Thermographic evaluation of corticosteroid efficacy in amphotericin B-induced arthritis in ponies

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Abstract
SUMMARY: Thermographic evaluation of corticosteroid efficacy in amphotericin B-induced intercarpal and tibiotarsal arthritis was done in 12 ponies. Arthritis was induced in 8 joints by intra-articular injection of 10 mg of amphotericin B. Eight joints each were treated with intra-articular injection of 100 mg of methylprednisolone acetate before or after arthritis induction. AU joints were evaluated by physical examination, thermography, acid phosphatase activity in synovial fluid, radiography, and necropsy. Intra-articular corticosteroid therapy, either before or after arthritis induction, was effective in alleviating the clinical signs of lameness in comparison with the clinical signs of nontreated arthritis. It was difficult to distinguish increased thermal patterns between corticosteroid-treated and nontreated joints on days 1 and 2 after arthritis induction; therefore, it was important to correlate the physical findings and distribution of increased heat patterns. There was no significant difference (P > 0.05) in the return to normal thermographic patterns between any treated intercarpal joints; corticosteroid therapy did not decrease the healing time of intercarpal arthritis. In contrast, corticosteroid therapy, before or after arthritis induction in the tibiotarsal joint, significantly decreased (P < 0.05) the time for return to normal thermographic patterns. This apparent difference between the intercarpal and tibiotarsal joints was not explained. Acid phosphatase activity was highest and persisted longest in the synovial fluid of nontreated induced arthritis. Radiographic evidence of osteoarthritis was found in 3 of 8 nontreated cases of induced arthritis. Production of osteoarthritic changes by induced synovial inflammation supports previous evidence that chronic arthritis without articular fracture may cause degenerative joint disease in the equine species. Thermography was useful in detecting inflammation in the absence of clinical signs and aided the evaluation of the healing processes in amphotericin B-induced arthritis.