To investigate the anatomic feasibility and simulation effect of sacroiliac screw implanted from the front of the ilium (SIS-FI).

Pelvis CT data for 80 healthy adults (40 males and 40 females) collected from Imaging Department database of Wuxi No. 9 People's Hospital from January 2019 to May 2020 were analyzed retrospectively. Anatomic parameters of screw channel were measured by CT digital reconstruction technique to simulate SIS-FI fixation. Under the control of an aiming device, taking 6 mm backward from 2 o'clock or 10 o'clock of the posterior edge of the acetabulum as the entry point, and the base of the superior facet of S1 as the exit point, SIS-FIs with a diameter of 6.5 mm and 7.3 mm respectively, and a length of 90 mm were implanted on the two sides of the 40 3D printed models of the pelvis (1∶1). The implantation of screw was observed.

The entry point was located at the position of (5.78±1.35) mm horizontally backward from the posterior edge of the acetabulum and (2.48±0.50) mm vertically downward from the upper edge of the acetabulum. The upward angle between the central axis of the channel and the line parallel to the superior endplate of S1 was (42.99±5.16)°, and the inward angle between the central axial of the channel and the longitudinal axis of the human trunk was (43.79±2.83)°. The length of the screw channel was (102.55±7.64) mm, the minimum width was (16.55±1.77) mm, and the minimum height was (18.78±1.44) mm. All the implanted screws were located within the channel, but screws in one case were longer and penetrated a little behind the posterior part of the channel.

At least one screw with a diameter of 6.5-7.3 mm and a length of 85-95 mm for SIS-FI can be implanted into the pelvis of Chinese. SIS-FI implanted with the aid of an aiming device has high accuracy. However, its clinical value needs further study.