Preoperative Frailty Predicts Mechanical Complications After Adult Spinal Deformity Surgery: A Retrospective Study

Adult spinal deformity (ASD) surgery is associated with high rates of mechanical complications, including rod fracture, pseudarthrosis, and implant failure. Although frailty has emerged as a superior predictor of adverse outcomes compared with chronological age or comorbidity burden alone, its specific relationship with long-term mechanical complications remains incompletely characterized. This study evaluated whether preoperative frailty independently predicts the development of mechanical complications after ASD surgery.

This retrospective cohort study included consecutive patients who underwent long-segment ASD corrective surgery with minimum 24-month radiographic follow-up. Frailty was assessed using the 5-item modified Frailty Index (mFI-5). The primary outcome was the occurrence of mechanical complications (rod fracture, pseudarthrosis, or implant loosening). Secondary outcomes included medical complications, estimated blood loss, and hospital length of stay. Multivariable logistic regression was performed to determine the independent association between frailty and mechanical complications.

A total of 185 patients were included, of whom 55 were frail (mFI-5 ≥3) and 130 were nonfrail (mFI-5 <3). Frail patients had significantly higher rates of overall hardware failure (50.9% vs 33.1%, P = .034), rod fracture (32.7% vs 16.2%, P = .020), and pseudarthrosis (41.8% vs 23.8%, P = .023). On multivariable logistic regression adjusting for age and body mass index, frailty remained an independent predictor of overall hardware failure (odds ratio 2.97, 95% CI, 1.47-6.00, P = .002), as well as rod fracture and pseudarthrosis. Frailty was not associated with medical complications, estimated blood loss, or hospital length of stay.

Preoperative frailty is independently associated with mid- to long-term mechanical complications after ASD surgery. Routine incorporation of mFI-5 assessment into preoperative evaluation, combined with targeted bone-health optimization and frailty-adapted construct planning, may improve risk stratification and construct durability. Prospective multicenter studies are needed to validate whether multimodal interventions can reduce mechanical failure rates in frail patients.