Factors associated with mobility outcomes in older people post-ankle fracture: an observational cohort study focussing on peripheral vessel function.

Abstract

There are increasing numbers of older persons sustaining ankle fractures. This injury often results in a degree of functional limitation, particularly in older patients. There is currently limited research into factors associated with mobility outcomes. Observational cohort study. Hospital Trauma Department, UK. Persons aged 60 years or over who sustained an unstable ankle fracture with no established peripheral arterial disease pre-injury. This study investigated the association between ankle-brachial pressure index (ABPI) and extended timed 'up and go' (TUG) measures. Associations between TUG outcomes and age, pre-morbid functional mobility (Olerud-Molander Ankle Score) and fracture severity (number of malleoli injured) were also explored. Complete cases (n=76; 84% of cohort) were entered into univariate and multivariate linear regression. No association was found between ABPI and TUG at 6 months in unadjusted and adjusted analyses. Pre-morbid functional mobility (B=-0.34, 95% confidence interval (CI) -0.45 to -0.23, p<0.001) and age (B=0.46, 95% CI 0.25-0.66, p<0.001) were associated with extended TUG values (r2=0.53, p<0.001). Fracture severity was not a significant independent predictor variable. Peripheral vessel function and fracture severity may have a limited independent influence on mobility outcome after ankle fracture in those patients who do not have established pre-injury peripheral arterial disease. Age and pre-morbid mobility gave an indication of mobility outcome, but a substantial amount of variance remains unexplained. Limitations of this study, including missing data and potential residual confounding, indicate the need for caution in generalising these results. The study provides a basis on which to plan larger studies of the factors associated with mobility outcome after ankle fracture in older populations.