The Military Athlete

Introduction

While the military generally represents a young, athletic population, it is distinct in many ways. Functional outcomes are different when compared to the civilian population, largely because the definition of success and the functional demands of the soldier are unique. To better understand this, one must first recognize what the military does. Simply stated, the purpose of the military is to protect the nation and win wars. However, with a military that is spread across the world and has been at war for the past 16 years, the demands placed on soldiers, sailors, marines, and airmen are unparalleled in the civilian population. The US military is an all-volunteer force that only comprises 0.4% of the American population, yet we place great demands on these select few, which can inherently lead to increased physical strain and eventual musculoskeletal injury.

The armed forces represent a highly active population with strenuous occupational demands. The routine physical fitness and rigorous combat training mirrors that of an athletic population. Musculoskeletal injuries are exceedingly common and often present as either traumatic in nature or the result of overuse injuries. Overuse injuries are seen most commonly during initial entry training into the military, as well as in the later stages of a military career. In fact, it is estimated that 25% of males and 50% of females sustain a physical training injury during basic training, with the vast majority being overuse injuries.

Musculoskeletal injuries continue to place a huge burden on our military force. They are the leading cause of lost work time and disability leading to medical separation. The reason these injuries are so prevalent is multifactorial. There has been much speculation regarding the effect of the combat load that soldiers carry and its effect on overuse injuries. Over the past two decades, the average external load carried by a soldier has increased to roughly 100 pounds ( Fig. 26.1 ). This is often carried in austere environments with uneven terrain, and potentially while maneuvering under enemy fire. Biomechanical changes in gait patterns have been documented with these increased loads, to include increased step rate, decreased stride length, and forward trunk lean. With a concomitant rise in lower extremity overuse injuries, it is reasonable to infer a detrimental effect of these increased external loads. However, roughly 75% of musculoskeletal injuries can be attributed to physical training and sports-related activities. These nonbattle injuries remain the leading cause of evacuation from Iraq and Afghanistan.

The other unique aspect of the military athlete is that of functional outcome. Historically, the outcomes within military populations do not mirror those of the civilian population. In general, the military athlete is required to do more in less time. There are strict physical fitness requirements tested on an annual or biannual basis. Each of the services (Army, Air Force, Navy, Marines) has different requirements and frequency, all testing strength, endurance, and agility. The Air Force and Navy require a passing score in a 1.5-mile timed run, timed push-ups, and timed sit-ups. The Navy can select a 500-meter swim as a test of endurance instead of the 1.5-mile run. The Army requires a passing score in a 2-mile timed run, timed push-ups, and timed sit-ups. The most strenuous, the Marine Corps requires a passing score in a 3-mile timed run, timed crunches, and pull-ups/dead arm hang for males/females. The Marines also employ a combat fitness test (CFT) that evaluates simulated combat conditions with sprinting, lifting, and agility testing. Furthermore, soldiers in combat arms branches, as well as elite units and special forces operators from each of the units, have even greater physical demands and requirements. Most units require daily physical training, usually in small groups. If a service member is injured, they typically have a year to recover before the medical separation process begins. Military outcomes focus predominantly on the ability to return to full duty in this finite period of time.

The focus of this chapter will be injuries sustained about the foot and ankle of our military service members. This will include the prevalence of these injuries and their outcomes. Ultimately, the goal will be to have a better understanding of the impact of these injuries on our military forces and how they differ from a young, active population.

Ankle Sprains and Instability

Ankle sprains are one of the most common athletic injuries and account for nearly half of all sport-related injuries. The incidence rates (IR) of ankle sprains in the general population range between 5–7 per 1000 person-years. Yet, the IR in the military is much higher. One study reported the IR of ankle sprains among service members at 34.95 per 1000 person-years, while a second study examining cadets at the United States Military Academy reported an IR of 58.4 per 1000 person-years.

These disparities are likely explained in part by the fact that the military represents an athletic population that has an increased exposure to at-risk activities. In fact, cadets with higher levels of fitness and those that participated in intercollegiate athletics were more likely to sustain an ankle sprain. While there is no correlation between length of service and an isolated ankle sprain, those with recurrent ankle sprains and instability tend to have shorter service times when compared to those who do not sustain an ankle sprain.

While 95% of these service members are able to return to sports and physical training within 6 weeks of injury, nearly half will still have residual pain at 6 months postinjury. Furthermore, the average rehabilitative period following an ankle sprain is 40 days, creating a significant burden on force readiness. Even with appropriate functional rehabilitation, 10% to 30% will develop chronic ankle instability and possibly require surgery. Because of the prevalence of these ankle injuries, the Department of Defense recommends the use of a semirigid ankle brace when participating in high-risk physical activity. However, outside of parachuting, there is little evidence to suggest a protective benefit of prophylactic bracing in the military population.

Those who develop chronic instability refractory to physical therapy undergo a lateral ligament reconstruction with concomitant procedures performed as necessary. In our practice, we have found that the Broström-Gould–type ankle reconstruction (advancement of the ankle capsule and contained ligaments, augmenting with the inferior peroneal retinaculum) provides adequate stability without sacrificing sub-talar joint mobility and range of motion. In selected cases where there is inadequate soft tissue for reconstruction, or the patient has failed a prior Broström-Gould reconstruction, nonanatomic reconstructions are utilized. We favor the modified Broström-Evans described by Anderson for revision cases, as the ankle capsule and soft tissues can be repaired again and augmented with good outcomes. In cases where there is not sufficient ankle capsule or soft-tissue we recommend augmentation with an allograft tendon (semitendinosis) with a modified Chrisman-Snook. One study on the long-term outcomes of athletes undergoing ligament reconstruction demonstrated that 58% were able to return to their pre-injury level of sport, 16% were able to compete at a lower level, and the other 26% discontinued sport but were still able to remain physically active.

Fractures

Foot and ankle fractures are common in the military, second only to hand fractures. These present as either acute fractures or chronic stress fractures. Within the military, fractures account for 40% of injury-associated hospitalizations and 26% of combat injuries. Orr et al. demonstrated that 83% of service members undergoing operative fixation for an ankle fracture were able to remain on active duty. However, at 3 years postsurgery, 36% were unable to return to the required level of running and 17% were medically separated. This seems to coincide with civilian outcomes, which demonstrate roughly 50% of patients have pain, stiffness, and swelling at 1-year postsurgery. Additionally, only 25% of patients were able to return to sports at 1 year following surgery.

Stress fractures, on the other hand, continue to be one of the leading causes of injury in new military recruits. The incidence of lower extremity stress fracture for initial-entry military training is 0.8% to 6.9% for males and 3.4% to 21% for females. Prevention of overtraining, particularly in new recruits with lower baseline fitness levels, has proven effective in reducing the incidence of stress fractures. In fact, the military has decreased the number of stress fractures by 40% in the past 15 years by implementing modified physical training plans aimed at gradual progression of activity and appropriate cross-training to reduce repetitive stress. Nonetheless, stress fractures continue to result in significant morbidity and often require long recovery periods. Adequate nutrition is critical to ensure balance between energy intake and expenditure. Calcium and vitamin D supplementation can be both protective and therapeutic. Female Navy recruits placed on calcium and vitamin D therapy had a 20% lower incidence of stress fractures.

Metatarsal stress fractures account for 16% of all stress fractures. First described in Prussian soldiers in 1855, they were initially named march fractures. Increased marching and running in minimalist footwear without a gradual transition are both risk factors for metatarsal stress fractures. The majority of the fractures can be managed with modified activity and weight bearing in a fracture boot. If pain persists, then a period of nonweight bearing may be necessary. The one exception is the fifth metatarsal stress fracture. Given the high nonunion rate, fifth metatarsal stress fractures are often treated with intramedullary screw fixation, with or without supplemental bone grafting.