Myositis ossificans in children: a review

The formation of lamellar bone in the soft tissues, where bone normally does not exist, is called myositis ossificans. However, it would be more accurate to describe as myositis ossificans the involvement of skeletal muscles and as ectopic or heterotopic ossification the involvement of soft tissues in general. The lesion is subdivided in genetic and non-genetic or acquired types. Myositis or fibrodysplasia ossificans progressiva is a debilitating rare genetic disorder. Clinical suspicion of the disease in the newborn on the basis of malformed great toes may lead to early clinical diagnosis, confirmatory diagnostic genetic testing and avoidance of iatrogenic harmful procedures. Acquired lesions involve the neurogenic myositis ossificans and the non-neurogenic disorder. The latter is defined either as circumscribed myositis ossificans that is post-traumatic or as idiopathic/pseudomalignant myositis ossificans that is non-traumatic and may be a form fruste of fibrodysplasia ossificans progressiva. Ossification in fibrodysplasia ossificans progressiva is irreversible, unlike other forms of heterotopic ossification. In this retrospective study, a total of 22 children with myositis ossificans treated in a 20-year period were identified and classified. Two patients were diagnosed with myositis/fibrodysplasia ossificans progressiva, one with neurogenic myositis ossificans, one with idiopathic/pseudomalignant myositis ossificans and 18 patients with circumscribed myositis ossificans. The clinical features, imaging and histological findings as well as treatment modalities and complications of myositis ossificans in our patients are presented and discussed.