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Turning Tides: Evolving Comorbidity Profiles, Demographic Shift, and the Unexpected Rise of Major Lower Extremity Amputations
*Panos Kougias¹, *Sherene Sharath¹, *Claire Ferguson¹, *Sundar Natarajan², *Steven Medvedovsky¹, *Danylo Orlov¹, David H. Berger^1
1Surgery, SUNY Downstate Health Sciences University, Brooklyn, NY; ²Medicine, NYU Grossman School of Medicine, New York City, NY

Objective. An increasing emphasis on structured amputation prevention programs and widespread adoption of sophisticated revascularization techniques suggests the potential for significant reductions in major lower extremity amputations. We sought to identify predictors of and trends in the incidence of above (AKA) and below (BKA) knee amputations in a nationwide sample.
Methods. Inpatient admissions with a diagnosis of atherosclerosis and/or related amputation were identified from the National Inpatient Sample. The primary outcome was the trend in BKA and AKA incidence. Multilevel logistic regression, stratified by landmark periods, was used to identify amputation predictors over time by comparing amputees to patients admitted with a diagnosis of atherosclerosis who did not undergo amputation. Population attributable fractions (PAF) were used to estimate the proportion of each outcome, due to a specific risk factor.
Results. Between January 1993 and December 2021, we identified 197,018 patients who underwent BKA and 151,018 who underwent AKA. BKA incidence decreased from 12/100,000 people in 1993 to 8/100,000 in 2010 (2.2% reduction per year). This trend reversed after 2010, ending in 13/100,000 in 2021 (9% increase per year; P <0.001). AKA incidence decreased from 11/100,000 people in 1993 to 6/100,000 in 2012 (2.1% reduction per year). This trend reversed in 2012, ending in 8/100,000 in 2021 (4% increase per year; P <0.001; Figure 1). The mean age for BKA decreased from 68 years in 1993 to 61.6 years in 2021; and for AKA, from 75 years to 66.7 years (P <0.001 for both; Figure 2). We compared admissions for major amputation to 2,421,352 admissions for atherosclerosis without amputation. After 2010, BKA patients were more likely to be younger (Odds Ratio [OR] 1.0 vs. 0.97), white (OR: 0.73 vs. 1.02), obese (OR: 0.91 vs. 1.24) and hypertensive (OR: 0.97 vs. 1.07; ORs presented for pre- and post-2010 periods, respectively). After 2012, AKA patients were younger (OR: 1.04 vs. 0.99), less likely to be female (OR: 1.04 vs. 0.75), and showed shifts in effect size but not direction of important risk factors such as white race (OR: 0.61 vs. 0.9), hypertension (OR: 0.79 vs. 0.92), and obesity (OR: 0.73 vs. 0.91). The PAFs confirmed a progressive shift in the effect of risk factors on the changing incidence of both BKA and AKA. The effect of other risk factors such as diabetes (OR: 4.3 and 1.6 for BKA and AKA, respectively) and dialysis (OR: 2.4 and 2.1 for BKA and AKA, respectively) remained unchanged over time.
Conclusion. Major amputation incidence has steadily increased since 2010, accompanied by a substantial shift in the associated comorbidity and demographic profile. This shift is particularly striking among patients with BKA who, after 2010, are more likely to be younger, white, obese, and hypertensive. Treatment paradigms to address this serious public health issue will need to be reconsidered to reflect increasing attribution to metabolic syndrome.
Figure 1. Trends in incidence of major amputations between 1993 and 2021 among patients with atherosclerotic disease.