Virtual reconstruction of unilateral pelvic fractures by using pelvic symmetry.

PURPOSE: Pelvic fractures are known to be one of the most difficult injuries to treat. The objective of this study is to introduce a novel technique for virtual unilateral pelvic fracture reconstruction. Since the pelvis exhibits remarkable left-right symmetry, the contralateral hemipelvis can be used as a template for rebuilding the fractured hemipelvis. METHODS: CT scan data of the pelvic region of eight subjects with acute unilateral pelvic fractures were involved in this study. Computer-aided design software was used to create 3D models of these pelvises. The contralateral hemipelvis of each subject was then reflected across the sagittal plane, and the fractured hemipelvis was rebuilt by aligning the bone fragments with their equivalent location on the reflected side. To evaluate the quality of this reduction process, a 3D deviation analysis was conducted to calculate the differences between the reflected intact hemipelvis and the reconstructed hemipelvis. RESULTS: Results showed that the average root mean square (RMS) of deviations and average percentage of points within a +/- 2 mm predefined threshold was 1.32 +/- 0.22 mm and 88.4 +/- 3.78%, respectively. The deviation color maps obtained indicated that the largest differences were along the fracture lines and on the non-articular surfaces of the pelvises. CONCLUSION: These results allowed us to conclude the validity of this procedure, since the average RMS difference was below 2 mm and the average percentage of points within +/- 2 mm was high. The proposed technique will allow surgeons to provide their patients with more accurate reconstruction procedures which can potentially improve surgical outcomes.