Each year, more than 150,000 persons 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.
The Egyptians were the first to describe the diagnosis and to recommend a treatment for the spine and spinal injuries (2500 BCE to 1900 BCE).
Hippocrates (400 BCE) described the clinical consequences of a thoracic fracture and recommended a method of reducing the gibbus often associated with these injuries. He designed a racklike traction device (scamnum) to reduce the bony abnormalities of thoracolumbar spine fractures. The patient was extended in the prone position with leather straps at the hips and shoulders, while a reducing force was manually placed over the site of the kyphosis. This device was introduced as an alternative to "succussion," which consisted of tying the patient upside down to a ladderlike device that was suddenly dropped, extending the patient's spine in an attempt to reduce the spinal deformity.
In the seventh century, Paulus of Aegina employed an external fixation device made of thin sheets of wood to secure the reduction. Paulus of Aegina was the first clinician to suggest that laminar fragments pressing on the spinal cord were a source of pain; he advocated laminectomy to debride the fracture site. Whether this operation was ever actually performed during his career is uncertain.
Duhamel first demonstrated osteogenesis in 1739, when he showed that new bone surrounded silver wires implanted within the periosteum. During the 19th century, Heine, Fluorens, and Ollier demonstrated the osteogenic capacity of periosteum. Clinical bone transplantation began with the transfer of a free autograft by Walther in 1820 and a free allograft by Macewen in 1878.
In the early years of the 20th century, Albee popularized bone grafting in spinal surgery. He published his experiences with 3000 bone graft operations. Bauer investigated the preservation and storage of canine allografts in 1910, and in the 1940s, the storage of autogeneic and allogeneic human bone was reported. After World War II, scientists at the Navy Tissue Bank in Bethesda, Maryland, investigated the preservation, sterilization, and distribution of cadaveric allografts and revealed that the freezing of bone reduces its immunogenicity.
Since Mixter and Barr first described an operative procedure for the management of lumbar disk disease, the goals of spinal surgery have been decompression of the neural elements and preservation of normal anatomy and biomechanics. Numerous investigators have attempted to define stability and to recommend treatment based on the presumed injury mechanism.
In the 1930s, Watson Jones considered spinal fractures to be pure flexion fractures and treated them with hyperextension casts. In 1949, Nicoll reported on 166 thoracolumbar fractures in coal miners and classified these injuries as anterior wedge fractures, lateral wedge fractures, fracture dislocations, and neural arch fractures. In 1949, Nicoll attempted to define stable versus unstable fractures using an anatomic classification. In his view, the major determinant of stability was the integrity of the interspinous ligament.
Later, Holdsworth introduced the first modern classification, which was based on the two-column theory of spinal column stability. This classification had a major impact on the understanding of thoracolumbar injuries.
In the 1980s, Denis proposed the three-column theory of spinal instability, which remains widely accepted because of its simplicity and the anatomic description. This proposal was based on the meticulous analysis of 412 thoracolumbar spinal injuries.
In Great Britain, Ludwig Guttman pioneered current concepts of spinal cord rehabilitation in the 1940s. Before this time, the mortality for patients with spinal cord injury was 80-90% within the first year. Most patients developed pressure sores or urinary sepsis that led to death. Guttman obtained reduction of spine fractures using traction and postural reduction, revolutionized nursing techniques, and introduced a comprehensive program of rehabilitation. The dramatic reductions in mortality and morbidity obtained with these methods countered the perception that these cases were hopeless and caused surgical stabilization of the traumatized spine to be considered logical and practical.
Initial attempts at spinal instrumentation used wire and screw fixation for spinal fractures and were first reported in the late 1800s. However, these materials were not suitable for internal fixation. Metals were subject to electrolysis when placed in tissue. In 1930, Vitallium, an alloy of chromium, molybdenum, tungsten, and cobalt, was introduced for internal fixation.
However, significant advances in spinal instrumentation did not occur until after World War II, when Rogers described the interspinous wiring technique. Also in the 1940s, Harrington introduced the distraction rod fixation system, which, although introduced for the treatment of scoliosis, was found to be useful to reduce and stabilize spine fractures. In 1945, Cloward introduced the technique of posterior lumbar interbody fusion. In the 1970s in Mexico, Luque introduced the sublaminar wiring technique, which was combined with the use of rods.
The 1980s produced a proliferation of spinal instrumentation systems. Roy-Camille in France developed modern pedicle screws. Cotrel and Dubousset in France developed a system consisting of rods, multiple hooks, and screws. This system rapidly replaced the Harrington distraction rod and the Luque rod constructs in the treatment of thoracic spine injuries. Since then, multiple systems have become available for instrumental fixation of the spine based on the system introduced by Cotrel and Dubousset.
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 annulus fibrosus and the nucleus pulposus. The annulus 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.
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 annulus 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 annulus fibrosus receives most forces transmitted from one vertebral body to another, and it is designed to resist tension and shearing forces. The nucleus pulposus is best designed to resist 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.
The forces responsible for spinal fractures are as follows:
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. 
The National Spinal Cord Injury Registry, established by Ducker and Perot, reported that 40% of spinal injuries were caused by motor vehicle accidents, [6, 7] 20% by falls, and 40% by gunshot wounds,  sporting accidents,  industrial accidents, and agricultural accidents combined. Such injuries can also be the result of child abuse. 
The spectrum of injury severity related to motor vehicle accidents 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 gunshot wounds were second only to motor vehicle accidents as a cause of traumatic paraplegia. In a series of patients with spinal injuries in the south Florida region, gunshot wounds caused 34% of the injuries, and motor vehicle accidents caused only 28%. The remainder of the 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. 
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. 
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.  Direct trauma also can cause a fracture of an articular process.
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 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 spinal cord injuries. 
The thoracolumbar spine and lumbar spine are the most common sites for fractures because of the high mobility of the lumbar spine compared to the more rigid thoracic spine.  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 are unreliable because of the lack of accurate reporting. 
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 spinal cord injuries secondary to spinal fractures, 4200 of them die before reaching the hospital, nearly 5000 patients 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 spinal cord injuries, 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. [16, 17] 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, 18] 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.  See also the Fracture Index WITH Known Bone Mineral Density (BMD) calculator.
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 (within 72 hours of injury) include earlier patient mobilization and, probably, fewer septic complications related to pneumonia.
Patients who survive their original spinal cord injury have high residual morbidity. Studies of long-term survival among patients who sustain spinal cord injuries revealed that about 80% 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. 
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