THE EFFECT OF VANCOMYCIN ADDITION ON THE COMPRESSION STRENGTH OF ANTIBIOTIC-LOADED BONE CEMENT

Abstract

Introduction: There is extensive literature on the effect of vancomycin on the compression strength of plain cements, none however on antibiotic-loaded cements. The addition of vancomycin to antibiotic-loaded bone cement is common practice in revision joint replacement surgery for infection. The scope of this study was to record the effect of vancomycin addition on the compression strength of antibiotic-loaded bone cement and to compare the results with the international standard (ISO 5833–2) in order to evaluate safety in clinical use.

Materials & Methods: The formulations used were Palamed G, containing 0.55g of gentamicin; and Copal, containing 1g of gentamicin and 1g of clindamicin. Vancomycin concentrations of 2.5%, 5% and 10% per powder weight were added. The ISO requirements for the testing procedures were followed. Samples of Palamed G with 5% vancomycin and non-standardised mixing procedures were also tested, as well as samples of both bone cements without vancomycin, as controls.

Results: The mean compression strength of plain Palamed G was 91.08 MPa. With the addition of 2.5%, 5% and 10% vancomycin, the mean compression strengths were 79.82, 82.3 and 74.56 MPa respectively, a reduction of 12.36%, 9.64% and 18.13%. The mean strength of the Palamed G specimens with 5% vancomycin and non-standardised mixing was 72.88 MPa, a 19.9% reduction. The mean compression strength of the plain Copal was 86.27 MPa. With the addition of 2.5%, 5% and 10% vancomycin, the mean compression strengths were 76.59, 78.92 and 71.19 MPa respectively, a reduction of 11.22%, 8.52% and 17.48%. Copal with 10% and Palamed G with 5% vancomycin and non-standardised mixing, were the only cements with compression strengths not significantly exceeding the ISO standard of 70 MPa.

Conclusion: The addition of up to 5% vancomycin per powder weight to the antibiotic-loaded Copal and 10% to Palamed G bone cements can be considered safe. Care should be given to the mixing procedure of the cement, as it significantly affects its compression strength.