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

Brad M Isaacson,1,2 Thomas M Swanson,1,2,4 Benjamin K Potter,4 Paul F Pasquina2,3 1The Henry M Jackson Foundation for the Advancement of Military Medicine, 2The Center for Rehabilitation Sciences Research, Department of Physical Medicine and Rehabilitation, Uniformed Services University of Health Sciences, 3Department of Rehabilitation, Walter Reed National Military Medical Center, 4Department of Orthopaedics, Walter Reed National Military Medical Center, Bethesda, Maryland, USA Abstract: 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. Keywords: heterotopic ossification, osteogenesis, combat, trauma, ectopic bone, osteoprogenitor cells, Operation Iraqi Freedom, Operation Enduring Freedo