Accuracy and influencing factors of robot-assisted sacroiliac screw placement: a comparative study of short versus trans-cortical screws.

To systematically evaluate the accuracy of robot-assisted sacroiliac screw placement, compare the precision difference between short screws and trans-cortical (through-and-through) screws, and analyze factors associated with screw malposition. A retrospective analysis was conducted on 149 patients with pelvic fractures who underwent robot-assisted sacroiliac screw placement at Gansu Provincial Hospital from January 2021 to October 2025. A total of 149 sacroiliac screws (93 short, 56 trans-cortical) were included. Screw accuracy was assessed by postoperative pelvic CT using the Smith grading system. Functional outcomes were evaluated by Majeed score at 6 months. Univariate analysis was used to explore risk factors for malposition, but results are presented as exploratory due to the limited number of events. The overall accuracy rate was 98.0% (146/149). The accuracy of short screws (98.9%, 92/93) was significantly higher than that of trans-cortical screws (96.4%, 54/56, P = 0.035). All malpositioned screws were Smith grade I (cortical breach ≤ 2 mm). Univariate analysis suggested that screw type (P = 0.035) and BMI ≥ 30 kg/m² (P = 0.031) were associated with malposition, but these findings are exploratory and should be interpreted with caution, as they are based on only five malposition events. The excellent-good rate of Majeed score at 6 months was 91.4% (85/93) in the short screw group and 85.7% (48/56) in the trans-cortical group (P = 0.097). Robot-assisted sacroiliac screw placement demonstrates excellent overall accuracy. Short screws show a potential accuracy advantage over trans-cortical screws. However, given the small number of malposition events and the exploratory nature of the analysis, these results should be interpreted cautiously. The most common technical cause of malposition was oblique bone surface at the entry point, which deserves greater attention as a modifiable factor. Larger prospective studies are needed to confirm these preliminary findings.