASIS 23.74±8.89mm, inner 16.86±8.92mm; the AIIS superior pubic tuberosity 43.93±9.04mm, outer 70.16±6.39mm. The distance form AIIS to Lateral femoral circumflex artery is 23.24±5.33mm in male, and 17.82±3.26mm in female, the discrepance have statistic significance, Deep lilac circumflex artery is 16.26±1.77mm in male, and 14.06±2.16mm in female, the discrepance haven't statistic significance, femoral artery is 27.54±3.53mm in male, and 27.15±0.81mm in female, the discrepance haven't statistic significance, femoral nerve is 17.61±3.47mm in male, and 19.26±4.21mm in female, the discrepance haven't statistic significance. The pintract length is 147.76±7.39mm in male, and 142.75±6.36mm in female, the distance from anterior midline and posterior midine female is large than male 0.7mm and 9.5mm. The male pin track dense is thicker than female. Zone 1 is superior of acetabular rim 22.54±4.94mm, zone 2 is superior of arc line, zone 3 is superior of sciatic arch, and in this zone the superior gluteal artery and nerve ease to injury. Zone 4 is in the sacroiliac joint region.2. Biomechanical experiment: The biomechanical stability in supraacetabular is better than iliac wing external fixation, for it reconstruction the sacroiliac completion. Used supraacetabular external fixation is a good choice in Tile B1 pelvic fracture. In TileC1-2a1 fracture, locking compression plate biomechanical is better than isolate sacroiliac screw. Locking compression plate plus sacroiliac screw may improve the stability by the effection haven't significance.3. Finite element analysis: The CT images is supplied to established the 3D solid models of intact pelvis and four reconstructed pelvis assembled by different fixations; And after imported into FEA software Abaqus 6.7.2, the models will be executed the preprocessing and finite element calculation to analysis the displacement change and stress distribution. The supracetabular external fixation can reconstruction introduced the stress from the normal iliac to the fracture lateral, and reconstruction the sacroiliac completion. For the dense bony of supraacetabular, more thick pin can be inset and offer more strength.4. Clinic research: The follow up period was 6.3 months (range, 3-12months). The average intraoperative time was 70 minutes (range, 40-120minutes), and no patient underwent blood transfusion for the intraoperative blood loss was only 80-400ml. The external fixation maintained for 11 weeks (range 6-16 weeks). Mean fracture healing time were 14 weeks (range 12-19 weeks), partial weight bearing was 4 weeks. There was no severe iatrogenci nerve injury and complications.Conclusion: External fixation especially supraacetabular pin insert were useful ways for instability for anterior pelvic ring fractures, it can also support the stability of sacroiliac joint. The biomechanical stability was better than iliac wing pin location, and was the good fixation choice for Tile B1 pelvic fracture. Locking compression plate can use in posterior pelvic ring fractures, combine these two technical in specially type of pelvic fracture, can reconstruct pelvic ring by simply and rapidly ways with minimal invasive methods.
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