Regional limb perfusion for the treatment of orthopedic infections in horses
This research investigated regional limb perfusion for the treatment of orthopedic infections in horses. The objectives of the first study were to compare the distribution of 99m technetium pertechnate following intraosseous or intravenous perfusion of the distal limb and to determine if a tourniquet is necessary to achieve and maintain high radionuclide counts in the treated limb. The objectives of the second study were to describe a technique for intraosseous perfusion of the distal limb in standing sedated horses, and to determine concentrations of gentamicin in the synovial structures and bones of the distal limb. In the first study, nuclear scintigraphic imaging of both forelimbs showed that radionuclide activity in the treated distal limb was not significantly different in the intraosseous tourniquet and intravenous tourniquet groups. The intraosseous no tourniquet and intravenous no tourniquet treatment groups had significantly less radionuclide activity in the distal limb. The intraosseous and intravenous routes, with the use of a tourniquet, are likely to be of similar efficacy for antibacterial therapy of orthopedic infections in the lower limb. In the second study, a cannulated bone screw was placed in the distal third of the metacarpus in standing sedated horses. Gentamicin solution was infused through the cannulated screw following application of a tourniquet to the proximal metacarpus. The described technique resulted in peak synovial fluid concentrations of gentamicin 25 to 50 times the MIC for bacteria susceptible to gentamicin and peak bone concentrations of gentamicin 2 to 6.8 times the MIC for bacteria susceptible to gentamicin. Conclusions of the second study were that intraosseous perfusion of gentamicin achieves high concentrations of gentamicin in the synovial structures and bones of the distal limb of the horse, and that placement of an intraosseous screw in standing horses can be performed safely. These studies provide further data supporting the use of regional limb perfusion for the treatment of orthopedic infections in horses. Future studies focusing on the efficacy of regional limb perfusion for the treatment of orthopedic infections when the causative organism is resistant to the chosen antibiotic at concentrations achieved from systemic administration.