Therapy with gentamicin-PMMA beads, gentamicin-collagen sponge, and cefazolin for experimental osteomyelitis due to Staphylococcus aureus in rats

Introduction In spite of new surgical techniques and recently developed antibiotics, there is no satisfactory solution for the treatment of chronic posttraumatic osteomyelitis. The introduction of local antibiotic treatment with gentamicin- PMMA beads according to Klemm has provided new stimuli for the treatment of chronic osteomyelitis. With the development of collagen as an absorbable carrier substance, the disadvantages of the rigid carrier system became evident. Due to the varying surgical techniques and different forms of adjuvant therapy, it is difficult to assess therapeutic methods and compare different studies. Therefore, it seemed appropriate to study the effect of local treatment with different antibiotic carriers in the setting of an animal study. Materials and methods The proven rat model for Staphylococcus aureus-induced osteomyelitis was used to compare the results of monotherapy with cefazolin, gentamicin- PMMA beads, or gentamicin-containing collagen sponge with the combination of local and systemic antibiotic treatment. Results Single-agent therapy with parenterally administered cefazolin reduced the CFU from 3.7 x 10(6) to 2.9 x 10(4) g(-1) of tibial bone. The effect on osteomyelitis was more pronounced with the local application of antibiotics. The best results were achieved with the gentamicin- containing collagen sponge which reduced the bacterial colony count to 1.4 x 10(2) CFU/g compared with 9.8 x 10(2) CFU/g achieved with gentamicin- PMMA beads. The effect was most marked using a 4-week combination therapy with local application of the gentamicin- containing collagen sponge and systemic administration of cefazolin. In 9 of 11 animals, no bacteria could be detected in the bone. Conclusion Each of the treatment modalities resulted in a significant therapeutic effect. Due to its ability to quickly release large amounts of gentamicin, the flexible gentamicin-containing collagen sponge proved to be superior to the rigid PMMA system. Although the gentamicin-containing collagen sponge provided high antibiotic concentration at the site of implantation, an additive effect was attained when combined with systemic antibiotic treatment.