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

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.

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

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.

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.

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.