The effect of implanting gentamicin-impregnated polymethylmethacrylate beads in the tarsocrural joint of the horse.
Authors: Farnsworth K D, White N A, Robertson J
Journal: Veterinary surgery : VS
Summary
# Editorial Summary Farnsworth, White and Robertson (2001) evaluated whether gentamicin-impregnated polymethylmethacrylate (PMMA) beads could safely deliver therapeutic antibiotic concentrations to the equine tarsocrural joint, implanting 300 mg of gentamicin across three bead strands into one joint of five healthy horses whilst using the contralateral joint as a control. Peak gentamicin concentrations of 27.9 µg/mL were achieved within 24 hours and remained above the therapeutic threshold of 2 µg/mL for nine days, with negligible systemic absorption—a significant advantage for minimising nephrotoxicity risks associated with parenteral aminoglycosides. However, the beads triggered a considerable inflammatory response: synovial fluid white blood cell counts remained elevated for 72 hours, total protein concentration stayed raised for three weeks, diffuse synovitis developed in all treated joints, and superficial cartilage erosion occurred despite preserved glycosaminoglycan content. Whilst these findings support the theoretical potential of gentamicin-impregnated PMMA for treating septic arthritis where sustained high intra-articular antibiotic concentrations are critical, the tissue damage in normal joints raises important questions about timing of bead removal and the balance between infection control and secondary joint pathology—making careful case selection and close intra-articular monitoring essential before adopting this technique clinically in horses.
Read the full abstract on PubMed
Practical Takeaways
- •Gentamicin-impregnated PMMA beads can deliver therapeutic antibiotic concentrations to the tarsocrural joint for up to 9 days, making them potentially useful for septic joint management when high sustained antibiotic levels are needed
- •The inflammatory response and cartilage damage induced by the beads themselves must be weighed against infection control benefits; consider this approach primarily for infected joints where infection risk exceeds damage risk
- •Systemic antibiotic levels remain negligible with this delivery method, reducing systemic side effects but limiting the approach to localized treatment
Key Findings
- •Gentamicin-impregnated PMMA beads achieved peak concentration of 27.9 µg/mL within 24 hours and maintained therapeutic levels (>2 µg/mL) for 9 days in synovial fluid
- •Treatment induced diffuse synovitis with elevated WBC count for 72 hours and increased synovial protein for 21 days in treated joints
- •Superficial cartilage erosion occurred in all treated joints despite no difference in cartilage glycosaminoglycan content between treated and control joints
- •No systemic absorption detected—gentamicin remained undetectable in plasma and control joints