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Antibiotic Cement Spacer Increases Risk of Acute Kidney Injury

Acute kidney injury occurred in roughly 15 percent of patients receiving an antibiotic cement spacer during total knee arthroplasty (TKA) revision for periprosthetic joint infection (PJI). This news comes from a study presented at the annual meeting of the American Academy of Orthopedic Surgeons (abstract 5921). The study also demonstrated that anemia raised the risk of developing kidney injury, suggesting that clinicians should monitor anemic patients for kidney damage when implanting an antibiotic cement spacer.

"The key findings of this study are that acute kidney injury happens at a rate which is unexpectedly high and anemia is a predisposing factor," said Jose Rodriguez, MD, a study co-author and an orthopedic surgeon at Hospital for Special Surgery. "In this particular population that is at-risk, we may need to be more vigorous in monitoring for anemia and then treating with a transfusion earlier than we otherwise might have."

PJI is one of the most devastating and frequent complications that can occur after lower extremity joint arthroplasty, such as total knee replacement. The incidence of PJI varies by institution, from about .5 to 4 percent, and often requires revision surgery. Multiple procedures are sometimes necessary to eradicate infection and restore functionality, and even with successful eradication of infection, patients may not achieve optimal functional outcomes.

Mounting evidence suggests that treatment of PJI of the knee with an antibiotic cement spacer may increase the risk for acute kidney injury. "The concept for the study was that when we use a spacer for PJI, we are putting high concentrations of antibiotics in it, usually vancomycin which is renal toxic, in addition to sometimes treating these patients with intravenous vancomycin," said Dr. Rodriguez. "The question we wanted an answer to is what is the incidence of in-hospital acute kidney injury following treatment with an antibiotic spacer?"

To shed light on the issue, the researchers retrospectively identified 75 patients (39 male, 36 female) that received a static or articulating antibiotic cement spacer in New York City from 2007-2017. They collected and analyzed information on patient demographics, comorbidities, dose of antibiotic powder incorporated into the cement spacer, intravenous antibiotics administered, preoperative and postoperative creatinine, blood urea nitrogen and hemoglobin values. Acute kidney injury was defined as a more than 50 percent rise in serum creatinine from preoperative baseline to at least 1.4 mg/dL. A multivariate model was used to control for the demographics of age, gender, body mass index, and baseline creatinine.

The researchers found that in-hospital acute kidney infection occurred in 14.6 percent patients, at an average of 6.3 days (range, 2-8 days). A lower preoperative hemoglobin (OR=.55, P=.015) significantly increased the risk for infection on univariate analysis. Diagnosis of either hypertension or diabetes also showed a strong statistical trend for an increased risk of acute kidney infection (P=.056). When controlling for age (P=.0854), gender (female, P=.404), BMI (P=0.426), and baseline creatinine (P=0.340) on multivariate regression, lower preoperative hemoglobin significantly correlated with a greater percent rise in creatinine postoperatively (B=.304, P=.015).

Anemia is a well-known risk factor for postoperative AKI in patients undergoing cardiopulmonary bypass surgery, and the researchers believe that a lower baseline hemoglobin may be involved in the etiology of AKI in patients undergoing total knee revision. "The major risk factor was a lower hemoglobin level, so anemia predisposes patients to kidney injury, and these patients should receive closer monitoring," said Dr. Rodriguez.

The study was a collaboration among researchers at Lenox Hill Hospital, Monmouth Medical Center, Columbia University Medical Center, and HSS.