Taking a holistic approach to managing difficult stress fractures

The holistic approach

Stress fractures occur along a continuum of severity and may occur in nearly any sports or repetitive activity [1]. Certain sports are more commonly associated with stress fractures, including running (69 %), fitness class/cross-fit (8 %), racket sports (5 %), and basketball (4 %) [2]. In order to optimize a patient’s recovery and outcome from these injuries, a holistic approach should be taken by orthopedists and sports medicine practitioners that includes specialists in athletic training, nutrition, endocrinology, psychology, sports-specific mechanics, and physical therapy.

Treatment principles for stress fractures include re-establishing the normal balance between the creation and repair of microcracks in the bone [3]. In order to decrease this repetitive microtrauma, providers must evaluate the patient’s training regimen, biomechanics, and equipment. Maximizing the patient’s biologic capacity to repair microcracks requires an assessment of the athlete’s general health focusing on nutritional behaviors, hormonal status, and medication and tobacco use [4].

Neuromuscular hypothesis

Muscle strength can also affect an individual’s susceptibility to stress fractures. Proper neuromuscular function can dissipate the energy of externally applied impact loads on the bones and joints that can occur during running and jumping. Muscle fatigue may be an important factor in fatigue fractures [8]. This is referred to as the neuromuscular hypothesis [1, 4]. As muscle fatigues, its capacity to absorb the energy of an externally applied load diminishes, resulting in higher peak stresses and more rapid accumulation of microdamage [8]. Overall, general fitness is protective, and studies have shown that military recruits with higher activity levels before enlistment had fewer stress fractures during basic training [8].

Overtraining syndrome

Overtraining has been a recognized cause of injury since the ancient Greek Olympic games. Endurance sports training require a balance between workload and recovery. Athletes such as competitive runners and triathletes often exercise longer and harder in order to improve performance, but work overload and too little time for recovery may lead to physical and psychology symptoms of overtraining syndrome [9]. This condition frequently occurs in athletes who are training for competition or a specific event and train beyond the body’s ability to recover [10]. The muscle fatigue and repetitive impact on hard training surfaces increases the athlete’s risk of developing stress fractures. Without adequate rest and recovery, overly aggressive training regimens increase the risk of injury, cause negative feelings for the activity and those involved in the training, and paradoxically decrease athletic performance [10]. Rest, adequate hydration and caloric intake, and varying the training program with cross-training activities are the mainstays of recovery [9].

Vitamin D insufficiency

Recent studies have evaluated the potential association between serum vitamin D levels and stress fractures [11]. A prospective study of Finnish military recruits found that the average serum vitamin D concentration was significantly lower in the group that had sustained a stress fracture [12]. Another randomized, double-blind, placebo-controlled study examined whether calcium and vitamin D intervention could reduce the incidence of stress fractures in female recruits during basic training [12]. This level 1 study suggests that calcium and vitamin D supplementation may have prevented a significant percentage of their recruits from sustaining a stress fracture along with a significant decrease in morbidity and financial burden [12].

It is recommended that most patients should receive 800–1000 IU (or perhaps as much as 2000 IU) of vitamin D3 daily because it is relatively safe and has a high therapeutic index. Serum 25(OH)D₃ level is the study of choice for identifying vitamin D deficiency [13]. In those individuals with low vitamin D or low bone mineral density, the therapeutic goal for supplementation should range from at least 50 nmol/L (20 ng/mL) to as high as 90–100 nmol/L (36–40 ng/mL) based on the Food and Nutrition Board recommendations [13]. Although higher dietary intake of vitamin D may provide some protective effect against fractures, the exact role of vitamin D in fracture prevention is still up for debate.

Caloric insufficiency and the female triad

Inadequate caloric intake may play a role in amenorrhea, which has been linked to an increased incidence of stress fractures. Dietary intake and disordered eating patterns have been linked to amenorrhea in a number of studies. A concept that has been developed supporting the link between dietary intake and amenorrhea is the so-called energy drain hypothesis. If caloric intake is too low, production of hormones such as estrogen and progesterone are moved lower on the list of priorities. These hormones may not be produced in amounts high enough to allow for menstruation to occur [14].

Endocrine and nutritional conditions can impair the delicate balance between bone formation and resorption, thus predisposing athletes to stress fractures. Oligomenorrheic or amenorrheic female athletes are at increased risk for developing stress, likely secondary to decreased estrogen levels and increased osteoclastic activity [15]. Stress fractures are also associated with lower fat intake, lower calorie intake, eating disorders, and body weight of <75 % ideal body weight. The female athlete triad (menstrual irregularity, inadequate caloric intake, and decreased bone mineral density) has been associated with increased susceptibility to stress fractures and may contribute to the increased stress fracture risk seen in female athletes and female military recruits compared with males performing the same activities [16]. High-intensity training may suppress menses, which may exacerbate these risk factors [17].

A recent pilot study indicated that female track and field/cross-country runners had an increased risk of developing stress fractures if body mass index (BMI) was less than 19. The authors of this case series found that female athletes with BMI of 19 or lower took significantly longer to return to unrestricted training and competition than those with a BMI above 19 [18].

The male endurance athlete tetrad

Recent literature suggests that male runners may be predisposed to decreased bone mineral density. This has been shown to be the most notable in the lumbar spine and radius. The cause of this decreased density is most likely multifactorial. Inadequate caloric intake, decreased testosterone levels, and a genetic predilection are suspected of being the main culprits [19]. Decreased energy availability may be the key factor for low bone mineral density. Decreased testosterone levels have been shown to be present in males who participate in prolonged endurance events [19]. To prevent severe or irreversible effects of low BMD, it is necessary to assess the nutritional behaviors of male endurance athletes [20].

Radiography

Two thirds of initial radiographs are normal early in the course of a stress fracture, but half ultimately prove positive once healing begins to occur making standard radiographs specific but not sensitive [26]. Even after healing has begun to occur, radiographic findings can be subtle and may be easily overlooked [26, 27]. Figure 2 demonstrates a radiograph of a subacute stress fracture of the scaphoid waist in a gymnast with chronic wrist pain.

Bone scintigraphy

Bone scintigraphy had for many years been regarded as the gold standard for evaluating stress-induced injuries. Although recently supplanted by magnetic resonance imaging (MRI), it continues to be widely utilized in many situations [28]. Bone scintigraphy measures bone response to injury by depicting areas of increased osseous metabolism through the localization of radionuclide tracers, particularly Tc-99m-MDP [28]. The degree of uptake depends on the rate of bone turnover and local blood flow, and abnormal uptake may be seen within 6 to 72 h of injury [29]. Whole body bone scans can be performed with relatively low cost and have the advantage of being able to image the entire skeletal system at once. The sensitivity of bone scintigraphy is nearly 100 % [29]. The disadvantage of this technique is that the images may demonstrate for up to 2 years after the fracture site has become asymptomatic [28].

CT

Computed tomography (CT) delineates the bone well and is useful when the diagnosis of a stress injury is difficult, particularly in the case of tarsal navicular stress fractures (Fig. 3) as well as linear stress fractures that may occur in the tibia [4, 27, 30, 31]. CT scanning is useful for demonstrating evidence of healing by clearly demonstrating the periosteal reaction and the absence of a discrete lucency or sclerotic fracture line [4, 27, 31]. It is also helpful in determining if the fracture is complete or incomplete.

MRI

MRI is an effective diagnostic technique in patients who show strong clinical manifestations of a stress fracture but have normal initial radiographs [32–34]. Like scintigraphy, MRI depicts changes in the bone and periosteum weeks before any radiographic abnormality develops [35]. The early stages of a stress fracture are characterized by focal hyperemia and bone marrow edema that correlates with the development of microfractures and osseous resorption (Fig. 4). Endosteal reactive changes, periostitis, and peri-osseous edema are important early observations on short-tau inversion recovery (STIR) or T2-weighted spin-echo images and are the characteristic of stress reactions [32, 35, 36]. The most common patterns of a fatigue stress fracture on MRI are a linear, uni-cortically based abnormality of low signal intensity surrounded by a larger, ill-defined region of marrow edema or a linear cortical abnormality with adjacent muscular or soft tissue edema. The presence of callus indicates a more chronic stress fracture.

MRI has comparable sensitivity to nuclear scintigraphy [37]. Specificity, accuracy, positive predictive value, and negative predictive value are all superior at 100, 90, 100, and 62 %, respectively [27, 32, 35]. Additionally, MRI has a distinct advantage by depicting the surrounding soft tissues, thus permitting concomitant evaluation of muscular, tendinous, or ligamentous structures [37, 38]. In the athletic population, injuries to any of these structures may mimic the symptoms of a stress fracture, which are sources that reduce the specificity of nuclear scintigraphic studies [39, 40].

Classification/grading

In addition to knowing the classification of whether a stress fracture is high risk or low risk as determined by its anatomic site, the extent of the fatigue failure or “grade” of the stress fracture is preferred to completely describe the injury and make appropriate treatment plans [1, 41].