Steroid shots given too close to hip/knee replacement may up infection risk

By Megan Brooks

NEW YORK (Reuters Health) - Pain-relieving steroid injections given in the months prior to hip or knee replacement may increase the risk of postoperative infection, according to research presented today at the American Academy of Orthopaedic Surgeons (AAOS) annual meeting in Orlando, Florida.

In one study, researchers from Iowa used the Humana Inc claims database to identify more than 83,000 patients who underwent a first total knee arthroplasty (TKA) between 2007 and 2014. Of these, 35% had an injection at least one year prior to TKA.

Rates of any surgical-site infection (SSI) were significantly higher in patients who had an injection prior to surgery than those who did not (4.4% vs. 3.6%; odds ratio, 1.2; p<0.0001), as were rates of infection requiring a return trip to the operating room (1.5% vs. 1.0%; OR, 1.4; p<0.0001).

Stratification by timing showed that the closer the proximity between injection and TKA the higher the odds of infection (out to seven months), with an OR of 1.8 (p<0.0007) for an injection occurring within one month of TKA and an OR of 1.4 (p=0.048) with injection occurring six to seven months prior to TKA.

"This association between injection and infection after TKA is important to consider during an arthroplasty surgeon's management of patients who have undergone injection," the researchers conclude in their conference abstract.

"We expected there to be some association between injection and TKA infection," lead investigator Dr. Nicholas Bedard, an orthopedic surgeon at University of Iowa Hospitals and Clinics in Iowa City, told Reuters Health by email.

"Currently there are no specific recommendations stating how long to wait to perform TKA following a knee injection. We hope these finding bring increased awareness to this association between injection and TKA. Until further research is available to better clarify the infection risk of injection prior to TKA, we would recommend being selective when indicating patients for injection and limiting use of this modality to those unlikely to undergo TKA in the near future," Dr. Bedard advised.

In the other study, researchers from New York used large population-level databases from California and Florida to evaluate ties between preoperative hip injection and risk of periprosthetic joint infection in a cohort of more than 177,000 patients who had total hip arthroplasty (THA).

They found that injections given within three months of THA were associated with a 40% increased risk for postoperative periprosthetic infection. The infection rate after one year was 2.88% in patients who had an injection within three months prior to surgery versus 2.04% in patients who did not, according to a conference statement.

"This large population-level study is the first to provide strong evidence of increased risk of periprosthetic joint infection when an injection is administered within 12 weeks before THA (number needed to harm = 189)," the authors conclude in their meeting abstract. "THA should not be performed within three months of hip injection to avoid elevated risk of infection, but appears safe if performed more than three months preoperatively."

"This data allows patients and surgeons to have a candid discussion about the risk of infection after total hip arthroplasty if a hip injection has been given in the prior three months," lead investigator Dr. William Schairer, an orthopedic surgeon at the Hospital for Special Surgery in New York, added in a statement.

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