Modified 6-Factor Frailty Index Enhances Risk Stratification in Revision Total Hip Arthroplasty.

INTRODUCTION: The 5-item modified frailty index (mFI-5) estimates perioperative risk in revision total hip arthroplasty (rTHA), but may miss nutritional vulnerability. We evaluated a novel six-item extension (mFI-6) and hypothesized that adding a point for hypoalbuminemia (less than 3.5 g/dL) would improve discrimination for 30-day adverse outcomes after rTHA. METHODS: We performed a retrospective cohort study of adults undergoing rTHA (procedure codes 27134, 27137, and 27138) using the American College of Surgeons National Surgical Quality Improvement Program from 2015 to 2020. After excluding patients who had missing data for mFI-5-defining variables, albumin, body mass index, or key perioperative variables, 10,040 cases were analyzed. Discrimination of mFI-5 versus mFI-6 was compared using areas under the receiver operating characteristic curves. Multivariable logistic regression analyses assessed associations of mild (2.5 to less than 3.5 g/dL) and severe (less than 2.5 g/dL) hypoalbuminemia with 30-day outcomes across mFI-5 nonfrail (0), prefrail (1), and frail (≥ 2) strata. RESULTS: The mFI-6 demonstrated greater discrimination than mFI-5 for any adverse outcome (area under the curve, 0.618 versus 0.570), reoperation (0.574 versus 0.549), readmission (0.588 versus 0.563), mortality (0.757 versus 0.687), and wound complications (0.575 versus 0.541; all adjusted P < 0.001). Mild hypoalbuminemia was associated with 2.56- to 3.27-fold higher odds of any adverse outcome across frailty strata, while severe hypoalbuminemia was associated with 3.56- to 8.98-fold higher odds. Similar patterns were observed across secondary outcomes. CONCLUSION: The mFI-6 provided predictive value beyond mFI-5 alone in rTHA, with worsening albumin levels associated with progressively higher risk across frailty strata. Incorporating albumin into frailty assessment may improve preoperative risk stratification for rTHA.