Incidence and outcomes of spinopelvic fixation loosening following adult spinal deformity surgery

Abstract Purpose To identify the incidence and clinical outcomes of spinopelvic fixation loosening following surgical correction of adult spinal deformity (ASD). Methods A single-institution retrospective cohort of 152 consecutive patients meeting inclusion criteria who underwent long-segment fusion with pelvic fixation for correction of ASD was reviewed. Pelvic screws were assessed on follow-up post-operative standing radiographs for evidence of loosening. Surgical revision of spinal instrumentation served as the primary outcome. PROMIS Pain Interference and Physical Function T-Scores were assessed as secondary outcomes among the subset of cases ( n = 92) with available scores. Results Pelvic screw loosening was appreciated in 25 cases (16.4%) with initial evidence of loosening identified a median 1.1 years (Q1: 0.8, Q3: 2.5) following surgery. Loosening of pelvic screws (OR 3.0, 95% CI 1.2–7.3, p = .017) was associated with significantly increased odds of eventual instrumentation revision surgery, including specifically surgical revision of spinopelvic fixation (OR 5.5, 95% CI 1.6–18.5, p = .006). 4 of 26 cases (15%) with S2-Alar-Iliac (S2AI) screws required revision surgery compared to 37 of 126 cases (29%) without S2AI screws. PROMIS T-Scores were significantly worse for patients requiring instrumentation revision surgery but did not differ between cases with and without loosening. Conclusion Loosening of spinopelvic fixation occurs frequently following correction of ASD and can develop years following surgery. While distal construct screw loosening may be appreciated incidentally at follow-up, loosening of pelvic screws was associated with significantly increased odds of eventual instrumentation revision surgery.