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Updated: Jan 30, 2026
A Teleoperated Robotic System-Assisted Percutaneous Transiliac-Transsacral Screw Fixation Technique
Published on: January 6, 2023
Optimized posterior starting point of sacral-alar-iliac screw/reverse sacral-alar-iliac screw for sacroiliac joint
Shihao Du1, Zeqing Li2, Dong Li3
1Department of Orthopaedics, Wuxi Ninth People's Hospital Affiliated to Soochow University, No. 999 Liangxi Road, Wuxi, Jiangsu, 214062, China.
Background:
A classic posterior starting point of sacral-alar-iliac screw (SAIS) for spinopelvic fixation may not be optimal for sacroiliac joint fixation. We aimed to compare the safety and biomechanical performance of SAIS/reverse SAIS (RSAIS) implanted via the classic (lateral S1-S2 dorsal foramina border) versus modified (medial S1-S2 dorsal foramina border) posterior starting point for sacroiliac joint fixation.
Methods:
Eighty normal pelvic CT scans were used to measure the outer widths (OWs) of the SAIS/RSAIS posterior starting point of the classic and modified methods. 7.3 mm SAIS were implanted using the two methods on each side of 20 3D-printed models to examine sacral-side screw trajectory penetration. Fourteen Tile C1 injury models were divided into two groups and fixed with S2AIS implanted using either the classic (penetrating) or modified (non-penetrating) method to compare the stiffness and maximum loads of the final fixations. Six patients received percutaneous SAIS/RSAIS fixation using the modified method. Screw positions (Smith criteria), pain (visual analogue scale, VAS) and function (Majeed score) were assessed.
Results:
The modified method gave larger OWs for both S1AIS (7.80 vs. 5.11 mm) and S2AIS (5.85 vs. 3.04 mm) and reduced sacral-side screw trajectory penetration (S1AIS: 2.5% vs. 25%; S2AIS: 60% vs. 95%) than the classic method (all p < 0.05). Modified method fixation exhibited 13.8% higher stiffness and 26.2% greater maximum load than the classic method (p < 0.05). All SAIS/RSAIS positions were rated "excellent". During a postoperative follow-up of 7-20 months, no screw loosening or fixation failure occurred. Mean VAS increased from 5.6 preoperatively to 1.6 postoperatively, and mean Majeed from 59.7 to 81.
Conclusion:
The medial border of S1-S2 dorsal foramina provides a safer and more stable posterior starting point for SAIS/RSAIS in sacroiliac joint fixation, particularly for S2AIS/RS2AIS, outperforming the lateral border method.
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