A prospective observational cohort study to investigate the effect of frailty on mortality of adults following lower limb amputation

Introduction Frailty is common in patients with atherosclerotic disease and is associated with substantially increased morbidity, mortality and significant economic and resource implications. Major limb amputation (MLA) secondary to critical limb threatening ischaemia (CLTI) is also associated with high mortality rates. This study aims to examine the association between frailty, as defined by the Rockwood Clinical Frailty Scale (CFS), on mortality rates in patients undergoing MLA for CLTI. Methods This multi-centre, prospective observational cohort study will collect data on MLA performed for CLTI between November 2017 to December 2021 (North Bristol Trust) and January 2016 to October 2021 (NHS Greater Glasgow & Clyde). All patients undergoing MLA for CLTI will be included. Exclusion criteria are MLA for other aetiology, insufficient data to generate CFS score and minor lower limb amputations. Data collected includes age, sex, deprivation index and Charlson Comorbidity Index variables. A consultant/registrar with specialist-interest in frailty will allocate CFS scores based on pre-operative functional status. Three categories will be used: robust (CFS 1-3), mildly frail (CFS 4-5) and frail (CFS 6-8). CFS 9, ‘terminally ill’, will be presented separately. Primary outcome is all-cause mortality following MLA. Secondary outcome is length of stay. Sample size calculation assumed a mortality of 30% in robust and 40% in frail patients (HR=0.7) in a 1:2 ratio (robust:frail), calculating 1000 patients required, using a 0.05 significance level and 90% power. Outcome data will be analysed by multivariable Cox proportional baseline hazards regression controlling for demographic and operative variables (e.g., sex, age, deprivation index, comorbidity index, urgency of operation). Discussion It is expected the study results will inform clinical decision-making and contribute toward an evidence pool which will inform service planning. KEY STUDY CONTACTS STUDY SUMMARY FUNDING AND SUPPORT IN KIND PROTOCOL CONTRIBUTORS Study contributors NBT vascular department – proving data on all patients that have undergone LLA in the last 5 years. NHSGGC vascular department – proving data on all patients that have undergone LLA in the last 5 years.