Heterotopic Ossification

The term heterotopic ossification (HO) refers to the formation of mature lamellar bone in nonosseous tissue. Crudely translated, HO literally refers to bone formation in other location. In the civilian setting, HO is usually associated with severe systemic inflammation stemming from spinal cord injury, traumatic brain injury, or neoplasm.^1-9 HO also complicates the wounds of total hip arthroplasty, as well as fractures of the acetabulum and elbow, particularly those requiring operative fixation. This implies a relationship between HO and muscle trauma, whether due to high-energy injury or operative dissection.^10-25 Genetic causes of heterotopic bone formation include fibrodysplasia ossificans progressiva and progressive osseous heteroplasia.^26-28 Although both proven risk factors and genetic predispositions exist, the underlying cause(s) of HO is largely unknown, and the entity itself remains a source of limb pain, stiffness, and subsequent disability.