The value of routine aspiration of a symptomatic total knee replacement before reoperation was evaluated. The study group consisted of a consecutive series of 69 knees in 67 patients in which preoperative aspiration was performed. All aspirations were performed on an outpatient basis in a clinic setting. Local anesthetics and saline washings were not used. 20 knees were determined to be infected and 49 knees were not infected. Preoperative aspiration had an overall sensitivity of 55%, specificity of 96%, accuracy of 84%, positive predictive value of 85%, and negative predictive value of 84%. 16 patients were taking antibiotics at the time of referral including 12 of 20 (60%) who had infected knees. 7 of these 12 (58%) had no growth on their initial knee aspiration. 4 of these had their knees reaspirated at a later date because of a high index of suspicion for infection and the subsequent aspiration revealed the infecting organism in all 4 cases. 2 of the remaining 3 patients had signs of sepsis develop and reaspiration was not performed because immediate reoperation was indicated clinically. The initial aspiration on the third patient was performed after antibiotic therapy was discontinued for 4 weeks and a repeat aspiration was not deemed necessary. When the results of the reaspirations are included, the overall aspiration results improved to a sensitivity of 75%, specificity of 96%, and accuracy of 90%. The results of the study support the use of routine preoperative aspiration before total knee revision. Previous antibiotic use increases the risk of a false negative result, and reaspiration at a later date can be expected to significantly improve the value of this test in such cases.
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The value of routine aspiration of a symptomatic total knee replacement before reoperation was evaluated. The study group consisted of a consecutive series of 69 knees in 67 patients in which preoperative aspiration was performed. All aspirations were performed on an outpatient basis in a clinic setting. Local anesthetics and saline washings were not used. 20 knees were determined to be infected and 49 knees were not infected. Preoperative aspiration had an overall sensitivity of 55%, specificity of 96%, accuracy of 84%, positive predictive value of 85%, and negative predictive value of 84%. 16 patients were taking antibiotics at the time of referral including 12 of 20 (60%) who had infected knees. 7 of these 12 (58%) had no growth on their initial knee aspiration. 4 of these had their knees reaspirated at a later date because of a high index of suspicion for infection and the subsequent aspiration revealed the infecting organism in all 4 cases. 2 of the remaining 3 patients had signs of sepsis develop and reaspiration was not performed because immediate reoperation was indicated clinically. The initial aspiration on the third patient was performed after antibiotic therapy was discontinued for 4 weeks and a repeat aspiration was not deemed necessary. When the results of the reaspirations are included, the overall aspiration results improved to a sensitivity of 75%, specificity of 96%, and accuracy of 90%. The results of the study support the use of routine preoperative aspiration before total knee revision. Previous antibiotic use increases the risk of a false negative result, and reaspiration at a later date can be expected to significantly improve the value of this test in such cases.
Copyright remains with the authors and publisher.