Developing and validating a scoring system for measuring frailty in patients with hip fracture: a novel model for predicting short-term postoperative mortality

Objectives Frailty is common among patients with hip fracture and may, in part, contribute to the increased risk of mortality and morbidity after hip fracture surgery. This study aimed to develop a novel frailty score for patients with traumatic hip fracture that could be used to predict postoperative mortality as well as facilitate further research into the role of frailty in patients with hip fracture. Methods The Orthopedic Hip Frailty Score (OFS) was developed using a national dataset, retrieved from the Swedish National Quality Registry for Hip Fractures, that contained all adult patients who underwent surgery for a traumatic hip fracture in Sweden between January 1, 2008 and December 31, 2017. Candidate variables were selected from the Nottingham Hip Fracture Score, Sernbo Score, Charlson Comorbidity Index, 5-factor modified Frailty Index, as well as the Revised Cardiac Risk Index and ranked based on their permutation importance, with the top 5 variables being selected for the score. The OFS was then validated on a local dataset that only included patients from Orebro County, Sweden. Results The national dataset consisted of 126,065 patients. 2365 patients were present in the local dataset. The most important variables for predicting 30-day mortality were congestive heart failure, institutionalization, non-independent functional status, an age >= 85, and a history of malignancy. In the local dataset, the OFS achieved an area under the receiver-operating characteristic curve (95% CI) of 0.77 (0.74 to 0.80) and 0.76 (0.74 to 0.78) when predicting 30-day and 90-day postoperative mortality, respectively. Conclusions The OFS is a significant predictor of short-term postoperative mortality in patients with hip fracture that outperforms, or performs on par with, all other investigated indices.