8 Thoracic and Thoracolumbar Fractures
The thoracic and thoracolumbar regions are common fracture sites in aging adults. Multiple classification systems have been developed to facilitate discussion of different fractures and guide surgical decision-making. The four main types of fracture are compression, burst, flexion-distraction, and fracture-dislocation. Conservative management with analgesics, bracing, medical management, and physical therapy is recommended for most stable fractures without neurologic deficit. Surgical decompression and stabilization is generally appropriate for fractures with neurologic deficit, progressive vertebral column collapse, deformity, and/or persistent pain. In the aging population consideration of medical comorbidities and osteoporosis are paramount in surgical decision-making.
Vertebrae of the thoracic and thoracolumbar spine are prone to fracture in older adults.
Current classification systems generally categorize fractures as compression, burst, flexion-distraction, and fracture-dislocation.
Conservative therapy with analgesics, bracing, medical management and physical therapy is recommended for most stable fractures without neurologic deficit.
Surgical decompression and stabilization is generally indicated for fractures causing neurologic deficit, progressive deformity, and/or persistent pain.
Medical co-morbidities should be carefully considered in this patient population.
The thoracolumbar region is the longest segment of the human spine and a frequent site of fractures, especially in the aging population. One of the major medical conditions which affects older adults and predisposes this patient population to fractures is osteoporosis. For these patients, any type of fracture may be more severe than expected from the mechanism of injury—for example a fall—given the poor bone density typical of the aging.
Osteoporosis is estimated to affect over 100 million people worldwide and at least 10 million people in the United States. 1 In the United States, about 700,000 osteoporotic vertebral compression fractures occur annually, of which 70,000 result in a hospitalization, with an average duration of eight days. 1 Burst fractures are the second-most common injury to the thoracolumbar spine, after compression fractures, with about 25,000 occurring annually in the United States. 2 In situations of severe trauma, thoracolumbar fractures are often associated with other vertebral and nonvertebral fractures and injuries to internal organs. In these situations, the diagnosis of thoracolumbar spine fracture itself may initially be missed. 3 The sequelae of thoracic and thoracolumbar fracture include pain, deformity, and loss of neurologic function. 4 , 5 , 6 , 7 The goal of therapy is to relieve pain, prevent or reverse neurologic deficit, and prevent bony deformities.
8.2 Biomechanical Considerations
The thoracic and lumbar spine is comprised of the thoracic vertebrae, T1-T12, and the lumbar vertebrae, L1–5. The thoracic vertebrae form a rigid unit with the ribs and sternum compared to the more mobile lumbar vertebral column. The thoracolumbar junction, T10-L2, represents the transition between the kyphosis of the thoracic spine and the lordosis of the lumbar spine. The juxtaposition of the stiff thoracic spine with the relatively more mobile lumbar spine creates a site that is subject to increased forces during traumatic injuries. Thoracolumbar fractures are commonly associated with high-energy situations such as motor vehicle accidents, falls, sports injuries, and violence. Associated injuries are common, and may include pneumothorax, rib and long-bone fractures, and penetrating injuries to the lungs, heart, and visceral organs. Ruling out visceral injuries to other organ systems is critical in the evaluation of these patients, particularly if planning a surgical intervention. Paying attention to the mechanism of injury should provide an index of suspicion for injuries to regional organ systems. For example, a pelvic fracture associated with a traumatic thoracolumbar spine injury could put a patient at risk of injury when positioning the patient prone.
In the aging population, osteoporosis is common, especially in women. The United States Preventative Services Task Force currently recommends screening all women over age 65. 8 Osteoporosis is likely prevalent in many elderly men as well, but the current evidence is insufficient for guidelines. In patients with osteoporosis, the spine is commonly affected, as the amount of bone present in each vertebral body is generally decreased. Typically, the cortical layer of each vertebra is thinned, and the cancellous bone has low trabecular continuity. Osteoporosis can be assessed by bone density tests, but such tests are typically not part of any routine trauma evaluation. Most elderly patients with established primary medical care may have an underlying diagnosis of osteopenia or osteoporosis, for which they are followed longitudinally. In the acute setting of managing and planning the treatment pathway for an acute thoracic or thoracolumbar fracture, the treatment history of the osteoporosis is important to know, as the spine fracture may be the patient’s first bone fracture. For long-term management of bone health, this may prompt the patient’s primary medical provider to start medical treatment or refer to an endocrinologist for further discussion regarding treatment options. For patients without established medical care at this age, there are usually greater issues of general medical health and chronic medical illnesses which may have not been adequately addressed or managed. In these situations, the spine fracture is a small part of a greater issue. Nonetheless, any new spine fracture in the elderly population should prompt follow-up with a medical provider for evaluation and treatment of osteoporosis.
The aging spine is typically less flexible secondary to spondylosis and resultant osteophyte formation. Other conditions can accelerate this stiffening, including diffuse idiopathic skeletal hyperostosis (DISH) and ankylosing spondylitis. Care should be taken to identify these underlying conditions because the stiffened spine can increase the leverage at the fracture site, leading to more significant risk of instability. Fractures in these patients are more like long-bone fractures and are more likely to benefit from internal fixation.
8.3 Common Injury Types
There have been many attempts to classify traumatic injuries to the spine. One of the first classification systems proposed by Holdsworth et al in 1968 sorted injuries according to mechanism of injury and radiologic findings and was based on a two-column (anterior and posterior) model of the spine. 9 , 10 Denis et al in 1983 advocated a three-column model consisting of the anterior 2/3 of the vertebral body, the posterior 1/3 of the vertebral body, and the posterior column. 11 In light of the new data provided by CT and MRI scans, further classification systems were proposed. 12 , 13 , 14 More recently, in 1994 the AO (Arbeitsgemeinschaft für Osteosynthesefragen, German for “Association for the Study of Internal Fixation”) Foundation created the “AO Classification,” a comprehensive classification based on pathology and morphology. 15 They defined three major types of injuries: A. compression, B. distraction, and C. rotation. Each type has several groups and subgroups based on the pathophysiology and morphology of the injury (Table 8‑1). This classification of thoracic and thoracolumbar fractures has facilitated research by providing precise and comprehensive diagnostic criteria but has proved to be cumbersome for routine clinical practice.
More recently, Vaccaro et al in 2005 developed the Thoracolumbar Injury Classification and Severity Score (TLICS) (Table 8‑2) by using clinically important criteria of morphology, neurologic status, and the integrity of the posterior ligamentous complex as assessed by CT or MRI imaging. 16 , 17 A TLICS score of < 4 indicates nonsurgical management, a score of > 4 indicates surgical management, and a score of 4 is equivocal. This score has been verified by other investigators. 18
The most widely accepted classifications of injuries today all use three-column models. Specifically, the anterior column includes the anterior longitudinal ligament, and the anterior 2/3 of each vertebral body and annulus. The middle column includes the posterior longitudinal ligament and the posterior 2/3 of each vertebral body and annulus. The posterior column consists of the multiple structures forming the posterior housing of the spinal cord, including the pedicles, lamina, facets, spinous processes, and the ligamentum flavum and posterior ligamentous complex (supraspinous ligament, interspinous ligament, ligamentum flavum, and facet capsule).
In what follows, the most common thoracic and thoracolumbar spine injuries in patients are discussed: compression fractures, burst fractures, flexion-distraction fractures, and fracture-dislocation injuries.
8.3.1 Compression fractures
Compression fractures involve collapse of the vertebral body in the vertical axis and are classified as AO type A. 15 They are generally stable fractures that spare the posterior ligamentous complex. These are by far the most common type of thoracic and thoracolumbar fractures, especially in elderly patients with osteoporosis. With advanced osteoporosis, compression fractures may occur with little or even no axial load. They are more likely to occur in women than men, given the higher rates of osteoporosis among women. A single fracture increases the risk of additional fracture. 19
These injuries may present with pain around the fracture or in the dermatomal region corresponding to the nerve root at the fracture site. A physical exam may reveal focal tenderness, mild local kyphosis in the case of one fracture or more obvious kyphosis in the case of multiple fractures, and nerve root deficits if the fracture is severe enough to cause foraminal stenosis. In these fractures, there is typically fracture and depression of the superior endplate of the vertebrae, causing a change in the radiographic appearance of the vertebrae (Fig. 8‑1). The vertebrae appear wedged in these fractures, with height loss of the anterior column. In the thoracic spine, there may be more than one fracture after a fall or injury. It is common to see consecutive vertebral compression fractures in patients with osteoporosis.
8.3.2 Burst fractures
A more severe type of compression fracture, known as a burst fracture (AO type A3 15 ) describes a compression fracture in which the vertebral body expands in all directions. Both the anterior and middle columns are involved, and the injury may be stable or unstable. Burst fractures are classified differently based on the condition of the superior and inferior endplates of the fractured vertebral body and whether any rotation or lateral flexion accompanies the burst fracture. These fractures often involve the entire vertebrae, and there are several characteristic imaging findings. On an axial CT image, there is often comminution and disruption of the cortical walls of the vertebrae with associated widening or splaying of the pedicles. There may also be retropulsion of the posterior wall of the vertebral body into the spinal canal (Fig. 8‑2). The amount of retropulsion into the spinal canal may be severe, and the axial image can be alarming with regards to the degree of retropulsion. The degree of retropulsion is not necessarily associated with the severity of neurologic deficit, if at all present, but careful neurologic examination is critical to assess for any signs of spinal cord or cauda equina compression causing urinary, motor, or sensory deficits.
Patients also may not have any symptoms while on bed rest or in the initial acute assessment while immobile. These patients need to be evaluated once mobilized, as additional weight-bearing and loading of the spine may exacerbate or produce symptoms, which may then prompt more urgent intervention or reconsideration of operative intervention. It is not uncommon for patients to lose bladder function or develop leg weakness once mobilizing from a recumbent to weight-bearing position. This does not necessarily mean that the fracture pattern has changed but demonstrates the general inability of the spine to withstand these loads. Patients may also experience stronger radicular pain when sitting or standing. This is due to further foraminal height loss and compression. This mechanical type of radiculopathy is difficult to treat with bracing alone, because braces do not provide significant resistance to axial load to maintain the height of the foramen and avoid nerve impingement.
Burst fractures are usually associated with high-energy events, including motor vehicle accidents and falls. They are the second most common injury to the thoracolumbar spine after compression fractures, with about 25,000 occurring annually in the United States. The osteoporotic bone of elderly patients can increase the risk of such fractures. Burst fractures may be accompanied by other spine fractures, particularly laminar fractures, which may be associated with dural tear and entrapped nerve roots. Imaging studies, including plain film radiography, CT and MRI scans, may reveal increasing spacing between vertebral bodies, suggesting ligamentous disruption, or direct visualization of ligamentous compromise.
Flexion-Distraction injuries (AO type B 15 ) occur with sudden flexion of the spine— as in the case of a motor vehicle accident causing acute flexion at the waist—and distraction of the posterior elements of the spine (Fig. 8‑3). These fracture types are also called “seatbelt fractures” or, eponymously, Chance fractures. The posterior column is always involved and the middle and anterior column is commonly involved. The instantaneous axis of rotation, or hinge, is created anteriorly to the spine as the abdomen is compressed around an object such as a seatbelt. The fracture may occur through the bone of the vertebral body (AO type B2) or through the ligamentous elements, including the intervertebral disk (AO type B1). 15 Of these two injury patterns, the ligamentous injury is less stable. There is a less common pattern of injury in which the anterior longitudinal ligament is disrupted, in addition to the posterior and middle columns (AO Classification B3 15 ). These injuries usually require an impact with significant energy to the abdomen and commonly result from violent trauma, prompting need for thorough assessment by physical examination and imaging of the visceral organs for other injury.
8.3.4 Fracture dislocations
Fracture dislocations (AO type C 15 ) involve disruption of the entire spinal column along the horizontal axis; they are inherently unstable and are generally associated with the highest-energy injuries. These injuries most commonly occur at the thoracolumbar junction, because the juxtaposition of the stiffer thoracic spine and the relatively mobile lumbar spine creates a site that is prone to shear forces. These injuries are associated with a very high risk of injury to the spinal cord, and they most commonly occur at the thoracolumbar junction. In these cases, the dislocation may result in severe deformity of the spinal column in multiple planes. The spine is often rotated and translated as a result of these fractures (Fig. 8‑4). Injuries to surrounding visceral organs are also common.
8.4 Treatment Options
For all fractures, treatment options include nonoperative and operative options. A major consideration in the older patient is the morbidity of surgery and the potential complications of surgery. In this patient group, the sequelae of chronic illness such as hypertension, diabetes, obesity, cancer, and osteoporosis all play a role in the decision-making process. Elderly patients may be deconditioned at baseline with poor nutrition, a low level of activity, and poor cardiopulmonary reserve. As such, sometimes surgery is not considered an option, even in the most severe fracture types, due to the patient’s underlying medical and functional status. Having an understanding of fracture classification schemes, the mechanism of injury, and the biomechanics of a disrupted spinal column are all essential, but the decision to operate does not necessarily follow a flow-chart diagram in most cases, and reliance on dogmatic algorithms is not recommended.
8.4.1 Nonoperative Treatment
Most thoracic and thoracolumbar spine fractures are stable and do not require surgery. Historically, prolonged bed rest was advised, but bracing is currently a mainstay of conservative management. 20 , 21 , 22 , 23 , 24 External support may be provided with an over-the-counter brace or a molded orthotic device. These devices permit early ambulation, which is preferred to prolonged bed rest. 21 In some cases, no external support is necessary, and conservative management focuses on pain control and rehabilitation. 24 Even injuries with up to 70% compromise of the spinal canal may not require surgery. 21 , 24 , 25 , 26
8.4.2 Operative Treatment
While there is consensus regarding the role of conservative management in these simple and stable fractures, some studies suggest that these injuries might benefit from surgery. 27 To help guide surgical decision-making, the angle of kyphosis at the fracture site should be assessed and monitored. Over time, settling may occur and cause the angle of kyphosis at the fracture site to worsen. This has been shown, however, not to correlate consistently with pain. 20 , 21 , 23 , 24 , 28 , 29 Surgery should be considered if the angle of kyphosis worsens by more than 10°, or if pain increases significantly. 30 While some flexion-distraction injuries may be eligible in younger patients for conservative management—particularly if the fracture is through the bone—in the aging population, conservative management is less suitable. Fracture-dislocation injuries are by definition unstable and require surgery. In cases in which nonoperative treatment —bracing or casting— is appropriate, operative treatment may still be helpful for those who cannot tolerate months of immobility in an orthosis. 31 In these cases, operative management may allow for earlier mobilization and engagement with rehabilitation while maximizing decompression and alignment.
Here, we discuss nonoperative and operative treatment options for each of the four major categories of thoracic fractures.
8.4.3 Compression Fractures
Most compression fractures can best be managed by nonoperative treatment. The standard treatment is bed rest with encouragement for early mobilization. External support with over-the-counter braces or individually molded orthotics has been and continues to be commonly used. However, there is some evidence that these devices are being used less frequently, and strong evidence that their benefit is lacking. 30
Operative treatment for compression fractures include minimally invasive augmentation techniques using vertebral cement, namely vertebroplasty and kyphoplasty. In vertebroplasty, a needle is used to inject cement under pressure into the collapsed vertebral body. In kyphoplasty, a balloon is used to expand the collapsed vertebra and create a space for the cement to be injected into.
The most recent guidelines released by the American Academy of Orthopedic Surgeons (AAOS) in 2011 strongly recommend against the use of vertebroplasty. 32 Kyphoplasty is recommended if patients continue to experience severe pain after undergoing 6 weeks of nonoperative management.
8.4.4 Burst Fractures
Burst fractures are considered stable if the posterior ligamentous complex is preserved. If the posterior ligamentous complex is not preserved, or if any neurologic deficit is present, the fracture is likely unstable, and surgery is generally indicated. The ligamentous complex can be imaged with MRI. However, many factors impact the decision to pursue surgery, including the location of the fracture, the degree of vertebral destruction, neurologic involvement, the degree of kyphosis, and the stability of the posterior column. In burst fractures, neurologic involvement is usually caused by retro-pulsed bony fragments impinging upon the spinal canal. However, these fragments can resorb and do not usually cause progressive worsening of neurologic function; moreover, the canal itself can remodel after the fracture, creating a new space for the cord to occupy without impingement. 20 , 21 , 22 , 28 , 33 , 34 , 35
In patients who are neurologically intact and mechanically stable and/or have a TLICS score of 3 or lower, nonoperative management may be used. External support in the form of a brace or orthosis is commonly used and may provide symptomatic relief, though published evidence of their long-term benefit is scarce.
Posterior spinal fusion with pedicle screw fixation and no decompression may be used if there is radiologically confirmed injury to the posterior ligamentous complex or progressive kyphosis without significant compression of the spinal canal.
Anterior decompression of the fracture and spinal stabilization may be used, depending on the degree of vertebral body damage, the extent of spread of fracture fragments, and the angle of kyphosis. If neurologic deficits are present and attributable to vertebral fragments retro-pulsed into the canal, an anterior approach facilitates direct visualization and removal of these fragments. However, in elderly patients, the morbidity of anterior transthoracic or combined retroperitoneal approaches may not be justified. In these patients, especially those with osteoporosis, posterior fixation is preferred, as multiple points of fixation for instrumentation is readily available through a standard posterior approach. As such, several levels above and below the fracture level can be stabilized. Laminectomy can also be performed at the same time through the same incision.