Low-risk stress fractures

Stress fractures can occur in almost any bone in the body, with the lower extremity weightbearing bones, especially the tibia, tarsals, and metatarsals, being affected most frequently. Although the cause of these fractures is multifactoral, repetitive physical forces without adequate rest are the primary culprits. Stress fractures may be broadly classified as low-risk or high-risk injuries. Low-risk stress fractures, the topic of this review article, can be diagnosed through a thorough history, physical examination, and radiographs. Nuclear scintigraphy is occasionally necessary for confirmation, especially for fractures of the spine and pelvis. When diagnosed early and treated with restriction of activity, low-risk stress fractures have a favorable prognosis.     

Stress fractures of the upper extremity

Stress fractures are common injuries in the athletic population. Although much of the published literature has focused on lower extremity stress injuries, these injuries also occur in the upper extremities. Stress injuries of bone result from repetitive loads smaller than would be required to cause an acute fracture. As bone is repetitively stressed, it behaves like any solid substance. If deformity occurs within its elastic range, it returns to its original configuration. If stressed into its plastic range, permanent deformity occurs, and microfractures propagate, causing structural failure and complete fracture of the involved bone. High clinical suspicion is required for diagnosis because of historical and physical features can be vague. Plain radiographs are often inconclusive, but bone scans and MR imaging usually help elucidate the diagnosis. Most upper extremity stress injuries will heal with nonoperative management. In rare situations these injuries can progress to nonunion, which requires surgical correction.     

Imaging of stress injuries of the pelvis

Stress fractures are common, representing the final stage in a continuum of bone response to continued mechanical damage. Encompassing fatigue- and insufficiency-type fractures, stress fractures of the pelvis are likely underreported. Radiographs are insensitive to stress injuries, particularly those in the pelvis, whereas scintigraphy and magnetic resonance imaging are exquisitely sensitive. In this article we discuss the pathophysiology and imaging appearances of stress injuries of the pelvis and sacrum. Relevant literature regarding risk factors, problem-solving issues, and an imaging algorithm are discussed, with the goal of improving accuracy in the diagnosis of these common injuries.     

The radiology of sports of injuries

Sports injuries may be either acute or chronic. Most acute injuries occurring in sports are similar to those sustained in other activities, but many have an increased frequency peculiar to a given sport. On the other hand, chronic injury entails repetitive activity which results in repeated stresses applied to various portions of the musculoskeletal system. Prolonged and repeated activity may result in hypertrophy of both muscle and bone. Stress fractures and certain soft-tissue injuries occur when the cumulative effect of the stress exceeds the capacity of the body to repair. Each sport is associated with its own set of peculiar stresses. Knowledge of these peculiar stresses and the potential for injury in any given sports activity can lead to a more accurate diagnosis and satisfactory treatment. We have described many of the injuries associated with radiographic abnormalities.     

Stress fracture of the tarsal navicular

Stress fractures of the lower extremity are common among military members and athletes at all levels of participation. They typically occur when an individual begins a new or different type of physical training or during periods of abrupt increase in the level of training. Stress fractures represent an incomplete remodeling of bone that occurs secondary to repetitive mechanical loading. In response to this increased loading, the osteoclastic resorption of lamellar bone outpaces the ability of the osteoblasts to create new lamellar bone, eventually leading to structural failure. The following case report reviews the typical clinical presentation, imaging findings, and treatment of the tarsal navicular stress fracture.     

Stress fractures in elite male football players

The objective was to investigate the incidence, type and distribution of stress fractures in professional male football players. Fifty‐four football teams, comprising 2379 players, were followed prospectively for 189 team seasons during the years 2001–2009. Team medical staff recorded individual player exposure and time‐loss injuries. The first team squads of 24 clubs selected by UEFA as belonging to the 50 best European teams, 15 teams of the Swedish Super League and 15 teams playing their home matches on artificial turf pitches were included. In total, 51 stress fractures occurred during 1 180 000 h of exposure, giving an injury incidence of 0.04 injuries/1000 h. A team of 25 players can therefore expect one stress fracture every third season. All fractures affected the lower extremities and 78% the fifth metatarsal bone. Stress fractures to the fifth metatarsal bone, tibia or pelvis caused absences of 3–5 months. Twenty‐nine percent of the stress fractures were re‐injuries. Players that sustained stress fractures were significantly younger than those that did not. Stress fractures are rare in men's professional football but cause long absences. Younger age and intensive pre‐season training appear to be risk factors.     

An unusual stress fracture in a multiple sport athlete

Most overuse injuries are a direct result of repetitive stresses which may create a condition of maltraining. Young athletes are no exception to this rule. Swimming and baseball both create stresses to the humerus which may result in injuries to the shoulder and upper extremity. Stress fractures (fatigue fractures) are usually limited to the lower extremity (i.e., tibia or metatarsal). Upper extremity stress fractures, especially of the humerus, are very uncommon. Precipitating factors include repetitive stresses, low grade external forces, rapid application of muscular force to the bone, or an underlying disease or pathologic weakness of the bone. The majority of these fractures are primarily due to abnormal and repetitive stresses to bones. This case study examines the mechanism of injury, clinical presentation, and treatment of a clinically apparent stress fracture which ultimately converted to an overt humerus fracture in a 14-yr-old cross-trained athlete.     

Lower extremity and pelvic stress fractures in athletes

Stress fractures occur following excessive use and are commonly seen in athletes, in whom the lower limbs are frequently involved. Delayed diagnosis and management of these injuries can result in significant long-term damage and athlete morbidity. A high index of suspicion may facilitate diagnosis, but clinical presentation may be non-specific. In this regard, imaging in the form of plain radiograph, CT, MRI and bone scintigraphy may be of value. This article reviews the incidence, presentation, radiological findings and management options for athletes with stress fractures of the lower limb.     

Bone stress lesions in ballet dancers: scintigraphic assessment

Ballet dancers are athletes susceptible to ligamentous and bony injury. We reviewed retrospectively the bone scans (technetium-99m methylene diphosphonate) of 23 ballet dancers with pain in the back and/or lower extremities to determine the usefulness of scintigraphy in the detection of stress lesions of bone. The scintigraphic studies in 19 dancers identified multiple areas of stress injury in both symptomatic and asymptomatic locations. Thirteen dancers had 22 stress fractures (microfractures of trabeculae with associated bone repair) manifested by an intense focus of increased uptake of radiopharmaceutical, and 19 dancers had stress reactions (areas of accelerated remodeling and resorption of bone) demonstrated by diffusely increased uptake of radiotracer. Ten of the 13 dancers with stress fractures were symptomatic and six of the 19 dancers with stress reactions were symptomatic. The radiographs of 10 dancers with positive bone scans were normal or showed no distinction between acute and chronic injuries. Stress fractures were most prevalent in the feet, and stress reactions were most prevalent in the tibiae. The study confirmed that ballet dancers sustain significant bone stress in their legs and feet. Our results show that scintigraphy can be used to detect stress fractures and stress reactions at both symptomatic and asymptomatic sites in this population.     

Preventing and managing stress fractures in athletes

Stress fractures are common overuse injuries of bone resulting from the repeated application of submaximal load. Factors that reduce bone strength or increase the load applied to bone can place an athlete at risk of developing a stress fracture. These factors include low bone density, menstrual disturbances, inadequate dietary intake and eating disorders, training errors, inadequate muscle function and biomechanical features. Identification of the at-risk athlete can allow prevention strategies to be implemented. Diagnosis of a stress fracture is generally made clinically but investigations such as bone scan, CT or MRI can be performed to confirm the diagnosis, grade the stage of the bone response and localize the site. Most stress fractures will heal with modified rest and permit return to sport around 8 weeks. However, there is a group of stress fractures that requires additional treatment and special consideration. Treatment of the typical stress fracture requires pain management, modification (or cessation) of the aggravating activity, muscle strengthening and maintenance of aerobic fitness, identification and subsequent modification of risk factors and gradual resumption of bone loading activities. The use of braces has been shown to reduce the time to return to full activity in some lower limb stress fractures. Similarly the use of electrical stimulation and ultrasound may be helpful. Recovery should be monitored clinically.     

Hip and Pelvis Injuries in Runners

Injuries to the hip and pelvis make up a small but significant proportion of painful conditions in runners. Most of these injuries are due to overuse and some, such as femoral neck stress fracture, may involve significant morbidity. Apophyseal injuries are becoming more prevalent and should be considered in the skeletally immature athlete. Stress fractures and soft-tissue injuries occur in all age-groups, often because of excessive mechanical stress without adequate recovery periods. A systematic approach to evaluation and treatment—combined with knowledge of indications for surgical referral, training principles, and shoe-wear patterns—allows the physician to individualize the athlete's rehabilitation and return to running, and to help the athlete prevent re-injury.     

Stress fractures of the medial malleolus and distal fibula

Stress fractures of the medial malleolus and distal fibula are rarely encountered. They typically affect the athletic and running population and manifest the usual signs and symptoms of stress fractures. Axial and torsional forces, muscular contractions, and alignment are believed to play a role in their development. Plain radiographs are often initially nondiagnostic. The diagnosis can be confirmed with radionuclide bone scanning or MRI. Most injuries are amenable to nonsurgical management. An operative intervention for athletes with medial malleolar stress fractures has been advocated under certain circumstances.     

Acetabular stress fractures in military endurance athletes and recruits: incidence and MRI and scintigraphic findings

OBJECTIVE: To evaluate the incidence and the MRI and scintigraphic appearance of acetabular stress (fatigue) fractures in military endurance athletes and recruits. DESIGN AND PATIENTS: One hundred and seventy-eight active duty military endurance trainees with a history of activity-related hip pain were evaluated by both MRI and bone scan over a 2-year period. Patients in the study ranged in age from 17 to 45 years. They had hip pain related to activity and had plain radiographs of the hip and pelvis that were interpreted as normal or equivocal. The study was originally designed to evaluate the MRI and scintigraphic appearance of femoral neck stress fractures. Patients had scintigraphy and a limited MRI examination (coronal imaging only) within 48 h of the bone scan. Twelve patients demonstrated imaging findings compatible with acetabular stress fractures. RESULTS: Stress fractures are common in endurance athletes and in military populations; however, stress fracture of the acetabulum is uncommon. Twelve of 178 patients (6.7%) in our study had imaging findings consistent with acetabular stress fractures. Two patterns were identified. Seven of the 12 (58%) patients had acetabular roof stress fractures. In this group, two cases of bilateral acetabular roof stress fractures were identified, one with a synchronous tensile sided femoral neck stress fracture. The remaining five of 12 (42%) patients had anterior column stress fractures, rarely occurring in isolation, and almost always occurring with inferior pubic ramus stress fracture (4 of 5, or 80%). One case of bilateral anterior column stress fractures was identified without additional sites of injury. CONCLUSIONS: Stress fractures are commonplace in military populations, especially endurance trainees. Acetabular stress fractures are rare and therefore unrecognized, but do occur and may be a cause for activity-related hip pain in a small percentage of military endurance athletes and recruits.     

Part II: presentation,diagnosis, classification,treatment, and prevention of stress fractures in female athletes

ABSTRACT

Objectives: Stress fractures (SFx) occur as the result of repetitive loads over short periods of time, which leads to micro-damage of the bone through cortical resorption, ultimately leading to fracture. They are a common injury in female athletes and often cause significant morbidity. The goal of this study is to review the presentation, diagnosis, classification, treatment, and prevention of SFx in female athletes.

Results: A thorough history, physical exam, and appropriate imaging can facilitate early diagnosis of stress fracture (SFx) and faster resolution of symptoms with more conservative management. The female athlete triad is an especially important factor that contributes to the increased risk of SFx in females. The continuum of stress injuries ranges from mild microfailure to complete fracture, which has resulted in the development of newer grading schemas through MRI and radiographic findings. Stress fractures are also classified as low- or high-risk according to anatomic location, as blood supply and applied forces at different locations affect the likelihood of fracture propagation, displacement, delayed union, or non-union.

Conclusions: The ability to screen for at-risk athletes is paramount in preventing SFx. Recognition and prompt treatment of the female athlete triad requires a multidisciplinary approach in order to restore energy balance, correct menstrual irregularities, and improve bone health. This review provides a basis for understanding how to identify and treat stress fractures, which may allow treating physicians to diagnose this condition earlier and minimize any associated morbidity.     

Stress fractures: classification and management

Stress fractures occur as a result of microdamage secondary to repetitive strains. A mechanism for the development of stress fractures involves the accumulation of microdamage, which occurs with multiple subultimate failure loads applied to the bone. Stress fractures may be classified as high or low risk, depending on the grade of the injury. The most common site of injury is the lower extremity. In this article, we review the pathophysiology, etiology, diagnosis, and management of stress fractures, and present treatment guidelines for return to play.     

The pathophysiology of stress fractures

Stress fractures can occur in any active individual, from the weekend warrior to the elite athlete. As these injuries occur, it is important to understand how bones respond to the stresses placed on them. The understanding of potential intrinsic and extrinsic causes is important in treatment of these injuries. The proper identification and prevention of these stress injuries allows for athletes to return to activity expeditiously.     

Imaging of lower extremity stress fracture injuries

Stress reactions and stress fractures in the lower extremities occur frequently in military and athletic populations. As the clinical symptoms of stress fracture may mimic other less severe musculoskeletal injuries, the diagnosis of stress fracture can often be delayed. The following article reviews the characteristics, advantages and disadvantages of the various imaging tools available to detect stress fracture of the lower limbs in order to clarify their utility when diagnosing this condition. Plain radiography, the primary imaging tool for diagnosing suspected stress injuries, may not detect stress fracture injury until fracture healing is well underway. In some cases of suspected stress fracture, this delay in diagnosis can lead to catastrophic fracture and surgical intervention. Bone scintigraphy has long been recommended for the diagnosis of stress fracture, claiming that skeletal scintigraphy is 100% sensitive for the detection of stress fracture. However, there is a potential for a false negative examination and findings might be nonspecific as tumours or infections may mimic stress injury. In addition, bone scintigraphy involves ionizing radiation and it should not be used whenever there is an alternative. Computed tomography (CT) provides exquisitely fine osseous detail, but should be reserved only for specific indications because it also involves ionizing radiation. Magnetic resonance (MR) imaging, which is noninvasive, has no ionizing radiation, is more rapidly performed than bone scintigraphy, and should be the method of choice for stress fracture diagnosis whenever it is available. However, using MR imaging demands an experienced diagnostician in order to decrease reported false-positive injuries. The ultrasonography technique, which is being used increasingly in the evaluation of the musculoskeletal system has recently been shown to have some potential in the diagnosis of stress fracture; however, currently the imaging modalities are insufficient. The peripheral quantitative CT (pQCT) device, which has been developed to specifically assess skeletal status of the extremities, provides data on bone geometry, strength and density. However, the pQCT needs further evaluation prior to being considered for use in diagnosis stress changes in bone. This article reviews the utility of each of the imaging modalities currently available to detect stress fracture injuries of the lower extremities, as well as other utilization factors, which include exposure to ionizing radiation, the ability to detect early- and late-stage reactions in the bone and surrounding soft tissues, and the ability to differentiate between different types of bone lesions.     

Pelvic stress fracture in female runners

Stress fractures are a common injury in long-distance runners, and typically involve the lower extremities. Although relatively rare, pubic ramus stress fractures also occur, primarily in female runners. Bone imaging visualized a pubic stress fracture and a tibial stress fracture in a female long-distance runner with groin pain. Pubic stress fractures should be considered in female runners who present with groin pain. Radionuclide bone imaging is useful in diagnosing these lesions.     

Stress fractures in the female athlete

Stress fractures are common among female athletes, especially runners. Although both intrinsic and extrinsic factors can contribute to stress injury etiology, the female athlete triad—negative energy balance leading to menstrual irregularity, and reduced bone mineral mass—is a significant contributor to the incidence of stress fractures in the female athlete. When combined with impact weight-bearing activity, this triad puts these women at increased risk for stress fractures. Treatment must focus on reversing identified risk factors, in addition to relative rest, and maintenance of fitness. Most stress fractures heal without complication. High-risk stress fractures should be evaluated and treated by a practitioner with expertise in the care of these injuries.