Introduction: Increased age is a well-established risk factor for perioperative complications. Using age, however, may lead to crude generalizations given that patients present with varying degrees of comorbidities, cognition, and physical capabilities across all ages. Frailty, alternatively, utilizes a wide array of physical and mental assessments and better reflects physiological age than chronological age. With such a large proportion of lumbar fusions indicated for degenerative disorders amongst geriatric patients, it is important to stratify risk using an indicator that incorporates both age and functional capacity rather than using age alone. Despite the high incidence of degenerative spine conditions in elderly patients, efforts to better understand the impact of frailty in spine surgery have only recently emerged. To address this paucity within the literature, this study evaluates the impact of frailty status on postoperative complications in patients undergoing multi-level lumbar fusions.

Methods: The Nationwide Readmission Database (NRD) was retrospectively queried between 2016 and 2017 for patients receiving multi-level lumbar fusions. Demographics, frailty status, and relevant complications were queried at index admission and readmission intervals. Nearest-neighbor propensity score matching 1:1 cohorts was implemented to identify 3,544 patients in each frail and non-frail cohorts with similar demographic characteristics, diagnoses, and procedures. Patients under age 65, with spinal neoplasms, or spinal trauma were excluded. Primary outcome measures included perioperative complications and 30-, 90-, and 180-day complication and readmission rates. Perioperative complications of interest were infection, urinary tract infection (UTI), and posthemorrhagic anemia and only pertain to complications occurring between index procedure and discharge. Complications assessed at 30- and 90-days included infection, acute kidney failure (AKI), thromboembolism, wound dehiscence, hardware failure, neurological injury, and mortality. At 180-days, complications of interest were hardware failure and mortality. Secondary outcome measures included inpatient length of stay (LOS), adjusted all-payer costs, and discharge disposition. The analysis used nonparametric Mann-Whitney U testing and odds ratios.

Results: Frail patients encountered higher rates of perioperative complications including posthemorrhagic anemia (OR: 1.73, 95%CI: 1.50-2.00, p<0.0001), infection (OR: 2.94, 95%CI: 2.04-4.36, p<0.0001), UTI (OR: 2.57, 95%CI: 2.04-3.26, p<0.0001), and higher rates of non-routine discharge (OR: 2.07, 95%CI: 1.80-2.38, p<0.0001). Frail patients had significantly greater LOS and total all-payer inpatient costs compared to non-frail patients (p<0.0001). Frailty was associated with significantly higher rates of 90-day (OR: 1.43, 95%CI: 1.18-1.74, p=0.0003) and 180-day (OR: 1.28, 95%CI: 1.03-1.60, p=0.02) readmissions and higher rates of wound dehiscence at 90 days (OR: 2.21, 95%CI: 1.17-4.44, p=0.02).

Discussion: Patient frailty status functions as a meaningful, independent predictor of postoperative outcomes in patients undergoing multi-level lumbar fusion. The present study observed significantly increased rates of all perioperative complications in frail patients. Frail patients were also significantly more likely to be readmitted at 90- and 180-days and demonstrated higher rates of wound dehiscence at 90-day readmission. Finally, frailty was associated with significantly greater LOS, total all-payer inpatient costs, and non-routine discharges. These findings highlight the importance of frailty status, particularly in multi-level lumbar fusions, and provide implications for its substantive role in determining surgical candidacy, perioperative management, and postoperative follow-up planning.