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.
Keywords: Forward engineering; Pelvic fixation; Reconstruction; Sacral alar–iliac screw; Screw channel; Three-dimensional.