1. MSK Case Presentation David Stone May 22, 2008

2. 19 yo Lacrosse Player ~2 weeks ago, he was hit in his quadricep with a lacrosse stick. –Initial injury has improved some, but are has remained tender. –He returned to the field after 5 days. Presents with pain, tenderness, warmth, focal swelling of his thigh. New Development: He can palpate a new “lump” in the leg.

4. Myositis Ossificans Heterotopic bone formation in muscle in the setting of trauma. Injury: Compression of muscle tissue against underlying bone with injury to the muscle, blood vessels, and periostium. Seen radiographically about 2-4 weeks after initial hematoma.

5. Myositis Ossificans Bone will begin to grow 2-4 weeks after the injury and mature bone will be seen by 3-6 months. Most common in athletic adults in the 2 nd or 3 rd decade Usually in the setting of trauma. Most common locations: Quadriceps, Brachialis, Deltoid.

6. Myositis Ossificans Why do some develop this lesion? –Not applying ice and compression immediately after the injury. –Intensive physiotherapy, massage, or heat too soon after the injury. –Returning to play too soon after injury.

7. Major Differential Diagnosis Osteosarcoma –Sunburst Appearance

9. Radiological Comparison Myositis ossificans –Calcification begins at the periphery and progresses toward the center. –Radiographic stabilization or improvement at 3 to 4 months Osteosarcoma –Calcification begins at the center and progresses to the periphery. –Continued radiographic growth

11. Clinical Comparison Myositis Ossificans is favored with: –History of trauma to the affected site –Clinical improvement at 3 to 4 months Most Important: Pain lessens with time Pain with osteosarcoma is progressive and unrelenting.

12. Myositis Ossificans Treatment: Conservative –Rest, Immobilization, Ice Things that decrease initial hematoma Will usually resolve on its own –Surgery: Rarely indicated Only if it interferes with joint movement or it irritates a nerve. Usually wait 12 months for lesion to mature as shown by bone scan. If removed before mature, it will likely recur

13. References Essentials of Physical Medicine and Rehabilitation, 1 st edition DeLee and Drez’s Orthopedic Sports Medicine, 2 nd edition www.bonetumor.org