Frailty predicts readmission, reoperation, and infection after posterior spinal fusion: An institutional series of 3965 patients

Objective: Frailty is a measure of physiologic vulnerability conceptualized as the accumulation of deficits with aging, and may be useful for predicting risk of adverse events following posterior spinal fusion. Our objective was to investigate the utility of the Canadian Study on Health and Aging (CHSA) Modified Frailty Index (mFI) in patients undergoing posterior spinal fusion (PSF) as a predictor of several surgical quality metrics including readmission, reoperation, and surgical site infection.

Methods: We examined 3965 consecutive PSF patients treated at our institution between 2000 and 2015, and collected demographic, clinical, and frailty and comorbid disease burden measures using the mFI and Charlson Comorbidity Index (CCI). We examined trends and changes in these clinical and demographic characteristics over the course of the study period. We performed multivariable regression to identify independent predictors of readmission, reoperation, and surgical site infection.

Results: Over the course of the study period, the mean patient age increased linearly year-over-year (ß=0.60 [0.48, 0.72], p < 0.0001, R=0.94), while the SSI rate decreased linearly (ß=-0.14 [-0.27, -0.02], p = 0.0249, R=0.56), and frailty scores did not change significantly (p = 0.8124, R=0.065). Among all patients undergoing PSF, postoperative wound infection was independently associated with number of levels fused (OR=1.104 p < 0.001), frailty as measured by mFI (OR=1.150 p = 0.006), and BMI (OR=1.041 p = 0.008). Frailty was also independently associated with postoperative ICU admission (OR=1.1080 p = 0.005), 30-day readmission (OR=1.181 p < 0.001), and 30-day reoperation (OR=1.128 p < 0.001). Among all patients, rate of postoperative wound infection increased with increasing frailty (p = 0.0002) and increasing comorbid disease burden (chi-square p = 0.0012).

Conclusion: The mFI predicts adverse events among patients undergoing PSF, including readmission, reoperation, and surgical site infection. When controlling for frailty, age was not an independent predictor of adverse events.