Low Income Is a Risk Factor for Amputation in an Infected TKA, Study Finds
Above-knee amputation (AKA), a rare but severe complication of periprosthetic joint infection (PJI) after total knee arthroplasty (TKA), is more likely to occur in low-income patients, according to a study from The Rothman Institute published ahead of print by Clinical Orthopaedics and Related Research. Race and sex do not affect the risk of AKA after PJI, the researchers found.
The researchers identified 32,907 patients in the Nationwide Inpatient Sample who had been diagnosed with PJI after TKA between 2010 and 2014. Of these patients, 3% had undergone AKA. The researchers analyzed risk factors associated with AKA, focusing on socioeconomic measures (income and insurance status), race, and sex.
Socioeconomic factors were significantly related to AKA risk, even after adjustment for health status and other characteristics. Patients living in areas in the lowest one-fourth of income (based on ZIP code) were 58% more likely to undergo AKA than those living in the highest-income areas.
Patients with public insurance were also at higher risk: The odds of AKA were 94% higher for Medicare patients and 86% higher for Medicaid patients than for patients with private insurance.
The risk of AKA was not significantly different for black patients compared with white patients. That’s an important finding, as previous studies have suggested that black race might be a risk factor for AKA after TKA. The AKA risk was also similar for men and women.
Because of the large number of patients who undergo TKA and the poor functional outcomes associated with AKA, it is essential to understand the risk factors for this devastating complication. A recent study in Clinical Orthopaedics and Related Research reported that the occurrence of AKA due to PJI more than doubled over a 15-year period. 
The researchers were surprised to find that where the patient lived had such a major impact on AKA risk. “While ZIP code may not be a perfect measure of socioeconomic status, it is associated with the level of resources that may be available to people living in that area,” said lead author Shyam Brahmabhatt, MD.
He and his colleagues call for further studies to explore strategies to prevent PJI – particularly in patients from low-income areas.
In an accompanying Take 5 interview, Dr. Brahmabhatt and Daniel Wongworawat, MD, a senior editor of in Clinical Orthopaedics and Related Research, discuss the new evidence on how social factors may influence health outcomes and access to care for patients with complications after TKA.
“The message that I would impart is that upholding the principles of equity, social justice, and ensuring community health are important for all physicians,” Dr. Brahmabhatt said. “It’s important to remember that all specialties work together as a team to fulfill vital roles in helping our patients towards that goal.”
Lieber AM, Kirchner GJ, Kerbel YE, Moretti VM, Vakil JJ, Brahmabhatt S. Socioeconomic status is associated with risk of above-knee amputation after periprosthetic joint infection of the knee. Clin Orthop Rel Res. 29 March 2019 [published ahead of print]. doi: 10.1097/CORR.0000000000000634
- George J, Navale SM, Nageeb EM, et al. Etiology of above-knee amputations in the United States: is periprosthetic joint infection an emerging cause? Clin Orthop Relat Res. 2018 Oct;476(10):1951-1960. doi: 10.1007/s11999.0000000000000166.