title: Volume and surface area study of tobramycin-polymethylmethacrylate beads.
abstract: Polymethylmethacrylate bone cement beads impregnated with antibiotic are a common treatment for patients with persistent articular joint infections or osteomyelitis. They also are used as a prophylaxis for infection in patients with large soft tissue wounds. The current study was designed to evaluate the relationship between bead geometry and elution of the antibiotic tobramycin by methodically varying the shape of the beads for a given set of volumes. Beads of five shapes (spherical to ovoid) and two volumes were prepared and studied. Only 0.9% to 3.3% of the total amount of tobramycin present actually eluted from the beads in a 96-hour period and of this amount, approximately 1/3 eluted within the first 4 hours. The elution mass data indicate the benefit of numerous, small and elliptically shaped beads for maximal antibiotic availability. Additionally, a mathematical model is presented that describes these findings and can be used to predict tobramycin delivery rates from bone cement beads. This model assumes that the antibiotic is delivered through two mechanisms: fast dissolution of tobramycin initially adhering to the bead surface and slow release by diffusion through the polymer. The results generate diffusion coefficients for tobramycin in polymethylmethacrylate bone cement on the order of 2 x 10 cm/s.
authors.affiliation: Department of Science and Mathematics, Kettering University, 1700 West Third Avenue, Flint, MI 48504, USA.
authors.forename: Stacy K
authors.initials: SK
authors.lastname: Seeley
authors.forename: John V
authors.initials: JV
authors.lastname: Seeley
authors.forename: Paul
authors.initials: P
authors.lastname: Telehowski
authors.forename: Sidney
authors.initials: S
authors.lastname: Martin
authors.forename: Massoud
authors.initials: M
authors.lastname: Tavakoli
authors.forename: Stephanie L
authors.initials: SL
authors.lastname: Colton
authors.forename: Bryan
authors.initials: B
authors.lastname: Larson
authors.forename: Patricia
authors.initials: P
authors.lastname: Forrester
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Atkinson
mesh_terms: D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000493:pharmacokinetics*; D001843:Bone Cements; D017076:Computer-Aided Design; D004058:Diffusion; D004339:Drug Compounding; D004343:Drug Implants / Q000138:chemical synthesis*; D006801:Humans; D008962:Models, Theoretical; D019904:Polymethyl Methacrylate; D014031:Tobramycin / Q000008:administration & dosage / Q000493:pharmacokinetics*
chemical_list: D000900:Anti-Bacterial Agents; D001843:Bone Cements; D004343:Drug Implants; D019904:Polymethyl Methacrylate; D014031:Tobramycin