[Study on the precision of the robot-assisted sacroiliac screw placement].

Objective: To evaluate the precision of the robot-assisted sacroiliac screw placement for posterior pelvis injury and the impacting factors. Methods: The clinical data of twenty-four cases of posterior pelvic fractures treated by percutaneous sacroiliac screw placement in Yantai shan Hospital from August 2016 to May 2018 were studied retrospectively. There were 17 males and 7 females with a mean age of 44.1 years (ranged from 17 to 71 years). According to AO classification, 17 cases were type B fractures (9 cases of type B1 and 8 type B2), and 7 cases were type C factures (3 cases of type C1, 2 type C2 and 2 type C3). All cases were treated by robot-assisted percutaneous sacroiliac screw placement (AO cannulated screws with a diameter of 7.3 mm). In the posterior pelvic surgeries for the 24 cases, 26 S(1) sacroiliac screws fixations and 18 S(2) sacroiliac screw fixations were placed in total, with single S(1) segmental fixation in 8 cases, single S(2) segmental fixation in 3 cases, S(1) and S(2) combined fixation in 13 cases, S(1) unidirectional one-sided fixation in 18 cases, S(1) bidirectional two-sided fixation in 3 cases, S(2) unidirectional one-sided fixation in 14 cases, S(2) bidirectional two-sided fixation in 2 cases and S(1) unidirectional double screws fixation in 2 cases. X-ray and CT examinations were taken for all 24 cases after operation. The visual analogue scale (VAS) of pain were performed before and after the operation. Results: All the sacroiliac screws were successfully implanted at once as planned with the assistance of the robot. The postoperative X-ray films and CT showed that none of the sacroiliac screws broke through the sacral body and the contralateral sacral wing's frontal cortex nor did they stray into the sacral canal and the intervertebral space. In 3 cases, the sacroiliac screws went closely against and wore out the front edge of iliac cortical density line and sacral alar slope and finally re-entered the sacral body. In 3 cases, sacroiliac screws touched upon the sacral nerve canals but did not break through the nerve canals. The mean VAS of pain was improved from 7.1 points (4-10 points) before the operation to 1.9 points (0-3 points) after. Conclusions: The robot-assisted sacroiliac screw placement shows high precision, and hence is worthy of clinical promotion; however the primary role of the surgeon could not be replaced.

[Robot assisted sacroiliac screw placement with a modified method of screw path planning].

Objective: To introduce a robot-assisted modified method of sacroiliac screw path planning in order to reduce the incidence of screw misplacement. Methods: The study involved 13 patients suffering from posterior pelvic injuries treated by percutaneous sacroiliac screw in Yantai Shan Hospital from August 2016 to May 2018. The patients included 9 males and 4 females, aged from 18 to 70 years (mean age 46.2 years). Causes of injury were traffic accidents (n=7), crushing injury (n=4) and fall from height (n=2). According to AO classification, 8 cases were classified with type B fractures (3 with type B1 and 5 with type B2), and 5 cases with type C fractures (2 with type C1, 1 with type C2, 2 with type C3). All the patients were treated by robot-assisted percutaneous sacroiliac screws (AO cannulated screws with a diameter of 7.3 mm) with an improved method of screw path planning. The screw placement time, blood loss, postoperative neurological, vascular and visceral function etc were observed. X-ray and CT were checked in the follow-up after the operation. Visual analogue scale (VAS) score was used to assess the pain degree of patients one week after the surgery. Results: All the sacroiliac screws were successfully implanted once with the robot-assisted improved method of screw path planning. The mean placement time of single screw was 15.9 min and the mean blood loss for single screw placement was less than 1 ml. No clinical manifestations of injuries of blood vessels, internal organs and lumbosacral nerve was found after the operation. The postoperative X-ray films and CT showed that none of the sacroiliac screws wore out the sacral body or the sacral wing's frontal cortex. Also, it was found that none of the sacroiliac screws strayed into the sacral canal and the intervertebral space. The mean VAS score decreased from preoperative 6.9 (4-10) to postoperative 1.8(0-3). Conclusion: The robot-assisted improved method of screw path planning contributes to safe and accurate sacroiliac screw placement.