Iliac screw failures compromise long-term radiographic and clinical outcomes of adult spinal deformity surgery without impeding fusion at the lumbosacral junction: a retrospective study in Korea.

Abstract

Study design: A retrospective study.

Purpose: To investigate the effects of iliac screw failure (ISF) on L5-S1 fusion and long-term radiographic and clinical outcomes in adult spinal deformity (ASD) surgery.

Overview of literature: Iliac fixation is crucial for long-segmental fusion in ASD surgery to prevent mechanical failure at the lumbosacral junction. Despite numerous studies on ISF, its impact on surgical outcomes remains unclear.

Methods: We included 192 patients (mean age, 69.2 years; mean follow-up, 57.8 months) who underwent ≥5-level fusion with interbody fusion at L5-S1 and pelvic fixation using bilateral iliac screws between 2014 and 2022. Patients were categorized into no-ISF and ISF groups. Fusion status at L5-S1 was evaluated using computed tomography (CT) images at 2 years postoperatively. Mechanical failures (evaluated in terms of rod fractures and related revision surgery), radiographic outcomes, and clinical outcomes were compared between the groups.

Results: ISFs developed in 66 patients (34.4%) by 13.4 months post-surgery on average. At 2-year CT follow-up, no significant differences in fusion grades were observed between the two groups. ISF rates did not differ according to mechanical failure development in terms of rod fracture at L5-S1 (p =0.273) or at ≥L4-5 (p =0.432), or revision surgery at L5-S1 (p =0.144) or at ≥L4-5 (p =0.886). However, at the final follow-up, sagittal parameters, including pelvic incidence, were significantly worse in the ISF group than in the no-ISF group. The final clinical outcomes were also poorer in the ISF group.

Conclusions: ISF occurred in over one-third of patients after long-segment fusion. While ISF did not adversely affect radiographic and clinical fusion achievement at the lumbosacral junction, it was associated with inferior long-term radiographic and clinical outcomes.