Is Two Better Than One? Pelvic Fixation Strategies in Neuromuscular and Early-onset Scoliosis: A Comparative Analysis of S1S2-iliac and S2-iliac Screws.

Abstract

Background: In patients with neuromuscular (NM) and early-onset scoliosis (EOS), spinal instrumentation and fusion treatments present significant challenges, particularly in achieving stable pelvic fixation and correcting pelvic obliquity (PO). This study aimed to evaluate whether dual sacroiliac (S1-iliac and S2-iliac) screw constructs improve PO correction and reduce complications compared with S2-iliac screws alone in patients with NM and EOS.

Methods: A retrospective review of 77 patients with NM or EOS requiring pelvic fixation was conducted. Patients were divided into 2 groups: (1) bilateral S1-iliac and S2-iliac screws (S1-S2 group, n=22) and (2) bilateral S2-iliac screws alone (S2 group, n=55). Preoperative and postoperative major curves and PO were assessed, along with complication rates, including implant prominence, screw pullout, breakage, infection, and revision surgery.

Results: Both groups achieved similar main curve corrections at final follow-up (S2=53%, S1-S2=64%, P =0.121). The mean preoperative major curve for the S2 and S1-S2 groups was 63.7 degrees (range 20 to 106 degrees) and 68.9 degrees (range 39 to 135 degrees), respectively. At final follow-up, the mean curve measured 29.4 degrees (range 3 to 82 degrees) and 23.4 degrees (range 7 to 48 degrees), corresponding to 54% and 66% correction, respectively. Preoperative PO averaged to 11.1 degrees (range 0 to 36 degrees) and 17.5 degrees (range 2 to 36 degrees) in S2 and S1-S2 groups, respectively. At final follow-up, PO measured 4.5 degrees (range -3 to 23 degrees) and 6.3 degrees (range 0 to 15 degrees), respectively. In all, 18% (4/22) of patients in the S1S2 group and 23% (13/55) of patients in the S2 group showed complications. Implant breakage occurred in 1 patient in the S1S2 group and 7 in the S2 group ( P =0.427). Revision surgery was required in 5 patients in the S2 group and 1 in the S1S2 group ( P =0.668).

Conclusions: Bilateral S1S2-iliac screws were successfully placed and provided early improvements in PO correction compared with S2-iliac screws alone. However, differences in PO correction and complication rates were statistically insignificant at final follow-up. Further prospective studies with larger cohorts and longer follow-up are needed to assess potential long-term biomechanical advantages of dual fixation.

Level of evidence: Level III.