Correlation between ossification and inflammation using a rat experimental model.

In seronegative spondylarthropathies both inflammation and ossification can be demonstrated. Inflammation is a hallmark of diseases associated with antigen HLA-B27 in ankylosing spondylitis, Reiter's syndrome, and acute uveitis. Ossification is traditionally considered the end product of inflammation, but clinical examination does not show that this is always the case in man. The relationship between inflammation and ossification is not demonstrated in experiments on spinal involvement in adjuvant arthritis in the rat. Using that experimental model, we tested the efficacy of 3 nonsteroidal antiinflammatory drugs (indomethacin, naproxen, and phenylbutazone) given at dosages comparable to those employed in clinical practice, but at a lower level than those used by drug companies in animals. Results show that the drug exhibiting almost no antiinflammatory activity in the rat at the dosage used, phenylbutazone, was the most powerful inhibitor of ossification. Another mechanism of local osteogenesis must be sought to explain such a phenomenon.