Evidence of Racial Disparities Found in Above Knee Amputation Rates after Total Knee Replacement

By Jaiben George, MBBS, and Carlos Higuera-Rueda,MD

Success rates for total knee arthroplasty (TKA) have improved considerably with advancements in surgical techniques and implant designs, but complications are not uncommon after TKA. While the majority can be successfully managed with appropriate medical and surgical techniques, some complications, such as prosthetic joint infection (PJI), are extremely difficult to manage. Treatment options are limited after multiple failed attempts to control infection and unfortunately, surgeons sometimes must resort to above knee amputation (AKA). In addition to PJI, other TKA-related complications, including periprosthetic fractures, severe bone/soft tissue loss and intractable pain, can result in amputations.

Studying AKA after TKA specifically

Although racial disparities have been reported previously in the utilization of TKA and rates and level of amputation from vascular causes, racial disparities have not been studied with respect to AKA resulting from complications of TKA.

We became interested in this issue given the poor functional outcomes and broad societal implications of AKA and recognizing that information about demographic disparities in AKA is crucial for policy makers and healthcare professionals. We decided to examine national rates of AKA resulting from complications of TKA for different demographic groups. Our resulting paper was published in Clinical Orthopaedics and Related Research.

Our team identified AKAs resulting from complications of TKA in National (Nationwide) Inpatient Sample data. We analysed a combination of International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) procedure and diagnosis codes. From 2000 to 2011, a total of 341,954 AKAs were identified, of which 9,733 AKAs were the result of complications of TKA (8,104 septic complications/PJI and 1,629 aseptic complications). Standardized AKA rates were calculated for different age and gender racial groups by dividing the number of AKAs in each group with the corresponding number of TKAs and adjusting for demographics and comorbidities.

Results: disparities by race became clear

We found that black men had the highest rate of AKA after TKA (578 AKAs per 100,000 TKAs) after adjusting for age and comorbidities. The second highest rate of AKA was among black women and white men, and the lowest rate was among white women (Figure 1). Black men also had the highest rate of AKA after septic complications of TKA. The rates of AKA were higher in patients older than 80 years and, surprisingly, in those younger than 50 years.

The annual number of AKA procedures almost doubled, from 522 procedures in 2000 to 1,083 procedures in 2011. However, the amputation rate did not change over the years, suggesting that the risk of AKA after TKA may not have increased over time. Throughout the study period, septic complications contributed to the majority of AKAs.

Reasons for racial disparities not yet known

The reasons for racial disparities are not fully understood. Variances could be related to differences in true risks of AKA (i.e., blacks may have a higher risk of PJI and hence a higher risk of AKA), patient and surgeon preferences, and resource availability. For instance, previous studies have reported that blacks treated for peripheral vascular disease are less likely to undergo attempts at limb salvage than their white counterparts.

Why is AKA rate higher among younger patients?

Although a higher rate of AKA is expected in older patients due to underlying comorbidities,

More study, solutions needed

AKA is a morbid procedure and can result in severe impairment in quality of life for patients. Moreover, AKA results in severe economic burden for society due to the costs associated with repair and replacement of prostheses for patients’ remaining life years and indirect costs in the form of work loss, disability insurance and environmental modifications for the disabled. Further research might help us better understand factors responsible for these disparities and assess whether black patients prefer amputation over repeat revision TKA/arthrodesis and why.

With the number of TKAs projected to increase in the future, effective strategies need to be taken to prevent AKA and eliminate racial disparities in the rates of this procedure. Although our study did not evaluate suspected reasons for racial disparities, policies aimed at increasing health awareness and healthcare access among minorities might improve the outcomes of TKA and reduce the need for AKA in this population.

Dr. George is a research fellow in the Department of Orthopaedic Surgery. Dr. Higuera-Rueda is staff surgeon in the Adult Reconstruction Center, and Vice Chair for Quality and Patient Safety for the Orthopaedic & Rheumatologic Institute.