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Case of the Week 240

What's the most likely diagnosis?

  • 32 year-old in prior motor vehicle accident

  1. Osteosarcoma
  2. Paget's disease
  3. Healed Fracture
  4. Heterotopic ossification



4. Heterotopic ossification



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Heterotopic ossification

General considerations

  • Defined as the abnormal formation of true bone within extra-skeletal soft tissues
  • More common in males, especially following spinal cord injury, it is rare in young children
  • Formerly called myositis ossificans
    • That term has fallen out of favor because the condition is not always inflammatory and ossification occurs in soft tissues other than muscle
  • Strong association exists between HO and spinal cord or traumatic brain injury
    • About 20-30% of patients with neurologic deficits will develop HO, possibly higher with spinal cord injuries
  • It is also seen in burn patients, following surgery, and following blunt trauma such as horse riders may develop in the adductor muscles of the leg
  • There is an increased risk for HO in patients with Diffuse Idiopathic Skeletal Hyperostosis (DISH) and Paget’s Disease


  • Bone morphogenetic proteins may stimulate primitive stem cells in soft tissues to form osteoblasts under certain conditions
  • Following trauma, cartilage begins developing in soft tissues by 2nd week, with trabeculated bone appearing by 2-5 weeks

Clinical findings ...

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