Frailty Stratification Using the Modified 5-Item Frailty Index: Significant Variation within Frailty Patients in Spine Surgery

Frailty status has been associated with higher rates of complications after spine surgery. However, frailty patients constitute a heterogeneous group based on the combinations of comorbidities. The objective of this study is to compare the combinations of variables that compose the modified 5-factor frailty index score (mFI-5) based on the number of comorbidities in terms of complications, reoperation, readmission, and mortality after spine surgery. The American College of Surgeons - National Surgical Quality Improvement Program (ACS-NSQIP) Database from 2009–2019 was used to identify patients who underwent elective spine surgery. The mFI-5 item score was calculated and patients were classified according to number and combination of comorbidities. Multivariable analysis was used to assess the independent impact of each combination of comorbidities in the mFI-5 score on the risk of complications. A total of 167, 630 patients were included with a mean age of 59.9 ± 13.6 years. The risk of complications was the lowest in patients with diabetes + hypertension (OR = 1.2) and highest in those with the combination of congestive heart failure (CHF), diabetes, chronic obstructive pulmonary disease (COPD), and dependent status (OR = 6.6); there was a high variation in complication rate based on specific combinations. There is high variability in terms of relative risk of complications based on the number and combination of different comorbidities, especially with CHF and dependent status. Therefore, frailty status encompasses a heterogeneous group and sub-stratification of frailty status is necessary to identify patients with significantly higher risk of complications.