| Surgeons have been mixing antibiotics into bone cement for total joint surgeries for years. But mixing antibiotics intraoperatively into carefully composed bone cement formulas presents certain risks. For example, the surgeon can never be sure that the antibiotic is evenly distributed throughout the mixture, or that the mechanical properties of the cement will not be compromised. In addition, mixing antibiotics with bone cement during surgery wastes valuable operating room time. In comparison, commercially mixed antibiotic bone cement is guaranteed to be evenly blended, and has been shown to have higher effusion rates when compared to manually mixed cement.
Recently approved products for use in the second stage of a two-stage total joint revision following the elimination of an active infection are Depuy 1 Gentamicin Bone Cement by Depuy Orthopaedics, a Johnson & Johnson company, Palacos® G with Gentamicin by Biomet Orthopaedics, and Simplex™ P with Tobramycin by Stryker Orthopaedics.
Depuy Orthopaedics has a 40-year clinical history with Depuy 1 Bone Cement. Depuy 1 Bone Cement is a homopolymer,high viscosity cement, giving the working product a doughy consistency for easy handling. It has a quick setting time of only 11 minutes at 65° F. Depuy 1 Bone Cement has 90 seconds more working time and 90 seconds more overall time than Palacos G Bone Cement.
Depuy has mixed their popular Depuy 1 Bone Cement with 1 gram of gentamicin, preserving the mechanical properties of the cement. Gentamicin is a bactericidal aminoglycoside antibiotic that is effective against many strains of gram-negative bacteria, including species of Escherichia, Enterobacter, Klebsiella, Salmonella, Serratia, Shigella, some Proteus, and Pseudomonas aeruginosa. Gentamicin is also effective against some gram-positive strains, such as Streptococci.
Depuy 1 Gentamicin Bone Cement has been clinically proven in the international market for over a decade, and is now available in the U.S. for use in the second stage of a two-stage revision after an infection has been cleared.
Biomet Orthopaedic’s Palacos G with Gentamicin was the first examined antibiotic-mixed bone cement. Surgeons have been adding gentamicin to Palacos Bone Cement for over 30 years. Palacos G with Gentamicin, like Depuy 1, is a high viscosity, easy-to-handle bone cement that has a faster setting time than lower viscosity cements. Palacos G with Gentamicin is pre-colored green, enabling easy visualization, and is radiopaque. It contains only 0.5 grams of gentamicin, but studies have shown that the amount of antibiotic does not necessarily determine the amount of ellusion. Some studies, for example, show that Palacos G with Gentamicin leaches more antibiotic than bone cements mixed with 1 gram of antibiotic, such as Simplex P with Tobramycin.
Stryker Orthopaedic’s Simplex P Bone Cement, the most popular bone cement in the U.S with over 15 million doses implanted, is now available with tobramycin. The liquid monomer portion of Simplex P Bone Cement is unchanged, thereby retaining the original mechanical properties of Simplex P. Simplex P Bone Cement is composed of 75% Methyl methacrylate-Styrene-copolymer, 15% Ploymethylmethacrylate (for handling), and 10% Barium Sulfate (for radiopaqueness). Simplex P Bone Cement with Tobramycin contains 1 gram of tobramycin to 40 grams of cement powder and is a medium viscosity.
Antibiotic bone cements can be mixed using the same mixing systems as non-antibiotic bone cements. Stryker, Biomet, and Depuy all offer bowl or cartridge mixing systems that use vacuum to ensure perfect setup. Stryker offers Mixevac® III, a bowl system, and Revolution™, a cartridge mixing and delivery system. Biomet offers Optivac® Vacuum Mixing System (cartridge), and Depuy offers ULTRAMIX Vacuum Mixing System (cartridge).
With the recent availability of commercially-blended antibiotic bone cement, mixed with the same devices used to mix non-blended bone cement, surgeons now have an encouraging alternative to manually mixing antibiotics to bone cement. Commercially-blended antibiotic bone cement eliminates wasted O.R. time, is guaranteed to be evenly distributed throughout the cement, and has been shown to have higher effusion rates than manually-mixed antibiotic bone cement.
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