Loss of pre-fracture basic mobility status at hospital discharge for hip fracture is associated with 30-day post-discharge risk of infections - a four-year nationwide cohort study of 23,309 Danish patients

BACKGROUND: The loss of pre-fracture basic mobility status is associated with increased mortality and any readmission after hip fracture. However, it is less known if the loss of pre-fracture mobility has impact on acquiring a post-discharge infection.

PURPOSE: To examine if the loss of pre-fracture basic mobility status at hospital discharge was associated with hospital-treated or community-treated infections within 30-days of hospital discharge after hip fracture.

METHODS: Using the nationwide Danish Multidisciplinary Hip Fracture Registry from January 2014 through November 2017, we included 23,309 patients undergoing surgery for a first-time hip fracture. The Cumulated Ambulation Score (CAS, 0-6 points) was recorded using questionnaire at admission (pre-fracture CAS) and objectively assessed at discharge. The loss of any CAS-points at discharge compared with pre-fracture CAS was calculated and dichotomized (yes/no). Using Cox regression analyses, we estimated the hazard ratio (HR) with 95% confidence interval (CI) of any hospital-treated infection, hospital-treated pneumonia or community-treated infection adjusted for sex, age, body mass index, Charlson Comorbidity Index, residential status, type of fracture, and length of hospital stay (LOS).

RESULTS: Total of 12,046 (62%) patients lost their pre-fracture CAS status at discharge. Among patients who had lost their pre-fracture CAS, 6.0% developed a hospital-treated infection compared to 4% of those who did not lose their pre-fracture CAS. Correspondingly, 9.2% versus 6.2% developed a community-treated infection. The risk of 30-day post-discharge infection increased with increasing loss of any CAS points. The adjusted HRs for patients who had lost their pre-fracture CAS status, compared to patients who did not, was 1.34 (CI: 1.16-1.54) for hospital-treated infection, 1.35 (CI: 1.09 - 1.67) for pneumonia and 1.36 (CI: 1.21-1.52) for community-treated infection.

CONCLUSION: In this large national cohort study, we found that loss of pre-fracture basic mobility status upon hospital discharge was strongly associated with 30-day post-discharge risk of developing infection. These findings suggest a clinical importance of carefully focusing on regaining the pre-fracture basic mobility before discharging the patient.