Comparison of Sacral-Alar-Iliac and Iliac-Only Methods of Pelvic Fixation in Early-Onset Scoliosis at 5.8 Years’ Mean Follow-up

Study Design: Retrospective. Objective: Compare clinical outcomes in early-onset scoliosis (EOS) patients treated with sacral-alar-iliac (SAI) versus iliac-only methods of pelvic fixation at two years’ minimum follow-up. Summary of Background Data: Pelvic fixation in EOS is challenged by poor bone, anchor migration, and displacement. The long-term outcomes of SAI fixation in EOS is unknown. Methods: We retrospectively reviewed EOS patients in a single center from 2000 to 2017. Inclusion criteria were posterior spinal instrumentation with pelvic fixation before age 10 and 2 years’ minimum follow-up. Clinical and radiographic data were analyzed using chi-squared and Student t tests (significance defined as p <.05). Results: Seven subjects were included in the iliac-only fixation group (Galveston technique = 2, iliac screws = 5) and 17 in the SAI group. For the iliac-only group (mean follow-up = 6.8 years), pelvic obliquity improved from a mean of 18° at initial presentation to 11° at first instrumentation (p =.096), to 9° at end follow-up (p =.060), whereas the major curve improved correspondingly from a mean of 84° to 50° (p =.002) to 39° (p =.006). For the SAI group (mean follow-up = 5.5 years) at the same time points, pelvic obliquity improved from a mean of 25° to 6° (p <.001) to 5° (p <.001), whereas the major curve improved from a mean of 83° to 38° (p <.001) to 29° (p <.001). SAI fixation was associated with fewer complications (11 complications in 17 patients) compared to iliac-only fixation (10 complications in 7 patients) (p =.04). Neither method was associated with pelvic growth disturbances or neurologic deficits. Conclusions: In EOS patients at 2 years’ minimum (5.8 years’ mean) follow-up, both SAI and iliac-only methods corrected major curve, only SAI fixation corrected pelvic obliquity, and neither was associated with pelvic growth disturbances. SAI fixation was also associated with fewer complications. These findings may be due to the length and direction of the SAI anchors and abutment on the iliac cortex. Level of Evidence: Level III.