S2 alar-iliac screwing assisted by an individualized navigation template

Objective To evaluate the accuracy and feasibility of S2 alar-iliac screwing assisted by an individualized navigation template in clinic. Methods Five patients underwent S2 alar-iliac screwing from March 2015 to July 2017. They were 2 men and 3 women, aged from 41 to 61 years (average, 54.8 years). After their preoperative CT scan data of the pelvis were used for 3D reconstruction, their individualized navigation templates were designed, 3D printed and used to assist the implantation of S2 alar-iliac screws. After operation, their postoperative CT data were reviewed and reconstructed using software Mimics. The caudal angulation on the sagittal plane (sagittal angle, SA), lateral angulation on the transverse plane (transverse angle, TA), horizontal distance to the median sacral crest (horizontal distance, HD), and vertical distance to the first posterior sacral foramen's inferior margin (vertical distance, VD) of the screws were measured and compared with the corresponding values in the preoperative design. Results In the 5 patients, altogether 10 S2 alar-iliac screws were implanted through the sacroiliac joint without piercing the iliac bone cortex. There were no significant differences between the preoperative design and postoperative measurements in terms of SA (32.22°±5.57° versus 31.95°±5.78°), TA (42.59°±4.55° versus 42.21°±5.29°), HD (5.04±0.40 mm versus 5.00±0.41 mm) or VD (19.58±1.49 mm versus 19.54±1.12 mm) (P>0.05). Conclusion In the adult pelvic fixation, the S2 alar-iliac screwing can be assisted by an individualized navigation template to achieve high accuracy in implantation. Key words: Pelvis; Sacroiliac joint; Pelvimetry; 3D printing technology; Navigation template