Functional status and readmissions in unilateral hip fractures.

To test whether functional status is a robust predictor of acute care readmission risk in patients who have been discharged to an inpatient rehabilitation facility (IRF) following a unilateral hip fracture.Retrospective database study using a large administrative data set.A retrospective analysis of data from the Uniform Data System for Medical Rehabilitation from the years 2002 to 2011 was performed, examining patients with an impairment of unilateral hip fracture. A basic prediction model based on functional status was compared with competing models incorporating medical comorbidities. C statistics were compared to evaluate model performance.There were a total of 433,154 patients: 32,783 (7.87%) patients were transferred back to an acute hospital, including 7937 (1.91%) transferred within 3 days, 16,150 (3.88%) transferred within 7 days, and 32,607 (7.83%) transferred within 30 days after IRF admission. The C statistics for the Basic Model are 0.710, 0.674, and 0.667 at days 3, 7, and 30, respectively. Compared with the Basic Model, the best performing Basic-Plus model was the Basic+Elixhauser Model with C statistic differences of +0.013, +0.014, and +0.019, and the best performing Age-Comorbidity Model was the Age+Elixhauser Model with C statistic differences of -0.110, -0.079, and -0.065 at days 3, 7, and 30, respectively.Functional status is a robust and potentially modifiable risk factor for patients admitted to IRFs following a unilateral hip fracture.