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Orthopaedic Proceedings
Vol. 94-B, Issue SUPP_XXV | Pages 170 - 170
1 Jun 2012
Whiteside L Peppers M Nayfeh T Roy M
Full Access

Introduction

Resistant organisms are difficult to eradicate in infected total knee arthroplasty, and treatment of methicillin-resistant Staphylococcus aureus (MRSA) is especially challenging. Whereas most surgeons use antibiotic-impregnated cement during revision to treat infection, the delivery of the drug in adequate doses is limited in penetration and duration. This study presents the 2- to 8-year prospective results of one-stage revision and intraarticular antibiotic infusion protocol used to treat MRSA.

Methods

Eighteen knees (18 patients) with methicillin-resistant Staphylococcus aureus were treated between January 2001 and January 2007 with one-stage revision protocol that included débridement, uncemented revision of total knee components, and intraarticular infusion of 500 mg vancomycin via Hickman catheter once or twice daily for 6 weeks. (Figure 1) No intravenous antibiotics were used after the first 24 hours. Serum vancomycin levels were monitored to maintain levels between 3 and 10 μg/mL. The mean serum vancomycin peak concentration was 6 ± 2 μg/mL and the mean serum vancomycin trough concentration was 3 ± 1 μg/mL at 2 weeks postoperative.


Orthopaedic Proceedings
Vol. 94-B, Issue SUPP_XXV | Pages 171 - 171
1 Jun 2012
Roy M Whiteside L Nayfeh T Katerberg B
Full Access

Introduction

Recent clinical studies found no apparent reduction in wear using yttria-stabilized zirconia (Y-TZP) instead of cobalt chromium alloy femoral heads bearing against cross-linked UHMWPE. The purpose of this study was to compare the surface topography of retrieved Y-TZP and magnesia-stabilized zirconia (Mg-PSZ) femoral heads and evaluate the influence of time in vivo. The increase in average roughness (Ra, Sa) of Y-TZP due to phase transformation in vivo is well documented, while Mg-PSZ does not roughen or undergo phase transformation in vivo. However, the effects of phase transformation on the polarity (skewness, Ssk) of the surface of retrieved ZrO2 heads has not been reported. We hypothesized that phase transformation associated with the increased roughness of Y-TZP would influence skewness and thus the wear potential of the heads.

Materials and Methods

Y-TZP (n = 18) and Mg-PSZ (n = 17) femoral heads were retrieved from revision THA. Heads were cleaned and scanned by optical profilometry (magnification = 10x) at three locations per specimen. After subtracting the curvature of the heads, roughness statistics (Sa, Ssk) were calculated and averaged for each specimen and then correlated to age in vivo, with p < 0.05 for significance.