High Prevalence of SI Joint Pain in Patients Undergoing Thoracolumbar Fusion with Pelvic Fixation for Adult Spine Deformity: Initial Results from a Multicenter Randomized Trial

Introduction: Determine the clinical benefit of simultaneous placement of triangular titanium implants (TTI) adjacent to S2AI screws during multilevel spine fusion surgery with pelvic fixation. TTI are designed to fuse the SI joint.

Methods: Enrolled subjects underwent detailed clinical and radiographic assessment preoperatively, including physical examination and diagnostic SI joint blocks, when indicated, for suspected SI joint pain. Subjects were randomized 1:1 to receive either S2AI screws alone or S2AI + TTI. Baseline spinal deformity measures were read by an independent radiologist. Site-reported perioperative adverse events were reviewed by a clinical events committee. Quality of life questionnaires and other clinical outcomes are in process.

Results: 113 participants were assigned to S2AI and 109 to S2AI + TTI. 35/222 (16%) of all subjects had a history of SI joint pain or were diagnosed with SI joint pain during preoperative workup. All subjects had perioperative safety assessments; 3-month follow-up was available in all but 4 subjects.
TTI placement was successful in 106 of 109 (98%) subjects assigned to TTI. In 2 cases, TTI could not be placed due to anatomic considerations. Three TTI ventral iliac breaches were observed, which were managed non-surgically. One TTI subject had a transverse sacral fracture and one subject had TTI malposition.

Conclusion : SI joint pain is common in patients with adult spinal deformity. Concomitant placement of TTI parallel to S2AI screws during multilevel spine fusion surgery is feasible and safe. Further follow-up will help to determine the clinical value of this approach to augment pelvic fixation.