Morphological and clinical aspects of heterotopic ossification in sports. A case study

Heterotopic ossification (HO) caused through sport injuries is a rare, clearly defined lesion. In a considerable number of cases, however, no adequate trauma can be remembered or otherwise established in the "sporting history". Differential diagnosis of this non-traumatic HO variant often presents many problems which may lead to the wrong diagnosis of sarcoma. We looked at 28 cases, in which in more than 50% a sarcoma was discussed as primary diagnosis. These difficulties arise mainly in cases where clinical features suggest a tumor, radiological changes are unspecific, and the diagnosis is based on a small biopsy sample. We demonstrate and discuss the problems involved in differential diagnosis using the history of a matchgrade sportsman as a sample. Unlike in sarcoma, patients with HO usually suffer severe pain, and well over 50% of all patients develop the disease during the 2nd or 3rd decade. Over 90% of all patients with soft tissue sarcoma, however, are over the age of 30. From the morphological point of view, the different histological pattern of HO has to be taken into account, since early stages may mimick a sarcomatous lesion. If the clinical findings suggest the presence of HO, surgical intervention including the taking of biopsy sample should be postponed, so that instead of early highly mitotic active phases more mature bone structures, which are easier to classify, will be available for evaluation. Only a profound knowledge of the different phases of HO, together with clinical and radiological features, will clarify the differential diagnostic problems of the non-traumatic variant of this lesion in sportsmen.