Keywords

FormalPara Learning Objectives

  • Understand the mechanisms that lead to stress fractures in both the lumbar and cervical/thoracic spine.

  • Recognize the clinical presentation of lumbar and cervical/thoracic stress fractures.

  • Describe the various imaging modalities used to diagnose stress fractures of the spine.

  • Develop a therapeutic and rehabilitation plan to treat spinal stress fractures.

1 Introduction

The spine is a mobile segment of the axial skeleton subjected to high weight bearing loads and motion-induced mechanical stresses. When these stressors compound over time, mechanical failure can lead to stress fractures, termed spondylolysis, or bony defects involving the pars interarticularis (pars). Functionally, the pars acts as the bony bridge, or isthmus, connecting the superior and inferior articulating facets of the vertebra. Historically, spondylolysis has been classified into five distinct types (Table 28.1) based on the etiology of the fracture: dysplastic (I), isthmic (II), degenerative (III), traumatic (IV), and pathologic (V) [1]. Stress fractures of the spine are classified as isthmic type II spondylolysis. Isthmic spondylolysis can be either unilateral or bilateral, and may begin initially as increased stress to the pars interarticularis. However, repeated mechanical insults to the pars can eventually progress to bony stress fracture. In extreme cases, spondylolisthesis one vertebrae relative to another can occur.

Table 28.1 Types of spondylolysis
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While fractures can occur anywhere along the spinal column, stress fractures are most common in the lumbar spine, particularly at L5 [2]. Uncommonly, avulsion-type stress fractures can also occur in the cervical and upper thoracic spine [3,4,5]. Regardless of location, repetitive mechanical stress appears to be a major factor in the development of spondylolysis. As such, young athletes are particularly at risk for developing spondylolysis. In fact, over 70% of cases of back pain in the young athlete occur due to spondylolysis [6]. Back pain usually is the presenting complaint [7], and may accompany a history of repetitive twisting, axial loading, and repeated back extension.

Prompt diagnosis and appropriate management of spondylolysis in the athlete is critical. Often, young athletes will attempt to self-treat injuries with extended periods of rest, and this can lead to delays in diagnosis [8]. A solid understanding of diagnostic factors, as well as treatment modalities, is essential for the clinician to accurately manage spondylolysis. The purpose of this chapter is to provide a concise discussion of the epidemiology, presentation, diagnostic workup, treatment, associated complications, and prevention strategies of stress fractures in the athlete. This chapter will include a discussion of the more common lumbar stress fractures, as well as less common stress fractures in the cervical and thoracic spine.

2 Lumbar Stress Fractures

2.1 Epidemiology

Epidemiological studies of spondylolysis in the lumbar spine are widely available, and have sought to establish a mechanism for the development of spondylosis. However, the exact cause is still up for debate. Several studies have found that the prevalence of spondylolysis is higher in males compared to women, and most studies have found a 2:1 male to female ratio [2, 9,10,11,12]. The reason men tend to have a higher prevalence of spondylolysis is unknown. Other studies have focused on the relationship between repetitive mechanical stress on the pars, and this appears to be the most widely accepted hypothesis. As humans have developed the ability to walk on two legs, the axial skeleton, and the lumbar spine in particular, have evolved to support increased loads. Therefore, spondylolysis may be an acquired condition as a result of bipedal ambulation. In fact, studies of both non-ambulatory patients and infants have demonstrated no incidence of pars defects or spondylolysis [13, 14].

The overall prevalence of lumbar spondylolysis appears to be 3–6% and is associated with increasing age [12, 15, 16]. In a 45-year longitudinal study, Beutler et al. examined a population of 500 six-year-old children and found the prevalence of spondylolysis to be 4.4% [12]. Over time, the prevalence increased to 6%. However, at 45-year follow-up, three unilateral defects resolved spontaneously, and the progression of bilateral defects tended to slow with time. A study by Sonne-Holm et al. followed 4001 subjects with lumbar spondylolysis, and similarly found an increase in prevalence of spondylolysis associated with advancing age [15]. However, another study found no significant increase in prevalence of spondylolysis in patients over 20 years old [17].

The risk of lumbar spondylolysis is much higher in athletes relative to the general population. Several studies have estimated the incidence of spondylolysis in athletes to be between 47–70% [18,19,20]. Young patients with under-developed spinal muscles, or dysplastic or hypoplastic facet joints, may not be equipped to handle motion-related shearing forces that occur in the lumbar spine [21]. Repetitive loading seen in athletes may further increase these shearing forces, resulting in fatigue and fracture of the pars. Repeated extension of the lumbar spine seen in certain dynamic sports also results in cyclic collision between the articular facet of the superior vertebrae with the facet of the inferior vertebrae, which can further increase the stress on the pars [22].

In addition, the type of sporting activity seems to play a role in the development of lumbar spondylolysis. In certain sports, the incidence of spondylolysis can be as high as 63% [23]. In an analysis of 590 elite athletes with evidence of spondylolysis, Rossi and Dragoni demonstrated that the implicated sports diving (40.35%), wrestling (25%), and weightlifting (22.32%) [19]. In their study of 3152 Spanish athletes, Soler and Calderon also found differences in rates of stress fracture across sports, implicating dynamic throwing, gymnastics, and rowing [24]. Other sports that have been found to be associated with spondylolysis include American football [25], rugby [26], swimming [27], and several others [19, 24].

2.2 Classification

Ninety-five percent of cases of lumbar spondylolysis occur at L5, and the incidence decreases at each subsequent cephalad level [28]. The lower lumbar levels, L5 in particular, bear the most dynamic and static stress associated with daily activities. Athletes place even more stress across their lower spine as a result of their sport’s physical demands. For example, contact sports such as rugby and American football can place forces up to 8670 N across the lumbar spine [26]. Compressive forces combined with rotation or extension of the spine can also place particularly high levels of stress on the lower spine [29], and these movements are common in sports such as gymnastics, swimming, and diving. Other factors that increase the risk of spondylolysis at L5 include increased anterior tilt angle of the L5-S1 endplates and lumbar lordosis [30, 31]. These risk factors also result in poorer response to conservative treatment options [30, 31].

Spondylolysis can occur unilaterally or bilaterally. Often a unilateral stress fracture may progress to become bilateral, as the contralateral pars interarticularis can see 12.6-fold increases in stress following unilateral spondylolysis [32]. Unilateral stress fractures in athletes may be related to muscular asymmetry and differences in mechanical loading associated with throwing sports. Generally, unilateral spondylolysis is clinically benign, and more likely to respond to conservative treatment, whereas bilateral defects are less likely to achieve bony-union with conservative treatment and are associated with a higher risk of developing spondylolisthesis [12, 30, 33]. When an athlete initially presents with a unilateral spondylolysis but continues to experience persistent or worsening back pain, a bilateral spondylolysis should be suspected [32].

The severity of spondylolysis can be approximated using computerized tomography (CT). In 1995, Morita et al. proposed grading system based on CT findings, and divided spondylolysis in three categories: early, progressive, and terminal [33]. Early defects were characterized as minimal or hair-line fractures of the pars, progressive defects were grossly fractured, and terminal lesions were defined by sclerosis and pseudarthrosis. The grading of severity of the lesions is important, as clinical outcomes and expectations following treatment differ between the various classifications [30, 34].

2.3 Diagnosis

2.3.1 History and Physical Exam

Often, the presence of spondylolysis is an incidental finding in a young athlete. Findings of spondylolysis may have been picked up by imaging of the pelvis/abdomen. The athlete may present with no mechanical or neurological deficits, and not describe any traumatic event. They may endorse a history of paraspinal muscular fatigue and occasional back pain associated with overtraining. In such patients, a thorough work-up should be performed to rule out underlying spinal pathology.

When athletes with spondylolysis present, the most common complaint is low back pain [35]. The low back pain is localized to the midline, may involve the paramidline area where the facet joints are located, and may radiate to the buttock and upper thigh [35]. The pain is classically exacerbated by repetitive flexion and extension activities, and typically improves with rest. Radiculopathy, neurological symptoms, bladder dysfunction, and night pains are not typical, and may suggest another pathology.

Most patients will demonstrate a normal physical examination. Even in symptomatic patients, posture, gait, and strength is often normal. Patients can demonstrate hamstring or hip flexor tightness, both placing increased strain across the lower lumbar spine [36]. Direct inspection of the spine should be performed to look for signs of deformity, or hairy patches that suggest an underlying neurological condition such as spina bifida. Palpation of the lumbar spine, the paraspinal muscles, and sacroiliac joint should be performed, and may induce tenderness. Asking patients to “toe-walk” and “heel-walk” assesses gait, dorsiflexion and plantarflexion strength, and global balance. Neurological examination, as well as reflex testing, should be normal and not demonstrate any neurosensory deficits in myotomes or dermatomes. Special testing includes Adam’s forward bend test to expose any underlying deformity, and the straight leg test to rule out radicular pain. The Stork test, or the one-legged hyperextension test, (Fig. 28.1) has been traditionally viewed as a pathognomonic diagnostic test for spondylolysis [37, 38]. The tests begins with the patient hyperextending one leg while flexing the contralateral leg at the hip and knee. The test is positive if the pain is reproduced in the extended leg. However, some researchers have questioned the diagnostic utility of this test. Masci et al. conducted a study to assess whether a positive hyperextension test was predictive of spondylolysis, and found that a positive test did not correlate with evidence of spondylolysis on single-photon emission computerized tomography or magnetic-resonance imaging, highlighting the insufficiency of physical examination alone in diagnosing spondylolysis [39].

Fig. 28.1
figure 1

Demonstration of the one-legged hyperextension test, or Stork test, as viewed from the side (a) and front (b). The patient is instructed to stand on one leg with the opposite leg flexed at the hip and the knee. Next the patient is asked to extend at the low back. The test is positive if the movement elicits pain on the weight-bearing side

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2.3.2 Imaging Studies

Despite advancements in imaging modalities, plain radiography is the recommended first-line imaging method to evaluate symptomatic low back pain in young athletes. While anteroposterior (AP) and lateral views of the lumbar spine can be useful when evaluating adults, they may be insufficient in evaluating spondylolysis in the adolescent athlete [40, 41]. In cases of suspected spondylolysis, an oblique view, taken at roughly 45° from midline, provides the best view of the pars, highlighting the classic “Scotty-dog” appearance. Recently, however, the utility of oblique views has been challenged. Beck et al. compared the use of all three views (AP, lateral, and oblique) to only AP/lateral, and found no significant difference between the two approaches [41]. Furthermore, increased risks of additional radiation exposure may also negate the benefits of additional radiographic views, triggering the clinician to utilize alternative modalities in delineating spondylolysis.

Bone scintigraphy, or single-photon emission computerized tomography (SPECT), is a nuclear imaging test that identifies metabolic activity within the bone. SPECT is useful in distinguishing symptomatic pars defects with high metabolic activity from asymptomatic or chronic defects with less metabolic activity. Additionally, SPECT may be able to identify spondylolysis earlier than other imaging modalities such as CT or magnetic resonance imaging (MRI) [42]. However, this test lacks specificity, and additional imaging studies are needed to confirm, characterize, and distinguish spondylolysis from other spinal pathologies [43]. Limited resolution and added radiation exposure has called into question the utility of this imaging modality in spondylolysis and allowed for implementation of alternatives (Fig. 28.2).

Fig. 28.2
figure 2

(a) AP and (b) lateral radiographs of a 21-year-old elite-level baseball player with 1-month onset of back pain after batting. (c) Axial T2-weighted MRI and (d) axial CT further demonstrated an acute, left-sided unilateral L5 spondylolysis. He was successfully treated with rest and physical therapy

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CT similarly introduces ionizing radiation, and therefore CT (cut in 1 mm slices) is typically limited to the vertebral levels of interest, and offers excellent visualization of bony anatomy [44]. While useful for evaluating the extent and classification of spondylolysis, CT lacks the sensitivity of SPECT, and 20% of pars defects visualized with SPECT will not show up on CT [42]. Comparing CT to radiography, Fadell et al. demonstrated that CT outperformed 2-, 3-, and 4-view plain radiographs while maintaining a relatively low dose of radiation to the patient [45]. In their study, intergrader agreement was significantly higher in the CT group. These results suggest that CT may be the imaging modality of choice when evaluating an athlete with a high degree of suspicion for spondylolysis.

The applications of MRI have seen the greatest change in recent years. Specific to the adolescent athlete, MRI lends no ionizing radiation while allowing for evaluation of neurological and soft tissue structures, and can detect pars lesions earlier than CT [46]. Several studies have demonstrated the utility of MRI in diagnosing spondylolysis [47, 48]. A recent systematic review by Tofte et al. assessed the utility of various imaging modalities in diagnosing spondylolysis, and the authors concluded that a majority of studies recommended using MRI as an early or first-line diagnostic tool [47]. Dhouib et al. performed a meta analysis to determine the sensitivity and specificity of MRI in diagnosing pars lesions [48]. They found MRI was able to identify 81% of pars lesions with 99% specificity. Furthermore, newer MRI protocols and techniques are being developed to expand its utility in the context of spondylolysis. In their cadaveric study, Finkenstaedt et al., developed an ultrashort time-to-echo MR protocol to identify simulated pars defects, and found this new protocol to be superior to traditional MR protocols at 3 T [49]. While still in its nascience, MRI will likely continue to be refined and developed in the future for use in diagnosing spondylolysis.

Given the breadth of imaging modalities available for diagnosis lumbar stress fractures, diagnostic algorithms have been proposed to streamline their use. Tofte et al. proposed one such system [47]. Briefly, in athletes with low back pain without neurological signs, 2-view plain radiography may be the first test ordered due to its cost effectiveness and low exposures to radiation relative to other options. If these results are inconclusive, decisions about follow-up imaging can be made based on the chronicity of the lesion. Acute lesions likely are better evaluated with MRI, as MRI may highlight bony edema and identify lesions earlier than CT. Additionally, MRI should be performed in athletes presenting with concurrent neurological signs or symptoms. Chronic lesions and those unresponsive to treatment benefit from CT evaluation of non-unions. The authors recommended against the routine use of SPECT, unless the use of CT or MRI is contraindicated.

2.4 Treatment

Treatment modalities in the adolescent athlete should be carefully considered based on clinical presentation, as outcomes following treatment will vary depending on the presenting features. Additional considerations include the patient’s activity level, short and long term athletic goals, and preference for treatment. Many cases of spondylolysis will respond to conservative treatment. However, due to the variety of treatment options and relative lack of high-level evidence regarding treatment guidelines in the literature, therapeutic plans likely should be defined on an individual basis.

2.4.1 Bracing

Overall, the literature surrounding lumbar orthosis devices is mixed [50, 51]. Some believe the use of a lumbosacral brace provides adequate stabilization of the low back and limits the motion of the pars. However, in a meta analysis, Klein et al. found that the use of lumbosacral braces did not significantly alter clinical outcomes compared to other treatment strategies [51]. Interestingly, the authors also noted that many lesions did not achieve bony arthrosis, despite satisfactory clinical outcomes, suggesting that bony fusion is not critical for a good outcome. The use of bracing as a treatment option can likely be left up to the patient and physician and demonstrates more utility in cases of acute stress reactions. While there is little evidence for clinical benefits associated with bracing, this strategy lends itself useful in cases of noncompliant athletes or those under pressure to return to play rapidly.

2.4.2 Activity Modification and Pain Management

Activity modification and management of symptomatic pain is a mainstay of treatment for spondylolysis, and patients who take 3 months off from their sport allow for healing potential and may do better than those who play through their symptoms [52]. A recent review by Panteliadis et al. on spondylolysis in an athlete population found that athletes who stopped sport returned to play at an average of 3.7 months, while those that were treated surgically required 8 months to return to play [6]. Currently, no clear guidelines for return to play exist, and patients should initially be treated conservatively with rest for around 3–4 months. Close monitoring should be implemented for evidence of deterioration, which may prompt more aggressive care. Once pain is adequately controlled, patients may begin to be reintroduced to their sport with conditioning protocols and incremental increases in activity to limit reinjury [43].

Techniques such as low-intensity pulsed ultrasound (LIPUS) have emerged to expand the realm of conservative treatment. A study by Arima et al. compared the use of LIPUS to conservative and bracing management strategies to treat progressive-grade spondylolysis, finding that the LIPUS cohort achieved bony union at significantly higher rates than the conventionally treated group [53]. In addition to promoting bony fusion, LIPUS may also enhance patient response to conservative treatments. Tsukada et al. performed a case-control study of 82 athletes with spondylolysis, and assessed the differences in conservative treatment with and without LIPUS [54]. They found that the 35 athletes treated with combined LIPUS and conservative treatment returned to sport significantly faster than those that were only treated with conservative measures (61 vs. 167 days, respectively). While promising, more evidence is necessary to evaluate the use of LIPUS in managing spondylolysis, particularly as it applies to specific athletic populations.

2.4.3 Surgical Management

Surgical management is considered in the subpopulation of patients in whom conservative management fails or spondylolysis deteriorates into a terminal-grade lesion, or when patients develop worsening pain symptoms or neurological compromise. Overall, 9–15% of symptomatic patients with spondylolysis will require surgery [55]. While some studies suggest that return to play is accelerated with surgery [56], others suggest that surgery may prolong return to play, highlighting the relevance of attempting 6–12 months of conservative management before surgery is considered [6].

A direct repair of pars defects is indicated in various clinical settings, including L1–L4 isolated cases of spondylolysis without disc involvement, cases of multiple stress fractures, and low-grade spondylolisthesis. In athletes, this approach preserves the motion segment of the spine, offering a more optimal clinical outcome in this population. The Buck procedure, developed in 1970, utilizes a 3.5 mm screw to apply a perpendicular compressive force across to the fracture [57]. This technique has been updated over time, and recent techniques have shown good bony fusion using 4.5 mm screws and cancellous bone graft supplemented with defect decortication [58] (Fig. 28.3). In athletes with osteopenia or dysplastic lamina, screw placement may be contraindicated, necessitating other options such as the Scott’s technique, which involves placing two 2 mm holes in the bilateral transverse processes [59]. A 4 mm hole is then drilled into the spinous process and a 20-G wire is pulled through these holes in a figure-of-eight fashion to generate compression. More recently, minimally-invasive direct repair techniques have been proposed that have shown process to promote healing while sparing spinal musculature and preserving the native facet joint [60]. Other techniques have also been proposed, although the use of additional hardware may become symptomatic and require follow-up removal [61].

Fig. 28.3
figure 3figure 3

(a) SPECT scan in an 18-year-old baseball player with 9 months of low back pain that failed rest, which suggested increased uptake in the lower lumbar spine. Follow-up (b) AP and (c) lateral radiographs demonstrated L4 spondylolysis, and L4–L5 grade I isthmic spondylolisthesis. Preoperative (d) Axial and (e) sagittal CT, and (f) axial T2-weighted MRI cuts demonstrated subacute bilateral pars defects without evidence of healing. Fibular strut and cancellous allografts were placed in bilateral pars defects followed by 4.0 × 40 mm partially threaded cannulated screws to compress across the fracture seen on postoperative (g) AP and (h) lateral radiographs

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In more complex cases, such as those involving >30% slippage, stabilization techniques are preferred [62]. One area of controversy during stabilization is whether to reduce spondylolisthesis, as this could increase the surface area and improve fusion outcomes. When comparing in situ anterior fusion to combined posterior stabilization with anterior lumbar fusion, a study of 59 adolescent patients found that when posterior stabilization was coupled with anterior fusion, betters rates of fusion and shorter times to fusion were achieved [62]. Utilization of posterior instrumentation is therefore useful in cases of increased spondylolisthesis and minimizes the risk of pseudarthrosis. However, in cases of high-grade spondylolisthesis, wedged vertebral bodies may be difficult to reduce and increase the risk of complications. Furthermore, attempts at reduction involve increased surgical exposures, blood loss, operative times, and risk of nerve stretch injury, leaving vertebral reduction as a topic of continued debate. The use of interbody devices may also increase the surface area during fusion, and may also be useful when reduction is challenging or not possible, as in cases where vertebral bodies are oriented more vertically and cannot be reached from an anterior approach (Fig. 28.4). Other technique options include placement of fibular dowels with a Bohlman technique through the sacrum and into the L5 vertebral body. This technique, though less utilized, has been shown to have a high success rate [63]. On the other hand, Gill-type laminectomies, foraminotomies, and isolated anterior approaches can be implemented in adult athletes, necessitating instrumentation to balance these destabilizing procedures (Fig. 28.5).

Fig. 28.4
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(a) AP and (b) lateral radiographs of a 16-year-old elite gymnast, demonstrating bilateral L5 spondylolysis and Grade III spondylolisthesis. She was treated with an in situ L4-S1 decompression, sacral dome osteotomy, L5-S1 transforaminal lumbar interbody fusion, and posterior instrumentation L4-S1 utilizing both allograft and autograft as seen on postoperative (c) AP and (d) lateral radiographs. The patient healed uneventfully without complications

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Fig. 28.5
figure 5

(a) AP, (b) lateral, (c) flexion, and (d) extension radiographs of a 31-year-old prior athlete with chronic low back pain and an L5 radiculopathy. Imaging demonstrates bilateral L5-S1 grade II isthmic spondylolisthesis. Postoperative (e) AP and (f) lateral radiographs demonstrate how her neuroforaminal stenosis and spondylolisthesis was successfully treated with anterior lumbar interbody fusion (ALIF) and percutaneous posterior instrumentation

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2.5 Complications

Though positive outcomes following management of spondylolysis can be expected, pseudarthrosis is the most common complication following surgical management. As decreases in contact surface area will likely increase the risk of non-union, pseudarthrosis is more likely following in situ fusions lacking partial reduction. However, this must be weighed against the risk of iatrogenic neurologic injury. Patients who develop pseudarthrosis must be monitored for progressive listhesis, deformity, neurologic compromise, or persistent back pain, which may necessitate revision. In such cases, circumferential instrumentation with or without decompression should be considered [64].

While rare, the risk for neurological injury is increased after attempted reduction of high-grade spondylolisthesis. Clinicians should monitor the patient for postoperative development of bladder, bowel, sexual dysfunction, or the development of an L5 radiculopathy. The rates of radiculopathy associated with motor dysfunction after surgery vary, with some studies reporting rates as high as 29%, though the same series reported improvement in symptoms by 3 months [65].

2.5.1 Outcomes

Outcomes following diagnosis of spondylolysis have been favorable, and patients can return to pre-injury levels of performance with or without bony union. A review of 40 athletes nearly a decade after diagnosis of spondylolysis demonstrated insufficient healing of bilateral defects, though healing potential may be improved with prompt diagnosis [66, 67]. Degenerative changes are often apparent following spondylolysis with spondylolisthesis, though rarely symptomatic or progressive following skeletal maturity [2]. Moreover, studies have found that return to sport in athletes is not associated progression of the slip [68]. Regardless, surveillance radiography is warranted biannually, or at least annually, until bony maturity is reached in adolescents with concurrent spondylolysis and spondylolisthesis, as those with progression, or persistence or worsening symptoms may require surgical intervention [69].

2.6 Rehabilitation

While no clear guidelines or specific rehabilitation protocols exist currently, the majority of rehabilitation in lumbar spondylolysis centers on a gradual return to play model. As such, the three-tiered approach developed by Radcliff et al. can likely be used as a treatment model [70]. In this approach, the patient is limited for the first 3 months to only aerobic activities that maintain a neutral orientation of the spine. If the patient continues to be pain-free and tolerant of increased activity, higher impact and sport-specific activities may be incorporated around 4–6 months. Finally, the patient may be cleared if strength is restored, range of motion is full, and the patient is completely pain-free with sports-related movements [70]. Generally, if the patient progresses well through rehabilitation, complete return to sport can be achieved roughly 5–7 months following initial diagnosis [71].

2.7 Preventative Measures

Prevention of any sporting injury includes maintaining a healthy and balanced diet combined with a physically active lifestyle. Many factors go into a solid preventative program for sport injuries, including training content, duration of the program, frequency, and compliance of the athlete to complete the program [72]. Athletes, family members, coaches, and physical trainers should all be aware of the risk factors and general preventative measures to reduce injury in young athletes [72]. Nau et al. proposed a series of exercises and activity modifications for athletes with spondylolysis [73]. Bodyweight strengthening exercises focusing on core stabilization and lower body strength are useful while implementing techniques that promote hip, pelvis, and lower extremity mobility and flexibility.

3 Cervical and Thoracic Stress Fractures

3.1 Epidemiology

Compared to lumbar spondylolysis, fewer studies have looked at stress fractures in the cervical and thoracic spine, most of which are isolated case reports. Termed “clay shoveler’s fractures,” these injuries are defined as isolated cervical or thoracic spinous process fractures stemming from twentieth century manual laborers who engaged in digging or shoveling heavy loads, though are now observed in athletes [4]. Asymmetric loading of the upper spine is believed to result in whip-like pulling forces from upper back muscles on the spinous processes of the lower cervical and upper thoracic levels, resulting in avulsion fractures [4]. Repetitive shear forces during golf swings can result in multi-level injuries [5], while other sports such as baseball, wrestling [74], paddling [75], American football [76], volleyball [77], powerlifting [78], and indoor rock-climbing [79].

The spinous processes of C7 and T1 are the most commonly affected vertebra, while multi-level injuries have been associated with increased trauma and can affect other levels of the lower cervical and upper thoracic spine [3, 4, 80, 81]. The increased incidence of fracture at C7 and T1 is related to the long and horizontally-oriented spinous processes at these two levels (Fig. 28.6). Such an orientation places greater perpendicular forces on the spinous processes during upper back muscle contraction. The insertion of the ligamentum nuchae, as well as the trapezius and rhomboid muscles, at C7 and T1 also increases pulling forces at these levels [4].

3.2 Diagnosis

3.2.1 History and Physical Exam

The clay-shoveler’s fracture can occur as a result of acute trauma or repetitive pulling forces and muscular fatigue to the lower cervical and upper thoracic regions. Classically, patients will endorse an abrupt onset of severe “knife-like” upper back pain. The pain may be localized to between the shoulder blades. Additionally, a subset of patients may endorse an audible “pop” prior to the onset of symptoms.

Sensorineural evaluation should be intact in the upper and lower extremities. Upon inspection, the patient may demonstrate an antalgic posture, with slight neck flexion. The scapulae may be bilaterally elevated to limit motion through the upper spine. Upper extremity and neck range of motion will be limited secondary to pain, with often reproducible tenderness to palpation over the affected spinous processes as well as tight or spastic upper back musculature.

3.2.2 Imaging Studies

Initial AP and lateral radiographs of the cervical and thoracic spine are often sufficient in diagnosing stress injuries. One useful diagnostic clue visible on AP radiographs, the “double spinous sign,” is the presence of a double shadow of the spinous process [82]. Importantly, the spinolaminar line should not be interrupted in a typical clay shoveler’s fracture, which would suggest an unstable injury requiring further evaluation with CT or MRI may be necessary [80] (Fig. 28.5). When plain radiography is interpreted as normal despite increasing suspicion, follow-up imaging with CT and/or MRI is necessary [83].

3.3 Treatment

3.3.1 Bracing

Cervical bracing collars limit motion in the upper spine and specifically of the avulsed bony fragments, providing symptomatic relief, thereby limiting mobility may provide pain relief in the acute phase of treatment. Case reports have demonstrated a good patient response to cervical bracing for 3–4 weeks when applied to such stress injuries to the cervical and upper thoracic spine [5, 77, 80, 81]. Stress injuries to the mid- and lower-thoracic spine will not be addressed by cervical collars and requires thoracic-type bracing and may require a thorocolumbar orthosis. However, these injuries should be addressed on a case-by-case basis given the low incidence in the athletic population.

Fig. 28.6
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(a) AP and (b) lateral images of a 26-year-old construction laborer with subacute neck pain that were initially interpreted as normal but demonstrate a subtle vertically-oriented fracture line of the T1 spinous process. This was redemonstrated on (c) axial and (d) sagittal CT cuts. He was successfully treated nonsurgically with rest and physical therapy

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3.3.2 Activity Modification and Pain Management

Clay shoveler’s fractures are generally viewed as stable fractures, and outcomes following conservative treatment are generally excellent [3, 77]. Therefore, rest and activity limitation is the first line approach to managing this type of fracture. Current management plans recommend an acute period of rest with analgesic therapies, followed by 4–6 weeks of activity modification [4]. Patients are typically able to return to activity once pain has been adequately managed. Physical therapy lends itself useful to maintain and optimize upper extremity strength and mobility. Furthermore, modalities for neck and posture control and modalities for pain management demonstrate further utility. However, physical therapy should be used cautiously as it may aggravate pain symptoms in select individuals [5].

3.3.3 Surgical Treatment

In cases of severe or persistent pain, surgical intervention is warranted [4]. Typically, surgery involves excision and removal of bony fragments. In a unique case report, a 38-year-old male presented with a C7 clay shoveler’s fracture after playing a Wii video game [84]. He was treated conservatively with bracing and physical therapy for 3 months. However, his pain persisted and surgery was performed. Removal of the bone fragments completely resolved his pain. In a case series by Murphy and Hedequist, three athletes who were initially treated with rest and activity modification for a fracture at T1 continued to have persistent and debilitating pain after 10 months of treatment [85]. They were found to have non-union of the ossicle, and were treated with surgical removal of the loose fragments, followed by smoothing of the intact spinous process. This completely resolved their pain symptoms.

3.4 Complications and Rehabilitation

Overall, the outcomes following conservative treatment of cervical and thoracic stress fractures are excellent. Though rare, non-union is the most commonly-faced complication. Patients with chronic non-union may report chronic upper back pain and muscle weakness [4]. However, patients with a non-union may have positive outcomes, and therefore surgery should be reserved for those patients with persistent symptoms.

For most patients, a period of rest, with or without bracing, followed by activity modifications will likely result in symptom resolution. No explicit guidelines exist for managing the clay shoveler’s fracture, although several case reports have detailed their management suggestions. In a case by Olivier et al., an amateur paddler with a fracture at T1 was initially treated with complete rest and analgesic medication 2 weeks. Between 2–4 weeks, the patient was allowed to begin cycling and running provided he was pain-free. At week 6, he was allowed to begin light swimming. By week 12, he was able to completely return to his normal sporting activities. In another case of a clay shoveler’s in a rock climber, the patient was restricted from sport-specific activity for 4 months until his pain resolved [79]. With rest, pain management, and gradual reintroduction to activity, patients typically are able to return to full levels of activity anywhere from 3 weeks to 4 months [3, 74, 75, 79].

3.4.1 Preventative Measures

Prevention of cervical and thoracic stress fractures follows recommendations similar to those for the lumbar spine—maintaining a healthy lifestyle. Specific to the clay shoveler’s fracture, athlete education regarding repetitive, strenuous movement involving the neck. There is no evidence to support restricting upper body exercises to prevent such injuries, though future investigations may shed light on specific preventative interventions and protocols to prevent stress injuries to the cervical and thoracic spine.

4 Summary

Athletes are often well-tuned to their bodies and are able to identify subtle changes in their physiology that alter their level of play. However, stress fractures of the spine may go undiagnosed as patients self-diagnose with muscular strains and rest, increasing the time to diagnosis. In cases of clinical suspicion, plain radiography is often able to diagnose fractures, though advanced imaging including CT and MRI should be implemented if symptoms persist or diagnosis. Bracing has demonstrated mixed results, though rest is most useful in the acute stage of treatment. Surgical intervention varies with the complexity of the case

Clinical Pearls

  • Lumbar spondylolysis is a common stress injury in athletes, with an incidence between 47–70%.

  • The development of lumbar stress fractures involves cyclical loading of the low back through a combination of flexion/extension, compression, and rotation.

  • The treatment of lumbar spondylosis includes a combination of rest, pain management, activity modification, surgical repair if necessary, and a gradual return to play rehabilitation plan. Most athletes will completely recover in 5–7 months following the initial diagnosis.

  • Clay shoveler’s fracture is an uncommon upper spinal stress fracture that has been associated with several sports, including golf, paddling, rock climbing, volleyball, baseball, and American football.

  • Patients will often report a “pop” and a knife-like plan in the upper spine following the avulsion fracture.

  • Most patients will benefit from a brief period of bracing and pain management, followed by 4–6 weeks of activity modification before returning to their previous level of activity. In patients with persistent pain that does not improve with conservative management, surgical removal of loose bony fragments usually will resolve their pain.