Triangular Osteosynthesis as a Surgical Treatment Option for Unstable Sacral Fracture Fixation with Sacroiliac Dislocation: A Case Report.

Introduction: Sacral fractures, which can occur in young individuals following road traffic accidents or falls from a height, as well as in elderly individuals with osteoporosis after minor trauma, are considered a diverse type of fracture. The incidence of non-osteoporotic sacral fractures is estimated to be 2.1/100,000 people, whereas osteoporotic fractures are estimated to affect 1-5% of elderly individuals at risk. Triangular osteosynthesis is a relatively new fixation technique used as a surgical treatment for unstable sacral fractures. It combines transverse fixation with lumbo-pelvis distraction osteosynthesis, providing stability in different planes. The subcategory of triangular osteosynthesis encompasses spinopelvic fixation, which involves the fusion of transverse sacral alar fracture fixation (such as iliosacral screw/s and sacral plate) and unilateral lumbopelvic fixation from the pedicle of L5 to the ipsilateral posterior ilium. The utilization of this technique provides a mechanically advanced approach for stabilizing unstable sacral alar fractures with vertical shear. Once the pelvic ring injury has been reduced, lumbopelvic fixation can assist in preventing the recurrence of vertical displacement in the unstable hemipelvis.

Case Report: The patient, a 29-year-old male, experienced a road traffic accident resulting from a collision involving a motorcycle. As a result of the incident, he suffered from an unstable lateral compression type 1 pelvic ring injury, accompanied by an ipsilateral sacroiliac dislocation and a vertical sacral fracture on the opposite side. Computed tomography imaging revealed a right sacroiliac dissociation, a left sacral fracture classified as AO type B1, as well as fractures in both the superior and inferior pubic rami. The pelvic ring of the patient was subjected to closed reduction and percutaneous fixation, accompanied by minimally invasive spinopelvic fixation. The surgical procedure was performed in a single session, involving the reduction and fixation of the right sacroiliac dissociation, followed by lumbopelvic fixation while in the prone position. After a 1-month follow-up, the patient demonstrated the ability to walk without experiencing pain, and the X-ray revealed a stable spinopelvic and sacroiliac fixation.

Conclusion: The utilization of triangular osteosynthesis fixation provides a reliable form of fixation that enables the patient to bear complete weight at an early stage of 6 weeks while also preventing any reduction loss in vertical shear transforaminal sacral fractures.