Intraosseous gentamicin perfusion of the distal metacarpus in standing horses.

The research study documented the levels of gentamicin, a type of antibiotic, in the tissues of standing horses after it was infused directly into the bone. The results highlighted that this method led to antibiotic concentrations in the synovial structures and bones of the horses that were high enough to inhibit common pathogens associated with equine orthopedic infections.

Methodology

• The study involved twelve standing horses. Under sedation, a cortical bone screw was inserted into the dorsolateral aspect of the metacarpus (a part of the limb) in each horse. A tourniquet was applied above this region.
• A solution of gentamicin diluted in sterile saline was infused through the screw. The dosage used was 2.2 mg/kg of body weight, and the saline solution volume was 0.1 mL/kg of body weight.
• Two horses were euthanized and sampled at each of the following time intervals: 0, 2, 6, 12, 24, and 36 hours post-infusion.
• Samples of synovial fluid and bone were collected from regions distal to the screw insertion site in both forelimbs of each horse.
• The gentamicin concentration in these samples was quantified using a method called fluorescence polarization immunoassay.

Results

• The highest gentamicin concentrations were found in the synovial fluid, with varying levels across different joints and structures. The metacarpophalangeal joint, proximal interphalangeal joint, distal interphalangeal joint, digital flexor tendon sheath, and the navicular bursa showed considerable concentrations.
• The gentamicin levels were also measured in various bones, including the distal metacarpus, proximal, middle, and distal phalanges, and proximal and distal sesamoid bones.
• In both fluid and bone samples, the concentrations exceeded the minimum inhibitory concentration for pathogens typically implicated in equine orthopedic infections.

Conclusions

• The research findings suggest that standing intraosseous perfusion of gentamicin resulted in sufficient local antibiotic concentrations in the associated synovial structures and bones.
• This potentially effective method should be considered for treating orthopedic infections in horses, especially when such infections are localized in the distal aspect of the limb (the lower part of the leg).