Heterotopic ossification: a systematic review

Heterotopic ossification (HO) is the formation of mature lamellar bone in extraskeletal soft tissues. It was first described 1000 years ago in the healing of fractures, and in relation to military wounds, texts from the American Civil War and World War I refer to HO specifically. It continues to cause problems to injured service personnel; the consequences of wound and soft tissue complications in traumatic amputations pose particular problems to rehabilitation and prosthetic use. While HO is seen in rare genetic conditions, it is most prevalent after joint replacement surgery and trauma. In the civilian setting HO has been commonly described in patients after traumatic brain injuries, spinal cord injuries and burns. Militarily, as a consequence of recent operations, and the characteristic injury of blast-related amputations, a renewed interest in HO has emerged due to an increased incidence seen in casualties. The heterogeneous nature of a blast related amputation makes it difficult for a single aetiological event to be identified, although it is now accepted that blast, amputation through the zone of injury, increased injury severity and associated brain injuries are significant risk factors in HO formation. The exact cellular event leading to HO has yet to be identified, and as a consequence its prevention is restricted to the use of anti-inflammatory medication and radiation, which is often contraindicated in the acute complex military casualty. A systematic review in PubMed and the Cochrane Database identified research articles related to HO to illustrate the military problem of HO and its management, current research concepts and experimental theories regarding HO. This also served as a gap analysis providing the researchers detail of any knowledge deficit in this field, in particular to the military aspects of HO; 637 out of 7891 articles initially identified that referenced HO were relevant to this review.