A biodegradable system of poly-D,L-dilactide releasing ciprofloxacin was
assessed in a Pseudomonas aeruginosa osteomyelitis model after
inoculation of the test pathogen into the left tibia of 76 New Zealand
White rabbits; 31 were controls (group A), and 45 were implanted with
the polymer at the infection site (group B). The rabbits were killed on
a weekly basis, and cancellous bone was harvested for histopathology and
for estimation of bacterial growth and the concentrations of
ciprofloxacin. Tibial X ray was performed immediately before the animals
were killed. The total number of fistulas with purulent discharge that
developed after inoculation of the pathogen was counted, and fistulas
with purulent discharge were found in 16 animals in group A (51.6%) and
3 animals in group B (6.7%) (P < 0.0001). The animals in group A had a
profound loss of body weight compared to the animals in group B. The
main radiological finding was the presence of sequestra in 25 animals
(80.6%) in group A and 6 animals in group B (13.3%) (P < 0.0001). The
bacterial load in group B was significantly reduced compared to that in
group A, possibly due to the prolonged local antibiotic release at
concentrations exceeding even 80 times the MIC for the test pathogen.
The histology of animals killed after week 49 revealed a mild
inflammatory reaction accompanied by difuse fibrosis and new bone
formation in group A animals and the presence of small polymer particles
in group B animals. It is concluded that the system described achieved
eradication of the pathogen, accompanied by clinical and radiologically
confirmed benefits, so this treatment may be a candidate for the
management of difficult orthopedic infections