Skin commensals blamed for TKA revisions ‘going troppo’

When the rain buckets down during the wet season in tropical regions of Australia, the rates of prosthetic joint infection go up, according to a review of data from the National Joint Replacement Registry.

A review of revisions for prosthetic joint infection following primary total knee arthroplasty during 2011-2015 found climate factors appear to be associated with patient outcomes.

Overall, it found early revision rates were 0.73% in the tropics north of Rockhampton compared to 0.37% in southern climes.

In addition there was a significant increase in the rates of infection requiring revision during the summer/autumn wet season in the north – 0.98% compared to 0.51% in winter and spring.

There was no corresponding seasonal variation in infection rates in non-tropical regions of Australia.

The findings support other research showing a seasonal variation in rates of other musculoskeletal infections such cellulitis, myositis and osteomyelitis.

“The characteristic climatic difference between the upper tropical zone and the lower nontropical zone of Australia is the large variation in humidity. Tropical regions have a small variation in temperature throughout the year but a large variation in humidity with a peak during the monsoonal wet season,” the researchers said.

Co-author Dr Ben Parkinson, a Cairns orthopaedic surgeon, told the limbic Staph aureus carriage on the skin was probably part of the problem.

“So we are looking at whether people in tropical areas have a higher incidence of Staph on their skin, maybe because of climate factors, than people who live in drier parts of the country.”

“And if we give everyone Staph decolonisation before surgery, is that effective at eradicating Staph?”

Dr Parkinson said another potential intervention was intraosseous administration of prophylactic antibiotics to achieve much higher doses of antibiotics in the knee.

“If someone gets a proper deep infection in their prostheses, then the generally accepted treatment all over the world is that it usually needs to be removed and redone.”

“There is unfortunately a group of patients who end up with uncontrolled infections or revisions and it’s a pretty miserable complication which we are trying to avoid.”

While the absolute risk was low, the more than two-fold increase in risk had to be addressed.

“If 200 patients have an operation in summer in northern Australia, then there may be one extra infection so the effect size is actually quite tiny but still important.”

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