Gentamicin concentrations in synovial fluid obtained from the tarsocrural joints of horses after implantation of gentamicin-impregnated collagen sponges.

The research assesses the presence and side-effects of gentamicin, a type of antibiotic, on horse joints when implanted via a collagen sponge. The study concluded that the process results in the rapid release of gentamicin, but does not trigger significant inflammation or damage to joint tissues.

Research Methodology

• The research involved six healthy adult mares. These horses were selected to assess the gentamicin concentrations and potential adverse impacts on the synovial membrane and articular cartilage of tarsocrural joints following the implantation of a gentamicin-impregnated collagen sponge.
• The researchers used a purified bovine type I collagen sponge, impregnated with 130 mg of gentamicin. This sponge was inserted in the plantarolateral pouch of one tarsocrural joint of each horse. The opposite joint functioned as a sham-operated control joint.
• Gentamicin concentrations in the synovial fluid and serum were observed and recorded for 120 hours (5 days) post-implantation using a fluorescence polarization immunoassay, a method commonly used to measure drug concentration.
• Five days following implantation, synovial membrane and cartilage specimens were collected and evaluated under a microscope for any histologic changes.

Findings

• The median peak synovial fluid gentamicin concentration reached 168.9 microg/mL three hours after the placement of the sponge. The range was 115.6 to 332 microg/mL among the different horses. This indicated a rapid release of the antibiotic post-implantation.
• By the 48th hour, gentamicin concentrations in the synovial fluid had dropped to less than 4 microg/mL, indicating a rapid decline.
• Comparisons between gentamicin-implanted joints and control joints did not show substantial histologic differences in the synovial membrane. This suggests that implantation of the gentamicin-impregnated sponge is not causing significant cellular changes or inflammation.
• The safranin-O fast green stain was not reduced in cartilage specimens from treated joints compared to those from control joints. This further implies that there was no prominent damage to the articular cartilage.

Conclusion

• The implantation of a gentamicin-impregnated collagen sponge in the tarsocrural joint of horses led to a swift release of gentamicin. For common pathogens that infect horses, peak concentrations were more than 20 times the minimum inhibitory concentration. This indicates that the sponge could be a highly effective antibiotic delivery method.
• A quick decrease in synovial fluid gentamicin concentrations was detected, suggesting the body quickly metabolizes or removes the antibiotic.
• Notably, the purified bovine type I collagen sponges did not induce notable inflammation in the synovial membrane nor caused damage to the articular cartilage. This highlights the safety of this drug delivery method.