# Clinical Outcomes Associated with Screw Loosening in S2 Alar-Iliac Fixation in Adult Spinal Deformity

## TL;DR

This study found that screw loosening after S2 alar-iliac fixation in adult spinal deformity surgery is common but does not significantly affect long-term patient outcomes.

## Contribution

The study provides new evidence that S2 alar-iliac screw loosening does not compromise clinical outcomes in adult spinal deformity surgery.

## Key findings

- Screw loosening was observed in 78% of patients.
- No significant differences were found in JOABPEQ scores or spinal alignment between groups.
- Corrective surgery improvements were maintained despite screw loosening.

## Abstract

Purpose: To explore the clinical outcomes associated with screw loosening after S2 alar-iliac (SAI) screw fixation for adult spinal deformity (ASD). Overview of the literature: SAI fixation is widely used in ASD corrective surgery; despite the biomechanical advantages of this screw, complications such as screw loosening remain a significant concern. Methods: We retrospectively reviewed 27 patients undergoing corrective surgery for ASD using SAI as the distal fixation point at a single institution between February 2013 and February 2018. Patients were divided into non-loosening (N) and loosening (L) groups based on radiological evidence of screw loosening (radiolucent area of 1 mm around the screw) and compared for demographic characteristics, bone mineral density (T-score), spinal alignment parameters, and patient-reported outcome using the Japanese Orthopaedic Association Back Pain Evaluation Questionnaire (JOABPEQ) scores. Results: Screw loosening was observed in 78% of patients (n = 21/27); however, there were no statistically significant differences between the N and L groups in terms of the preoperative and 5-year postoperative JOABPEQ scores (p > 0.05 across all domains) and spinal sagittal alignment (p > 0.05). The improvements achieved through corrective surgery were largely maintained regardless of the presence of screw loosening. Conclusions: SAI screw loosening is a common sequela in ASD surgery; however, its loosening might not affect long-term clinical outcomes. Therefore, the choice of fixation should be individualized based on patient factors such as age and bone quality.