Heterotopic ossification in wartime wounds

Heterotopic ossification (HO) refers to the formation of mature lamellar bone in nonosseous tissue. In the setting of high-energy wartime extremity wounds, HO is expected to complicate up to 64% of patients, has a predilection for the residual limbs of amputees, and remains a significant source of disability. Although the inciting events and the definitive cell(s) of origin continue to remain elusive, animal models and human histology samples suggest that HO formation follows a predictable sequence of events culminating in endochondral ossification. Primary prophylaxis is not medically or logistically practical in most cases because patients have generally sustained massive wounds and are undergoing serial debridements during an intercontinental aeromedical evacuation. Surgical excision of symptomatic lesions is warranted only after an appropriate trial of conservative measures and is associated with low recurrence rates in appropriately selected patients. Future research regarding prognostication and defining the early molecular biology of ectopic bone may permit individualized prophylaxis and development of novel targeted therapies.