We reviewed all patients with unstable bilateral sacral fractures treated in our department from March 2016 to April 2019 and identified twenty patients. Inclusion criteria were: (1) unstable bilateral sacral fractures of which duration from trauma to surgery was less than 3 weeks, (2) treated with lumbopelvic fixation associated with sacroiliac screws under robotic guidance, (3) patients whose epiphysis was closed. Exclusion criteria were: (1) sacral fractures associated with cauda equina neurologic deficits need to be decompressed, (2) patients with severe thoracic or craniocerebral trauma who could not tolerate on a prone position, (3) vestibular deformity or mal-reduction of S1 which is not enough to pass through a cannulated screw with the diameter of 6.5 mm, (4) transverse fracture line which is located at S1 vertebra.
Twelves patients were excluded because of the exclusion criteria. Eight of them associated with cauda equina syndrome which need to be decompressed via open approach, three of them were treated with open reduction and internal fixation because duration from trauma to surgery was more than three weeks. One case was treated conservatively because of severe craniocerebral trauma. According to the inclusion and exclusion criteria above, eight patients were enrolled in this study (Table 1).
Table 1
Clinical data of cases in our study group
NO. | Age | Gender | Type of trauma | Classification | Disruption of the anterior pelvic ring | Duration from trauma to surgery(days) | Operation time(min) | Blood loss(ml) | Follow-up (months) | Clinical outcome |
Gibbons | Denis |
1 | 23 | M | Suicidal jump | II | III | Yes | 4 | 110 | 90 | 22 | excellent |
2 | 13 | M | Suicidal jump | II | III | Yes | 10 | 200 | 110 | 24 | good |
3 | 37 | F | Accidental fall | | III | No | 5 | 95 | 70 | 12 | excellent |
4 | 54 | M | Accidental fall | II | III | No | 7 | 125 | 100 | 15 | excellent |
5 | 53 | M | Suicidal jump | | III | Yes | 20 | 220 | 120 | 14 | good |
6 | 42 | F | Accidental fall | II | III | No | 8 | 180 | 60 | 20 | excellent |
7 | 35 | F | Suicidal jump | | II | Yes | 7 | 120 | 70 | 12 | good |
8 | 39 | M | Car accident | | III | No | 7 | 155 | 80 | 17 | excellent |
This retrospective study protocol was approved by Medical Ethics Committee in our institution, and written Informed consent was obtained from all participants included in the study.
The average age at the time of trauma was 38.5 years (range, 19–60 years). There were 5 men and 3 women, with an average Injury Severity Score of 26 (range, 16–38). The Type of trauma included the following: falling or jumping from height (seven patients) and being involved in a car accident (one patient). Seven sacral fractures were type III and one was type II which has been classified by Denis [16]. According to the sharp of the sacral fractures, there were one case with simple bilateral vertical fracture lines, six cases with “U” and one case with “H”. Except one case without transverse fracture line on sacrum, seven of eight sacral fractures that involved sacral canal were classified with type I in two cases, type II four cases and type III one case on the basis of Roy-Camille classification [1]. According to Gibbons classification [17] of neurologic deficits, there were three cases combined with sacral nerve injury of grade II. Of the eight cases with unstable bilateral sacral fractures, four cases combined with pubic ramus fractures and one case with transverse acetabulum fracture.
Patients with unstable hemodynamics were treated with blood volume expansion therapy after admission. Femoral condyle skeletal traction was undergone bilaterally except the nondisplaced sacral fracture. Once the general condition was sufficiently stable, routine images such as X-ray, CT scans, and 3D reconstruction were obtained and concomitant injuries were treated urgently and continuously in necessary (Fig. 1a-d). We measured bilateral vestibular anatomy of S1 with CT scans to exclude developmental deformity and to determine if a cannulated screw with the diameter of 6.5 mm can pass through. According to CT data, 3D model with equal proportion was created printed, and then simulated operation was performed (Fig. 2a-b). On one hand, we ensured the precise entry point and position of the screws and robs with 3D printing models. On the other hand, the required fracture reduction degree was determined by preoperative planning so as to achieve the anatomical reconstruction more easily during the surgery. Additionally, the individual projection angulation of inlet and outlet views were confirmed with X-ray images for the convenience of actual operation. After surgical feasibility had been manifested, implants were removed and recorded to guide the intraoperative application (Fig. 3a-d). Finally, ultimate surgery, minimally invasive lumbopelvic fixation combined with sacroiliac screws under robotic guidance, was performed according to the preoperative planning (Fig. 4 Management algorithm).
The timing of surgical treatment, operative time and estimated blood loss were recorded. Immediate postoperative X-ray and CT scans were reviewed to evaluate the reduction and hardware position. Maximum residual displacement in various directions were recorded and graded according to the imaging standard of Mears and Velyvis [18]. The reduction qualities of pelvic fractures were classified as follows: extremely satisfactory reduction (anatomical reduction), satisfactory reduction (vertical and / or horizontal displacement < 1 cm and / or rotation < 15 °), and unsatisfactory reduction (vertical or horizontal displacement > 1 cm and / or rotation > 15 °). A modified Gras classification was applied to assess the positioning of pedicle and sacroiliac screws under CT visualization [19]. The classification of the screw placement positioning on the tomographic image of CT scans consisted of a three-grade score: Grade I, secure positioning, completely in the cancellous bone; Grade II, secure positioning, but contacting cortical bone structures; Grade III, misplaced positioning, penetrating the cortical bone. Follow-ups were routinely scheduled at 6-week, 3-month, 6-month, 1-year and thereafter 1-year intervals postoperatively. The function outcomes were evaluated with Majeed’s scoring system [20], and clinical outcome was graded as follows: excellent (85–100), good (70–84), fair (55–69), and poor (< 55). Anticoagulation was used from the admission until patient was able to get out of bed. Patients began weight bearing 6 weeks after surgery.
Surgical Equipment And Instrument
The TiRobot system, the third generation TianJi robot for orthopaedic surgery (TINAVI Medical Technologies, Beijing, China), is composed of a main console, surgical planning and controlling software, an optical tracking system, a robotic arm with six joints, a main control workstation, and a navigation and positioning toolkit. Additional surgical equipment included a C-arm X-ray and CT machine (Siemens, Germany), φ6.5-mm cannulated screw, φ7mm polyaxial iliac screw and φ6-mm polyaxial pedicle screw systems (Kanghui Medical Instruments, China).
Surgical Procedures
All procedure were performed by a group of orthopedic surgeons with rich experience.
The patients were administered general anesthesia with tracheal intubation after being placed with the prone position on a radiolucent table. Draping began from the mid thoracic spine to above the natal cleft, including both flanks laterally. Intravenous antibiotics were administered within 30 minutes of the skin incisions.
Pelvic anteroposterior, inlet, outlet and Judet views were obtained using the image intensifier to identify feasibility of these images preoperatively. First, a navigation tracker was fixed on L3 spinous process percutaneously. After L5 initial intraoperative CT images were obtained using a C-arm machine, they were transmitted to the robotic planning system. Based on preoperative planning combined with L5 vertebra anatomic feature, the length, angulation and direction of bilateral pedicle screws were designed and the simulation of the screw placement was completed on the images (Fig. 5a). Then a sterile working environment for the robotic arm was established by assembling and fixing the locator and the sterile protective sleeve. After the navigation planning was established, the robotic arm began to move following the guidance in the preplanned trajectory outside the body. Next, the sleeve was placed onto the bone surface via a percutaneous incision and a guide pin was inserted into the pedicle after the trajectory was recalibrated (Fig. 6a). Furthermore, a cannulated polyaxial pedicle screw 6 mm in diameter was inserted along the pin. Finally, the contralateral same screw was inserted in the same way.
After the pedicle screws were fixed, the bilateral posterior superior iliac spines (PSIS) were exposed subperiosteally through 3 cm incisions. Next, we resected part of PSIS to avoid skin irritation caused by protruding screws, and then inserted a polyaxial iliac screw 7 mm in diameter 10 cm deep on each side. Meanwhile, we had to make sure that the direction was from PSIS to anterior inferior iliac spine (AIIS) and between the medial and lateral lamina of the iliac wing. Then the bilateral pre-contoured rods with the diameter of 6.5 mm were inserted subfascially and connected to the pedicle screw and iliac screw. Once the bilateral vertical and rotational displacement was corrected through the distraction of the lumbopelvic devices with reduction clamps, all connectors were fixed rigidly (Fig. 6b). The reduction quality of the posterior pelvic ring fracture was manifested intraoperatively with C-arm fluoroscopy.
The last part of management of the posterior pelvic ring was the insertion of bilateral S1 sacroiliac screws. After the navigation tractor was then fixed to PSIS, intraoperative anteroposterior, inlet, outlet and Judet views of the pelvis were obtained and transmitted to the robotic planning system again. Then the angulation and direction of bilateral sacroiliac screws were designed and the simulation of the screw placement was completed on the images. With the guidance in the preplanned trajectory, the sleeve carried by robotic arm carrying moved to target area. A guide pin was drilled into sacrum via a percutaneous incision after the trajectory was recalibrated (Fig. 5b). Finally, a cannulated sacroiliac screw with a diameter of 6.5 mm was inserted into S1 vertebra along the pin on each side. After the reduction and fixation were checked again with fluoroscopy, the skin and subcutaneous tissues were sutured (Fig. 6c and Fig. 7a-c).
Postoperative Management
All patients underwent the same management with intravenously administered antibiotics postoperatively continued for 24 hours. Low-molecular-weight heparin (LMWH) was used for deep venous thrombosis prophylaxis during hospitalization. Patients were encouraged to use wheelchairs for mobility 2 weeks after surgery. Partial weight bearing was initiated usually 4 weeks and full weight bearing was permitted 8 weeks after surgery. However, the details about weight-bearing activity should also be considered depending on the recovery of concomitant injuries.