Compression Strength and Porosity of Single-Antibiotic Cement Vacuum-Mixed with Additional Vancomycin

Introduction Frequently in joint replacement surgery, antibiotics are combined with acrylic cement to provide high local drug concentrations for prevention and treatment of infection. In 2003, the FDA approved the sale of single-antibiotic cement for use in septic arthroplasty cases. Such cements can now be purchased from various manufacturers. A major disadvantage of adding antibiotics to bone cement is the detrimental effect antibiotics have on cement strength. Seeking even greater advantages over infection, surgeons have recently began adding an additional antibiotic, vancomycin, to these already single-antibiotic cements. The objective of this study was to determine the maximum amount of vancomycin that could be added (vacuum-mixed) to two commonlyused commercially available single-antibiotic cements while still maintaining an ultimate compression strength (UCS) above the International Organization for Standardization’s (ISO) minimum of 70 MPa. We also investigated surface characteristics of the cement to elucidate the mechanism for this detrimental effect. We hypothesized that antibiotics decrease the strength of bone cement by increasing porosity.