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

A retrospective study. 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. 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. 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. 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. 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.