Session I - Pelvic Trauma

Percutaneous Stabilization of U-Shaped Sacral Fractures Using Iliosacral Screws: Technique and Early Results

Sean E. Nork, MD; Clifford B. Jones, MD; Susan Harding, MD; Sohail K. Mirza, MD; M.L. Chip Routt, Jr., MD, Harborview Medical Center, Seattle, WA

Purpose: U-shaped sacral fractures are uncommon and poorly understood. Associated neurological deficits are common and treatment alternatives are limited. The purpose of this study is to evaluate percutaneous stabilization of these complex injuries.

Materials and Methods: Over a 38-month period, 442 patients with pelvic ring disruptions were treated at a level one trauma center. Only thirteen (2.9%) of these patients had displaced U-shaped sacral fractures. There were 11 male and 2 female patients, ranging in age from 21 to 60 years (mean 39 years). Mechanism of injury included accidental falls from heights in four patients, suicide attempts in three, motor vehicle accidents in two, industrial accidents in two, motorcycle accident in one, and pedestrian versus motor vehicle in one. All fractures were coded as 54A.3 according to OTA guidelines. The sacral injuries were further classified according to Roy-Camille based on plain pelvic radiographs and computerized tomography scans. There were one type 1, eight type 2, and four type 3 fracture patterns. All of the fractures were through the upper two sacral segments. Clinical signs of hemodynamic instability were present in seven patients, and four patients had traumatic brain injuries. Spinal fractures at more cephalad levels were noted in five patients and calcaneal fractures were noted in three patients. Lateral sacral plain radiographs were obtained in all patients and best identified these unusual fractures. Neurologic abnormalities were diagnosed in eight patients. Another patient developed progressive paresthesias and motor weakness while in the hospital. All thirteen patients were treated operatively according to a management protocol for their U-shaped sacral fractures. In situ fracture stabilization was accomplished using fluoroscopically-guided iliosacral screws inserted percutaneously with the patient positioned supine. Neurodiagnostic monitoring was not used during screw insertions.

Results: Twenty-five fully threaded cancellous 7.0 mm cannulated screws were used. Eleven patients had bilateral screw fixations, one patient had unilateral double screw fixation, and one patient had unilateral single screw fixation. Operative time for screw insertion averaged 48 minutes, with 2.1 minutes of fluoroscopy. Blood loss per screw averaged 8.6 milliliters (range, 5 to 25 mls). Subsequent neurological decompressions were not performed in any patients. All of the patients were immobilized after surgery with an orthosis for 12 weeks. Accurate and safe screw insertions without foraminal or canal violations were confirmed in all patients with postoperative pelvic plain radiographs and computerized tomograms (CTs). A paradoxical inlet view of the upper sacral segments on the injury AP pelvis was seen in 12 of 13 patients (92.3%), and the diagnosis was confirmed with the lateral sacral view in 100% of patients. There were no deaths. Preoperatively, sacral kyphosis averaged 29 degrees, while postoperative sacral kyphosis averaged 28 degrees. One screw disengagement occurred without fixation failure in the only patient treated with a single unilateral screw. All of the fractures healed clinically and radiographically. There were no wound infections. Of the nine patients with preoperative neurologic abnormalities, four patients had residual neurologic deficits. Of these, two patients had multiple lumbar burst fractures that required decompression and instrumented fusions. The third patient had bilateral calcaneus fractures, which made lower extremity neurologic assessment difficult. The fourth patient developed paresthesias and weakness associated with closed treatment prior to operative stabilization.

Discussion: The diagnosis of U-shaped sacral fractures is difficult. A paradoxical inlet of the upper sacrum on the AP radiograph should alert both the radiologist and the orthopaedic surgeon to this injury and suggests the need for lateral sacral imaging. In this series, the lateral sacral radiograph and the CT scan demonstrated the injury in all patients. Surgical stabilization allows safe and early mobilization of the patient from recumbency. Percutaneous fixation should diminish potential blood loss and operative times compared to open techniques. Iatrogenic neurologic injuries and screw errors were avoided in this series despite the use of extra long iliosacral screws (up to 150 mm). This series was limited to kyphotic deformities which allow in situ fixation. Progressive kyphosis was not observed despite this limited internal fixation. Complete neurologic recovery occurred without sacral decompression in five patients. Sacral decompression may improve this recovery.

Conclusions: Because of difficulty in diagnosing this injury, these fractures should be suspected in patients who fall or jump from heights. Frequently associated injuries complicating patient management include spine fractures at a more cephalad level and calcaneus fractures. Delayed diagnosis is avoided by a high clinical suspicion and early lateral sacral radiographs and pelvic CT scans. Early percutaneous iliosacral screw fixation is safe and effective for these injuries. The role of sacral decompression is not defined in this study.