Thoracolumbar and Lumbar Spine Injuries
Although thoracolumbar fractures make up just over half of the total number of spine fractures, these fractures are commonly associated with concomitant injuries and prolonged hospitalization.1,2 The most common level injured is L1, followed by L2, L3, and T12. The high prevalence of injuries at the thoracolumbar junction, as well as the specific vertebral injuries seen, has been attributed to several factors. First are the anatomic differences in the thoracic and lumbar regions. These include the transition from thoracic kyphosis to lumbar lordosis, the change in the orientation of the facet joints from a coronal to a sagittal orientation, and a change in the relative flexibility of the spine as one transitions from the thoracic to the lumbar region.3 Specific anatomic features of the vertebral bodies themselves also influence the pattern of fractures seen in this region. Stress concentrations in the vertebral bodies tend to be greatest at the base of the pedicles, where there is thinning of the posterior vertebral body cortex. This is also the area of greatest tensile and compressive strain, therefore causing this to be a common area of fracture initiation.3,4
Classification
Any classification system must serve several purposes and meet several requirements: it should provide understandable terminology to facilitate communication and research; it should be easy to implement; it should be comprehensive and intuitive; and it should ultimately guide the choice of treatment. In addition, the system must be reliable and reproducible.5 Since Bohler′s first attempt at classifying thoracolumbar fractures in 1929, classification systems have slowly evolved to reflect conceptual and technological advances in the evaluation and treatment of thoracolumbar fractures.6 These classifications have been based on various aspects of the injury, including the morphology, the mechanism, and the resultant stability.6,7 Yet, despite the multitude of classifications available, there is no single classification that is universally accepted. However, the most recent systems have finally been able to help the clinician determine which injuries require surgical intervention.8,9
Perhaps the simplest and most widely utilized modern classification is that of Denis.10,11 Using computed tomography (CT), Denis was the first to popularize the concept of the three-column spine and describe its relationship to spinal stability. In defining three columns of the spine, he simply expanded upon the two-column concepts that had previously existed. According to Denis, the posterior column consists of the posterior bony arch (specifically the pedicles, lamina, spinous process, and transverse process) as well as the alternating ligamentous structures, namely, the supraspinous ligament, interspinous ligament, facet capsule, and ligamentum flavum. The middle column is the posterior longitudinal ligament, the posterior annulus, and the posterior half of the vertebral body including the posterior wall, whereas the anterior column consists of the anterior longitudinal ligament, the anterior annulus, and the anterior half of the vertebral body. Using these definitions, Denis then described four anatomic types of thoracolumbar injuries, along with subclassifications. The mechanism of each type of fracture was also described, but this classification was an anatomic classification.
The first type of fracture described was a compression fracture, which consisted of failure of the anterior column under compression, with tensile failure of the posterior column associated with severe anterior collapse (Fig. 12.1). The defining feature of this injury is that the middle column is intact, and there is no subluxation or retropulsion of bone toward the neural elements. Compression fractures are subdivided into anterior and lateral compression subtypes.
The second type of fracture, the so-called burst fracture, results from an axial loading force. In this type of fracture, there is failure of both the anterior and middle columns with retropulsion of the posterior cortex of the vertebral body back toward the neural elements. The posterior column is often involved as well, usually with a sagittal split of the lamina and widening of the interpedicular distance (Fig. 12.2). These fractures are further subclassified into types A through E.
The third type of fracture described by Denis is the seat-belt–type injury. This describes failure of the posterior and middle columns under tension, with the axis of rotation about the anterior column, which acts as a hinge (Fig. 12.3).
Finally, Denis11 described the fracture-dislocation, which involves failure of all three columns (Fig. 12.4). Instability was then defined as mechanical, neurologic, or both, and depends on the integrity of the middle column. Denis hypothesized that loss of the integrity of the middle column, in conjunction with injury to either the anterior or posterior column, resulted in instability. Despite the popularity of this classification, it does not provide specific treatment recommendations. However, a significant contribution of the Denis classification is that it is the first recognition of the importance of neurologic status.
In an effort to help the surgeon plan specific treatment, others have developed more detailed and comprehensive classification systems that take into account other factors associated with the injury, including comminution, deformity, and displacement.12–15 The most comprehensive of these is the classification of Magerl et al,5 routinely referred to as the AO classification. This classification is based on the morphological characteristics of the injury. It is comprehensive and can also help guide treatment. The classification first categorizes the fracture based on one of three types of spinal injury that can be discerned on routine radiographs, with an increasing scale of severity from type A to type C. Type A fractures consist of vertebral body compression injuries, type B fractures consist of distraction injuries, and type C fractures consist of rotational injuries or those with multidirectional instability. Each type of injury is then divided into three groups and then into subgroups according to more detailed morphological criteria. This classification, though more complicated than that postulated by Denis, is comprehensive and can be used to help formulate both operative and nonoperative treatment options. However, validity testing has shown the classification to be only moderately reliable and reproducible.16
More recently, the Spine Trauma Study Group developed a classification system designed to more specifically guide treatment decisions. The Thoracolumbar Injury Severity Score (TLISS) takes into account three components of the injury critical to predicting treatment and outcome17: the mechanism of injury, the integrity of the posterior ligamentous complex (PLC), and the patient′s neurologic injuries. For injury mechanism, which is determined on imaging studies, compression injuries are the least severe and are assigned a score of 1, and burst fractures are assigned a score of 2. A rotational or translational injury is assigned a score of 3, and a distraction injury is the most severe and thus assigned a score of 4. It is important to note that TLISS defines a distraction injury as the most severe. This is different from the AO classification, which defines a rotational injury as the most severe.
The integrity of the PLC is determined either clinically, through palpation, or radiographically by looking for widening of the spinous processes in the area of the injury. An intact PLC is assigned a score of 0, an indeterminate disruption is assigned a score of 2, and a definite disruption is assigned a score of 3. Magnetic resonance imaging (MRI) is useful for evaluating the PLC with a high degree of sensitivity and specificity.18–20
Finally, the patient′s neurologic injury is scored according to its severity and the potential for recovery. Thus, a patient who is neurologically intact is assigned a score of 0, a nerve root injury or complete spinal cord injury is assigned a score of 2, and an incomplete spinal cord injury or cauda equina injury is assigned a score of 3.
Then the scores of the three components are totaled. An injury that has a total score of 5 or more requires surgical intervention, whereas those with a score of 3 or less can be treated nonoperatively. Injuries assigned a score of 4 are indeterminate, and the decision for surgery is made at the discretion of the surgeon.21
The Spine Trauma Study Group also devised a similar classification system, the Thoracolumbar Injury Classification and Severity Score (TLICS) (Table 12.1 .)22 This differs from the TLISS classification in that injury morphology is considered, rather than injury mechanism, whereas assessment of the PLC and the neurologic injury is unchanged. The validity of these classification systems have been more thoroughly studied than any others.9,16,21,23,24 Although the conclusion of these studies varies somewhat, this system has demonstrated moderate to high reliability. Interestingly, it seems that as clinicians gain more experience with the classification system, it becomes more reliable and reproducible.23 Whang et al7 also suggested that TLISS, with its assessment of fracture mechanism, is more reliable than the TLICS system. Nevertheless, both these classifications aid the clinician greatly as they directly address whether surgical intervention is necessary for a specific injury.
Source: Adapted from Vaccaro AR, Lehman RA Jr, Hurlbert RJ, et al. A new classification of thoracolumbar injuries: the importance of injury morphology, the integrity of the posterior ligamentous complex, and neurologic status. Spine 2005;30:2325–2333.
Most recently, a new classification has been proposed that combines elements of the AO classification and the TLISS system, the AOSpine Thoracolumbar Spine Injury Classification System.25 This classification considers the morphology and neurologic status of the injury, but also adds a final modifier. Specifically, the morphological characteristics of the injury are classified follows: type A, compression injury; type B, failure of the anterior or posterior ligaments without translation; and type C, failure of all elements, bony or otherwise, leading to dislocation or translation in any plane. There are subtypes for each type. Next, the neurologic status is assessed. This is graded as N0, no neurologic deficit, to N4, complete spinal cord injury. Finally, two potential modifiers are added: M1 designates an injury in which the status of the PLC is indeterminate either clinically or on imaging, and M2 designates a potential comorbidity that may influence the decision regarding surgery, such as ankylosing spondylitis, burns on the skin, or osteoporosis. An injury severity score can also be added to account for the international variations in treatment that must be accounted for in any universal classification system.25 Although initial reliability studies have been done, this classification must still be validated through more extensive testing and study.
Nonoperative Treatment
The goals of treatment of thoracolumbar fractures are clear: to ensure spinal stability, to maintain appropriate spinal alignment, and to potentiate neurological recovery. As with any fracture, nonoperative treatment of thoracolumbar injuries is desirable if the treatment leads to clinical success without increased morbidity. Although the role of nonoperative treatment for thoracolumbar fractures is clearly established for some fracture types, its utility for other types is highly debatable. In fact, the clinician really has very little level I evidence to support decision making. Unfortunately, even the ultimate anatomic parameters that need to be achieved to ensure a good result are debatable.26,27 Spinal stability must be achieved, although stability is difficult to define. Whitesides28 defined a stable spine as a spine that can withstand forces in multiple directions without progressive deformity or progressive neurologic deficit. In injuries with complete bony and diskoligamentous disruption, the spine is unstable to any and all forces, and the need for operative stabilization is clear. In instances where spinal stability to only isolated forces is compromised, the relative merits of operative repair are less clear and are dependent on the nature of the injury. We will discuss nonoperative treatment for each specific Denis fracture type.
Compression Fractures
Nonoperative treatment is appropriate for the vast majority of Denis compression fractures. These fractures correspond with Magerl type A1 and A2 injuries. By definition, compression fractures are not associated with a neurologic deficit; however, they are potentially unstable to flexion and compression forces.5 Classically, the need for operative stabilization has depended on the degree of vertebral body collapse and resultant kyphosis, although the thresholds for operative intervention are variable. Acceptable amounts of local kyphosis at the fracture site have varied by author and ranged from 15 to 50 degrees.27 To further complicate the issue, no studies have been able to identify a strong correlation between final kyphosis and residual pain or disability.27,29,30 Currently, the vast majority of compression fractures are treated nonoperatively. However, surgery should be considered for patients with disruption of the PLC. This is consistent with the conclusion of the TLISS classification for these injuries. Such an injury would be assigned a score of 4—one point for the compression fracture and three points for disruption of the PLC. This total score of 4 would mean that surgery is potentially indicated at the discretion of the surgeon.17 The integrity of the PLC can be inferred from CT or radiographs by looking for widening of the spinous processes. MRI can evaluate the integrity of the PLC as well.18–20 T2 fat-suppressed sagittal images have been shown to the most sensitive and specific in detecting PLC disruption.18 Even a compression fracture with a PLC injury is not an absolute indication for surgery. Other factors that are important to consider before recommending nonoperative management are the overall sagittal alignment of the spine and pain. Patients should be aggressively mobilized, and prolonged recumbency should be avoided.27,29,31 A hyperextension brace can be used, but with the knowledge that there is no conclusive evidence that bracing influences the ultimate result of treatment.32 Upright, weight-bearing radiographs are obtained prior to discharge and during follow-up. The purpose of these radiographs is to identify fractures with progressive collapse indicative of disruption of the PLC that would potentially need surgery.
Burst Fractures
The fracture type that generates the most debate regarding the role of nonoperative treatment is the Denis burst fracture, or Magerl type A3 fracture. Although most all authors agree that patients with a neurologic deficit require operative intervention, it is the burst fracture without neurologic deficit that generates the most controversy.33–35 Traditionally, the need for operative intervention for a thoracolumbar burst fracture without neurologic injury has been determined based on canal compromise, vertebral body collapse, and kyphosis.36 Each of these factors has been studied to determine if parameters can be established that influence the ultimate result of treatment. Several authors have studied the natural history of canal compromise with no surgical intervention. These investigators found that retropulsed bone is resorbed from the spinal canal in patients who are treated nonoperatively.34,37,38 In fact, a meta-analysis of published trials showed that ultimate canal compromise is essentially no different between comparable groups of patients treated operatively and nonoperatively.33 Neurologic deterioration has been observed, but the incidence is quite low.33,39 Therefore, given that the degree of canal compromise reliably improves and that the incidence of neurologic deterioration is low, the decision to treat a burst fracture surgically in a neurologically normal patient based on canal compromise alone is unfounded.
Although canal compromise reliably improves with non-operative treatment of thoracolumbar burst fractures, the same cannot be said for kyphosis and vertebral body collapse. Vertebral body collapse has been cited as a reason to treat a burst fracture operatively.36 Although the relation of vertebral body collapse to pain at the conclusion of treatment has not been studied nearly as extensively as kyphosis, there is no evidence that pain is related to the extent of collapse.33,40,41 Therefore, vertebral body collapse in and of itself is not a strong indication for operative intervention. The main issue pertaining to vertebral body collapse is the resulting spine deformity, which is chiefly kyphosis. Numerous authors have observed that kyphosis cannot be improved with nonoperative treatment, and, in fact, kyphosis usually progresses somewhat in the initial period following injury.26,33–35 In a recent meta-analysis, this progression was shown to be minimal, and estimated to be less than 5 degrees.33 Even when there is initial improvement in kyphosis through use of a rigid brace or cast, this is usually lost as treatment progresses.26 In fact, patients treated with no external mobilization, even in the presence of posterior element fractures, do not seem to develop any more deformity than patients who are braced.42 Therefore, if the degree of kyphosis needs to be reduced, it must be done operatively. However, the degree of acceptable kyphosis is questionable. Long-term follow-up studies indicate that the degree of kyphosis does not correlate with pain and disability.26,33,34,43 This has also been the conclusion of recent meta-analyses of the available literature.40,41 The one exception to this may be patients with greater than 30 degrees of final kyphosis, though the evidence demonstrating this is somewhat limited.44 Therefore, although kyphosis is an often-measured parameter in the outcome of patients following a thoracolumbar burst fracture, the decision to treat a patient surgically based on kyphosis alone is not supported by current literature.33,34,42
The decision, then, to treat a thoracolumbar burst f racture nonoperatively cannot be based solely on canal compromise, vertebral body collapse, or kyphosis. Other essential factors to consider are the patient′s neurologic status and the integrity of the PLC.21,45,46 The TLICS succinctly summarizes these important factors. It gives definitive recommendations for nonoperative versus operative management of these injuries.17,21 Therefore, burst fractures without neurologic impairment and with an intact PLC are amenable to nonoperative treatment. However, in fractures with isolated nerve root injuries or a suspected PLC injury, the TLICS indicates that either operative or non-operative treatment would be appropriate.22 In this instance, other factors related to the injury need to be used to decide if nonoperative management is appropriate. The clinician can consider local kyphosis, with nonoperative management more certainly recommended for injuries with 20 degrees of kyphosis or less. More specifically, one should consider the overall sagittal contour of the patient′s spine and the ability of the patient to compensate for any local kyphotic deformity while maintaining normal overall spinopelvic balance. Although this is difficult to assess in the setting of an acute fracture, patients with obvious preexisting sagittal deformities would best be served by surgical treatment of fractures that are amenable to operative or nonoperative treatment.47
Nonoperative treatment should consist of early mobilization and use of a brace, however, no clinical studies can support or disprove the efficacy of bracing.32 Yet emerging literature does indicate that bracing may not improve the nonoperative result.48 At the least, the use of a brace can significantly reduce pain, enabling patients to more easily increase their activities. The patient should be fitted with a hyperextension thoracolumbar sacral orthosis (TLSO) that can be worn either full time or only when the patient is out of bed. The patient should be restricted from activities that involve repeated bending or twisting, and lifting should be restricted to no more than 10 pounds. Prior to discharge, it is imperative for the clinician to obtain weight-bearing radiographs. These are done to evaluate the patient for progressive collapse or kyphosis indicative of a significant posterior ligamentous injury. These radiographs have been shown to be effective in recognizing previously undiagnosed structural lesions that may require surgery.49 A significant change in kyphosis on weight-bearing radiographs should prompt further evaluation of the patient with an MRI. Surgical intervention should then be recommended if a distinct ligamentous injury is evident. The patient may slowly progress their activities over the next 12 weeks, ultimately returning to unrestricted activities at this juncture.34,50
Flexion-Distraction Injuries
The indications for nonoperative management of Magerl type B fractures, which include Denis seat-belt–type injuries, are limited. Invariably, these injuries involve an injury to the PLC, rendering it unstable. Perhaps one exception, historically, has been patients with transverse bony disruption of the posterior elements and middle vertebral column. These injuries are classified as Magerl type B2.1, or the single-level Chance fracture, according to Denis.5,11 These patients have been treated by extension reduction and immobilization in either a TLSO or a cast. Because the injury is entirely bony, there is excellent healing potential.44 However, particularly with the emergence of minimally invasive instrumentation techniques, nonoperative treatment should be reserved for only those cases where operative intervention is not possible.
Fracture-Dislocations
Nonoperative treatment of Magerl type C fractures or Denis fracture-dislocations is mentioned only to discourage it. Because of the global instability resulting from the multicolumn injury, there is no way to mobilize the patient and still maintain spinal alignment nonoperatively. When used, nonoperative treatment must consist of prolonged recumbency. In turn, prolonged recumbency results in prolonged hospitalization and a high rate of complications associated with prolonged bed rest, such as venous thromboembolism, stasis ulcers, and pulmonary complications. The standard of care for fracture-dislocations is operative treatment and early mobilization.
Indications for Surgical Treatment
Operative indications differ among the various types of fractures and will be discussed relative to each separate fracture type.
Compression Fractures
As previously mentioned, Denis compression fractures, corresponding to Magerl type A1 and type A2 fractures, rarely require surgical intervention. By definition, these fractures do not result in neurologic injury. Surgical intervention can be considered in instances where there is disruption of the PLC.21 It also may be considered in instances where kyphosis is greater than 30 degrees, as some evidence exists that kyphosis of this magnitude left untreated can result in increased pain postinjury.44 This most commonly occurs with multiple-level fractures. The final surgical indication is a Magerl pincer fracture (type A2.3). Surgery should be considered for this injury, as disk material can interpose itself between the split fragment and the main portion of the vertebral body. This can then result in a nonunion and progressive kyphosis. This fracture should not be confused with a coronal split fracture (Magerl type A2.2) where the fracture fragments are nondisplaced and the risk of progressive kyphosis is much lower (Fig. 12.5).5
Burst Fractures
The operative indications in Denis burst fractures, or Magerl type A3 injuries, are still controversial. An absolute operative indication is a fracture with an incomplete spinal cord, conus medullaris, or cauda equina injury. This is consistent with the recommendations of the TLISS classification.21 Surgery should be strongly considered for fractures with complete spinal cord injuries and isolated root injuries. Another absolute surgical indication is burst fractures with a documented injury to the PLC.21 Those fractures with suspected ligamentous disruption can be treated nonoperatively, as long as they are carefully followed for progressive collapse and kyphosis. As previously described, operative indications based on degrees of canal compromise, percent of vertebral body collapse, and kyphosis, particularly in those patients without neurologic injury, are not absolute and generally without scientific merit. This is particularly true in light of the available data that fail to correlate patient outcome with ultimate degrees of deformity or vertebral collapse.26,33,34,40,41,43 There is no absolute value that mandates surgery for any one of these parameters. Surgical intervention should be strongly considered in patients with greater than 30 degrees of kyphosis or overall sagittal decompensation.44,47 In patients with stable kyphosis of less than 20 degrees, operative intervention is rarely indicated. Progressive kyphosis is often an indication of an injury to the PLC and therefore requires surgery.
Flexion-Distraction Injuries
Operative treatment of flexion-distraction injuries, or AO type B injuries (tension band injuries), is the rule. In fact, both the TLISS and the TLICS consider these injuries the most unstable.21,22 Nonoperative treatment may be appropriate in the rare instance when the injury involves predominantly the osseous structures in a patient without neurologic injury. If the fracture can be posturally reduced and the reduction maintained with either a custom-molded hyperextension TLSO or cast, it will reliably heal because these injuries are stable in extension. However, full-time brace wear is cumbersome, and the patient must be carefully followed for loss of reduction. Admittedly, the patient with a flexion-distraction injury amenable to nonoperative treatment is quite rare. Most commonly, these injuries require surgery. This is particularly true in injuries that disrupt the posterior ligamentous structures. Also, those that involve the disk have no ability to heal nonoperatively even if anatomically reduced. Therefore, flexion-distraction injuries through the disk by definition require surgery. Finally, flexion-distraction injuries with neurologic injury all require operative intervention.21
Fracture-Dislocations
Denis fracture-dislocations or AO type C injuries (translational) are universally unstable and, of all the injuries, are most commonly associated with neurologic injury.5 Due to the inherent instability of these injuries, they are very difficult to treat nonoperatively and maintain stability and alignment. Therefore, they all require surgery. Non-operative treatment is only appropriate in patients who are unable to undergo operative intervention for medical reasons.
Surviving the Night
Patients with thoracolumbar spine fractures often have serious concomitant solid organ and visceral injuries. This is particularly true for distraction-type injuries.103 Therefore, the first critical issue in the urgent evaluation and treatment of patients with thoracolumbar fractures is to ensure that no life-threatening injuries exist. Thus, any patient with traumatic thoracolumbar fracture requires evaluation by a trauma surgeon for concomitant injuries. Attention to significant visceral injuries takes precedent over treatment of the spinal injury as long as proper spine precautions are maintained to avoid secondary injury to the neurologic elements. Neurologic deterioration can occur in up to 30% of patients after admission to the hospital.104 These precautions should consist of bed rest with the patient lying flat. The common practice of “log-rolling” a patient with an injured spine can still result in significant motion of unstable thoracolumbar segments. Alternative techniques such as the six-person lift, a kinematic therapy bed, or an air mattress transfer system can significantly decrease the motion of unstable spinal segments during care and transfer of the patient with an unstable injury, decreasing the probability of secondary neurologic injury.104 These precautions should be maintained until either surgical stabilization has occurred or the decision to treat a patient nonoperatively has been confirmed.
Although there is no consensus regarding the optimal timing of surgery in patients with thoracolumbar fractures, the current literature supports the emerging concept that early surgical stabilization results in decreased overall complication rates and shorter hospital stays. The exact definition of early intervention varies, with most suggesting surgery within 72 hours of admission, but others advocate surgical stabilization within 24 hours.105–107 The ability of early surgery to improve neurologic recovery is controversial, although some data does suggest that early decompression within 24 hours may lead to an increased chance of neurologic recovery,108–110 although the evidence is not definitive and more investigation is required.111 The patient with a progressive neurologic deficit does require emergent surgery. The patient first must be identified through careful serial neurologic exams. When a progressive deficit is identified, the patient requires immediate neurologic imaging, followed by surgical decompression, reduction, and stabilization. Likely causes of the progressive deficit are persistent compression due to spinal malalignment or an epidural hematoma. Otherwise, in a patient with a stable neurologic status, the medical condition of the patient needs to be optimized prior to surgical intervention. Taking an unstable patient to surgery, particularly when the anticipated procedure may entail significant blood loss, is not wise and can result in increased complications and mortality.
Finally, the administration of high-dose methylpredniso-lone (MP) in the setting of acute spinal cord injury is a controversial topic. The National Acute Spinal Cord Injury Study (NASCIS) II and III addressed this topic specifically.112,113 Although these studies were purported to demonstrate benefits of high-dose MP administration when given within an 8-hour window of injury, further analysis demonstrated significant problems with data collection and analysis, including an inconsistent reported benefit demonstrated on post hoc analysis of only a portion of the data.114 As such these studies are considered no higher than level III evidence. In addition, the reported complication rate of the patients that received MP was considerable, including gastrointestinal hemorrhage, sepsis, and death. Besides the NASCIS studies, other level III studies have suggested the neuroprotective effect of high-dose MP, but these all involve reporting of incomplete data derived from retrospective analysis of larger populations. No level I or level II evidence exists supporting the efficacy of MP in this population. As such, at this time, routine administration of high-dose MP to patients with acute spinal cord injury is not recommended.114
Surgical Treatment
Once the decision has been made to treat a fracture surgically, the surgical approach—anterior, posterior, or circumferential (both)—as well as the type of surgery—minimally invasively or traditional open—must be decided upon. The decision as to which approach is most appropriate is based on the goals of the surgery, such as decompression of the neurologic structures, restoration of spinal alignment, rigid stabilization of the unstable spinal segments, or ultimate bony healing of the affected motion segments. If an arthrodesis is involved, it is also desirous to fuse as few motion segments as possible.
Reduction and Stabilization of Spinal Deformity
The first factor that must be considered in choosing the most suitable surgical approach is the ability to reduce the injury from the selected approach. Anatomic reduction and maintenance of that reduction can be expected with either anterior or posterior approaches for the vast majority of thoracolumbar injuries.51–76 One exception to this is a fracture-dislocation. This injury cannot be reliably reduced anteriorly, particularly the associated facet dislocation, so it needs to be addressed posteriorly. For a given injury, a logical assessment of the injury pattern and associated instability can guide the choice of surgical approach. Whenever possible, stabilization of a thoracolumbar fracture should directly reconstruct the bony and ligamentous structures that have been most importantly injured causing the resultant deformity or instability.
The surgeon should avoid disrupting any remaining intact stabilizers. The ultimate stability of the construct depends on the number of motion segments instrumented, the forces that must be resisted by the construct following reduction, and the initial degree of instability. In general, the technique that ultimately results in fusion of the fewest motion segments is preferable. In addition, the chosen approach should be the one that reduces the chance of significant perioperative morbidity due to violation of surrounding structures, invasiveness of the procedure, or blood loss. Finally, the chosen approach must afford a reasonable chance of a solid arthrodesis to maintain ultimate correction and alignment. Fusion of the posterior elements alone, especially in the setting of high-energy fractures, results in a higher rate of pseudarthrosis compared with intervertebral fusion.60
Neurologic Decompression
The second goal of surgery, in the face of a neurologic injury, is decompression of the affected neural elements. The approach that best accomplishes this depends on the region of the spine affected, the degree of compression, and the location of the compression in the spinal canal. Decompression of the spinal cord and the conus medullaris must use a technique that spares traction or manipulation of the subarachnoid space to avoid iatrogenic neurologic injury. Both anterior and posterior approaches can be used to reduce anterior compression, whereas a posterior approach is necessary to address posterior neural compression. Although classically it was thought that patients with profound anterior compression, particularly in the spinal cord region, would benefit most from an anterior decompression, this has not been validated in studies.60,76 Particularly with advances in posterior access to the anterior spine, decompression can be performed via an anterior or posterior approach.65 The cauda equina can be carefully retracted during surgical decompression to assist in removal of bony or soft tissue fragments. A further consideration in the lumbar spine is compromise of the intervertebral neuroforamina. Although these can also be decompressed through either approach, the posterior approach is preferable. A circumferential (combined anterior-posterior) approach is almost never necessary to fully decompress the neural elements.
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