Under the intraoperative CT navigation system, we explain the techniques for the pelvic ring fractures using the INFIX technique and TITS screw fixation.
INFIX Approach Using Intraoperative CT Navigation
Stabilization of the anterior pelvic ring was performed using intraoperative CT navigation in a manner based on the INFIX technique described by Vaidya et al [19].
The patient was operated on under general anesthesia based on the anesthetists’ decision. She was placed in a supine position on the operating carbon table (OSI Modular Table System; Jackson table; Mizuho, Union City, CA, USA) for the CT scan by O-arm (O-arm2® imaging system, Medtronic plc, Dublin, Ireland). Standard spine instruments and navigated spinal instruments were used for the surgery. After proper painting and draping, the navigation reference frame was fixed to the iliac crest (Figure 1). The O-arm was then positioned, and 3D-reconstructed images were obtained and transmitted to the StealthStation surgical navigation system (S7; Medtronic Sofamor Danek, Minneapolis, MN, USA) and integrated. The relative spatial position of the patient's tracker and pelvis should not change during surgery.
Navigation was confirmed, and skin markings were made to identify the anterior superior iliac spine and pubic symphysis. After every navigated spinal instrument was verified, the best entry point on the anterior inferior iliac spine (AIIS) was marked by the navigated pinpoint probe.
Through a 2- to 3-cm vertical incision centered on the AIIS, the entry point on the AIIS was approached by careful dissection through the interval between the sartorius and the tensor fascia lata, taking utmost care to protect the lateral femoral cutaneous nerve.
The navigated high-speed burr Stealth–Midas System™ (Medtronic Sofamor Danek), pedicle probe, and tap were used to make the screw hole, and then a CD Horizon® Ballast™ screw (Medtronic Sofamor Danek) was inserted (Figure 2).
Screw Implant Selection
We used the Ballast™ screw, which is a polyaxial head screw in the present study. The ring notch at the base of the Ballast™ screw head provides a swing angle of up to 40°, making it easy to connect the rods. While looking at the virtual line on the navigation monitor, the Ballast™ screw was advanced from the AIIS. Even though it decreases the overall strength, it provides greater adjustments for the placement of the rod to decrease abdominal impingement.
Navigation was also used to size the screw according to the patient’s physique, but most surgeons use multiaxial pedicle screws with a diameter of 8.5 mm and a length of 80 mm, with at least about 60 mm of the screw being intraosseous and about 20 mm outside the bone. We ensured that the pedicle screw head remained above the deep fascia to avoid compression on the femoral nerve and inguinal ligament.
To confirm the screw placement, the C-arm fluoroscopy was adjusted to show the iliac view, and the awl was advanced directed towards the ischial spine (Figure 3).
Rod Selection and Formation
The required rod length was measured and the rods were bent in semblance with the contour of the anterior pelvis. A 5.5-mm titanium rod was tunneled subcutaneously, connected to Ballast™ screw heads, and locked at one end (Figure 4). The rod was inserted from one side and guided gently in the subcutaneous plane towards the other side. Once the rod was near the contralateral screw, it was guided onto the opposite pedicle screw using rod-holding forceps. The blocker was locked onto the Ballast™ screw head on one side once the rod was in position.
Reduction of the anterior pelvic ring injury was achieved by compression or distraction over rods as appropriate prior to locking the remaining screw head. The reduction was also done by distraction/lateral compression of the pelvic ring/traction and internal rotation.
The quality of reduction and implant position was confirmed on C-arm fluoroscopy anteroposterior, inlet, and outlet views. The final tightening was done after confirming a satisfactory reduction. Finally, the position of the rod was checked by inserting two fingers between the rod and bone. At least 1 cm of the rod was kept proud on each side to help in removal.
We present a video about the INFIX technique with intraoperative CT navigation (Supplemental Video 1).
Placement of IS or TITS Screws
The fixation of IS screws including the TITS screw placement under C-arm fluoroscopy is a technically demanding procedure, which includes multiple fluoroscopic confirmations due to complex posterior pelvic structures and a high degree of upper sacral variability.
In our procedure, percutaneous screw fixation using 6.5-mm diameter titanium cannulated cancellous screw (CCS) (Meira, Nagoya, Japan) was performed with intraoperative CT navigation together with C-arm fluoroscopy depending on the morphology and displacement of the sacrum (Figure 5). CCS fixation is usually applied to the ipsilateral side of the sacrum. Our approach was with the navigated Universal Cannulated Screw Set (UCSS, Medtronic) using the hollow to insert the guide wire. The navigated cannulated pedicle awl was moved until the direction of the cannulation was completely consistent with the planned screw position. The position of the virtual cannulated on the coronal, sagittal, and cross section of the target segment was observed on the screen. The direction is prepared by placing the navigated cannulated pedicle awl over the guide wire and twisting it into the iliac and sacrum. After that, we used a cannulated drill tap to make a screw hole. The guide wire is held in position when removing the precision tap. CCSs were placed and tightened sequentially through the inserted guide wire, and finally X-rays were obtained. In cases of bilateral or transverse sacral fractures, fixation is performed bilaterally using a TITS screw method. Many external fixators were removed preoperatively. However, the reduction position is judged, and it is decided whether to remove it during the operation. After all treatments, the skin was washed and sutured (Figure 6). We present a video about the IS screws techniques including the TITS screw placement (Supplemental Video 2).
Although the patients' walking start time varies, we allowed our patients to ride in a wheelchair and walk according to pain from the day after the operation during the early postoperative period.