Practice Essentials
Each year, more than 150,000 individuals in North America sustain fractures of the vertebral column. Injuries to the thoracolumbar and lumbar spine constitute most of these fractures. The immediate neurologic damage that accompanies the bony destruction results in nearly 5000 cases of paraplegia per year. The mechanisms and severity of injuries reflect a mechanized and risk-taking culture.
Patients with lumbosacral fractures present with severe pain, deformity, and neurologic deficits related to compression of neural structures. Fractures of the thoracolumbar junction can produce a mixture of cord and root syndromes caused by lesions of the spinal cord, conus medullaris, or thoracic and lumbar nerve roots. Lower lumbar fractures may cause solitary or multiple root deficits. (See Presentation.)
Skin overlying the fracture should be inspected for abrasions or contusions. Attention should be paid to general deviations from normal spine curves. The spine should be palpated for areas of tenderness or fractured or displaced spinous processes. Any neurologic deficit should be documented according to the American Spinal Injury Association (ASIA) Motor Index, and impairment should be assessed according to the ASIA impairment scale.
Information obtained from the combination of plain radiography, computed tomography (CT), and magnetic resonance imaging (MRI) allows classification of the injuries and identification of unstable injuries, as well as facilitates selection of the proper instrumentation for stabilization. Electromyography (EMG), nerve conduction studies, urodynamic studies, and evoked potentials may be helpful. (See Workup.)
Since operative management of lumbar disk disease was first described, the goals have been decompression of the neural elements and preservation of normal anatomy and biomechanics. The decision whether to perform surgery in the acute setting is made by the surgeon. In general, decompressive surgery is not indicated for patients with complete deficit lasting more than 48 hours and is advocated for patients with partial cord or cauda equina injuries. Factors to be considered in the selection of the surgical approach include bone destruction, associated ligamentous injury, neurologic deficit, patient age and medical condition, and other associated injuries. (See Treatment.)
This article reviews the diagnosis and management of acute lumbar vertebral fractures. (For more information, see Lumbar Compression Fracture and Lumbar Spine Trauma Imaging.)
Anatomy
The lumbar spine consists of a mobile segment of five vertebrae, which are located between the relatively immobile segments of the thoracic and sacral segments. The thoracic spine is stabilized by the attached rib cage and intercostal musculature, whereas the sacral segments are fused, providing a stable articulation with the ilium.
The lumbar vertebrae are particularly large and heavy as compared with the cervical and thoracic vertebrae. The bodies are wider and have shorter and heavier pedicles, and the transverse processes project somewhat more laterally and ventrally than other spinal segments. The laminae are shorter vertically than are the bodies and are bridged by strong ligaments. The spinous processes are broader and stronger than are those in the thoracic and cervical spine.
The intervertebral disks consist of two components, the anulus fibrosus and the nucleus pulposus. The anulus is a dense fibrous ring located at the periphery of the disk that has strong attachments to the vertebrae and serves to confine the nucleus pulposus.
Because the lumbar spine must transmit all of the compressive, bending, and rotational forces generated between the upper and lower body, it is surrounded by powerful musculature and ligaments.
Biomechanics
The lumbar spine is a complex three-dimensional structure that is capable of flexion, extension, lateral bending, and rotation. The total range of motion is the result of a summation of the limited movements that occur between the individual vertebrae. Strong muscles and ligaments are crucial in supporting the bony structures and in the initiation and control of movements.
During flexion, the intervertebral disk is compressed anteriorly, and the spinal canal is widened. Some sliding movement of the articular process occurs in the zygapophyseal joint. This movement is limited by the posterior ligamentous complex and the dorsal muscles.
Extension of the lumbar spine is more limited, producing posterior compression of the disk and narrowing of the spinal canal, along with sliding motion of the zygapophyseal joint. The anterior longitudinal ligament, ventral muscles, lamina, and spinous processes limit the extension of the lumbar spine.
Lateral bending involves lateral compression of the intervertebral disk on the concave side and sliding separation of the zygapophyseal joint on the convex side. An overriding of the zygapophyseal joint occurs in the concave side. The intertransverse ligaments limit the lateral bending of the spine.
Rotation of the lumbar spine involves compression of the anulus fibrosus fibers. It is limited by the geometry of the facet joints and the iliolumbar ligaments.
The motion of the lumbar spine cannot be considered without considering the synchronous movements of the cervical and thoracic spine. The entire spinal column moves as a whole in all planes of motion. Each region of the spine has its own characteristic curvature. These curves allow an upright posture while maintaining the center of gravity over the pelvis and lower limbs. Most rotation is accomplished by the cervical spine; flexion and lateral bending are primarily cervical and lumbar functions.
The intervertebral disks are thick and strong. The anulus fibrosus receives most forces transmitted from one vertebral body to another, and it is suited for resisting tension and shearing forces. The nucleus pulposus is best suited for resisting compression forces. It receives primarily vertical forces from the vertebral bodies and redistributes them in a radial fashion to the horizontal plane. This structure allows the intervertebral disks to dissipate the axial loading.
Pathophysiology
The forces responsible for spinal fractures are as follows:
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Compression
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Flexion
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Extension
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Rotation
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Shear
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Distraction
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Combination of one or more of these forces
The most common acute fractures are compression fractures or vertebral endplate fractures caused by sudden axial loading, transverse process avulsion by the origin of the psoas muscle, spinous process avulsions, and acute fracture of the pars interarticularis from hyperextension.
Vertebral body compression is more common in patients with decreased bone density. [1, 2] In adolescents, it is relatively common to find endplate fractures or apophyseal avulsion fractures. All of these injuries generally are stable and heal with immobilization and nonsurgical management. [3, 4]
Spinous process fractures may occur as a result of direct trauma to the posterior spine or as a result of forcible flexion and rotation. These injuries usually are not associated with neurologic deficits. Violent muscular contraction or direct trauma can cause fractures of the transverse processes. For example, a football helmet blow to the back can cause fractures of either the spinous or transverse process. Despite their relatively innocuous appearance, these fractures can cause significant bleeding into the retroperitoneal space, resulting in acute anemia or ileus.
Acute traumatic spondylolisthesis usually is associated with major trauma and usually is caused by extreme hyperextension. Although patients with a new fracture of the pars interarticularis may have a slip present at the time of the injury, a slip can occur months to years later as the disk degenerates under shear loads that it cannot sustain. [5]
Etiology
The National Spinal Cord Injury Registry, established by Ducker and Perot, reported that 40% of spinal injuries were caused by motor vehicle accidents (MVAs), [6, 7] 20% by falls, and 40% by gunshot wounds (GSWs), [8] sporting accidents, [9] industrial accidents, and agricultural accidents collectively. Such injuries can also be the result of child abuse. [10]
The spectrum of injury severity related to MVAs ranges from minor soft tissue contusions to paraplegia and death. Numerous variables relating to the type and severity of the crash, the type of vehicle, and the use of safety restraints have an impact on the frequency and severity of the spinal injury.
An analysis of patients admitted to Rancho Los Amigos Spinal Cord Injury Center from 1966 to 1972 showed that GSWs were second only to MVAs as a cause of traumatic paraplegia. In a series of patients with spinal injuries in south Florida, GSWs caused 34% of the injuries, and MVAs caused only 28%; the remaining injuries were attributable to falls (19%), sports- and water-related injuries (8%), and other causes, including industrial accidents (12%). For a study of 49 cases in South Africa, see Le Roux and Dunn. [8]
After autopsies on more than 5000 service members killed in Iraq and Afghanistan, Schoenfeld et al found than 38.5% had sustained at least one spinal injury. This is a higher percentage than was previously thought. [11]
Spinous process fractures may occur as a result of direct trauma to the posterior spine, and violent muscular contraction or direct trauma can cause fractures of the transverse processes. [12] Direct trauma also can cause a fracture of an articular process.
Epidemiology
Accidents are the fourth leading cause of death in the United States, after heart disease, cancer, and stroke. Annually, accidents account for about 50 deaths per 100,000 population. Of these deaths, approximately 3% are the direct result of spinal fractures with spinal cord injury (SCI) from trauma. More than 150,000 persons in North America sustain fractures of the vertebral column each year, and 11,000 of these patients sustain SCIs. [13]
The thoracolumbar spine and lumbar spine are the most common sites for fractures because of the high mobility of the lumbar spine as compared with the more rigid thoracic spine. [14] A study using data from the National Electronic Injury Surveillance System (NEISS) determined that the annual incidence of lumbar fractures in the United States, as reported by participating emergency departments, was 14.6/100,000 in 2010 but rose to 22.5/100,000 in 2018. [15] The total number of such fractures was 34,328 in 2010 but rose to 57,098 in 2018.
Injury to the cord or cauda equina occurs in approximately 10-38% of adult thoracolumbar fractures and in as many as 50-60% of fracture-dislocations. The rate of bony injury without neurologic consequence is undoubtedly higher. However, statistics have not been entirely reliable, because of the lack of accurate reporting. [16]
A high percentage of lumbosacral fractures occur in individuals younger than 30 years. Nearly 60% of patients have serious disabling deficits. Each year, approximately 12,000 persons sustain SCIs secondary to spinal fractures, of whom 4200 die before reaching the hospital, nearly 5000 develop paraplegia, and an additional 1500 die during the initial hospitalization.
In a study performed among navy aviators, the overall incidence of thoracolumbar fracture was 12.8 cases per 100,000 aviators per year. Helicopter crashes and parachuting accidents accounted for 73% of fractures, and neurologic injury occurred in 10% of aviators.
The international rate of spinal fractures is difficult to determine because of differences in data collection and reporting among countries. In developed countries, traffic accidents seem to be the most common causes of spinal fractures and SCIs, whereas in less developed countries, the most common causes seem to be falls.
Osteoporosis is a known risk factor for the development of spinal compression fractures. [17, 18] In an analysis of patients with osteoporosis in Oviedo, Spain, the prevalence of vertebral fractures ranged from 17.4% to 24.6%. Fractures were more common in women than in men, and a relatively high frequency of vertebral fractures was seen in men aged 50-65 years. [1, 2, 19] The trabecular bone score (TBS) may prove useful as a complementary tool for assessing fracture risk in the setting of osteoporosis. [20, 21]
In a study of 402 women living in Beijing, China, the prevalence of vertebral fractures was 5% in a group aged 50-59 years and 37% among women aged 80 years or older. [22] See also the Fracture Index WITH Known Bone Mineral Density (BMD) calculator.
Prognosis
The outcome and prognosis of patients with lumbosacral fractures depends on their neurologic condition. Patients with no neurologic deficits or partial deficits generally have a good prognosis, whereas those with complete injuries remain paraplegic. Other factors (eg, age, comorbid conditions, associated injuries, and general medical complications) also have an impact on outcome.
Although little consensus exists regarding the optimal timing of spine fracture fixation following blunt trauma, potential advantages of early fixation (≤ 72 hr after injury) include earlier patient mobilization and, probably, fewer septic complications related to pneumonia.
Patients who survive their original SCI have high residual morbidity. Studies of long-term survival among patients who sustain SCIs revealed that about 80% of patients with spinal injuries live 10 or more years after injury, compared with a normal 10-year life expectancy of 97%. Survival rates are much lower for patients with complete lesions than for patients with incomplete cord injuries. For a study of the direct medical costs of spine fractures, see van der Roer et al. [23]
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A 42-year-old man fell from a tree. He arrived at the hospital with a complete paraplegia. Plain radiographs reveal a fracture of L2 with L2-L3 subluxation.
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CT scan of a 42-year-old man who fell from a tree. He arrived at the hospital with a complete paraplegia (same patient as in Image above). Note the large amount of bone retropulsed inside the spinal canal.
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CT scan showing a burst of the L2 vertebral body.
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Postoperative lateral radiograph; although the patient was paraplegic, in order to prevent severe kyphotic deformity of the spine and to allow a rapid mobilization, a posterior arthrodesis was performed with pedicle screws, hooks, and rods.
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A 37-year-old man who underwent an anterior approach for an unstable L1 burst fracture. A corpectomy was performed, with a vertebral reconstruction with Harms cages and a screw to stabilize the cage. The patient subsequently underwent a posterior arthrodesis with iliac crest bone graft and transpedicular screw placement.
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A 52-year-old man was involved in a severe motor vehicle collision. He arrived at the hospital with severe pain but no neurologic deficit. Lateral plain radiographs show a fracture at T12.
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Sagittal T2-weighted image of a 52-year-old man who was involved in a severe motor vehicle collision. He arrived at the hospital with severe pain but no neurologic deficit (same patient as in the previous image). Image reveals a significant mass effect within the spinal canal.
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Patients with compression fractures not compromising the spinal canal can be treated by means of kyphoplasty. Use of a percutaneous balloon allows for expansion of the fractured vertebrae. Then, the void created by the balloon is filled with bone cement.
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Patients with an acute compression fracture treated with kyphoplasty. AP and lateral views demonstrate a good expansion of the compressed vertebral body and good filling with cement.
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A 47-year-old man was involved in a motor vehicle accident. He arrived at the hospital with paraplegia but preserved sensation in both lower extremities. He was immediately taken to surgery for an open reduction of the fracture, decompression of the cauda equina, and arthrodesis of the spine. He regained motor function following the surgery.
