Myositis Ossificans in the Lumbar Spine: A Case Report

Abstract

Objective: Relatively rare case.
Background: Myositis ossificans is a benign condition which appears as a heterotopic, well defined bone formation in muscles and soft tissues. It is most common in children and young athletes. Most myositis ossificans occur in the large muscles of proximal extremities such as the quadriceps and brachialis and it is rare to occur in the lumber spine.
Case Report: We present a case of a 12 year-old Japanese boy with severe lower back pain. On physical examination, a severe tenderness and swelling was present in the left lumbar region, at level of L4/5. He had a traumatic history of his back. He hit nunchak (one of tools of Chinese martial arts) on the back when he was practicing it at school three months ago. Both lumbar radiograph and lumbar Computed Tomography (CT) examination showed a ring like osteoblastic lesion calcification around left facet joint of L4/5 suggestive of myositis ossificans. He received conservative treatment. His back pain and swelling disappeared in 2 months. Follow up lumbar CT examination 8 months later showed the osteoblastic lesion calcification was more prominent than the one in the previous CT. Soft tissue swelling around the osteoblastic calcific area was not detected.
Conclusion: This case was unusual location for myositis ossificans. Careful correlation of the clinical and radiological findings is necessary to avoid surgical treatment.