Physical, mechanical and pharmacological properties of coloured bone cement with and without antibiotics.

Coloured bone cements have been introduced to make the removal of cement debris easier at the time of primary and revision joint replacement. We evaluated the physical, mechanical and pharmacological effects of adding methylene blue to bone cement with or without antibiotics (gentamicin, vancomycin or both). The addition of methylene blue to plain cement significantly decreased its mean setting time (570 seconds (SD 4) vs 775 seconds (SD 11), p = 0.01), mean compression strength (95.4 MPa (SD 3) vs 100.1 MPa (SD 6), p = 0.03), and mean bending strength (65.2 MPa (SD 5) vs 76.6 MPa (SD 4), p < 0.001) as well as its mean elastic modulus (2744 MPa (SD 97) vs 3281 MPa (SD 110), p < 0.001). The supplementation of the coloured cement with vancomycin and gentamicin decreased its mean bending resistance (55.7 MPa (SD 4) vs 65.2 MPa (SD 5), p < 0.001).The methylene blue significantly decreased the mean release of gentamicin alone (228.2 µg (SD 24) vs 385.5 µg (SD 26), p < 0.001) or in combination with vancomycin (498.5 µg (SD 70) vs 613 µg (SD 25), p = 0.018) from the bone cement. This study demonstrates several theoretical disadvantages of the antibiotic-loaded bone cement coloured with methylene blue.