All cause mortality, re-amputation and readmission rates following below knee amputation in 24,711 diabetic patients; a 25-year England population study (1998 to 2023)

ObjectivesTo study changes in all cause mortality of patients with diabetes following below knee amputation (BKA) in England from 1998 to 2023; identifying at risk patients. To equip patients and healthcare providers with accurate estimates of serious adverse events including 90-day complications, reoperation, readmission and further lower limb amputation rates. DesignNational population based cohort study. SettingHospital Episode Statistics database for NHS England linked to ONS mortality records. Participants24,711 patients with diabetes who underwent a below knee amputation in England between April 1998 and April 2023. Main outcome measuresPrimary outcomes were all cause mortality rate and amputation free survival calculated with Kaplan-Meier curve analyses. Multivariate logistic regression was used to stratify patient variables associated with mortality and/or re-amputation rate. Secondary outcomes included causes of death, re-amputation rates, temporal variation in post BKA mortality and rate of 90-day peri-operative complications and readmission rates. ResultsWe identified 24,711 BKA on patients with diabetes in the 25-year period. The rate of BKA decreased from 2002 (5.9/100,000; 95% CI 5.6-6.1/100,000) to 2012 (4.4/100,000; 95% CI 4.2 - 4.5/100,000) and plateaued between 2012-2022 (4.3/100,000 in 2022; 95% CI 4.1 - 4.5/100,000). BKA rates were significantly higher in males (6.7/100,000; 95% CI 6.4 - 7/100,000) compared to females (2.0/100,000; 95% CI 1.8 - 2.1/100,000, P<0.05). The mortality rates following BKA were 4.6% (30 days), 11.3% (90 days), 23.6% (1 year), and 58.2% (5 years). Only 13% of patients survived to 15 years. The commonest causes of death were chromic ischemic heart disease (16.3%), acute myocardial infarction (10.03%) and medical complications of diabetes (9.0%). Cox Proportional Hazard modelling found female patients (HR 1.08; 95% CI 1.05 - 1.12), increasing age (HR 1.79; 95% CI 1.73 - 1.86 in 60-79 year olds), and higher Charlson co-morbidity index (HR 2.60; 95% CI 1.74 - 3.88) were associated with significantly higher risk of mortality. 90-day post operative complications included reoperation (20.7%), myocardial infarction (3.2%), cerebrovascular accident (1.5%), and pulmonary embolus (0.59%). The ipsilateral re-amputation rate was 10.4% (n=2909), and the contralateral amputation rate was 11.4% (n=2304). The average length of stay was 33 days (IQR 29, 1-152). 23.4% of patients were readmitted to hospital within 90 days. ConclusionsThis landmark 25-year England population study has revealed that BKA in patients with diabetes is still associated with high mortality rates, high rate of further amputation and high incidence of significant complications. Nearly a quarter of patients require readmission within 90 days. Severely co-morbid female patients over the age of 60 years have the highest mortality rate and represent an at risk group in need of national intervention.