Mechanisms involved in mandibular condylopathy secondary to intraarticular injections of glucocorticoids.

Pharmacologic doses of triamcinolone hexacetonide were injected intramuscularly or intraarticularly in immature Papio papio baboons. The mandibular condyle served as a model for histologic examinations concerning the effect of glucocorticoid hormone on cartilage and bone. Biochemical examinations of blood and urine indicated the development of distinct hypophosphatemia, hypercalcemia followed by hyperphosphaturia, and hypocalciuria. Serum alkaline phosphatase activity rose during the initial phases of the experiment but decreased considerably after the sixth injection of the hormone. Hyperglycemia and an increase in serum amylase were noticed along with signs of moderate metabolic acidosis. Histologic examinations disclosed signs of severe destruction of cartilage and bone. By the sixth intraarticular injection, definite fibrillation was noted in the articular cartilage, followed by complete disappearance of cartilage. The subchondral bone appeared to be adversely affected by the hormone as it lost its typical lamellar organization and attained the characteristics of woven bone. The condyle showed clear signs of fibro-osseous transformation, with fibrosis as the dominant structural feature. The preceding biochemical and morphologic findings are indicative of parathyroid hyperactivity.