Myositis ossificans

Background
  • Also known as heterotopic calcification
  • Benign bone deposition within soft tissues, most often skeletal muscle.
  • Usually arises secondary to trauma (either one larger traumatic event or repeated small traumas) and will generally be localized to a single muscle or group of muscles involved in the trauma.[1][2]
    • Alternatively, can be generalized, widespread, progressive and unrelated to trauma - this is thought to be a hereditary form with a separate pathogenesis and treatment
  • Pathophysiology not completely understood - may be related to inappropriate differentiation of mesenchymal cells into chondrocytes and osteoblasts in the setting of trauma/inflammation[3]
Plain radiograph taken two months after injury demonstrates irregular calcification located along muscle on medial aspect of right thigh. Diagnosis was myositis ossificans

Clinical Features
  • Length of pain out of proportion to trauma
  • Decreased range of motion
  • Palpable, painful mass (generally forms within 2 weeks of initial trauma)

Differential Diagnosis

Extremity trauma

Evaluation
  • Plain radiograph showing peripheral soft tissue calcifications
    • Early radiographs may be non-diagnostic
  • Biopsy may be required if concern for malignancy, calcified peritendonitis/bursitis, etc[1][4]

Management
  • Generally self-limited disease process (may take up to 1 year to resolve)[1]
  • Supportive care, including pain control and physical therapy, is the mainstay of treatment

Disposition
  • Discharge with referral to orthopedic surgery or sports medicine[5]

See Also


References
  1. Walczak BE, et al. Myositis Ossificans. J Am Acad Orthop Surg. 2015;23(10):612-22.
  2. Ropper AH, et al. Chapter 48. Diseases of Muscle. In: Ropper AH, Samuels MA, Klein JP. eds. Adams & Victor's Principles of Neurology, 10e. New York, NY: McGraw-Hill; 2014.
  3. Kan L, et al. Dysregulation of local stem/progenitor cells as a common cellular mechanism for heterotopic ossification. Stem Calls. 2009;27(1):150-156.
  4. Trojian TH. Muscle contusion (thigh). Clin Sports Med. 2013 Apr;32(2):317-24.
  5. Tintinalli JE, et al. Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 8e. New York, NY: McGraw-Hill; 2016.
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