Stress Fracture Implications within the IET Environment

Stress fractures, also known as march or fatigue fractures, have been a recognized hazard of military training since their initial description by a Prussian military physician in 1855.1 These fractures can be serious and life-altering injuries and significantly impair the efficiency of initial entry training (IET) centers throughout the Army. The high-incident rate among military recruits stifles military medical facilities and imposes a substantial increase in medical costs. Problems associated with stress fractures within the U. S. Army Training and Doctrine Command (TRADOC) were identified as early as 1974, when a medical survey of all TRADOC basic training centers revealed that 4.8 percent of all trainees sought medical care for stress injuries of bones.2 Similar data was recently collected from the 194th Armored Brigade (then the 1st Armor Training Brigade), at Fort Knox, Kentucky, in February 2007. Interestingly, this data also revealed a 4.8 percent incident rate for stress fractures. Although very prevalent in military populations, stress fractures occur much less frequently among civilian populations of athletes and are often misdiagnosed due to their infrequency. Basic Science of Stress Fractures To understand the etiology of stress fractures, one must understand the concept of mechanical stress. Stress is actually an engineering term that describes the internal force per unit area which apart of a body on one side of a plane exerts on that part of the body on the other side of the plane.3 Simply defined, stress is the force per unit area of a load-bearing structure. Relating this to bone, stress is produced in a bone whenever the bone is subjected to a loading force such as running, walking, or even standing.4 As a result of stress, bone will strain or change dimensions. When this stress reaches a critical level, the bone will be damaged. This most often occurs when soldiers go from a period of less physical activity, such as a sedentary lifestyle at home, to the physically demanding environment of IET. If the rate of damage exceeds the body’s ability to heal the bone, then it will eventually fracture. This can happen as quickly as a few days, but it is very important to note that stress fractures most often occur during weeks 1 and 2 of IET. Common Sites of Stress Fractures The long bones of the feet (metatarsals) are the most commonly reported location of incidence in scientific literature, followed by the shin bone (tibial shaft), the heel bone (calcaneous), the knee (tibial plateaus), and the hip (femoral neck). In the 194th Armored Brigade, based on unpublished data collected from the 46th Adjutant General (Reception) Battalion, the knee (medial tibial plateau) appears to be the most common site for stress fractures. It is currently unclear why the knee is the most common site among recruits in the 194th Armored Brigade. Diagnosing Stress Fractures When a soldier is first seen at sick call and has a physical exam consistent with stress fracture pathology, medical providers will most commonly order an x-ray. An x-ray is quick and relatively inexpensive; however, stress fractures appear on x-rays only 15 percent of the time, due to low sensitivity of the test to pick up this type of pathology in its early stages. If the x-ray reads “normal,” but the medical provider still has a high suspicion of possible stress fracture, they will order a bone scan. Bone scans are considered the “gold standard” for evaluating stress fractures, based on the equipment’s ability to demonstrate subtle changes in bone breakdown long before they are visible on plain radiography. The bone scan is performed in the nuclear medicine department and is conducted by injecting the patient with a radiopharmaceutical (technetium-99m). This substance circulates through the body and is absorbed at sites where there is bone trauma such as a stress fracture. The degree of absorption is determined by how badly the bone is damaged and can be measured by using the bone scan machine. Very focal uptakes of the radio-pharmaceutical indicate a stress fracture, which is a more serious injury, where less intense uptake represents a “pre-fracture” or stress reaction. Areas of stress reaction have been shown to heal more quickly than stress fractures. Common Misconceptions about Stress Fractures There are several prevalent misconceptions concerning stress fractures. One misconception is that stress fractures are not serious injuries, but in fact, if they occur within the tibial plateau of the knee, or in the femoral neck of the femur, they can cause devastating injuries requiring surgery and long rehabilitation. Another misconception is that stress fractures are the same as shin splints. In actuality, these are two different injuries. Shin splints are irritation to the outer coating of the bone, called the periostium, where various muscles of the lower extremity attach along the shaft of the tibia or shin bone. Stress fractures are actual breaks in the bone caused by overloading or overusing the bone. Intrinsic and Extrinsic Risk Factors for Developing Stress Fractures Based on studies at Fort Jackson, South Carolina, conducted by the Center of Health Promotion and Preventive Medicine (CHPPM), there are several intrinsic risk factors in developing stress fractures.5 Intrinsic factors are those factors that we have very little influence on because they are of the very nature of the soldiers coming to us. These include very low body mass index, poor previous level of physical fitness, smoking, and poor flexibility. Based on unpublished data gathered from the 46th Adjutant General “Extrinsic risk factors for stress fractures are extraneous and are imposed by the rigors of the IET environment; however, unlike intrinsic risk factors many of these can be modified. Extrinsic risk factors include stand ing for long periods of time, inadequate amounts of rest, running too much and too soon, and wearing boots for an extended time.” — 41

Battalion, it was found that soldiers who score poorly on push ups, coupled with a poor run time during the initial modified Army Physical Fitness Test, were also most susceptible to developing stress fractures during IET.6 Extrinsic risk factors for stress fractures are extraneous and are imposed by the rigors of the IET environment; however, unlike intrinsic risk factors many of these can be modified. Extrinsic risk factors include standing for long periods of time, inadequate amounts of rest, running too much and too soon, and wearing boots for an extended time. Healing Time for Stress Fractures Healing time for stress fractures depend on several factors, including the soldier’sage and the severity and location of the stress fracture. A stress fracture involving the long bones of the feet (metatarsals) typically take 4 to 6 weeks to heal. Stress fractures involving the long bones of the thigh (femur) or shin (tibia) take 8 to 12 weeks to heal. Fractures involving the tibial plateau and femoral neck are more devastating and take 4 months or longer to heal. Effect of Stress Fractures on Training Soldiers who are diagnosed with stress fractures and are experiencing pain too severe to continue training are sent to the Figure 1. Hip arterial supply. The susceptible artery (medial femoral circumflex artery) is indicated. Physical Training and Rehabilitation Program (PTRP) where they are placed into a more conducive healing environment. Here, they perform injury rehabilitation and have a more flexible schedule to see physical therapists and other health care providers. Currently, the average length of stay in the PTRP for a stress fracture is 137 days. It is also important to note that only 30 percent of soldiers with stress fractures return to duty from the PTRP, which is a reflection on the extensive amount of time and difficulty in the rehabilitation and treatment of these injuries. Femoral Neck Stress Fractures Stress fractures that involve the anatomical neck of the femur bone, near the hip, are serious and potentially devastating injuries that can have life-altering consequences. The incident rate among soldiers in IET environments is unknown; however, over the past year there have been six soldiers identified with this injury. This injury, if not detected early in the disease process, is considered a medical emergency and usually requires the femur bone to be pinned at the hip. The injury is very significant because of the vascular anatomy. Anatomically, there is only one artery (see in Figure 1) that feeds the femoral head, which becomes easily compromised when there is a stress fracture through this region. Once the arterial supply has been compromised, the bone is highly susceptible to vascular necrosis, or bone death. Treating a femoral neck stress fracture consists of surgically pinning the femoral neck with surgical hardware by an orthopedic surgeon (See Figure 2). Recovery and rehabilitation for this injury is very long and arduous and can result in permanent disability for the soldier. Symptoms for a femoral neck stress fracture usually consist of a deep dull ache in the groin, usually not palpable, that can refer pain down the anterior portion of the thigh to the knee. A soldier with a femoral neck stress fracture will usually have a noticeable limp and is aware that the injury worsens with prolonged standing or marching. A soldier with these symptoms should be immediately referred to the troop medical clinic for further examination by a medical provider. 42 — Figure 2. Radiographs of soldier with a femoral neck stress fracture after surgical procedure by orthopedic surgeon. Femoral Neck of Femur Surgical Hardware Acetabulum Anatomical Neck of Femur Susceptible Artery

Preventing Stress Fractures It is important for leaders, drill sergeants, and cadre members in IET environments to understand and recognize that stress fractures are a result of a cumulative overuse effect of standing, marching, and running in the early phases of IET. They are not typically caused by one specific training event. Overuse, coupled with the inherent intrinsic risk factors that soldiers have, make stress factors the most common injury in training environments. It is imperative that we all look for ways to improve how we train, especially during weeks 1 and 2, so we can help lower the incident rate of stress fractures. Detecting the injury early, before it develops into a full-blown fracture, improves chances for a full recovery. It is recommended that leaders monitor each company during the first few weeks of IET to ensure extrinsic risk factors are controlled, but at the same time, not compromise tough, challenging training. Stress fractures are the most common orthopedic injury seen among IET soldiers. They are significant and serious injuries that require long healing times and extensive rehabilitation, and based on recent studies, are the number one reason soldiers are medically discharged from the 194th Armored Brigade. Prevention and mitigation are possible through an understanding and knowledge of what encompasses these injuries. Action is needed to help identify and reduce extrinsic risk factors that are occurring during weeks 1 and 2 of IET training. Notes 1T. J. Scully and G. Besterman, “Stress fracture—a Preventable Injury,” Military Medicine, 147, 1982, pp. 285-287; and J. Breithaupt, “Zur Pathologies des Menschilichen Fusses,“ Med Zeitun, 24, 1855, pp. 169-171. 2Unpublished data report at Annual Meeting, Society of Military Orthopedic Surgeons, El Paso, TX, 1973. 3Scully and Besterman. 4G. Lease and F. Evans, “Strength of Human Metatarsal Bones under Repetitive Loading,” Journal of Applied Physiology, 14, 1959, pp. 49-51. 5B. H. Jones, Body Composition and Physical Performance, National Academy Press, 1992, pp. 141-173; B. H. Jones, USARIEM Army Technical Report T19-88, Natick, MA, 1988; and B. H. Jones, et al, “Epidemiology of Injuries Associated with Physical Training among Young Men in the Army,” Medicine and Science in Sports and Exercise, 25(2), 1993, pp. 197-203. 6A. K Brenner, Unpublished data report at the 10th Annual Armed Forces Health Protection Conference, Louisville, KY, 2007. Major Alex Brenner is currently serving as commander, B Company, Physical Training and Rehabilitation Program (PTRP), 46th Adjutant General (Reception), Fort Knox, KY. He received a B. S. from the University of Tampa, and an M. S. from Baylor University. He has served in various command and staff positions, to include chief, Physical Therapy, U. S. Army Health Clinic, Vicenza, Italy; assistant chief, Physical Therapy, Ireland Army Hospital, Fort Knox, KY; platoon leader, 50th Medical Air Ambulance Company, Fort Campbell, KY; and platoon leader, C Company, 426th Forward Support Battalion, Fort Campbell. “It is important for leaders, drill sergeants, and cadre members in IET environments to understand and recognize that stress fractures are a result of a cumulative overuse effect of standing, marching, and running in the early phases of IET. They are not typically caused by one specific training event. Overuse, coupled with the inherent intrinsic risk factors that soldiers have, make stress factors the most common injury in training environments.” — 43