Spinal Dislocations

The unique anatomy of the thoracolumbar junction predisposes this level of the spinal column to dislocation fractures. As the thoracic spine loses its structural rigidity with floating ribs at T11 and T12, the orientation of the facet joints also changes from a more frontal projection to oblique and then sagittal in the upper lumbar spine. These spinal dislocation fractures result from violent traumatic injuries and are associated with a very high incidence of neurologic deficit resulting from the translation of the spine.

Approximately 90% of dislocations above T10 result in complete paraplegia, and 60% of dislocations below T10 result in complete neurologic deficit. The spinal cord ends at the L1-2 level in most adults; the cauda equina represents the terminal nerve roots of the lumbosacral spine present below this site. The prognosis for a pure nerve-root injury is much better than for an actual spinal-cord injury. In some of these injuries, spinal-cord injury and nerve-root damage are combined.

Of the injuries affecting the thoracolumbar spine, dislocation fractures are the most unstable, secondary to the soft-tissue and bony disruption resulting from the high-energy mechanics of injury. This injury is associated with the highest incidence of neurologic deficits and chest and abdominal trauma. Involvement of all three spinal columns (see Pathophysiology) generally necessitates operative intervention to stabilize the spine and optimize neurologic recovery and patient rehabilitation.

Spinal injuries with resulting paralysis have been recognized since the writings of the Edwin Smith papyrus as "an ailment not to be treated."[1, 2]  Various authors proposed postural reduction on frames with prolonged bedrest as a means of achieving spinal stability. Nicoll favored early return of function regardless of nonanatomic alignment of the spine.[3]

None of these early series provided techniques for reducing and stabilizing the thoracolumbar spine; however, such techniques are available to contemporary surgeons. With the advent and use of Harrington rod instrumentation, a debate arose about nonoperative versus operative care for these highly unstable injuries. Fixation devices have been devised that allow fewer segments to be incorporated in the surgical construct. Whereas the posterior approach is used most often, anterior procedures also may be important in reconstruction after these devastating injuries. The surgical approach allows earlier mobilization, minimizing medical complications and preventing progressive deformity.

The thoracolumbar junction represents a region of the spine in which the relatively rigid thoracic area transitions to the more mobile lumbar spine, on the basis of anatomic changes in the vertebral body, facet joints, and adjacent ribs.

The anterior column of the spine in this area consists of the following:

• Vertebral bodies
• Superior and inferior disks

The vertebral bodies increase in size in both anteroposterior (AP) and medial and lateral planes. The disk heights also increase, allowing more motion.

The posterior column, which acts as a tension band, consists of the following:

• Pedicles
• Facet joints
• Lamina
• Transverse and spinous processes

Ligamentous structures add stability and are most effective in resisting loads in the planes in which the fibers run. They tighten under tension and buckle under compression. These include the following:

• Anteriorly - Anterior and posterior longitudinal ligaments (which attach to the vertebral bodies and disks)
• Posteriorly - Intertransverse, capsular, interspinous, and supraspinous ligaments

The ligamentum flavum attaches to the anterior-inferior border of the laminae above and the posterior-superior border of the laminae below. These ligaments tend to be thicker in the thoracic region and have a midline cleavage plane throughout. Because of the large amount of elastin present, this tissue is the most elastic tissue in the spine.

The orientation of the facet joints changes from the frontal plane in the thoracic spine to the more oblique plane at the thoracolumbar junction.

Dislocation fractures of the thoracolumbar junction involve disruption of all three spinal columns resulting from a combination of mechanisms, including the following:

• Compression
• Tension
• Rotation
• Shear injury

Although the shear component may occur from anterior to posterior, it more frequently occurs from posterior to anterior with sequential failure of the posterior ligamentous complex, fracture of the lamina, buttressing of the facet joints, and, finally, anterior vertebral body compression. The rotational insults are recognized by the fractures of the transverse processes and adjacent lower ribs. The fracture through the lamina frequently results in dural tears and entrapped nerve roots. This may have a bearing on the initial surgical approach to reconstruction of the spine.[4, 5, 6]

The most frequent causes of spinal-column injuries are motor vehicle accidents (45%), falls from heights (20%), sports-related injuries (15%),[7] and acts of violence (15%).[8] A large-scale study of spinal trauma in China that included more than 82,000 patients identified a specific cause in more than 64,000 patients. Motor vehicle accidents were the leading cause (33.51%), followed by high falls (31.25%) and trivial falls (23.23%).[9]

Spinal-cord injury continues to be a significant source of morbidity and mortality among the young adult population in this country. Each year, approximately 10,000 new patients with spinal-cord injuries are added to the 180,000-200,000 individuals already living with spinal-cord injuries.

Incomplete injuries at the level of the cauda equina tend to have a more favorable recovery rate than mixed conus and cauda equina lesions or lower spinal-cord injury. According to a multicenter study reported by Gertzbein, the prognosis for bowel and bladder recovery appears to be improved with anterior decompression.[10]  Complete neurologic deficits continue to have a grim prospect for recovery, and emphasis on rehabilitation and incorporation of the individual with paraplegia into society is aided by regional spinal-cord injury centers.

Long-term management of bowel and bladder dysfunction should include the use of stool softeners, suppositories, a high-fiber diet, and intermittent urinary catheterizations to decrease the residual urine volume. Despite these efforts, chronic urinary tract infections continue to plague patients with paraplegia.

The ultimate functional outcome may be affected significantly by the patient's age, body habitus, general medical condition, and cognitive and motivational factors. Depression is quite frequent in this patient population and can adversely affect the recovery and rehabilitative process. A multidisciplinary approach, including physical and occupational therapists as well as psychological support, is desirable.

With motor grade strength improvement greater than 3 (antigravity level), ambulation may be possible with the use of adjunctive orthoses. This may result in extreme energy requirements and may interfere with the performance of upper-extremity activities while standing. Simplification of daily routines can help in conserving energy and improving the lifestyles of patients with spinal injuries.

Patients with spinal injuries should be questioned about any transient paralysis or paresthesias involving the lower extremities. The history of the accident should include attention to mechanisms, including the following:

• Whether the patient was the driver or the passenger
• Whether the patient was restrained or unrestrained
• What the vehicle's rate of speed was
• What distance the patient fell (for injuries from falls from heights)
• What weights were applied to the spine at the time of injury

If the patient is unable to relate the history, it may be obtained from emergency medical personnel on the scene or other witnesses. Schouten et al emphasize the importance of the initial assessment.[11]

The physical examination should initially include attention to the details relevant for all traumatized patients (ie, the ABCs [patent airway, spontaneous breathing, stable circulation], blood pressure, and pulse). In the spinal examination, specific attention should be paid to direct palpation for tenderness, deformity, or defects.

The unique finding in thoracolumbar dislocations is that of a fixed gibbus deformity at the level of injury. The patient is most appropriately placed in the lateral decubitus position with the knees flexed if any neurologic compromise is present. This maximizes the residual diameter of the narrowed spinal canal.

A thorough neurologic examination should include the following:

• Graded motor function of the major muscles in the lower extremity (0-5)
• Sensory examination to both sharp and dull stimuli
• Reflex evaluation

In addition to the tendon reflexes, the bulbocavernosus and cremasteric reflexes and the perianal wink should be recorded. A rectal examination documenting the status of the patient's rectal tone must be routinely performed. Dermatomes can be assessed quickly, and landmarks, such as the umbilicus (T10), anterior knee (L3), dorsolateral foot (S1), and perianal region (S3-5), can be used.

Usually, an indwelling catheter is inserted into the bladder, and urine output is monitored.

The laboratory workup for spinal dislocation parallels that for any patient with complex traumatic injuries and should routinely include the following:

• Complete blood count (CBC)
• Comprehensive metabolic profile
• Urinalysis

The workup frequently also includes clotting studies (prothrombin time [PT] and activated partial thromboplastin time [aPTT]).

If the patient presents in shock, urgent type and crossmatch is necessary for blood administration. Given that a dislocation fracture requires a significant insult, associated chest and abdominal injuries are not uncommon.

Plain radiography

Imaging for spinal dislocation begins with high-quality plain radiographs taken in the anteropoesterior (AP) and lateral views.[12] These most often demonstrate the severity of the injury. A well-centered lateral view provides information on alignment and associated fractures, primarily of the anterior column. The AP view demonstrates associated injuries to the ribs and transverse processes, which are an indication of the violent nature of the injury. Associated pneumothorax may also be demonstrated from this view. (See the images below.)

Computed tomography

Computed tomography (CT) supplements the information gathered from plain radiography and provides pertinent data on the injuries to the posterior elements, including lamina and facet injuries. The empty facet sign is a complete dislocation of these joints and is a hallmark finding with these injuries as well as severe flexion-distraction–type traumas. These studies usually are obtained with 3-mm cuts and can be reformatted in the frontal and sagittal planes.[13]

Magnetic resonance imaging

Magnetic resonance imaging (MRI) is infrequently required; plain radiographs and CT scans can provide most of the data needed to treat these injuries. If the neurologic examination findings do not correlate with the level of injury determined from plain films, then MRI may be indicated to provide additional information on adjacent levels of involvement. The neural elements and disk injuries are better depicted by MRI.[14, 13]

Ultrasonography

In some centers, ultrasonography has been used intraoperatively to assess canal clearance. Specific expertise in the interpretation of these intraoperative ultrasonograms is required and is not always available.

Many classification systems for thoracolumbar fractures exist. None are universally accepted, but each has its own merits and limitations. Important factors in the application of any classification system include simplicity, reproducibility, and the ability to assist in making management decisions.[15, 16, 17]

Historically, Holdsworth viewed the spine as a two-column structure, with the vertebrae representing the anterior loadbearing column and the posterior elements (pedicles, laminae, spinous processes, and attaching ligaments) functioning primarily as a tension band resisting tensile loads. Involvement of either structure or both structures, according to Holdsworth, necessitated potentially different modes of reconstruction.[18]

Currently, the AO classification has many advocates.

Magerl basically divided thoracolumbar fractures into the following three groups[19] :

• Group A involves compression injuries
• Group B involves distraction mechanisms
• Group C involves torsional injuries

Further subdivisions are based on the morphology of the fracture and its associated ligamentous components. This system and others base their classification on findings from plain radiographs and CT scans. Although it is extremely inclusive and comprehensive, interobserver agreement appears to be no greater than 67%.[15]

The usual indications for surgical reconstruction include loss of mechanical stability and neurologic compromise. With the high incidence of neurologic deficits associated with dislocation fractures, surgical management remains a primary tool for the recovery of these patients. Because all three columns of the spine are involved, reconstruction may include an anterior or a posterior approach. Not infrequently, both approaches may be necessary to maximize neurologic recovery and to reestablish spinal column integrity.

If the neurologic deficit is complete with return of reflex function, recovery is unlikely, and surgery is performed to expedite rehabilitation. When the injury results in an incomplete deficit that is progressing, urgent decompression and stabilization are indicated to halt progressive neurologic loss and to hasten recovery.

Care should be taken in positioning the patient with a thoracolumbar dislocation. It has been demonstrated that supine positioning further narrows an already compromised spinal canal. Turning the patient to a lateral position with the spine slightly flexed may improve function in an incomplete injury. Attempts at closed reduction are usually unsuccessful with these injuries, and operative intervention is necessary for definitive reduction and stabilization.

Contraindications for surgical treatment are few. Surgery is contraindicated in patients on warfarin or other anticoagulants. In these patients, reversal of the anticoagulated state is required befpre the operative procedure. Surgery may be contraindicated in patients with medical conditions such as acute myocardial infarction.

Treatment methods have evolved over the past 50 years, and means of minimizing the extent of injury are employed. Such treatment has included the acute administration of high-dose steroids on the basis of the results of three studies published by the National Acute Spinal Cord Injury Study (NASCIS), as well as the use of gangliosides as reported by Geisler et al.[20, 21, 22, 23, 24, 25, 26]

Timely canal decompression and stabilization of the affected areas have been made possible by the introduction of modern instrumentation systems and improved surgical approaches. Research continues to address spinal-cord recovery and has included laboratory experiments in neural element transplantation and fetal cell transplants. Firm supportive data for these efforts remain to be obtained in a clinical setting; however, research must continue in order to aid this growing population of patients.

Fracture dislocations are associated with the highest incidence of neurologic injury. In individuals with incomplete or normal neurologic examination findings, the spinal injury has still resulted in significant instability. To allow early mobilization and afford the chance for neurologic improvement, surgical management is almost always indicated. Closed reduction of these injuries is quite difficult, if not impossible. Maintenance of the reduction without operative intervention is problematic.

Most often, dislocation fractures can be managed via an entirely posterior approach. Reduction of the malalignment results in spinal-canal clearance in most individuals. Significant residual compression can be addressed through an anterior approach either in a staged manner or on the same day, depending on the circumstances. The posterior instrumentation and fusion allow reestablishment of the tension-band function of this segment of the spine; however, if significant anterior column loss (burst component) exists, anterior reconstruction may be indicated.[27]

Daniaux described the use of transpedicular bone grafting.[28, 29] In this approach, the defect created by the reduction is filled with autologous bone. The graft is intended to fill the anterior half of the body and to avoid posterior extravasation. Arnold suggested a second means of posterior grafting, which involved performing a basal osteotomy of the transverse process and filling the body through a posterolateral window.[30, 31, 32, 33, 34, 35]

Preparation for surgery

The patient's blood is usually typed and crossmatched, and 2 units of blood are made available preoperatively. In the unusual case of a patient who is neurologically intact, neuromonitoring would be warranted. The anesthesiologist may place an arterial line or may establish central access, depending on the individual patient and any other injuries that may be present. A Foley catheter is inserted to monitor urinary output throughout the procedure.

The patient is placed prone on the operating table, and chest rolls or a Wilson frame may be used after careful logrolling. All bony prominences are padded carefully, and superficial nerves (eg, the ulnar nerve) are protected. The arms are placed on arm boards, and hyperabduction of the shoulders should be avoided.

Operative details

A midline incision extending from one level above to one level below the proposed segments to be instrumented should be used.

Once the incision has been carried down to the tips of the spinous processes, careful subperiosteal dissection should be continued bilaterally to the facet joints. Frequently, much of the dissection has already occurred from the injury, with muscle and soft tissues displaced from the bony elements. A good rule is to start above and below in normal anatomy and work carefully towards the injured zone. Packing with gauze sponges helps tamponade the bleeding, and packing can be replaced as the exposure continues.

The transverse processes are then stripped of overlying muscle until the tips are exposed. Bipolar and unipolar cauteries are used to maintain hemostasis. Because the spinal canal may be open and the dura exposed, care must be taken in approaching this area. The exposed facet joints at the level of dislocation may be denuded of their articular cartilage before reduction.

Frequently, an associated fracture is present. Resection of bone should be avoided at the joint level, because this further destabilizes the spine. Reduction is generally achieved by means of gentle distraction with a lamina spreader and manipulation with bone-holding forceps or towel clips. Once the reduction has been obtained, a single wire or cable may be passed through the adjacent spinous processes before definitive fixation.

At this point, options for fixation include multiple hooks in a claw construct two ro three levels above and one or two levels below. Depending on the individual anatomy, pedicle screw fixation may be used from two segments above to one or two segments below. The landmarks for insertion for pedicle screws in the lumbar spine include bisection of the transverse process as it abuts the superior articular facet. The angle of inclination varies from 10-15° at L1 to 25° at L5.

Thoracic screw insertion is performed 3 mm lateral to the center of the facet joint, just below the articulation. Image intensification, in addition to surface landmarks, may be used in the thoracic region. Intraoperative stereotactic guidance has been used in a number of centers but has not been universally applied. Although a compression construct provides the most rigid stabilization, the risk of disk herniation increases; accordingly, this construct should be used with caution in the patient who is neurologically intact or not.

An autograft may then be harvested from the iliac crest, and decortication for fusion purposes generally is performed for the length of the instrumentation. Studies have demonstrated that instrumented segments that are not formally fused usually undergo ankylosis, and application of the graft may be limited to one segment above the disruption to one segment below. Closure is performed in a layered fashion over a Hemovac drain, which is removed 1-2 days postoperatively.

Postoperatively, the patient should be turned frequently, and thromboembolic prophylaxis should be addressed with compression devices and, in certain instances, medically with either low-molecular-weight heparin (LMWH) or warfarin. In certain cases where anticoagulation is contraindicated (eg, with gastrointestinal ulcers or intracranial injuries) or pulmonary embolism has occurred despite adequate anticoagulation, mechanical vena cava filters may be inserted.

Early mobilization is encouraged, and bracing may not be necessary (depending on the degree of stability obtained during surgery). In a patient who is neurologically intact, close monitoring and early mobilization should minimize skin breakdown.

The Foley catheter should be removed, and intermittent catheterization should be performed as soon as the patient's general medical condition permits. An early bowel regimen should be initiated, and alternate-day suppositories should be used.

Once the patient is medically stable, transfer to a rehabilitation facility with special expertise in spinal injuries is beneficial to the recovery process. In such a facility, the physical and psychological issues facing the individual patient and the family can be addressed in an environment that includes other patients with similar problems.

Complications can be subdivided into two major groups, as follows:

• Complications related to the operative procedure
• Complications secondary to the spinal cord or cauda equina injuries

Surgical complications can be further classified as related to the following:

• Positioning
• Intraoperative occurrences
• Postoperative complications

Patients with spinal injuries should be positioned carefully at the time of surgery to avoid compression of bony prominences. The arms should be placed at right angles to the body or tucked by the sides. The ulnar nerve is particularly vulnerable, and pressure at the elbow should be avoided.

Intraoperative complications include the following:

• Dural tears
• Misdirected instrumentation
• Excessive bleeding necessitating transfusions and fluid replacement

Although the level of injury is usually obvious at the time of surgery, intraoperative imaging can be extremely valuable for documenting the levels of stabilization and the positions of pedicle screws and hooks. Placement of hooks in the thoracic region may compromise canal space; a staggered hook construct, if feasible, avoids excessive canal stenosis at each level. With close attention to the positioning of pedicle screws, malplacement can be avoided. The tip of the screw should not cross the midline on an anteroposterior (AP) radiograph but should generally point toward the midline.

Postoperative attention to adequate resuscitation is of the utmost importance. Frequently, fluid and electrolyte concerns, including serum magnesium replacement, must be addressed. Correction of clotting abnormalities may necessitate the administration of fresh frozen plasma and platelets; however, mild deficits usually correct rapidly in the absence of significant liver abnormalities.

Postoperative hematomas may have to be drained, and persistent drainage should be aggressively managed to avoid an underlying deep infection. The appearance of the skin may be misleading, and certainly, if a spiking temperature occurs in this setting, early exploration is warranted. Unrecognized cerebrospinal fluid leakage may be heralded by postural headaches and clear drainage from the wound. Eismont suggested open operative repair when possible, but the use of closed drainage techniques for 3-5 days has also been recommended to manage this problem.[36]

The sutures generally can be removed after approximately 10 days, and rehabilitation can be initiated as soon as the general medical condition of the patient allows.

Arthrodesis progresses over a 3- to 6-month period, and serial radiographs should be obtained to assess the alignment and progressive union of the bone grafting. It is not uncommon to see gradual loss of 10° of correction with posterior-only procedures.

Bracing, usually involving a removable thoracolumbosacral orthosis (TLSO), is employed for 3-6 months. In individuals who are paraplegic, close attention must be paid to skin pressure and potential breakdown.