Risks and Risk Factors for Ipsilateral Re-Amputation in the First Year Following First Major Unilateral Dysvascular Amputation

Abstract

To identify timing, incidence, and risk factors for ipsilateral re-amputation within 12 months of first dysvascular amputation and to determine specific subgroups of patients at each amputation level that are at increased risk. A retrospective cohort study evaluating 7187 patients with first unilateral transmetatarsal (TM), transtibial (TT), or transfemoral (TF) amputation secondary to diabetes and/or peripheral artery disease (PAD) were identified in the VA Surgical Quality Improvement Program database between 2004 and 2014. Re-amputation was defined as any subsequent ipsilateral soft tissue/bony revision or amputation to a higher level. Twenty-three potential pre-operative risk factors (and nine potential interactions) were identified. A backward stepwise Cox regression was used to identify risk factors. Incidence rates and hazard ratios (HR) with 95% confidence intervals (CI) were computed. The median time to highest level of re-amputation in the first year was 33 (interquartile range, 13-73) days. Risk of requiring at least one re-amputation was 41% (TM), 25% (TT), and 9% (TF). Risk factors associated with requiring re-amputation included chronic obstructive pulmonary disease, elevated white blood cell count, abnormal ankle brachial index (ABI), history of revascularisation, and alcohol misuse. TM patients who had diabetes only (HR 1.9; 95% CI 1.4-2.5), diabetes with an abnormal ankle brachial index (ABI) score (HR 2.4; 95% CI 1.8-3.2), and kidney failure (HR 1.7; 95% CI 1.3-2.1) were at the greatest risk of re-amputation. TT amputees who were smokers were also at an increased risk (HR 1.4; 95% CI 1.2-1.6). This research identified important risk factors for failure of primary healing and need for re-amputation at the TM and TT level. If considering a TM amputation, caution should be exercised in patients with diabetes, in particular those with an abnormal ABI and/or renal failure. At the TT level, caution should be exercised in those who smoke.