AAOS Now

Published 10/1/2014
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CPT Christina Hylden, MD; LTC Anthony Johnson, MD; MAJ Jessica Rivera, MD

Casualty Sex Differences: A New Dilemma in Modern Warfare

War has evolved over the centuries—from the Greek Phalanx, the Roman Legion, and the British Cavalry to armored regiments, missile defense teams, and naval battalions. Projectile weaponry has advanced from arrows and muskets to high-powered rifles and missiles. War zones have moved from designated lines of conflict with highly visible opponents to guerilla tactics, drone attacks, and inconspicuous (but highly explosive) packages.

With the evolution of weaponry and fighting tactics—as well as the developments in medicine—came a change in the injuries and illnesses that wound and kill soldiers and civilians alike. In the American Civil War, soldiers were more likely to die of dysentery than direct conflict with the enemy. The most recent conflicts in Iraq and Afghanistan have shown casualty survival rates of greater than 90 percent. Advancements in body armor and medical care (both at point of injury and at local base hospitals) have enabled more service members to survive their initial wounds.

Musculoskeletal injuries are of particular interest. Because body armor protects the thorax and abdomen from life-threatening internal organ damage and tourniquets are more readily and expediently used, survival rates for individuals with severe extremity injuries have improved. Increased battlefield survival has led to a higher clinical burden of extremity trauma injuries.

Women in warfare
Women have been warriors throughout history as well (Table 1). Mythical tales of Amazons gave way to historical accounts of individual leaders such as Joan of Arc. Modern armies now include women among the ranks, treated as equals to their male counterparts.

Not only is the current U.S. military an all-volunteer force, but an increasing proportion is female. During the World Wars, the women closest to the front lines were nurses; today they are pilots, flight surgeons, and supply drivers. In 2013, Defense Secretary Leon Panetta lifted the ban on women serving in combat roles, resulting in women serving in front-line direct combat units such as infantry, armor, and artillery. The addition of women to the direct fighting force has an important impact on medicine, which should be acknowledged and studied.

Women are still a minority in the U.S. military. Among all active-duty personnel, 14.6 percent are female and 85.4 percent are male. Considering that females have not been assigned to front-line positions for most of the current conflicts, it can be expected that they account for an even smaller percentage of casualties. A recent review of the Department of Defense Trauma Registry (DoDTR) found that, over an 8-year span, 1.9 percent of all casualties and 2.4 percent of all deaths were female service members.

Despite these lower numbers, this study found that female casualties were more likely to die of their wounds compared to their male counterparts, even though the prevalence of injury severity was similar between the sexes. This also contrasts with civilian trauma literature, which generally shows better survival rates for females as compared to males with comparable injury severity.

Another retrospective analysis compared two cohorts (425 females and 14,982 males on the DoDTR who sustained musculoskeletal injuries from October 2003 to December 2012) for significance in demographics (age, service, rank, and military operation) and injury characteristics (injury severity score [ISS], abbreviated injury score [AIS], injury type, injury cause, and injury date).

Differences among military branches based on the demographics of the services were found. The Army, for example, had a higher proportion of injured females while the Marine Corps had a higher-than-expected proportion of injured males. Female casualties were slightly younger (mean age, 26.1 years) than males (mean age, 27.8 years).

Differences were also found in injury characteristics: females on average had more severely rated injuries, with combined ISS averaging 9.68 compared to the male average of 7.49. AIS specific to the skeletal anatomic body region were also statistically significant, with females averaging slightly higher scores (2.36 versus 2.06 for males).

Females were less likely than males to be injured in battle (33.1 percent versus 70.9 percent). For both sexes, the most common mechanism of injury during battle was explosive devices; the most common non–battle-related mechanism of injury was a fall. The second most common non–battle-related mechanism for females was a motor vehicle collision; for males, it was a machinery-related cause.

Females are a minority of the casualties in recent conflicts (2.75 percent during the studied time frame). They are also less likely to be involved in explosions or be injured during battle. Because recent research has often focused on casualties exposed to blast injury on the battlefield, the population of female casualties during deployment has received little attention.

The results of a recent retrospective query show that despite lower rates of battle-related and explosion-type injuries, female casualties have sustained higher ISSs. This is somewhat counterintuitive because explosion and battle injuries are expected to average higher severity scores. These data, in conjunction with previous evidence that the case fatality rate may be higher for females, raise questions about why female casualties are sustaining such severe injury patterns. Further investigation is required and being pursued.

To best treat our current and future military, we, as orthopaedic surgeons, must ensure that our research studies focus on all of our troops—both male and female. This is increasingly important as the number of females on the front lines or in direct danger from the enemy rises. As long as discrepancies in injury severity and casualty death rate between sexes exist, researchers must continue to pursue answers and investigate solutions.

CPT Christina Hylden, MD, and MAJ Jessica Rivera, MD, are orthopaedic surgeons at San Antonio Military Medical Center, Fort Sam Houston, Texas; LTC Anthony Johnson, MD, is a member of the AAOS Women’s Health Issues Advisory Board.

Putting sex in your orthopaedic practice
This quarterly column from the AAOS Women’s Health Issues Advisory Board and the Ruth Jackson Orthopaedic Society provides important information for your practice about issues related to sex (determined by our chromosomes) and gender (how we present ourselves as male or female, which can be influenced by environment, families and peers, and social institutions). It is our mission to promote the philosophy that male and female patients experience and react to musculoskeletal conditions differently; when it comes to patient care, surgeons should not have a one-size-fits-all mentality.

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