Thallium-201 accumulation in myositis ossificans and in juxta-articular ossification.

We present the findings on 201Tl and 99mTc-MDP scintigraphy in three patients suffering from heterotopic ossification (two patients presenting with myositis ossificans and one patient presenting with juxta-articular ossification in combination with myositis ossificans). Since resection of the lesions has to be delayed until stabilization, 99mTc-MDP is often used as a parameter of lesional activity, although it is not optimal. For this clinical problem, we evaluated 201Tl scintigraphy as a marker of metabolic activity. In addition to the well-documented uptake of 99mTc-MDP, marked accumulation of 201Tl was observed in all heterotopic ossification sites. Hence, our results support the use of 201Tl scintigraphy in the therapeutic management and monitoring of conditions associated with ectopic ossification. On the other hand, although myositis ossificans is sometimes clinically, radiographically and even histologically confused with extraosseous osteogenic sarcoma, 201Tl accumulation may not be a helpful factor in the differential diagnosis due to the presence of tracer accumulation in both disorders.