Thoracic and Lumbar Spine Injuries

Evaluation and Diagnosis

Diagnosis of spinal injury, especially of the thoracolumbar spine, is often delayed or missed in severe trauma victims. This has been attributed to numerous factors, including distracting injuries, mental status changes, suboptimal or absent imaging studies, noncontiguous spinal injuries, and failure to seek medical attention. An analysis of the German Trauma Society’s Trauma Register concluded that almost 50% of severe spinal injuries were not clinically suspected during the initial patient trauma evaluation, and further studies have demonstrated that subsequent diagnosis of thoracolumbar injuries can take as long as a month in patients initially misdiagnosed. As nearly half of significant thoracolumbar fractures are estimated to be unstable, this places patients at increased risk of permanent deformity and disability. The significance of timely diagnosis of these injuries cannot be understated.

Assessment in the Emergency Department

Any patient subjected to high-energy trauma should be thoroughly examined using guidelines established by Advanced Trauma Life Support protocols. Additionally, once preliminarily stabilized, patients should be thoroughly examined for spine injuries, including identifying the presence of tenderness, step-offs, gaps between spinous processes, or malalignment, any of which may suggest spinal instability. A complete neurological examination is essential to identify any deficits that may have resulted from spinal column injury, including the status of the bulbocavernosus reflex, as this can aid diagnosis of spinal shock, as well as rectal tone and perineal pinprick sensation, which assist in assessing the vitality of the sacral nerve tracts, i.e., sacral sparing. More frequently, the benefit of high-dose methylprednisolone in the treatment of acute spinal cord injuries has been questioned; therefore, administration of steroids should be based upon provider preference and patient-specific factors.

For thoracolumbar fractures resulting in spinal cord injury (SCI), the American Spinal Injury Association (ASIA) Impairment Scale is useful for classifying both the severity of SCI and its associated prognosis ( Table 37.1 ). SCIs can range from complete loss of motor and sensory function below the level of injury, designated ASIA A, to completely recovered motor and sensory function, designated ASIA E. Patients with ASIA A injuries have an 8.3% probability of walking independently at 1 year postinjury, compared with ASIA B with a 39.4% probability, ASIA C with a 61.8% probability, and ASIA D with a 97.3% probability.

Imaging

Diagnostic imaging is critical to identifying and classifying injuries of the thoracic and lumbar spine, especially given their variable and occasionally occult clinical presentations. In terms of plain radiographs, anteroposterior and lateral views are the gold standard following spinal trauma. However, multidetector computed tomography is now routinely used, given its high sensitivity and specificity for detecting these injuries. Fine-cut axial and sagittal reconstructions also provide information regarding stability and the integrity of the spinal canal. Magnetic resonance imaging (MRI) scans are generally reserved for examining the soft tissue envelope after identification of a thoracolumbar fracture, assessing the integrity of neurological structures in patients with deficits, and identifying possible ligamentous or occult bony injuries in patients with negative radiographs but clinical presentation highly consistent with spine injury. ^,

Classification of Thoracolumbar Fractures

Several classification systems have been proposed to provide a universal language for discussing thoracolumbar injuries and to capture the most important characteristics for guiding treatment of these fractures. Today, the most commonly used classification systems for thoracolumbar injury are the Denis three-column system, the Margel AO System, the Thoracolumbar Injury Classification System (TLICS), and most recently, the AOSpine Thoracolumbar Spine Injury Classification System.

Denis Three-Column Classification System

Formulated in 1983, the Denis three-column system was the earliest of the four proposed classification systems listed above used for thoracolumbar fractures, and many of its core principles have been incorporated into more modern classification systems. In this classification system, spinal injuries are divided into major and minor categories, referencing three distinct regions of the spinal elements, termed “columns,” when describing the location of injury ( Fig. 37.1 ). The anterior column is composed of the anterior longitudinal ligament, the anterior annulus fibrosis, and the anterior part of the vertebral body. The middle column comprises the posterior half of the vertebral body, including the annulus fibrosus and posterior longitudinal ligament. Finally, the posterior column includes the region from the posterior longitudinal ligament to pedicle, and associated posterior soft tissue elements.

Denis describes four major types of thoracolumbar fractures: compression fracture, burst fracture, seatbelt-type injuries, and fracture-dislocations. A compression fracture occurs when the anterior column is compressed while the middle column stays intact; however, in more severe cases the posterior column can be distracted ( Fig. 37.2 ). In comparison, a burst fracture is a failure of both the anterior and middle columns owing to an axial load, whereas the posterior column remains intact ( Fig. 37.3 ). In seatbelt-type injuries, there is distraction of both the posterior and middle columns because of tension forces produced by flexion, and although the anterior column may compress under these forces, it continues to act as a hinge ( Fig. 37.4 ). Finally, a fracture-dislocation is the most unstable of the injuries, caused by a failure of all three columns because of compression, tension, rotation, or shear forces ( Fig. 37.5 ). Fraction-dislocations most often occur at the thoracolumbar junction and have been associated with neurological injury in up 75% of cases, with 52% of neurologically injured fracture-dislocation patients demonstrating complete paraplegia.

In addition to major injuries, Denis identifies four types of minor injuries, which include fractures of the transverse processes, facets, pars interarticularis, and spinous processes. These minor fractures are more localized, involving only a part of the posterior column, and rarely cause acute spine instability. ^, Patients with transverse process fractures were noted to have more neurological deficits in the T1‒T2 and L4‒L5 regions, whereas those with spinous process fractures tended to have more temporary loss of neurological functions, which were regained around 1 week postinjury. Facets and pars interarticularis fractures rarely resulted in associated neurological deficits.

The Denis system was the first classification model to account for clinical symptomatology, which influenced treatment plans by introducing the concept of “degrees of instability” that could be mechanical or neurological in nature. Mechanical instability is caused by fractures that decrease the structural integrity of the spine, whereas neurological instability pertains to those that increase the vulnerability of the patient to spinal cord or peripheral nerve injuries. First-degree instability is characterized by mechanical instability only, second-degree instability is characterized by neurological instability only, and third-degree instability is characterized by both mechanical and neurological instability. In regards to treatment plans, it was recommended that two- or three-column injuries be treated with surgical intervention; however, more recent studies have demonstrated that nonoperative treatments are just as viable for these types of injuries, and could even provide better long-term function and reduced pain. Although components of this system have been incorporated in more modern classifications, the Denis three-column system has been criticized for its poor interrater reliability and its inability to distinguish between stable and unstable burst fractures. ^,