COMPUTER-ASSISTED CT NAVIGATION OF POSTERIOR PELVIC SEGMENT OSTEOSYNTHESIS - A CASE REPORT

Summary

INTRODUCTION: Osteosynthesis of posterior pelvic segment injuries with iliosacral screws is one of the most commonly used methods today. The most accurate method of checking these types of operations is the CT navigation. The aim of this study was to evaluate the use of computer-assisted CT navigation during osteosynthesis of posterior pelvic segment in a case report.

METHODS AND RESULTS: A 58-year-old patient with pelvic injury underwent osteosynthesis of the left sacroiliac joint disjunction using a cannulated screw. This operation was performed under the control of computer- assisted CT navigation. The time of individual parts of the surgery as well as the dose of perioperative X-ray irradiation were monitored.

DISCUSSION: Currently, computer-assisted CT navigation is not commonly used in pelvic trauma; there is more experience with CT-guided pelvic surgery. In the world literature, there are papers on smaller cohorts of patients where its benefit over standard methods is demonstrated.

CONCLUSION: The use of computer-assisted CT navigation in posterior pelvic segment osteosynthesis allows better orientation in the sacroiliac region. Precise targeting of screws to the sacrum in segments S1, S2 is possible.

Keywords:

osteosynthesis – Computer-assisted CT navigation – iliosacral screw

INTRODUCTION

Osteosynthesis of posterior pelvic segment injuries with iliosacral screws is one of the most commonly used methods today. Thorough preoperative preparation is necessary as there are significant morphological differences in the anatomical shape of the sacrum [14]. By default, the surgery is performed under the skiascopic control; however, computer-assisted navigation has been increasingly used in recent years [4, 9, 17]. Currently, 2D, 3D computer-assisted device and also CT navigation are available. The 2D computer-assisted navigation works with perioperative images of the pelvis created by the skiascopy C-arm. Pelvic projections are usually made - inlet, outlet, lateral, sometimes anteroposterior. On the navigation monitor it is possible to perform virtual placement of the screw in the individual X-ray images and also to determine its dimensions [7, 11, 19]. The 3D navigation works with the perioperative 3D scan performed by the respective C-arm [3, 10, 16]. The instrument produces a 3D image of the pelvic skeleton within a scope of a cube sized approximately 10x10x10 cm. Again, planning of screw placement is possible with the screw course being visible even inside the bone. The 3D scan image is not completely sharp and its size is not sufficient, and therefore there are programs that allow to combine the preoperative CT of the pelvis with the perioperative 3D scan. CT navigation is currently the most accurate method of checking these types of operations. It works with a perioperative CT image sized approx. 30x30x30 cm, with sharpness similar that of a CT scan. CT scanning is performed at the beginning of the operation with a special mobile CT device or in a hybrid theatre with CT scanning capability. On the navigation monitor, it is possible to plan the screws in the individual incisions so that they pass through the safe zone of the respective sacral region.

THE AIM of this study is to document the osteosynthesis of the pelvic posterior segment of using a cannulated screw under the control of computer-assisted CT navigation, focusing on time, accuracy and perioperative doses of X-ray irradiation.

METHOD AND RESULTS

In a car accident, a 58-year-old patient suffered a fracture of ribs 3 to 7 on the right side with apneumohemothorax, multiple contusions, concussion, and an AO/OTA type 61B2.3 pelvic fracture with 25 mm symphyseolysis and 8 mm left sacroiliac joint disjunction (Fig. 1). As a part of damage control, urgent drainage of the right chest and stabilization of the pelvic ring with an external fixator was performed. He was subsequently monitored in the ICU, with a complex treatment including supplementation of blood counts with 3 units of packed red blood cells. Due to persisting dislocation in the left sacroiliac joint, cannulated screw osteosynthesis was indicated. This operation was scheduled after stabilization of the patient‘s overall condition on day 3 after the car accident. Preoperative planning revealed a relatively flat sacral body in the S1 segment, therefore osteosynthesis under computer-assisted CT navigation was indicated (Fig. 2). This system uses navigation and mobile CT - O arm by Medtronic (USA). Computer-assisted CT navigation has been used in our hospital in neurosurgical theatres since 2020. Its benefits include the accurate imaging of the skeleton in a scope sufficient for osteosynthesis of both the spine and pelvis. After preoperative preparation, we loaded the navigation probe onto the body of the external fixator (Fig. 3). Then a CT scan of the pelvis, in the shape of a cylinder 15 cm in size and 40 cm in diameter, was taken by the X-ray technicians and sent to the navigation computer (Fig. 4). This part of the surgery took 15 minutes. Then, within 5 minutes, we planned the placement of the screw in the S1 region on the computer monitor (Fig. 5). Using a navigation finder, we introduced a 2.8 mm guide wire into the SI area, and the direction and course of insertion were controlled simultaneously in the coronal, frontal and sagittal planes (Fig. 6). After insertion of the guide wire, its position was checked skiascopically using a prepared O-arm device (Fig. 7). After measuring the length, we drilled the canal and inserted a 6.5x85 mm cannulated screw with a washer. This part of the surgery took 20 minutes. The resulting screw placement and position in the SI joint was checked again with a CT scan using an O-arm device (Fig. 8). Total perioperative dose of X-ray irradiation during CT scans (DLP) was 1488 mGycm, skiaskopy dose (DAP) was 649cGy/cm². The CT scan time was 38 seconds in total, the skiascopy time was 12.77 seconds. Total operation time was 45 minutes. On the second day after surgery, a pelvic scan was performed (Fig. 9). The postoperative course was complicated by a transient ischemic attack on day 4 after the surgery, without pathological findings on brain CT and carotid arteries, which faded away without any neurological deficit. At 6 weeks after the operation, the patient started the verticalization, and at 10 weeks after the operation, the external fixator was removed. At 16 weeks after surgery, the patient is able to walk without the aid of crutches even for longer distances and reports mild pain in both sacroiliac joints after prolonged walking. A follow-up radiogram of the pelvis was taken 5 months after the injury and after 3 months of loading. (Fig. 10). The position of the pelvic ring is satisfactory.

DISCUSSION

Currently, the greatest application of computer-assisted navigation in neurosurgery is in brain surgery and also in spondylosurgery [5, 18]. There is also a large number of papers in the world literature describing the experience with the use of 2D and 3D computer-assisted navigation during osteosyntheses in pelvic region. Recently, 3D navigation based on the perioperative scan performed with the skiascopic C-arm has been described [1, 2]. No larger cohorts of patients with posterior pelvic segment osteosynthesis performed using computer-assisted CT navigation have been described in the literature yet. There are cadaveric studies that confirm the accuracy of the use of computer-assisted CT navigation [8]. Ghisla and colleagues describe the use of O-arm CT and computerassisted navigation in 21 patients with higher accuracy in the placement of osteosynthetic material compared to other methods [6]. Similar experiences are described by Coste and co-authors in their study of 6 patients [13]. The average operative time in this study was similar to ours (40 minutes) Perioperative X-ray irradiation doses are not described in these studies. A study by Lu and colleagues on 40 patients published this year describes a shorter operative time for surgeries performed under computer-assisted CT navigation control versus the operative time for surgeries performed using the skiascopy (33.19 vs. 48.35 min.) and better postoperative results [12]. In the Czech Republic, the largest experience with computer-assisted CT navigation is at the University Hospital Prague-Vinohrady. The study by Džupa et al. describes a similar experience to our case report in a larger cohort of patients. [20]. A paper of the team of authors of the Liberec Traumatology Department should be highlighted, which describes the principles and extensive experience with the insertion of screws into the pelvis under perioperative CT control before the development of computer-assisted CT navigation [15].

CONCLUSION

The use of computer-assisted CT navigation in posterior pelvic segment osteosynthesis allows better orientation in the sacroiliac region. Precise targeting of screws to the sacrum in segments S1, S2 is possible. It minimizes the risk of injury to intraforaminal structures as well as injury to tissues ventral and dorsal to the sacrum. After mastering the preoperative preparation and operation of the navigation device and CT scanner, the operating time will be reduced. The perioperative X-ray load will be evaluated in a larger cohort of patients.

This paper was supported by project No. CZ.02.1.01/0.0 /0.0/17_049/0008441 „Innovative Therapeutic Methods of Musculoskeletal System in Accident Surgery“ within the Operational Programme Research, Development and Education financed by the European Union and by the state budget of the Czech Republic.