Stress fracture represents an overuse injury of the bone resulting from excessive repetitive stress. Diagnosis in most cases is based on clinical evaluation. Plain radiographs may show characteristic changes 2 to 4 weeks from onset of symptoms. Increasingly, magnetic resonance imaging is recognized as the study of choice in the evaluation of stress injury of the bone. Most stress fractures at low-risk sites can be managed in the primary care setting with conservative measures. From a primary care perspective, orthopedic or sports medicine consultation is considered for stress fractures at high-risk sites. This article reviews general principles of diagnosis and management of stress fractures in adolescents.
Stress fracture represents an overuse injury of the bone, and is one stage on a continuum of stress injury of the bone. Stress injury of bone can be either a fatigue reaction (or fracture) or insufficiency reaction (or fracture). Fatigue fracture results from cumulative microfractures because of excessive repetitive strain to a structurally normal bone. Insufficiency fracture can result from normal stress to a structurally abnormal bone. In otherwise healthy adolescent athletes, stress injury to the bone is typically a fatigue reaction or fracture. Individuals with disorders that affect bone structure, such as metabolic bone disease or osteoporosis, are at risk for insufficiency fracture.
Repetitive, excessive stress results in microfractures within the bone. This often occurs within 6 to 8 weeks of rapid increase in physical activity, not allowing sufficient time for bone remodeling and adaptation to stress. Continued stress to the bone can lead to propagation of microfracture and eventual macrofracture. The pathogenesis of stress injury to the bone is multifactorial ( Table 1 ).
| Training related | High training volume, rapid increase in training volume |
| Footwear | Poor shock absorption, old shoes (more than 6 mo old), poor shoe-fit (especially in women) |
| Training surface | Uneven running surface, hard surface (equivocal evidence) |
| Gender | Female gender, may be secondary to other factors such as hormonal and nutritional |
| Race | Higher in white and Asian women than in African American women |
| Fitness level | Poor muscle strength and endurance |
| Bone mineral density | Low bone mineral density |
| Bone geometry | Reduced bone cross-sectional areas and bone resistance to bending |
| Anatomic | Equivocal evidence for rigid pes cavus, leg-length discrepancy, genu valgus, and increased Q angle |
| Hormonal | Hypoestrogenic states in female athletes, delayed menarche, amenorrhea, oligomenorrhea |
| Nutritional | Low calcium intake, low vitamin D intake (equivocal evidence), energy deficit |
Epidemiology
Snyder and colleagues extensively reviewed epidemiologic studies on stress fractures in athletes. It is difficult to generalize data from different studies because of methodological differences among them. Factors that influence the acquisition, results, and interpretation of data include differences in definition of injury exposure, study designs, definition of injury, and accuracy and method of diagnosis (clinical, radiological). Given these limitations, several conclusions are drawn.
Stress fractures affect 1.0% to 2.6% of college athletes. Of the recreational or competitive athletes who visit a sports medicine or orthopedic clinic, 0.5% to 7.8% have stress fractures. Data are not sufficient to estimate accurately the incidence of stress fracture by type of sport; however, most data suggest highest incidence in track and field and long-distance running. The cumulative annual incidence of stress fractures in track and field athletes is reported to be 8.7% to 21.1%. In track and field athletes, stress fractures account for 6% to 20% of all injuries. Of runners seen in an orthopedic clinic, stress fractures accounted for 15.6% of all injuries. Athletes in certain sports are more at risk for specific stress fractures ( Table 2 ).
| Fracture Site | Sport |
|---|---|
| Tibia | Aerobics, basketball, ballet dancing, running, soccer, swimming |
| Fibula | Aerobics, running, skating |
| Femur | Jumping activities |
| Calcaneus | Basketball, other jumping activities |
| Metatarsal | Soccer, swimming |
| Patella | Baseball, basketball |
| Pubic ramus | Fencing, jumping, running |
| Pars interarticularis | Gymnastics |
| Ribs | Baseball |
| Scapula | Baseball |
| Humerus | Baseball, cricket |
| Ulna | Curling, javelin, tennis |
| Metacarpal | Handball, tennis |
Although a significantly higher incidence of stress fractures is reported in certain groups of female athletes, overall data provide equivocal evidence to support female gender as an independent risk factor for stress fractures. Similarly, age has not been found to be an independent risk factor for stress fractures. Stress fractures are most frequently reported in lower extremities; tibia being most affected followed by metatarsals and fibula. Stress fractures of upper extremities are rare. The duration from time of diagnosis to return to play varies depending on the type, site, and grade of severity of the fracture, and ranges from 7 to 17 weeks.
Diagnosis
Activity-related, insidious onset of pain that is localized to the affected area is the cardinal presenting symptom of stress fracture. Initially, the pain is reduced or transiently relieved with rest, allowing the athlete to continue the activity; however, progression of stress injury results in increased intensity of pain and functional deterioration or limitation of activity, which prompts the athlete to seek medical attention. Pain from stress fracture is usually described as dull aching, and in the case of lower extremity injury is often aggravated by weight bearing. Onset, duration, progression, and modifying factors for the pain should be characterized. Additional history should ascertain information about other possible contributing factors for stress factors as listed in Table 3 . The affected area is usually tender to palpation. In the case of lower extremity fractures, the athlete may have a limp because of increased pain on weight bearing. If the fracture is in close proximity to a joint or involves a joint, pain is aggravated on joint movement.
| Pain | Onset, duration, quality, progression, modifying factors, radiation, location, associated symptoms such as tingling, numbness, weakness |
| Training regimen | Recent increase in intensity, type of activity or sport, running surface |
| Footwear | Type of shoes, proper fit, how old, history of use of orthotics, inserts |
| Medical history | Known disorders that affect bone health, osteopenia, metabolic bone disease |
| Medications | Use of corticosteroid or other drugs that increase risk for osteopenia, use of depomedroxy progesterone |
| Performance | Anabolic androgenic steroids, growth hormone, other enhancing agents |
| Nutrition | Caloric intake, calcium intake, vitamin D intake, weight loss |
| Menstrual history | Onset of menarche, amenorrhea, oligomenorrhea |
| Stress fractures | Details of any previous stress fractures |
| Systemic symptoms | Fever, rash, joint pain, undue fatigue, unintended weight loss, loss of appetite |
Plain radiography is the initial study for confirming diagnosis of a stress fracture. Plain radiographs have a high rate of false negative results because the findings suggestive of stress injury of the bone are generally not evident on plain radiographs for 2 to 4 weeks after the onset of pain.
Notwithstanding the expense and accessibility, magnetic resonance imaging (MRI) has been shown to be most useful in the diagnosis of stress injury of the bone, and abnormal findings can be detected as early as within 1 to 2 days of injury. MRI is useful in delineating the differential diagnosis of stress fracture that includes soft tissue injuries affecting the same area, and more ominous conditions such as bone malignancy and osteomyelitis. Arendt and Griffiths have classified stress injury of the bone into 4 grades ( Table 4 ). The MRI grading system has been found to correlate with or has a prognostic significance for time to healing and return to play. Studies have shown that the average duration of recovery time for grade 1 stress injury is 3.3 weeks, whereas it is 14.3 weeks for grade 4 injury. MRI-based grading of stress injury of the bone has also been found to be useful in guiding management of stress fractures.
| Grade of Stress Injury | MRI Findings | Duration of Rest Needed for Healing, wk |
|---|---|---|
| Grade 1 | Positive STIR image | 3 |
| Grade 2 | Positive STIR plus positive T2-weighted images | 3–6 |
| Grade 3 | Positive T1- and T2-weighted images; no definite cortical break | 12–16 |
| Grade 4 | Positive T1- and T2-weighted images; fracture line visible | 16 |
The application of ultrasonography in the diagnosis of musculoskeletal disorders is increasing. Ultrasonography has been shown to be useful in the diagnosis of stress fractures of more superficial bones such as distal tibia and bones of the foot. The acuity of the fracture can be assessed by power Doppler ultrasonography, which provides a semiquantitative estimate of bone turnover.
Computed tomography (CT) can be used in patients in whom MRI is contraindicated. CT is sensitive in detecting stress injury of the bone and in differentiating stress fractures from other lesions of the bone such as osteoid osteoma. CT scan, especially single-photon emission CT (SPECT), has been found to be sensitive in detecting pars interarticularis stress fractures (spondylolysis).
Nuclear medicine scintigraphy is highly sensitive for evaluation of bone turnover and, therefore, for detecting stress reactions 3 to 5 days after onset of pain; however, findings are nonspecific for stress fractures. It also necessitates injection of a radioactive tracer with potential associated risks.
Diagnosis
Activity-related, insidious onset of pain that is localized to the affected area is the cardinal presenting symptom of stress fracture. Initially, the pain is reduced or transiently relieved with rest, allowing the athlete to continue the activity; however, progression of stress injury results in increased intensity of pain and functional deterioration or limitation of activity, which prompts the athlete to seek medical attention. Pain from stress fracture is usually described as dull aching, and in the case of lower extremity injury is often aggravated by weight bearing. Onset, duration, progression, and modifying factors for the pain should be characterized. Additional history should ascertain information about other possible contributing factors for stress factors as listed in Table 3 . The affected area is usually tender to palpation. In the case of lower extremity fractures, the athlete may have a limp because of increased pain on weight bearing. If the fracture is in close proximity to a joint or involves a joint, pain is aggravated on joint movement.
