A Review Paper Bone Stress Injuries in the Military: Diagnosis, Management, and Prevention Steven F. DeFroda, MD, MEng, Kenneth L. Cameron, PhD, MPH, ATC, Matthew Posner, MD, Peter K. Kriz, MD, and Brett D. Owens, MD Abstract Bone stress injuries occur when forces with radiographs alone. Making the correct di- applied to a bone for an extended period agnosis may require a combination of physical exceed the ability of the bone to adequately examination, advanced imaging, and an index remodel. These injuries, which range from of suspicion. Differences in injury location stress reactions to nondisplaced and even account for variations in risk for nonunion, displaced fractures, most often affect people displacement, and other complications. For who experience high levels of repetitive low-risk injuries, treatment typically consists of stress and loading in the lower extremity reduced weight-bearing for several weeks with or changes in physical activity level. For gradual return to activity. Higher-risk injuries example, stress fractures are common in need to be closely monitored for progression endurance athletes, in athletes engaged in and may require operative intervention. Even preseason and early-season conditioning, after surgery, some types of stress fractures and in military recruits. In the military, these may take several months to achieve radio- injuries are most often encountered during graphic union. In addition, underlying nutri- basic training, when new recruits undergo tional or metabolic deficiencies may need to the rigors of intense physical activity to be treated to prevent future injuries. which they may not be accustomed. Female In this article, we review the diagnosis, athletes and athletes with poor nutritional management, and prevention of bone stress status are at elevated risk for injury. injuries with a focus on more serious mani- Bone stress injuries are difficult to diagnose festations, such as stress fracture. one stress injuries, which are common in lower extremity loading, stress fractures typically military recruits, present in weight-bearing occur in the pelvis, femoral neck, tibial shaft, and B(WB) areas as indolent pain caused by metatarsals. Delayed diagnosis and the subse- repetitive stress and microtrauma. They were first quent duration of treatment required for adequate reported in the metatarsals of Prussian soldiers healing can result in significant morbidity. In a in 1855.1 Today, stress injuries are increasingly 2009 to 2012 study of US military members, Wa- common. One study estimated they account for terman and colleagues6 found an incidence rate 10% of patients seen by sports medicine practi- of 5.69 stress fractures per 1000 person-years. tioners.2 This injury most commonly affects mili- Fractures most frequently involved the tibia/ tary members, endurance athletes, and dancers.3-5 fibula (2.26/1000), followed by the metatarsals Specifically, the incidence of stress fractures in (0.92/1000) and the femoral neck (0.49/1000).6 military members has been reported to range In addition, these injuries were most commonly from 0.8% to 6.9% for men and from 3.4% to encountered in new recruits, who were less 21.0% for women.4 Because of repetitive vigorous accustomed to the high-volume, high-intensity Authors’ Disclosure Statement: The authors report no actual or potential conflict of interest in relation to this article. 176 The American Journal of Orthopedics ® July/August 2017 www.amjorthopedics.com S. F. DeFroda et al training required during basic training.4,7 Enlisted by a patient’s overall physiologic junior service members have been reported to ac- imbalance. Take-Home Points count for 77.5% of all stress fractures.6 Age under ◾ Stress injuries, specifical- 20 years or over 40 years and white race have also Diagnosis ly of the lower extremity, been found to be risk factors for stress injury.6 History and Physical Examination are very common in new The pathogenesis of stress injury is controver- The onset of stress reaction military trainees. sial. Stanitski and colleagues8 theorized that multi- typically is insidious, with the ◾ Stress injury can range ple submaximal mechanical insults create cumula- classic presentation being a new from benign periosteal tive stress greater than bone capacity, eventually military recruit who is experiencing reaction to displaced leading to fracture. Johnson9 conducted a biopsy a sudden increase in pain during fracture. study and postulated that an accelerated remodel- physical activity.15 Pain typically is ◾ Stress injury should be ing phase was responsible, whereas Friedenberg10 initially present only during activity, treated on a case-by-case basis, depending on the argued that stress injuries are a form of reduced and is relieved with rest, but with severity of injury, the healing, not an attempt to increase healing, caused disease progression this evolves location of the injury, and by the absence of callous formation in the disease to pain at rest. It is crucial that the the likelihood of healing process. physician elicit the patient’s history with nonoperative man- Various other nonmodifiable and modifiable risk of training and physical activity. agement. factors predispose military service members to Hsu and colleagues7 reported ◾ Modifiable risk factors stress injury. Nonmodifiable risk factors include increased prevalence of over- such as nutritional status, training regiment, and sex, bone geometry, limb alignment, race, age, weight civilian recruits, indicating even footwear should be and anatomy. Lower extremity movement biome- an increase in the number of new investigated to determine chanics resulting from dynamic limb alignment recruits having limited experience potential causes of injury. during activity may be important. Cameron and with the repetitive physical activity ◾ Prevention is a crucial colleagues11 examined 1843 patients and found encountered in basic training. part of the treatment that those with knees in >5° of valgus or >5° of Stress injury should be suspect- of these injuries, and external rotation had higher injury rates. Although ed in the setting of worsening, early intervention such as careful pre-enrollment variables such as sex and limb alignment cannot indolent lower extremity pain that physicals and vitamin be changed, proper identification of modifiable has been present for several days, supplementation can risk factors can assist with injury prevention, and especially in the higher-risk patient be essential in lowering nonmodifiable risk factors can help clinicians and populations mentioned. Diet injury rates. researchers target injury prevention interventions should be assessed, with specific to patients at highest risk. attention given to the intake of Metabolic, hormonal, and nutritional status is fruits, vegetables, and foods high in vitamin D and crucial to overall bone health. Multiple studies have calcium and, most important, the energy balance found that low body mass index (BMI) is a signif- between intake and output.16 Special attention icant risk factor for stress fracture.7,12,13 Although should also be given to female patients, who may low BMI is a concern, patients with abnormally experience the female athlete triad, a spectrum of high BMI may also be at increased risk for bone low energy availability, menstrual dysfunction, and stress injury. In a recently released consensus impaired bone turnover (high amount of resorption statement on relative energy deficiency in sport relative to formation). A key part of the RED-S con- (RED-S), the International Olympic Committee sensus statement14 alerted healthcare providers addressed the complex interplay of impairments that metabolic derangements do not solely affect in physiologic function—including metabolic rate, female patients. These types of patients sustain menstrual function, bone health, immunity, protein a major insult to the homeostatic balance of the synthesis, and cardiovascular health—caused by hormones that sustain adequate bone health. Beck relative energy deficiency.14 The committee stated and colleagues17 found that women with disrupted that the cause of this syndrome is energy deficien- menstrual cycles are 2 to 4 times more likely to cy relative to the balance between dietary energy sustain a stress fracture than women without dis- intake and energy expenditure required for health rupted menstrual cycles, making this abnormality and activities of daily living, growth, and sport- an important part of the history. ing activities. This finding reveals that conditions Examination should begin with careful evaluation such as stress injury often may represent a much of limb alignment and specific attention given to broader systemic deficit that may be influenced varus or valgus alignment of the knees.11 The feet www.amjorthopedics.com July/August 2017 The American Journal of Orthopedics ® 177 Bone Stress Injuries in the Military: Diagnosis, Management, and Prevention should also be Females should undergo testing of follicle stim- inspected, as pes ulating hormone, luteinizing hormone, estradiol, planus or cavus and testosterone and have a urine pregnancy test. foot may increase In patients with signs of excessive cortisone, a the risk of stress dexamethasone suppression test can be adminis- fracture.18 Iden- tered.21 In males, low testosterone is a document- tification of the ed risk factor for stress injury.22 area of maximal tenderness is im- Imaging portant. The area Given their low cost and availability, plain radio- in question