A new preoperative risk score for predicting mortality of elderly hip fracture patients: an external validation study

Abstract

Background: Hip fractures are common in the elderly and have a high risk of mortality. Several risk prediction models for mortality of hip fracture have been developed, but most of them are difficult to apply accurately in clinical practice.

Aims: The objective of the present study was to perform an external validation of a new published preoperative risk score for predicting mortality.

Methods: We carried out a retrospective cohort study from January 2014 to December 2018 for elderly hip fracture patients discharged from a orthopedic center in China. The preoperative risk score was calculated for each patient, and further divided into two groups: low-risk group (score < 24 points) and high-risk group (score ≥ 24 points) using the receiver operating characteristic (ROC) curve. The outcome was 30-day, 6-month and 1-year all-cause mortality, and the relationship between the risk score and mortality was assessed by univariate and multivariate Cox proportional hazard models. The area under the curve (AUC), Hosmer-Lemeshow test and calibration plots were used to test the discrimination and calibration.

Results: A total of 460 consecutive patients were included in the study, and high-risk score was an independent risk factor for 30-day mortality [Hazard ratio (HR) 6.70; 95% Confidence interval (CI) 1.82-24.69; p = 0.004], 6-month mortality (HR 2.94; 95% CI 1.68-5.17; p < 0.001) and 1-year mortality (HR 3.30; 95% CI 2.09-5.20; p < 0.001). Also, each point increase in the risk score resulted in a 11% increase in 30-day mortality (HR 1.11; 95% CI 1.07-1.16; p < 0.001), 6% increase in 6-month mortality (HR 1.06; 95% CI 1.04-1.09; p < 0.001), and 5% increase in 1-year mortality (HR 1.05; 95% CI 1.03-1.07; p < 0.001). Moreover, the risk score had an AUC of 0.89 (95% CI 0.80-0.98) for 30-day mortality, 0.77 (95% CI 0.70-0.83) for 6-month mortality, and 0.76 (95% CI 0.70-0.81) for 1-year mortality. Calibration plots showed a good calibration between observed and predicted mortality, which was also demonstrated by the Hosmer-Lemeshow test.

Conclusion: Our present study findings indicated that the preoperative risk score was an accurate mortality risk assessment tool for elderly hip fracture patients, regardless of short- and long-term follow-up.

Keywords: Elderly; Hip fracture; Mortality; Prognosis; Risk score.