Five-factor modified frailty index is a reliable indicator for predicting postoperative mortality in geriatric intertrochanteric fracture patients aged 80 years and older: a case-control study

To investigate the reliability and threshold of five-factor modified frailty index (mFi-5) for predicting postoperative mortality in patients aged 80 years and older with intertrochanteric fractures (ITF). This retrospective study included advanced-age ITF patients who underwent surgery between January 2016 and January 2020 at a single center, and the eligible patients were sequentially divided into six groups according to mFi-5 scores. The mortalities in in-hospital, 3-months and 1-year after surgery were defined as observed outcomes. Baseline characteristics, including age, gender, time to surgery, surgery time, length of hospital, anesthesia, anemia and hypoproteinemia at admission, were collected for logistic regression analysis. Then, Receiver-Operating Characteristic (ROC) was used to assess reliability, and decision curve analysis (DCA) was used to evaluate the clinical benefit of the mFi-5. 263 patients were included in the final analysis. The in-hospital, 3-month and 1-year all-cause mortalities of all patients were 4.2% (11/263), 14.1% (37/263) and 24.7% (65/263). Overall, the mortalities increased with mFi-5 score. There were no significant between-group differences of baseline characteristics between the groups. Multivariate regression analysis indicated only gender was an independent factor for in-hospital morality, gender, anemia and high mFi-score for 3-month mortality, and age, gender, anemia and high mFi-score for 1-year mortality. The ROC analysis shown that the areas under the curve of mFi-5 for predicting in-hospital, 3-month and 1-year morality were 0.862, 0.773 and 0.756, respectively P < 0.01). DCA demonstrated that using an mFi-5 threshold of ≥ 3 provided a higher net benefit. In conclusion, mFi-5 is a reliable prognostic predictor in the advanced-age ITF patients following surgery. Also, high risk of mortality is associated with a mFi-5 score no less than “three” especially in the much older male patient with anemia.