Non-traumatic myositis ossificans of the thigh. A case report.

Introduction: Myositis ossificans (MO) is an ectopic ossification characterized by an appearance of bone formation predominantly in muscle tissue. Trauma is the most common etiological factor, observed in almost 60-75% of cases, whereas a non-traumatic MO is rarely described in the literature. A diagnosis is based on clinical and radiological findings.

Presentation Of Case: A 75-year old female patient has been admitted to our clinic with a localized swelling of the posterior femoral compartment, presented on magnetic resonance as a calcification in the biceps femoris muscle. Laboratory test results were within the normal range. Surgical procedure consisted of excision of the tumor mass with primary wound reconstruction and drainage. The post-operative period was uneventful, and the patient was discharged from hospital on the seventh postoperative day. The pathohistology findings have shown the MO.

Discussion: A non-traumatic MO is scarcely described in the literature. A chronic microtrauma, tissue ischaemia and inflammation are listed as causal mechanisms of a non-traumatic MO. MO non-traumatica occurs more often in patients with a parallel, subdural or epidural haemorrhage and a hip surgery. Our case did not present any family history, trauma or associated anomalies of hands or fingers.

Conclusion: Myositis ossificans should be considered as the differential diagnosis of all soft tissue tumor masses, even if known risk factors are not present in the anamnesis. Surgery is a reasonable therapeutic strategy in the presence of a tumor mass in soft tissues, and definite diagnosis can be set only based on pathohistological findings.

Key Words: Ectopic ossification, Non traumatic myositis, Surgery.