Acute Kidney Injury After Placement of an Antibiotic-Impregnated Cement Spacer During Revision Total Knee Arthroplasty Travis J. Menge, MD,* John R. Koethe, MD, y Cathy A. Jenkins, MS, z Patty W. Wright, MD, y Andrew A. Shinar, MD,* Geraldine G. Miller, MD, y and Ginger E. Holt, MD* Abstract: We performed a retrospective cohort study of 84 patients to determine the incidence and predictors of acute kidney injury after antibiotic-impregnated cement spacer (ACS) placement for infected total knee arthroplasties. Acute kidney injury was defined as a more than 50% rise in serum creatinine from a preoperative baseline to a level greater than 1.4 mg/dL within 90 days postoperatively. Total incidence was 17% (n = 14; 95% confidence interval [CI], 10%-26%), and acute kidney injury was significantly associated with ACS tobramycin dose as both a dichotomous variable (N4.8 g; odds ratio, 5.87; 95% CI, 1.43-24.19; P = .01) and linear variable (odds ratio, 1.24 for every 1-g increase; 95% CI, 1.00-1.52; P = .049). Routine monitoring of serum creatinine and measurement of serum aminoglycoside levels in response to a threshold creatinine rise may be warranted after the placement of an aminoglycoside-containing ACS. Keywords: revision knee arthroplasty, antibiotic spacer, acute kidney injury. © 2012 Elsevier Inc. All rights reserved. Approximately 500 000 total knee arthroplasties (TKAs) are performed yearly in US hospitals, and an estimated 0.9% to 1.8% of prosthetic knee joints become infected over the duration of use [1-3]. An antibiotic-impreg- nated cement spacer (ACS) is frequently used in the revision of an infected TKA, with the twin goals of delivering a high local concentration of antibiotic in joint fluid and surrounding tissue while minimizing systemic exposure. It is generally accepted that the treatment of an infected TKA with a spacer is more effective than resection of hardware and intravenous antibiotics alone [4,5]. As the number of primary knee arthroplasties continues to rise, the number of infected prosthetic knee joints and placement of ACS are also expected to increase [6]. Several large studies have demonstrated the efficacy of ACS placement during the revision of infected arthro- plasties, but there are fewer published reports regarding safety [7-9]. Smaller studies (ie, n b 40 patients) reported minimal clinically significant renal dysfunction or attributable adverse reactions after ACS placement, but few data on participant baseline comorbidities were provided, and the applicability of these findings to patient populations with preexisting renal insufficiency, older age, or other conditions associated with renal dysfunction is unknown [10-12]. Temporary postoper- ative reductions in renal function may have clinical significance in the orthopedic population, as several studies report an association between transient eleva- tions in serum creatinine and increased length of hospital stay, increased cost, and increased long-term mortality despite subsequent normalization of renal function [13-16]. As a tertiary referral center, our hospital receives a wide range and large volume of patients with infected TKAs. Recently, we observed a rapid onset of acute kidney injury (AKI) in a woman with normal preoper- ative renal function after the serial placement of 2 ACSs, each containing 8 g vancomycin and 9.6 g tobramycin powder in 160 g of cement. After placement of the second ACS, her serum tobramycin level, measured in response to a rising creatinine, was 19.8 μg/mL and remained elevated at 3.0 μg/mL approximately 4 weeks From the *Department of Orthopaedic Surgery, Vanderbilt University School of Medicine, MCE South Tower, Nashville, Tennessee; yDivision of Infectious Diseases, Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee; and zDepartment of Biostatistics, Vanderbilt University School of Medicine, Nashville, Tennessee. Supplementary material available at www.arthroplastyjournal.org. Submitted August 3, 2011; accepted December 10, 2011. The Conflict of Interest statement associated with this article can be found at doi:10.1016/j.arth.2011.12.005. Reprint requests: Travis J. Menge, MD, Department of Orthopaedic Surgery, Vanderbilt University Medical Center, Medical Center East, South Tower, 1215 21st Ave S. Nashville, TN 37232-8774. © 2012 Elsevier Inc. All rights reserved. 0883-5403/2706-0065$36.00/0 doi:10.1016/j.arth.2011.12.005 1221 The Journal of Arthroplasty Vol. 27 No. 6 2012