Thoracolumbar injury classification and severity score: a new paradigm for the treatment of thoracolumbar spine trauma

Böhler2 initially attempted to classify thoracolumbar spine fractures using five injury types. He combined both anatomic appearance and mechanisms of injury to include compression fractures, flexion-distraction injuries, extension fractures, shear fractures, and rotational injuries in his classification scheme. Böhler, however, did not attempt to define instability patterns based on the anatomical appearance of the injury.

Watson-Jones3 recognized that the concept of “instability” would be crucial in any effective treatment algorithm on thoracolumbar injuries. He identified ligamentous integrity as one of the key determinants of stability in various injury subtypes. Nicoll,4 in a study of spine injuries in 152 miners, identified four anatomical structures (vertebral bodies, facet joints, posterior ligaments, discs) involved in any injury pattern. He, like Watson-Jones, emphasized the danger of progressive neurological injury and deformity if an instability pattern is overlooked.

Holdsworth,5 in his now classic scheme of injury patterns, introduced the columnar concept of stability. He visualized the spine as two columns: the anterior column consisting of the vertebral body and intervertebral disk, and the posterior column consisting of facet joints and the posterior ligamentous complex. He insisted that the integrity of the posterior column is necessary for stability of the thoracolumbar spine. His classification scheme, which includes anterior compression fractures, fracture-dislocation, rotation fracture-dislocation, extension injuries, burst fractures, and shear injuries, remains the most influential to modern classifications schemes. The most important criticism of this classification system was that it oversimplified the biomechanics of injury in thoracolumbar fractures. For example, unstable burst fractures based on their natural history were falsely categorized as “stable” when, in fact, many of these fractures progressed to kyphosis and increased neurological deficits.6,7

The era of computed tomography (CT) provided a new opportunity to improve on the existing thoracolumbar classification schemes. CT imaging allowed visualization of finer details of spinal injuries, including osseous anatomy surrounding the spinal canal. Using this technology, Denis introduced a classification scheme based on the three-column concept. Differing from Holdsworth’s system, Denis defined the anterior column as the anterior longitudinal ligament to the anterior two-thirds of the vertebral body, the middle column as the posterior one-third of the vertebral body including the anulus fibrosus and posterior longitudinal ligament, and the posterior column, which includes all structures posterior to the posterior longitudinal ligament. Denis defined four distinct fractures types: compression fractures, burst fractures, fracture-dislocations, and seatbelt injuries. Denis also recognized that mechanical instability and progressive neurologic deterioration could occur separately or together. Mechanical instability may lead to progressive kyphosis without neurologic instability, and neurologic deterioration may occur without radiographic signs of instability, as in the case of burst fractures. More unstable fractures, such as fractures associated with dislocations of the facets or disc interspace were usually associated with neurologic deterioration. Denis called isolated mechanical instability “first degree” injuries, neurologic deterioration as “second degree” injuries, and combined mechanical and neurologic deterioration as “third degree” injuries. This classification scheme remains the most popular to date, mostly because of its simplicity. Denis’ anatomic divisions of columns are easily visualized on CT images, and his original concept of instability has been oversimplified to state that instability exists if two of three columns are disrupted. This oversimplification, however, has led to the loss of Denis’ original emphasis on the distinction of mechanical and neurologic instability.

Denis’ classification does not clearly provide a useful algorithm for treating unstable injuries. With the oversimplification of his scheme, it has been widely accepted that when two of three columns are injured operative stabilization may be necessary for a satisfactory outcome. Several studies, however, have shown that nonoperative treatment of two-column injuries may achieve a satisfactory outcome.8‐10 Also, Denis’ classification is unclear on how ligamentous injuries (which may lead to occult, progressive instability) can be identified. Therefore, the subset of patients who require surgical intervention to prevent painful deformity or progressive neurologic deficit may be missed. With the advent of modern magnetic imaging (MRI) studies, occult ligamentous injuries may be easier to define. Yet, there is no classification to date that incorporates this new technology in its scheme.

A modern classification system, then, should incorporate the current understanding of the biomechanics of thoracolumbar injuries and the availability of modern imaging modalities including MRI; it should also acknowledge the advancements in anesthesia and internal fixation that may allow early mobilization and rehabilitation of the injured patient. The classification system should be relatively simple to achieve high inter- and intraobserver reliability. In addition, it should give general guidelines of treatment based on the current understanding of the natural history of thoracolumbar spine injuries.

The thoracolumbar injury classification and severity score (TLICS) was conceptualized based on a survey given to the Spine Trauma Study Group, which consists of worldwide experts in the field of spinal trauma. The goal of the survey was to identify similarities in treatment algorithms for common thoracolumbar injuries as well as to identify characteristics of injury that played a key role in the decision-making process. Using these data, a new classification system and algorithm of treatment was developed.11

The classification system is based on three major categories: the morphology of the injury; the integrity of the posterior ligamentous complex; and the neurologic status of the patient.11 To classify an injury, the treating physician first describes the morphology of injury followed by the status of the integrity of the posterior ligamentous complex and finally the patient’s neurologic examination. For example, a patient has a T7 flexion compression burst fracture with disruption of the posterior ligamentous complex and a complete cord injury on neurologic examination. The morphology of injury and the integrity of the posterior ligamentous complex are both defined by the appearance of the injury on imaging studies. Based on the severity of these categories, specific points are allocated, and the sum of the points defines the possible treatment alternatives (Table 1). Higher total points indicate a more severe injury, and those injuries are more likely to benefit from surgical intervention based on the opinions of the Spine Trauma Study Group.