The effect of systemic antibiotic and antibiotic-impregnated polymethylmethacrylate beads on the bacterial clearance in wounds containing contaminated dead bone.

A dorsal muscular wound model was used in 40 New Zealand White rabbits to study the effect of systemic and local antibiotics on the bacterial clearance of contaminated dead bone. Devitalized iliac crest bone preincubated with Staphylococcus aureus was implanted in each deep muscular wound with or without tobramycin-impregnated polymethylmethacrylate beads. Either systemic tobramycin or cefazolin was administered for 7 days. Animals were sacrificed at 7 and 14 days. The wounds containing tobramycin beads had significantly fewer bacteria than those without antibiotic beads (2.0 x 10(2) versus 1.3 x 10(6); p < 0.008). The reduction in bacteria due to the tobramycin beads did not differ significantly with respect to the concurrent systemic antibiotics or to the duration of incubation. We conclude that tobramycin-impregnated beads are effective in reducing bacterial count in contaminated bony wounds treated with systemic antibiotics. Furthermore, the bactericidal effect of the antibiotic beads is independent of and additive to the systemic antibiotic delivered to the wounds by well-perfused muscles.