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

Answer:

 

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

Pathophysiology

• 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 2^nd week, with trabeculated bone appearing by 2-5 weeks

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