Stress Fractures: Recognition, Management, and Pitfalls in the Emergency Department Setting
Authors: Andrew D. Perron, MD, Assistant Professor of Emergency Medicine and Orthopedic Surgery, Departments of Emergency Medicine and Orthopedic Surgery, University of Virginia School of Medicine, Charlottesville, VA; William J. Brady, MD, Associate Professor of Emergency Medicine and Internal Medicine, Departments of Emergency Medicine and Internal Medicine, Program Director, Emergency Medicine Residency, University of Virginia School of Medicine, Charlottesville, VA.
Peer Reviewer: Kenneth H. Butler, DO, FACEP, Associate Residency Director, University of Maryland Emergency Medicine Residency Program, University of Maryland School of Medicine, Baltimore.
Stress fractures represent an orthopedic dilemma being encountered more commonly by the emergency clinician; the noted increase in this type of fracture generally has resulted from a rapid growth in personal physical fitness. Breithaupt, a Prussian military physician, is credited with the initial description of the stress fracture; in 1855, he described what is currently known as a "march fracture"—a stress fracture of the metatarsal.1
Stress fractures account for approximately 10% of all injuries that are related to athletic participation,2 and have been described in association with a wide variety of sports and physical activities.3 With greater numbers of patients competing at various levels, the practitioner must be aware of these injuries.
The long-term management of these injuries is undoubtedly in the domain of the orthopedist or primary care physician, but the emergency physician will be called on to make the initial diagnosis, institute treatment, and even make recommendations regarding prevention of these injuries. With these clinical issues in mind, the purpose of this review is to sensitize the emergency physician to clinical presentations, radiographic findings, and specific fractures that are associated with stress fractures.— The Editor
Pathogenesis
Stress fractures result when forces—whether compressive, rotational, or tensile—are applied to bones that exceed the bone’s inherent strength. These forces cause microfractures; the microfractures are the cumulative result of repetitive, smaller loads and are directly influenced by the number and frequency of repetitions and the total load applied to the bone.2,4 Bone will remodel in response to the stressor, activating both osteoclastic (old bone resorption) and osteoblastic (new bone formation) activity.4 When the osteoclastic bone resorption exceeds the osteoblastic new bone formation, the weakened bone is much more susceptible to fracture. If the weakened bone is allowed to rest, osteoblastic activity can "catch up" to osteoclastic activity, and the bone ultimately can remodel and heal. If the stressor is allowed to continue, microfractures progress, and macrofracture may follow.4 The goal for the clinician is to diagnose the pathologic process and institute appropriate treatment before macrofracture develops.
Epidemiology
The stress fracture rate in the general population is not known, since virtually all of the literature had been derived from military and elite athletic populations. Epidemiologic data usually are reported in relation to specific sports, gender, and race; alternatively, anatomic involvement is another means of sorting data.
Stress fractures comprise between 1% and 16% of all reported injuries sustained by athletes,3 with distance running producing the majority of these injuries.2,5 Other "high-risk" sports include dance (particularly ballet), Australian-rules football, aerobics, and gymnastics.6 In the runner, stress fractures can be attributed to a number of factors related to the athlete’s regimen, including a recent, significant (> 10%) increase in total average mileage,4 lack of conditioning, changes in shoe type or running surface, individual anatomic considerations (e.g., leg-length discrepancy), and poor running biomechanics (e.g., hyperpronation).7
Greater than 90% of all stress fractures involve the lower extremities.8 The most frequently injured bones are the tibia and metatarsals.5 Other commonly involved weight-bearing bones include the tarsals, calcaneus, fibula, femur, pelvis, seasmoids, and spine.2,9,10 Stress fractures also can occur in non-weight-bearing bones, including ribs, upper limbs, and the pelvis.2,11
It has not yet been definitively determined whether age is an independent risk factor for stress fracture, again because virtually all studies review elite athletic or military populations. The reported peak incidence for stress fracture is in the 18-25 year age group.8 Some studies have identified a trend toward an increased incidence of stress fracture with age,12 but this has not been reproduced in other studies.13 It is intuitive that bone in older individuals would be less resistant to fatigue failure secondary to diminished bone density, but it also is usually subject to less repetitive stress cycles.
It previously was thought that females sustain a disproportionately higher number of stress fractures than males. This was studied, however, in military patient populations, where these is a significant gender difference in the incidence of stress fractures. Female recruits have a relative risk up to 10 times that of their male counterparts.4 This difference has not been nearly as evident with athletic populations, however. Most studies either show no difference between male and female athletes, or at most a slightly increased relative risk for women.4 The increased incidence of amenorrhea in female runners is felt to contribute to an increased theoretical risk of stress fracture, as amenorrhea is linked to a decrease in bone density.14 The incidence of amenorrhea in female athletes has been reported to be as high as 40%,14 whereas the incidence in the general population is thought to be less than 1%.15
General Diagnostic Considerations
It is important to make the diagnosis of stress fracture early, as a delay has the potential to increase the patient’s morbidity, especially with certain types of stress fractures. The diagnosis of stress fracture, however, can be difficult both clinically and radiographically. Because stress fractures remain an underdiagnosed entity, a high clinical index of suspicion must be maintained.16 One study found an average of 14 weeks between the onset of symptoms and definitive diagnosis.17
The history frequently involves a change in the "dose" of exercise, whether it is over an extended period of time or from a single event. The most common patient complaint is pain, which is usually gradual in onset and occurs over a period of weeks or longer. The pain initially is described as a "dull" or an "ache" after exercise. Initially, the pain may be relieved with a period of rest, but will predictably recur when activity is resumed. Over time, it will be experienced earlier in the course of activity and persist for longer periods of rest. Finally, the pain will persist despite continued rest. In general, the pain starts out as diffuse and difficult to pin-point, but as symptoms persist the pain becomes more localized to the site of the stress fracture.8
Physical examination is directed toward finding the point of maximal tenderness. The presence of localized pain, swelling, or warmth all can be indicative of the stress fracture location.5 The examiner must keep in mind that other entities may mimic stress fracture, including infection (osteomyelitis), tumor (osteoid osteoma), medial tibial stress syndrome ("shin splints"), and chronic compartment syndrome.
While many stress fractures can be diagnosed, or at least strongly suggested, by history and physical examination, corroborating studies are important for confirming the diagnosis. Early in the process, a plain film does little to establish the diagnosis. Findings may show normal bone, periosteal thickening, or early callus. Significant changes may not be evident on plain radiographs for up to three months after onset of symptoms,5,7 and up to 50% are never seen on plain films.4 In the emergency department, the real utility of the plain film early in the course of suspected stress fracture is in ruling out other, more significant pathology that requires urgent intervention. If the clinician wishes to pursue the diagnosis of stress fracture, the diagnostic gold standard is the technetium-99 diphosphonate three-phase bone scan.4 The triple-phase bone scan has been shown to be nearly 100% sensitive for the diagnosis of stress fracture, although its specificity is not nearly as high.8 The bone scan may show the stress fracture within 6-72 hours of symptom onset.2 Thus, it allows for much earlier diagnosis than plain radiography. Radionuclide bone scanning also can aid in the diagnosis of stress reaction (e.g., shin splints), and help estimate the age of the stress fracture, if one is found.18
Single-photon emission computed tomography (SPECT), magnetic resonance imaging (MRI), and computed tomography (CT) all have been used for the evaluation of stress fracture. SPECT may be particularly useful for the evaluation of suspected stress fractures of the spine and pelvis.19 MRI has not been shown to be more sensitive than bone scan for the detection of stress fracture, but it is more specific.4 It does have the advantage of showing soft-tissue detail if the diagnosis of stress fracture is not clear-cut. The main drawbacks to MRI are both its cost and its inability to image cortical bone to any significant degree.11 CT scanning is most useful when the physician wishes to confirm the fracture and further delineate its location, morphology, and degree of healing.4 While it is not required that the emergency clinician obtain these specialized studies in the acute care setting, referral for appropriate studies and follow-up can be made with the knowlege of which imaging modalities are most useful in the diagnosis of stress fracture.
General Management Issues
Limitation or complete avoidance of the inciting activity is the mainstay of treatment of most stress fractures, with a few notable exceptions. Rest allows bone repair to dominate over bone resorption. In general, one can expect this process to take 6-8 weeks to heal most fractures, although some (e.g., pubic rami) may take considerably longer.4 In the vast majority of cases, conservative management with rest is all that is required.11 The patient can maintain fitness during this period of respite from the offending activity by cycling, aqua-running, or resistance training utilizing equipment that does not involve the affected anatomic area. Return to activity should be dictated by symptoms, not radiographs. Patients can resume exercise when there is evidence of fracture healing. This would be indicated by lack of pain with activities of daily living, and lack of point tenderness on examination. Their return to activity should be gradual; for the runner this would include a regimen of walking, followed by light jogging, and then returning to a normal pace. Distance training similarly should be limited, starting with very short runs and slowly progressing with time.
Preventive Strategies
Ultimately, the key to prevention of stress fractures lies in the education of athletes, parents, coaches, trainers, and physicians. Properly selected and fitted equipment, particularly running shoes, is important for stress fracture prevention. Training should occur in a slow, cyclical progression that allows the body time to adapt. Significant rest and recovery periods should be incorporated into the patient’s training regimen. Quality of physical activity, rather than quantity, should be stressed in any exercise program. Finally, the athlete, coach, trainer, and even physician need to recognize that exercise regimens are not "one size fits all." A training regimen needs to be tailored for each participant’s baseline ability, previous experience, and current level of physical activity.
Diagnosis and Management of Commonly Encountered Stress Fractures
The Lower Extremity. Again, a majority of stress fractures occur in the lower extremities, with the tibia and metatarsals the most often affected.5,7
Pelvic Stress Fracture. Pelvic stress fractures most often involve the pubic ramus, and primarily are found in long-distance runners. Pain is reported in the inguinal, perineal, or adductor region following an increase in training level (i.e., distance, speed, or intensity). Physical examination usually demonstrates a painful, limping gait, a range of motion that may be limited by pain, and pain to palpation over the pubic ramus. Radiographs may not show any changes for 4-6 weeks. Positive findings are an irregular cortical margin or callus formation. Bone scanning is diagnostic. Treatment is rest, followed by gradual return to activity. Full healing may take 3-5 months, or even longer.
Femoral Neck Stress Fracture. Stress fractures of the femoral neck most often are seen in long-distance runners and ballet dancers. They are particularly worrisome because of their potential to result in fracture and subsequent long-term disability.20 Complications from femoral neck stress fracture may include avascular necrosis, nonunion, varus deformity, and displacement.21,22 As with other running injuries, the clinical history usually will reveal an increase in training intensity or distance in the recent past. Patients complain of pain in the groin, initially occurring with activity, and ultimately at rest. This pain also may radiate to the anterior thigh or medial knee. Night-time pain also is frequently reported.11 Most stress fractures in this region initially are mistaken for bursitis, synovitis, or muscle strain, and diagnosis often is delayed due the paucity of findings on physical examination.20 Physical examination may show painful range of motion in the hip and little else. Unlike most other stress fractures, these injuries most often do not demonstrate tenderness on palpation.11 Radiographs usually are not positive early in the course, and bone scanning is the radiographic study of choice. Figure 1 demonstrates a subacute femoral neck stress fracture; the fracture primarily is evident due to the callus formation. Femoral neck stress fractures are characterized as either compression type, affecting the medial cortex, or distraction type, affecting the lateral cortex. Distraction type have much greater risk of progressing to complete fracture and displacement, whereas compression type have increased risk of avascular necrosis and nonunion. Once diagnosed, the patient should be made non-weight-bearing, and urgent orthopedic referral should be pursued.23,24
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Figure 1. |
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Tibial Stress Fracture. Primarily found in runners, most tibial stress fractures occur in the distal third of the bone and respond well to rest, which may be followed by a gradual return to weight-bearing activities. Stress fractures in the middle third of the bone along the anterior tibial cortex are of much more concern, as they are prone to nonunion.
Physical examination will reveal localized pain to palpation, and periosteal thickening may be appreciable. Plain film radiographs may be diagnostic if symptoms have been present for 4-6 weeks; see Figure 2 for a tibial stress fracture. Bone scan will reveal a stress fracture as seen in Figure 3.
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Figure 2. |
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Figure 3. |
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Bone scans also will differentiate this entity from medial tibial stress syndrome (shin splints), which can mimic a stress fracture.7,25 Treatment of proximal or distal third tibial stress fractures involves relative rest. If the patient has pain with ambulation, then crutches are utilized until he or she can walk pain-free. Patients can return to running after 4-8 weeks of rest, being careful to slowly increase their training intensity and mileage. Any pain recurrence should prompt a return to whatever level of activity that can be performed pain-free.7
Patients with middle-third anterior cortex stress fractures deserve special mention. Characterized as the "dreaded black line" by Hamilton in 1992, these stress fractures are at risk of developing into acute transverse fractures of the tibia. Patients with this entity often have been symptomatic for months, and have continued to train despite symptoms. They need orthopedic referral for aggressive treatment, which can include being non-weight bearing for 3-6 months in a cast, vs. intramedullary rodding, which can return the athlete to sports in 8-12 weeks.6,25
Fibular Stress Fracture. Commonly seen in runners, fibular stress fractures are seen most often in the distal third of the bone, just proximal to the distal tibiofibular syndesmosis.20 Patients who over-pronate their feet are at increased risk for this fracture.7,20 Patients will be point-tender in this region. Plain films will not be positive for 4-6 weeks, but a bone scan may give the diagnosis within a week of symptoms. Treatment is conservative, with relative rest from the offending activity. For distal fractures, a rigid ankle brace may be helpful.
Metatarsal Stress Fracture. Metatarsal stress fractures were the first stress fractures described and characterized radiographically.20 The typical "march" fracture involves the second or third metatarsal shaft; they were more common in military recruits when training and running were performed in heavy combat boots. Their incidence has been greatly reduced now that such training occurs in athletic shoes. Clinically, the patient presents with pain on ambulation and point tenderness over the affected metatarsal. If the injury is chronic, fracture callus may be palpated along the metatarsal shaft. Plain film radiographs may reveal the fracture, which most often is evidenced by fluffy fracture callus around the painful area. (See Figure 4.)
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Figure 4. |
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A bone scan may be used to make the definitive diagnosis, and will be positive as soon as 48-72 hours from onset of symptoms. Treatment involves rest from the aggravating activity for 4-8 weeks, or until the patient is asymptomatic, and protection from excessive motion across the fracture (i.e., a post-operative wood-soled shoe). This can be used initially until the acute pain has subsided. If the fracture is diagnosed later and is associated with marked pain or minimal healing, a short-leg walking cast can be utilized. The patient is immobilized for 5-6 weeks until healing callus is seen radiographically. Uneventful healing usually is the rule with these stress fractures, and the patient typically can resume exercise after six weeks of conservative therapy.
Special mention is made in regard to stress fractures across the proximal fifth metatarsal. These generally occur distal to the tuberosity (approximately 1.5 cm from the proximal tip) at the junction of the metaphysis and diaphysis. These are problematic because they are prone to nonunion and refracture, which is thought to be due to the poor blood supply to the metaphyseal region. Treatment options are referral to an orthopedist for either prolonged casting (3-6 months) in a short-leg, non-weight-bearing cast or screw fixation.26 Surgery usually is recommended for anyone who could not tolerate prolonged immobilization.
Upper Extremity Stress Fracture. Upper limb stress fractures are far less common than those of the lower limb; such upper extremity injuries account for fewer than 10% of all stress fractures. They commonly are described in upper limb dominated sports such as tennis, baseball, and swimming. The physician should consider the diagnosis in any patient involved in an upper limb dominated activity who presents with bony pain of gradual onset.
Humeral Stress Fracture. Humeral stress fractures primarily are seen in younger athletes ("little leaguer syndrome") who are involved in sports that require throwing and weight lifting.6 The patient will complain of pain with throwing, lifting heavy weights, or supporting body weight with upper extremities. In throwing sports, the patient often will relate a recent increase in throwing intensity, as when the mound is moved back from home plate as a baseball player advances levels, or following increased frequency or number of pitches or learning a new type of pitch (particularly a curve ball). Physical examination will reveal pain with resisted motion and on palpation. If plain films are non-diagnostic, then bone scan or MRI are recommended to confirm the diagnosis.18 Treatment for humeral stress fracture involves a minimum of four weeks’ avoidance of the aggravating activity, and then gradual resumption of activity over an additional four-week period.6 An initial period of absolute rest in a sling may be beneficial in patients having pain at rest.
Olecranon Stress Fracture. An olecranon stress fracture should be considered in the differential of any patient presenting with symptoms of elbow overuse injury. It most often is seen in athletes who participate in throwing sports and in gymnastics. The patient history will reveal the gradual onset of pain in the elbow over a number of weeks. Physical examination shows point tenderness to palpation over the olecranon and pain with resisted tricep extension. If positive, plain films may show sclerosis at the triceps insertion or a transverse line across the olecranon. Bone scan or MRI may be used to confirm the diagnosis if plain films are unrevealing. Orthopedic treatment is initially conservative, but surgery is indicated if nonunion of bone becomes evident.6 Short-term immobilization in a sling to avoid triceps pull initially is used and is followed by gradual return to activity.
The Spine. Spondylolysis is a unilateral or bilateral stress fracture of the pars interarticularis. It can be seen in virtually any patient group, and occurs in 6% of the general population.27 It is most common in gymnasts, cheerleaders, weight lifters, and football linemen.27 It occurs most commonly at the L5 vertebral level, but also is frequently seen at both L4 and S1. Spondylolysis can progress on to spondylolysthesis, or slippage of one vertebral segment on another. While it can be clinically silent, symptomatic patients will give a history significant for the insidious onset of low back pain, often accompanied by significant back spasm. The patient often will report activity that requires repetitive extension loads on the back. Short periods of rest may temporarily relieve the pain, but return to activity results in immediate exacerbation of symptoms. Physical examination may demonstrate hyperlordosis and pain to palpation over the transverse process area. One-leg trunk extension test, performed by having the patient stand on the leg of the affected side and maximally extend the trunk, will reproduce the symptoms. Neurologic examination usually is normal.
Imaging of spondylolysis begins with plain films. While often negative early in the course, positive films will reveal sclerosis or even separation (the collar on the "Scotty Dog") in the pars region in oblique views. (See Figure 5.) SPECT scanning is most sensitive for spondylolysis, and is the definitive imaging modality to use when clinical suspicion is strong, but plain films are negative.28
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Figure 5. |
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Treatment of symptomatic spondylolysis usually is simple rest or rest with bracing for those whose symptoms continue despite rest.27 Once symptoms subside, flexibility training and a back stabilization and strengthening program can begin. Complete healing usually takes 3-6 months.
Summary
Stress fractures are an increasingly common injury encountered in a clinician patient population. Early diagnosis and prompt institution of conservative therapy is the treatment of choice for the majority of these injuries. While longitudinal care will come from orthopedists or primary care clinicians, the emergency physician needs to be skilled in the diagnosis and initial management of these injuries. Special attention to clues from the history and physical examination in an at-risk patient population will help lead the clinician to the right diagnosis. While most stress fractures resolve with rest and progressive reintroduction of stressors, certain injuries, such as femoral neck stress fracture and fifth metatarsal stress fracture, have a high risk of complication and require aggressive therapy.
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