Tourniquet use in combat-injured service members: A link with heterotopic ossification?

Tourniquet use during Operation Enduring Freedom (OEF) and Operation Iraqi Free­dom (OIF) has contributed to the high survival rate of combat-injured service members. While preservation of a life – even at the potential expense of a limb – should always take precedence, delayed perfusion in traumatized residual limbs may alter the proliferation, differentiation, and function of endothelial and osteoprogenitor cells. Given the synergistic relationship between angiogenesis and osteogenesis, and the influence of environmental conditions on bone formation, hypoxic conditions from tourniquets may in part explain the higher frequency of heterotopic ossification (HO) present during OIF/OEF. Determining a correlation between tourniquet usage/duration on subsequent HO formation remains challenging. Long-term retrospective investiga­tions have been limited, since the United States Army’s Institute of Surgical Research did not standardized tourniquet issuance until July 2004. Thus, associating tourniquet-induced HO in previous military conflicts is not feasible, since poor medical documentation and inadequate application of these medical devices prevent large-scale meta-analyses. Therefore, this article focuses on the basics of bone biology and how tourniquet usage following combat trauma may impact osteogenesis, and subsequently, ectopic bone formation.