Morphometric measurement and applicable feature analysis of sacral alar-iliac screw fixation using forward engineering

Purpose To evaluate S1AI-S4AI screw channels with three-dimensional digital technology simulation analysis and to study the feasibility and applicable features of sacral alar-iliac screw fixation in adults. Materials and methods Forty (20 men and 20 women) normal adult's pelvic CT scan data sets were selected to reconstruct the three-dimensional pelvic model. The ideal S1AI-S4AI screw channels were simulated, followed by precise measurement of their parameters. Results The results showed that there were no significant differences in the transverse angles, sagittal angles, radiuses of the maximal inscribed circles, or lengths of the screw channels in S1AI-S2AI screws between genders (P > 0.05). In contrast, the radiuses of the maximal inscribed circles on the left and right, respectively, were 5.93 +/- 1.02 mm and 5.92 +/- 1.04 mm in males and 4.64 +/- 0.98 mm and 4.59 +/- 0.95 mm in females, and there was a significant difference in S3AI screws between genders (P < 0.05). With a radius of 2.50 mm considered to be standard, there were 25 cases (62.5%) with an S4AI screw channel radius <= 2.50 mm in 40 adults, and 15 cases (37.5%; 9 males and 6 females) with a radius > 2.50 mm. Furthermore, the transverse angles, the sagittal angles, the lengths of the screw channels, and the radiuses of the maximal inscribed circles were significantly different between genders in 15 cases (P < 0.05). Conclusion Only one maximum ideal screw can be placed on one side at a time. With a radius of 2.50 mm considered to be standard, it is feasible to place S1AI-S3AI screws with a radius > 2.50 mm in the entire adult population and S4AI screws with a radius > 2.50 mm in some of the adult population. Furthermore, preoperative three-dimensional reconstruction and three-matic research software can effectively simulate the sacral alar-iliac screw channels, and they can provide accurate data for clinical applications.