2009 Abstract : 8

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Authors: Mortazavi J, Molligan J, Parvizi J, Austin M, Purtill J, Sharkey P, Hozack W, Rothman Institute, Philadelphia, PA

Title: Predictors of Infection after Total Knee Arthroplasty Revision

Purpose: The purpose of the current study was to determine the predictive risk factors for infection following revision TKA.

Methods: From March 1998 December 2005, a total of 499 TKA revisions were performed at our institution which included revision for infection in 102 knees and revision for aseptic failure in 397 knees. Patients undergoing repeat revisions (10 knees), or those who had resection arthroplasty at an outside institution (13 knees) were excluded leaving 476 knees (454 patients) to be included in the final analysis. Preoperative history, results of physical examinations, laboratory and radiographic results, joint fluid aspiration results along with analysis of intra-operative findings were all considered to make an assessment of septic versus aseptic failure modes. Patients were prospectively followed for 65 months (range, 25-159 months).

Results: Deep infection developed in 44 knees accounting for an overall infection rate of 9.2%. The infection rate was, however, much higher at 20.7% (23/91) for patients undergoing revision for infection compared to 5.4% (21/385) for the aseptic revisions. Using multivariate analysis predictors of infection were identified to be: revision for infection, higher BMI, and higher Charlson index.

Discuassion and Conclusion: The risk of infection for patients undergoing TKA revisions appears to be ten-fold higher than it is for patients undergoing primary TKA at our institution. Infection of primary TKA is the most important risk factor for subsequent infection of TKA revisions (Hazard Ratio: 2.21). The other possible explanation for this higher infection rate relates to the fact that some of these so-called aseptic cases in fact failed because of an infection that escaped detection using conventional diagnostic modalities.