Kd. Farnsworth et al., The effect of implanting gentamicin-impregnated polymethylmethacrylate beads in the tarsocrural joint of the horse, VET SURGERY, 30(2), 2001, pp. 126-131
Objective-To determine the effect of intra-articular gentamicin-impregnated
polymethylmethacrylate (PMMA) beads inserted in the equine tarsocrural joi
nt on the synovial fluid, synovial lining, and cartilage, and to determine
the peak and sustainable gentamicin concentrations in synovial fluid and pl
asma.
Study Design-Pharmacokinetic, cytologic, and histologic study of the effect
of gentamicin-impregnated PMMA on normal equine tarsocrural joints.
Animals-Five healthy adult horses.
Methods-Gentamicin-impregnated PMMA bead strands (3 strands each of 40 bead
s, 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 cel
l (WBC) count, gentamicin concentration, synovial histology, cartilage inte
grity, and cartilage glycosaminoglycan (GAG) concentrations were determined
.
Results-Gentamicin concentration (mean +/- SEM peak concentration, 27.9 +/-
2.27 mug/mL) occurred in the first 24 hours and remained above 2 mug/mL fo
r 9 days. Gentamicin concentrations in control joints and the plasma remain
ed below detectable levels. The synovial fluid WBC count for treated joints
was increased compared with control joints fur 72 hours, but was similar a
t day 6. The synovial protein concentration in gentamicin-treated joints re
mained increased for 21 days. Synovium in treated joints had diffuse synovi
tis, whereas control joints had less fibrovascular proliferation. Superfici
al cartilage erosion was present in all treated joints. There was no differ
ence 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 mug/mL) in the norm
al tarsocrural joint for 9 days; however, gentamicin-impregnated PMMA beads
induce synovitis and superficial cartilage erosion.
Clinical Relevance-Temporary intra-articular administration of antibiotic-i
mpregnated PMMA may be an effective way to treat septic joints that require
constant high concentrations of antibiotics. (C) Copyright 2001 by The Ame
rican College of Veterinary Surgeons.