OSTEOSYNTHESIS OF THE POSTERIOR PELVIC SEGMENT WITH ILIOSACRAL SCREWS UNDER 3D NAVIGATION CONTROL

Summary

INTRODUCTION: For fractures of the posterior part of the pelvis and disjunction of the sacroiliac joint, iliosacral screws are used, which transfix the sacral process of the hip bone with the sacrum in the region of the S1 or S2 segment. The correct placement of these screws in the sacrum is important in order to avoid injury to the sacral nerve fibres or soft tissue injury ventrally and dorsally to the sacrum. 3D navigation provides the possibility of more precise control of drilling and screw insertion. It works on the basis of a 3D scan taken directly in the operating room using a C-arm with the possibility of 3D scanning. The aim of the work is to determine the operating times, the dose of intraoperative X-ray radiation and also the occurrence of postoperative complications during the introduction of iliosacral screws into the posterior segment of the pelvis under the control of 3D navigation.

MATERIAL AND METHODS: In the years 2014–2020, we performed 13 osteosyntheses of the posterior segment of the pelvis using iliosacral screws under the control of 3D navigation at the Department of Surgery and Trauma and Emergency Surgery. We performed osteosynthesis using one or two cannulated screws with a diameter of 7.0 mm. The Ziehm Flat panel 3D fluoroscopy device and Vector Vision computer navigation were used during the surgery. For individual surgeries, we monitored the operating time in minutes, the dose of intraoperative X-ray radiation in cGY per cm², as well as the time of intraoperative fluoroscopy in seconds. Postoperatively, we performed an X-ray check of the location of the iliosacral screws in four projections, in case of uncertainty, we clarified the position of the screws by CT examination. We monitored the incidence of postoperative complications within 90 days after surgery. One year after the surgery, we performed a control X-ray of the pelvis in four projections with the aim of detecting possible migration of osteosynthetic material or dislocation of the posterior segment of the pelvis after osteosynthesis.

RESULTS: The group of 13 patients consisted of eight men and five women. All fractures were type C according to the AO-OTA classification. Eight patients (74 %) underwent osteosynthesis with one screw and five patients (26 %) with two screws. The median age of all patients in the cohort is 51 years (range: 33–73 years). The median weight of all patients in the cohort is 83 kg (range: 65–107 kg). The median intraoperative X-ray time of all patients is 1.14 min (range: 0.50–2.35 min). The median X-ray radiation dose is 853 cGy/cm² (range: 591–1369 cGy/cm²). The median total operative time is 42 minutes (range: 28–62 min).

CONCLUSION: Osteosynthesis of the posterior segment of the pelvis using 3D navigation is more accurate than fluoroscopic control of this surgical procedure and also 2D navigation because it allows drilling to be monitored in individual sections of the sacral bone. It is possible to assess the intraosseous position throughout the drilling of the channel for the iliosacral screw. In a small group of patients, we did not observe post-operative complications in the sense of injury to neurovascular structures and also malposition of screws.

INTRODUCTION

Pelvic fractures are usually the result of high-energy injuries in car accidents, falls from heights and crushing injuries at work [5, 26]. It is an urgent condition where emergency surgery is necessary – stabilization of the pelvic ring with an external fixator or a pelvic clamp – C clamp [1, 17, 19, 21, 24]. After stabilization of the general condition, definitive treatment of the pelvic ring is possible, depending on the type of injury [17]. In symphysiolysis and anterior pelvic ring fractures, plate osteosynthesis is usually used [24]. In posterior pelvic fractures and sacroiliac joint disjunctions, iliosacral screws are used to transfix the sacral process of the hip bone with the sacrum at the S1 or S2 segment, as appropriate [6, 11, 23]. Proper placement of these screws in the sacrum is important to avoid injury to the sacral nerve plexus or injury to the soft tissues ventrally and dorsally to the sacrum [31]. Preoperative analysis and planning are essential for safe placement of iliosacral screws. Conventional radiographs and axial, coronal, and sagittal CT images should be used to determine the individual anatomy of the upper sacrum and the ideal screw position [12, 27, 28]. Biomechanical studies have shown that the stability of this osteosynthesis is equivalent or better than other stabilization methods [9].

These screws are normally inserted under skiascopic control [7]. First, a guide wire is inserted into the iliosacral region, and its optimal placement is monitored during insertion by means of repeated X-ray images in designated views, performed with a C-arm fluoroscopy device. The channel is then drilled with a cannulated drill bit along the guide wire and the bolt is inserted after precutting with a tap. Recently, computer navigation has been used in this operation. 2D navigation works with perioperative X-ray images in different views – pelvic entrance, pelvic exit, lateral view and also anteroposterior projection of the pelvis. Once the X-ray images are stored in the navigation computer, the optimal placement of the iliosacral screws as well as their dimensions can be planned. Determination of the optimal direction for guidewire insertion is checked on the computer navigation monitor without the need for repeated skiascopies. The final placement of the wire as well as of the inserted screw is verified with the aid of skiascopy.

3D navigation provides more precise control of drilling and screw insertion. It works on the basis of a 3D scan taken directly in the operating room by a C-arm with 3D scanning capability. The instrument produces a 3D image of the pelvic skeleton within a scope of a cube sized approximately 10x10x10cm. 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 sometimes not sufficient, and therefore there are programs that allow to combine the preoperative CT of the pelvis with the perioperative 3D scan.

The aim of the study is to determine the operative times, the dose of perioperative X-rays and the incidence of postoperative complications during the insertion of iliosacral screws into the posterior segment of the pelvis under the control of 3D navigation.

MATERIAL AND METHOD

In the years 2014–2020, we performed 13 posterior pelvic segment osteosyntheses using iliosacral screws under 3D navigation control at the Department of Trauma Surgery. Osteosynthesis was performed using one or two cannulated screws with a 7.0 mm diameter. The fluoroscopy instrument Ziehm Flat panel 3D and Vector Vision computer navigation were used during the operations. The operations were performed on a carbon X-ray transparent operating table in the supine position. The navigation probe was fixed to the body of the external fixator or to the contralateral iliac bone wing using 2.5 mm Schanz screws. After connecting the fluoroscopy C-arm with navigation, we performed a 3D scan of the iliosacral region of the pelvis. The scan data was sent via data cable to the computer navigation system where it was displayed on the monitor. It was possible to plan the optimal placement of one or more screws and determine their dimensions (Fig. 1).

After calibrating the wire guide using the matrix, we introduced the wire guide with a drill, and its optimal direction was monitored on the navigation monitor in all of the said views simultaneously (Fig. 2). After inserting the wire, we checked its position using the C-arm, mostly we did not change its position any more. Then we drilled a canal with a cannulated drill bit and after reaming the thread with a tap tool, we inserted a bolt with a washer or a second bolt in a similar way.

From the medical and X-ray records, we extracted data on operative times, perioperative X-ray doses and postoperative complications of individual patients. For each operation, we monitored the operating time in minutes, the peroperative X-ray dose in cGY per cm², and the peroperative fluoroscopy time in seconds. Postoperatively, we performed radiographic checks of the iliosacral screw placement in 4 views; in case of ambiguity, we clarified the screw position by a CT scan. We monitored the incidence of postoperative complications up to 90 days after surgery. One year after surgery, we performed a follow-up X-ray of the pelvis in 4 views to detect possible migration of osteosynthetic material or dislocation of the posterior segment of the pelvis after osteosynthesis. We did not assess the overall clinical condition in view of the non-homogeneous types of anterior pelvic segment injuries and their management.

RESULTS

There were 8 men and 5 women in the cohort of 13 patients. All fractures were type C according to the AO-OTA classification. Osteosynthesis was performed with one screw in 8 patients (74 %) and with two screws in 5 patients (26 %). The median age of all patients in the cohort is 51 years (range: 33–73 years). The median weight of all patients in the cohort is 83 kg (range: 65–107 kg). The median perioperative X-ray time in all patients was 1.14 min (range: 0.50–2.35 min). The median X-ray dose is 853 cGy/cm² (range: 591–1369 cGy/cm²). The median total operation time is 42 min (range: 28–62 min). Results are available in Tab. 1.

In our cohort, the neurovascular structures around the sacral bone were not injured during surgery. We observed no infectious complications or screw malposition in the postoperative period and at 1-year follow-up.

DISCUSSION

In the world literature there are published works using all methods of perioperative control of iliosacral screw insertion - fluoroscopy, 2D, 3D navigation [2, 3,10, 16, 21]. More precise control of screw placement in the posterior pelvic segment is nowadays possible with 3D navigation devices including CT computer navigation [4, 8, 13]. A meta-analytic study showed a higher accuracy of iliosacral screw placement under navigation control compared with fluoroscopy, and the incidence of malpositioned screws is low for both methods (fluoroscopy 2.6 %, 2D and 3D navigation 1.3 % and CT computer navigation 0.1%) [29]. Another meta-analytic study compared 2D and 3D navigation, and demonstrated fewer screw malpositions and lower perioperative radiographic burden using 3D navigation [30]. Another study demonstrates higher accuracy of 3D navigation compared to 2D navigation and fluoroscopy, especially in anatomical dysmorphisms of the sacral bone [15]. The disadvantages of these techniques from our point of view are longer perioperative preparation and loading of the X-ray data into the computer navigation and the cost of the devices - computer navigation and C-arm with 3D scanning capability. There is also a need for sufficient education and experience of the staff, in particular X-ray technicians, in performing 3D scans on the skiascopic machine. The limitation of our study is the small number of patients and therefore the results of postoperative X-rays and individual time cannot be statistically assessed and compared with other methods.

CONCLUSION

Osteosynthesis of the posterior segment of the pelvis using 3D navigation is more accurate than skiascopic control of this operation and also 2D navigation, because it allows tracking of the drilling in individual section of the sacral bone. It is possible to assess the intraosseous position throughout the drilling of the canal for the iliosacral screw. In the small cohort of patients, we did not observe postoperative complications in terms of injury to neurovascular structures as well as malposition of screws. Given the small patient population, further follow-up and more detailed assessment of this method will be necessary.

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.