The effect of implanting gentamicin-impregnated polymethylmethacrylate beads in the tarsocrural joint of the horse.
OBJECTIVE
To determine the effect of intra-articular gentamicin-impregnated polymethylmethacrylate (PMMA) beads inserted in the equine tarsocrural joint on the synovial fluid, synovial lining, and cartilage, and to determine the peak and sustainable gentamicin concentrations in synovial fluid and plasma.


METHODS
Pharmacokinetic, cytologic, and histologic study of the effect of gentamicin-impregnated PMMA on normal equine tarsocrural joints.


METHODS
Five healthy adult horses.


METHODS
Gentamicin-impregnated PMMA bead strands (3 strands each of 40 beads, with each strand containing 100 mg gentamicin) were surgically inserted into one radiographically normal tarsocrural joint in 5 horses. Each horse had both joints flushed with 1 L of lactated Ringer's solution before bead administration. Synovial fluid total protein concentration, white blood cell (WBC) count, gentamicin concentration, synovial histology, cartilage integrity, and cartilage glycosaminoglycan (GAG) concentrations were determined.


RESULTS
Gentamicin concentration (mean +/- SEM peak concentration, 27.9 +/- 2.27 microg/mL) occurred in the first 24 hours and remained above 2 microg/mL for 9 days. Gentamicin concentrations in control joints and the plasma remained below detectable levels. The synovial fluid WBC count for treated joints was increased compared with control joints for 72 hours, but was similar at day 6. The synovial protein concentration in gentamicin-treated joints remained increased for 21 days. Synovium in treated joints had diffuse synovitis, whereas control joints had less fibrovascular proliferation. Superficial cartilage erosion was present in all treated joints. There was no difference in the GAG content of treated and control joint cartilage.


CONCLUSIONS
Short-term implantation of gentamicin (300 mg)-impregnated PMMA beads can provide therapeutic levels of gentamicin (>2 microg/mL) in the normal tarsocrural joint for 9 days; however, gentamicin-impregnated PMMA beads induce synovitis and superficial cartilage erosion.


CONCLUSIONS
Temporary intra-articular administration of antibiotic-impregnated PMMA may be an effective way to treat septic joints that require constant high concentrations of antibiotics.
Marion duPont Scott Equine Medical Center and the Department of Pathology, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Tech, Leesburg, VA, USA.
K D
KD
Farnsworth
N A
NA
White
J
J
Robertson
D020341:Absorbable Implants / Q000662:veterinary; D000818:Animals; D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000494:pharmacology*; D005839:Gentamicins / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000494:pharmacology*; D006736:Horses / Q000378:metabolism* / Q000601:surgery; D007270:Injections, Intra-Articular / Q000662:veterinary; D008863:Microspheres; D019904:Polymethyl Methacrylate; D013582:Synovial Fluid / Q000187:drug effects / Q000378:metabolism; D013643:Tarsus, Animal / Q000187:drug effects*
D000900:Anti-Bacterial Agents; D005839:Gentamicins; D019904:Polymethyl Methacrylate