Efficacy of gentamycin-impregnated resorbable hydroxyapatite cement in treating osteomyelitis in a rat model

Objective: To test the effectiveness of a self-setting hydroxyapatite cemen t (HAC) as a carrier of gentamycin for the treatment of chronic osteomyelit is in a rat model by using a void-fill placement technique. Design: Osteomyelitis of the tibia was created with Staphylococcus aureus ( ATCC 49230) in sixty retired female breeder Sprague-Dawley rats by using th e model by Korkusuz et al. (J Bone Joint Surg 1993;75B3111-114). At seven w eeks after infection, all animals demonstrated clinical and radiographic si gns of osteomyelitis and were debrided and divided into four treatment grou ps: A, debridement only; B, debridement and daily intraperitoneal gentamyci n (0.2 milligram per kilogram per day); C, debridement and gentamycin-impre gnated HAC in a void-fill model (1.0 milligram per kilogram of gentamycin); and D, debridement and gentamycin-impregnated polymethylmethacrylate (PMMA ) beads (1.0 milligram per kilogram of gentamycin). Tibiae were harvested a t zero weeks (control, n = 6), three weeks (n = 3 per group), five weeks (n = 4 per group), and seven weeks (n = 4 per group) and analyzed with quanti tative bacteriologic analysis. Outcome Measurement: Qualitative bacteriologic analysis was performed by us ing serial dilution plating of homogenized tissue samples on standard soy t rypticase agar plates. Reexamination by phage typing was performed to exclu de contamination. Results: The quantitative counts for Groups C (HAC) and D (PMMA) were signi ficantly less (p < 0.003) than those for Group A (debridement alone) or Gro up B (intraperitoneal gen tamycin) at all time points after time zero. Ther e was no difference between Groups C and D at any time point. Conclusion: HAC is an effective adjuvant in treating chronic osteomyelitis in a rat model when using a void-fill placement technique.