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A prosthetic joint is a foreign body, and its presence alone is a significant risk factor for infection.

I am changing gears today, and I am sure you are ready for a clinical discussion. As I near retirement age, I have been thinking to myself, “what I can leave you all when I go?” As a result, I am writing a book on all things ICD-10, clinical documentation integrity (CDI), and quality. I am organizing it from A to Z, and last weekend, I was working on complication of devices.

I ran across an American Hospital Association (AHA) Coding Clinic question that I must not have noticed when it came out in 2019 (Quarter 3), or I would have registered my dissatisfaction then. The question centers on a patient who has a left knee replacement and develops a dental infection after a wisdom tooth extraction. He is subsequently diagnosed with a hematogenous left knee prosthetic joint infection and requires revision of the arthroplasty and synovectomy. The question asked was: “does the term ‘hematogenous’ mean the prosthetic joint infection is due to the presence of the prosthesis, or instead is seeded from concurrent infection elsewhere?” They want to know if they should use T84.54XA, Infection and inflammatory reaction due to internal left knee prosthesis, initial encounter.

I strongly disagree with their answer. They respond that the infection of the knee is not due to the prosthetic joint, but occurred secondary to another source. They explain that “hematogenous” means the infection originated in the blood and spread by way of the bloodstream, and the advice is to use M00.862, Arthritis due to other bacteria, L knee, and the status code Z96.652, Presence of L artificial knee joint.

This advice is flawed in multiple ways. “Hematogenous” doesn’t mean it originated in the blood, although it does mean “spread by way of the bloodstream from a distant source during bacteremia.” If the incision site had become infected and spread to the joint, that would be referred to as “contiguous spread.” The prosthesis can also get inoculated at the time of implantation. But organisms don’t arise spontaneously; they come from somewhere, and then they attack a body part, resulting in an infection.

A prosthetic joint is a foreign body, and its presence alone is a significant risk factor for infection. It takes a smaller inoculum of germs to establish an infection, as compared to a native joint, and a prosthesis can promote formation of a biofilm that can impact the efficacy of antibiotics. The incidence of prosthetic joint infection is 1-5 percent, and it is divided into early (within the first four weeks after implantation), delayed (from three months to one year later), and late infection (over one year later), and is usually hematogenous. The microbes vary, depending on the time frame.

The T84.5- series is titled Infection and inflammatory reaction due to internal joint prosthesis. Inflammatory reaction may be literally “due to” the prosthesis, but infection is “due to” a microorganism. Whether the germs that started the infection were implanted with the prosthesis, spread from the skin to the joint, or traveled in the bloodstream from a far-off site is not relevant to the story. The prosthesis is infected, and that must be detailed here. Even advising use of V79.2, Prosthetic and other implants, materials and accessory orthopedic devices associated with adverse events, would have at least created some linkage.

“Arthritis” of a native joint might be able to be treated with antibiotics. An infected implant, regardless of where the germs originated, usually requires more extensive treatment, often necessitating explantation. The example presented to Coding Clinic did require surgical intervention.

In my opinion, the correct coding for this scenario was: T84.54XA, Infection and inflammatory reaction due to internal left knee prosthesis, K34.7, Periapical abscess without sinus, and a B95-B96 code, if determinable.

Maybe the Centers for Disease Control and Prevention (CDC) should change the title to “Infection and inflammatory reaction involving (due to) prosthesis,” to alleviate confusion. As it stands, the Coding Clinic advice does not tell the story, and they should revise it.

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