Because it is not possible to offer a comprehensive review of fractures in sport medicine in one chapter, several types of fractures are addressed in other chapters of this text that cover particular body parts. This chapter focuses on select fractures that have some specific implications for athletes, as well as stress fractures, which are a characteristic sport injury. Issues related to return to sport (RTS) decisions are also addressed. Sometimes more challenging than making the diagnosis or determining the treatment plan is deciding when to allow the athlete to return to training and competition. The concepts relevant to RTS decisions is presented in the final section of this chapter to offer some guidance and an algorithm to help guide clinicians.
Athletes are often exposed to high-intensity repetitive training activities. These training regimens allow them to develop their skills but also place them at high risk for the development of stress fractures. In a 10-year follow-up study by Iwamoto and Takeda, 2% of all visits to a dedicated sports medicine physician were for a stress fracture. In particular, stress fractures have been shown to be very common injuries in endurance athletes. The most common locations for stress fractures are the tibia (23.6%), tarsal navicular (17.6%), metatarsal (16.2%), femur (6.6%), and spine (0.6%). High-intensity or prolonged-duration activities result in repetitive microtrauma that weakens the architecture of the bone. This initial weakening of bone without cortical involvement is known as a stress reaction. This initial stage in the continuum of bone failure can subside or progress to a stress fracture.
Training errors are the most common cause of stress fractures. The total load on the tissues is based on a combination of the number of exercise sessions and the intensity and duration of the activity, superimposed on the unique demands of the activity. It is at this juncture that the concept of an FITT exercise prescription is helpful ( f requency, i ntensity, t ime, and t ype). One must bear in mind that if multiple aspects of the exercise prescription are changed at the same time, it can have the same effect as significantly increasing just one component. For example, increasing the duration of a run may have the same effect as changing the running surface (to sand or concrete). Changing both the surface (type) and duration (time) simultaneously may overload the bone. When the microstructural changes are unable to be compensated for by bone formation, the mismatch in bone turnover enables stress fractures to develop.
Several factors may contribute to this mismatch in bone turnover, including the patient’s biomechanics, hormonal influence, nutritional level, or the ingestion of substances such as corticosteroids, nicotine, or nonsteroidal antiinflammatory drugs (NSAIDs).
Biomechanical risk factors include limb alignment, gait pattern, muscle imbalances, and dynamic motions across their joints. For example, a high longitudinal arch, leg-length discrepancy, and excessive forefoot varus have all been demonstrated to be risk factors in persons with recurrent stress fractures. These biomechanical differences often generate unbalanced loads on one aspect of the bone, creating a tension and compression side. Whether the stress fracture is on the compressive or tension side of the bone is a key factor to consider when deciding on a treatment pathway (discussed later in this chapter).
The hormonal influence on bone biology in the athlete is most commonly discussed in relation to female athletes. A high-intensity female athlete is at risk of developing the female athlete triad, which consists of an eating disorder, osteoporosis, and amenorrhea. The alteration of the normal hormonal milieu associated with amenorrhea affects the normal bone turnover, placing the athlete at risk for stress fractures. In addition to the female triad, poor nutrition also has been implicated in the development of stress fractures. A Finnish study of male military recruits with stress fractures found low levels of 25-hydroxyvitamin D.
Examples of other exogenous substances that have been shown in the literature to affect bone turnover include nicotine and NSAIDs. Although no conclusive evidence exists to indicate that NSAIDs cause or interfere with the healing of stress fractures, animal studies on fracture healing have repeatedly demonstrated a negative effect. A negative effect also has been shown on the healing of osteotomies, fusions, and high-risk fractures in humans, perhaps because NSAIDs affect prostaglandin synthesis, which is essential in normal bone turnover and fracture healing. Thus an argument can be made to use other forms of analgesia in patients at risk. Findings of numerous studies have implemented nicotine as having an adverse effect on normal bone biology, leading to an increased incidence of delayed unions and nonunions.
In the next part of this chapter, several common locations for stress fractures will be presented and an overview of stress fractures at each location will be provided, along with an algorithm for the management of these injuries.
Femoral Neck Stress Fractures
Although femoral neck stress fractures constitute only 7% of all of stress fractures, they have the potential for the most serious complications. A displaced femoral neck fracture has the potential to lead to avascular necrosis, which would cause significant disability and even the requirement for a total hip replacement in a young patient. Femoral neck stress fractures typically occur in two separate populations: young high-impact repetitive training athletes and elderly osteoporotic patients. As with many stress fractures, the presentation is not always clear and can be confused with other causes or sources of hip pain. The patient usually has a history of discomfort with ambulation, particularly with impact loading, which is relieved at rest. Although the insidious onset of groin pain is classic, referral patterns may result predominantly in knee symptoms. The patient’s history can provide other clues, such as a change in an endurance athlete’s training regimen. The history should also evaluate the risk factors for stress fractures that were detailed at the beginning of this chapter.
A physical examination will help generate a differential diagnosis for these symptoms. The physical examination should include inspection, palpation, range of motion (ROM), neurovascular examination, and special tests, such as the hop test. Generally some discomfort occurs with end ranges of motion—in particular, internal rotation. Of course, this finding is also positive (i.e., the impingement sign) for femoral acetabular impingement. In addition to pain with end ranges of motion, athletes describe sharp pain with impact loading, which is assessed clinically with the hop test.
The differential diagnosis includes femoral acetabular impingement, femoral head avascular necrosis, degenerative joint disease, snapping hip syndrome, iliopsoas tendonitis, osteitis pubis, piriformis syndrome, or non–hip-related pathology that has referred symptoms.
The next step is to further investigate the hip with the use of imaging. The first imaging modality used should always be plain radiographs to assess for any bone irregularity. Unfortunately, results of these radiographs are frequently negative, and thus other imaging modalities are usually required to confirm the presence of a stress fracture. Several imaging techniques may be used to identify a stress fracture, including a bone scan, computed tomography (CT), and magnetic resonance imaging (MRI). Much debate has ensued about which technique is optimal; however, a recent set of guidelines issued by the American College of Radiology (ACR) provides help in making this decision. Of these modalities, MRI has been demonstrated to be the most sensitive, because it is able to identify subtle bone marrow edema in the femoral neck, and it is also the most specific ( Fig. 13-1 ). If access to MRI is restricted, a bone scan is also a sensitive test, although it is much less specific. As always, imaging findings should be correlated with the clinical picture.
Femoral neck stress fractures are classified into two types—compression and tension—based on their location in the femoral neck and forces acting on the fracture ( Figs. 13-2 and 13-3 ). Compression-type stress fractures constitute the majority in young athletes and military recruits. In one study of the relative incidence of femoral neck fractures, it was found that 65% were the compression type and 35% were the tension type. Compression-type fractures are located on the inferomedial cortex and are inherently stable because of the axis of force through the femoral neck compressing the fracture. As a result, these fractures can be treated conservatively with activity modification and an appropriate return-to-play algorithm when the patient is symptom free (outlined in detail in the next section of this chapter).
In contrast, tension-type stress fractures are located on the superolateral cortex and are a greater concern because of the distractive force across the fracture site. The high-risk nature of these fractures dictates operative management for this subtype in an attempt to treat it prior to displacement. In addition to displacement, these fractures are at high risk for nonunion and delayed union. In terms of fixation, several options are available, from cannulated screws to dynamic hip screws, but the key is to obtain and maintain an anatomic reduction if any displacement has occurred. Postoperatively, these patients are protected with partial weight bearing until evidence of healing is seen; they can then follow the return-to-play algorithm that will be detailed later in this chapter.
Tibial Stress Fractures
The tibia is the most common location for stress fractures in the lower extremity. The tibia has been found to represent approximately 24% of all stress fractures. Tibial stress fractures are subdivided on the basis of whether they are found on the posteromedial or anterior cortex ( Figs. 13-4 and 13-5 ). Their location, as in the femoral neck, correlates with the forces working on the fracture, and these forces in turn dictate the appropriate treatment. Kaeding et al. describe posteromedial stress fractures as the most common type, which correlate to a compression-type stress fracture. Anterior cortex tibial stress fractures are less common and are a tension-type injury.
Posteromedial tibial stress fractures typically occur in athletes, such as long distance runners, and can present with edema and focal tenderness located over the site of the fracture. The differential diagnosis for this history includes medial tibial stress syndrome, tendinosis, and exertional compartment syndrome. The fracture itself is generally transverse in nature, but atypical radiographic appearances such as longitudinal patterns may be present. These transverse fractures are generally easier to visualize, although results of most initial plain radiographs are negative. Additional imaging modalities are typically required, and based on the recommendations of the ACR. MRI provides the highest sensitivity and specificity compared with CT or a bone scan.
Given the forces acting on the fracture, compression-type injuries are thought to be stable. As a result, this type of tibial stress fracture can be treated conservatively and the return-to-play algorithm can be used to facilitate an expedited and safe return to activity. During the resolution of pain, the athlete can focus on nonimpact activities, such as use of a stationary bicycle or swimming, to avoid losing his or her overall level of conditioning.
Anterior cortex tibial stress fractures are more of a concern because of the risk of progression to delayed union, nonunion, and potentially even a complete fracture. The reason for the increase in potential complications is due to the distractive forces across these fractures, as well as the decreased vascularity in the mid shaft of the tibia. These fractures generally occur in athletes who perform a lot of jumping or leaping maneuvers. Results of initial radiographs are often normal for these patients, but a wedgelike defect in the anterior cortex may develop. This radiographic pattern is often referred to as the “dreaded black line” because of its propensity to develop into a nonunion (see Fig. 13-5 ). Treatment for this stress fracture is initially activity modification with alteration of the training regimen. If symptoms persist, the athlete should bear weight only partially and transition some of his or her impact activity to other forms of training (e.g., running in a pool). For athletes with recalcitrant symptoms, non–weight bearing or even immobilization may be required. Close radiographic and clinical follow-up is required to monitor the progression of healing. In some centers other modalities such as bone stimulation via ultrasound or electrical pulses have been used. However, despite evidence of efficacy for traumatic fractures, randomized controlled trials (RCTs) that have examined ultrasound and electrical stimulation in persons with stress fractures have not demonstrated any difference in healing time.
Any evidence of widening at the fracture site suggests a failure of conservative measures. Such evidence of widening, or the development of a complete fracture, makes operative management a serious consideration. The operative management of choice would be an intramedullary (IM) nail.
Proximal Fifth Metatarsal Stress Fracture
A stress fracture at the proximal metadiaphyseal region of the fifth metatarsal (Jones fracture) is challenging because it is a high-risk region for nonunion, delayed union, and refracture. Several factors contribute to the high risk, including its poor blood supply and the forces acting on the fracture. These fractures are more commonly found to occur in dancers and in basketball, football, and soccer players. The fractures typically present with the insidious onset of pain with activity and localized tenderness over the proximal fifth metatarsal. Stress fractures generally present with prodromal symptoms, and results of initial radiographs are often negative. For radiographic confirmation of a stress fracture, the ACR recommends the use of MRI rather than CT or a bone scan because it is more sensitive and specific than the other modalities. However, a bone scan remains a good screening tool. The stress fracture itself initiates on the lateral (tension) side of the proximal metadiaphyseal region of the metatarsal and propagates medially ( Fig. 13-6 ).
Initial management is to treat these stress fractures nonoperatively with activity modification and alteration of the training regime. If symptoms persist, the athlete should bear weight only partially and transition some of their impact activity to other forms of training (e.g., running in a pool). For athletes with recalcitrant symptoms, immobilization and non–weight bearing may be required. However, because of the prolonged healing time and risk of refracture, management has shifted to early surgical intervention for athletes. Surgery is also a consideration for patients who present with IM sclerosis or distraction at the fracture site. The operative procedure of choice is to use an IM screw to bypass the fracture and to fill the IM canal ( Fig. 13-7 ). Athletes with this injury who are treated operatively can start training with partial weight bearing (e.g., running in a pool) as soon as the wound is healed. Compared with nonoperative treatment, earlier weight bearing is possible, and the athlete typically can return to unrestricted activities after approximately 8 weeks, when evidence of some radiographic healing is seen and the athlete has an absence of pain.
Although the course of surgery is more predictable than that of the conservative approach, both conservative and operative management options are reasonable. Regardless of the approach selected, the athlete requires close radiographic and clinical monitoring and should follow the return-to-play algorithm outlined at the end of this chapter.
Navicular Stress Fracture
Navicular stress fractures are most commonly found in athletes who participate in impact loading sports such as basketball and running. Risk factors include a short first metatarsal, long second metatarsal, overpronation, or the presence of a calcaneonavicular coalition. These athletes present with pain along their medial arch and, specifically, over the dorsum of the navicular. The differential diagnosis includes other conditions involving the navicular bone such as accessory navicular syndrome, insertional posterior tibial tendonitis, calcaneo-navicular coalition, osteonecrosis of the navicular, and osteoarthritis of the talonavicular joint. The fracture itself occurs in the the saggital plane in the middle third of the navicular because this portion of the bone has a more tenuous blood supply and is the area of highest shear stress in the navicular. A high index of suspicion for this injury is required to diagnose this stress fracture, because most of these fractures are not visible on plain radiographs. Other imaging modalities used for the navicular include a bone scan, CT, and MRI. A bone scan is useful in localizing a stress fracture but does not provide information on the extent of injury or healing. A CT scan is more useful in determining the extent of the fracture and whether it is a complete fracture, which can alter management. As with other stress fractures, the ACR recommends MRI as the imaging modality of choice ( Fig. 13-8 ).