S2 Alar Iliac Fixation in Long Segment Constructs, a Two- to Five-Year Follow-up

Abstract

Study design: Retrospective review of patients having undergone S2 alar-iliac (S2AI) fixation for long fusions with a minimum two-year follow-up.

Objectives: To report on fusion rates, complications, technique-specific complications of patients having undergone S2AI fixation.

Summary of background data: Sacropelvic fixation continues to be a challenge when performing long fusions to the pelvis. S2AI screws have been found to provide solid biomechanical fixation and have been found to have good clinical results in short-term follow-up for pediatric and adult patients.

Methods: Cases were retrospectively reviewed in patients who had placement of S2AI screws for long fusions with at least a two-year follow-up. Demographic data, complications, and reoperations were reviewed. Complications were broken into minor and major categories similar to previous series on pelvic fixation.

Results: There were 86 cases identified. Minor and major complications occurred in 29% and 24% of patients, respectively, with the majority of minor complications being intraoperative dural tears. Revision surgery for all causes was performed in 23% of the cohort. Fusion rate at L5-S1 for patients without preoperative pseudarthrosis was 95.3%. Preoperative L5-S1 pseudoarthrosis was identified in 20 patients, 17 (95%) of these went onto fusion after one surgery. There was evidence of S2AI screw lucency in 10.4% of cases. However, the majority of these were asymptomatic.

Conclusions: Sacropelvic fixation using the S2AI technique provides safe, durable fixation with low rates of technique-specific complications and limited need for hardware removal. Complication rates in this series were similar to other series on long fusions to the pelvis. Additionally, fusion rates were high at L5-S1 for both patients with and without preoperative L5-S1 pseudarthrosis. It appears that the S2AI technique is a powerful option for patients with previous L5-S1 pseudarthrosis.

Level of evidence: Level III.

Keywords: Deformity; Long fusion; Pelvic fixation; Pseudarthrosis; Sacropelvic fixation.