Mortality After Nontraumatic Major Lower-Limb Amputations in Medicare Patients at a Large Metropolitan Prosthetic Facility
Authors: Krueger Max Donahue 
Published: September 2023

ABSTRACT

Introduction
Approximately 75% of Medicare patients sustain vascular-related major lower-limb amputations and die within 5 years postamputation. Studies have examined factors influencing mortality rates at 1 and 5 years postamputation. Lower-limb prosthesis users are assigned Medicare Functional Classification Levels (i.e., K-levels) at prosthetic evaluations. Higher K-level patients tend to ambulate faster and have lower comorbidity index scores. To date, no known studies have examined K-level classification as a mortality indicator. The study objective was to examine mortality rates and major nontraumatic lower-limb amputation Medicare patient demographics in the Chicago metropolitan area. A secondary goal was to explore how K-level classification coincides with mortality rates.

Materials and Methods
A total of 2833 lower-limb prosthetic patient evaluation records ranging from June 2014 to February 2019 were exported from Futura Practice Management. Only Medicare patients with major-lower limb amputations and information related to vascular etiologies were considered. Type and comorbidity quantity were assessed per record. K-levels used were those recorded; raw Amputee Mobility Predictor scores were not considered. The patients' living status was based on the dates of death found in the MYCGS database; living patients were assigned dates of database access. The number of days the patient survived postamputation was calculated as the difference between their living status and date of death. Descriptive statistics, binary logistic regression models with a confidence interval of 95%, and 5-year Kaplan-Meier plot were generated in SPSS. A truth table was created to determine eligible records for use in plots and mortality calculations at 5 years postamputation.

Results
A total of 502 patients were included after inclusion criteria application. Overall mortality rates at 1 year and 5 years postamputation were 33.6% and 73.59%, respectively. Transtibial and transfemoral mortality rates for 1 year and 5 years postamputation were 33.07%, 72.32%, 35.59%, and 77.78%, respectively. Comorbidity quantity had no statistical significance or influence on mortality rates at 1 year and 5 years postamputation. End-stage renal disease (ESRD) and heart condition had greater mortality association and increased mortality by a factor of 2.3 and 2.4, respectively. Kaplan-Meier results suggest that as K-level classification increases, so too does cumulative survival.

Conclusions
One-year and 5-year overall mortality rates fell within the ranges reported in the literature (33.6%, 73.59%). Transtibial and transfemoral mortality at 1 and 5 years postamputation were 33.07%, 72.32%, 35.59%, and 77.78%, respectively. ESRD and heart condition were indicators of mortality relative to other comorbid conditions. Higher K-level was associated with greater survival probability per Kaplan-Meier results.

Clinical Relevance
ESRD demonstrated greater association with mortality after 1 year postamputation, and heart condition had a greater association with mortality at 5 years postamputation, suggesting that patients should be encouraged to adopt healthier lifestyles/choices. Their activity level and corresponding K-level suggest that goals driven toward K-level improvement may in fact improve their survival and reduce mortality.