Experimental induction of rheumatoid arthritis in temporomandibular joint of the guinea pig: a clinical and radiographic study

Objective: To correlate the clinical and radiographic changes at different stages of experimentally-induced rheumatoid arthritis (RA) of the TMJ. Methods: Forty eight adult male guinea pigs, aged 4-6 months, were divided into two groups. Arthritis was induced in the experimental animals by intraperitoneal injection of heat-inactivated group A Streptococcus pyogenes. Four animals from each group were sacrificed and examined clinically and radiographically at intervals of 48 h and 1, 2, 4, 6 and 8 weeks. Results: The main clinical findings were stiffness, crepitation and reduction in mouth opening. Radiographically, the main features were condylar erosion, flattening and sclerosis subcortical cyst formation. Conclusion: RA passes through stages that can be correlated clinically and radiographically. Both the clinical and radiographic manifestations in this experimental model are comparable with those previously reported in the small joints of humans.