Penetrating Spinal Cord Injuries

Summary of Key Points

•

Penetrating injuries are a significant cause of spinal cord injury.
•

Injury mechanism and magnitude of injuries guide treatment of penetrating spinal injury.
•

Non-neurologic injuries associated with penetrating spinal trauma are common and take precedence over spinal injuries as they are often lifesaving.
•

The use of antibiotics has greatly reduced infectious complications of penetrating spinal cord injuries.
•

Despite advances in care, prognosis following penetrating spinal cord injury remains poor.

Penetrating spine injury is a major cause of spinal cord injury (SCI) in the United States. Gunshot injuries have been reported to be the third leading cause of SCI. In American service members deployed in Operation Iraqi Freedom and Operation Enduring Freedom, 38% of patients with penetrating spinal injuries also sustained SCI. Stab wounds and other penetrating injuries tend to occur less in the United States than in some other countries. In South Africa, they account for 25% of all SCIs. Avoiding complications in the management of patients with penetrating SCIs begins with meticulous attention to evaluation, resuscitation, and operative and surgical techniques.

Military Versus Civilian Gunshot Injuries

Most experience with the management of penetrating SCIs has been gained during wartime. During World War I, survival was uncommon after a complete myelopathy (72% mortality). Treatment of these injuries consisted of laminectomy for incomplete myelopathy and debridement of the entry and exit wounds for complete myelopathy. A high operative mortality rate (62%) added to the dismal outcome.

During World War II, advances were made in trauma resuscitation and therapy. These advances dramatically decreased the mortality from penetrating SCIs. Some surgeons reported neurologic improvement in patients who were managed surgically. During the Korean War, most patients with penetrating SCIs underwent surgical exploration. There were reports of significant improvement. Further improvements were made in trauma resuscitation, evacuation, and surgical treatment during Operation Iraqi Freedom and Operation Enduring Freedom, where spine combat casualty rates are the highest in recorded history. The treatment of civilian penetrating SCIs, however, has generated less optimism than previous military reports have. Despite these findings, some authors have demonstrated benefit with early surgical intervention following civilian gunshot wounds. This is likely related to the pathophysiology of this type of injury.

Military weapons fire high-velocity missiles, whereas civilian weapons (typically handguns) fire low-velocity missiles. The pathophysiology of the SCI differs on the basis of velocity. High-velocity missiles may produce SCI by a concussive effect of the bullet passing close to, but not through, the spinal canal. Most SCIs caused by high-velocity missiles fit this pattern. These types of injuries may have a slightly better prognosis. Low-velocity missiles are more likely to injure the spinal cord directly, without a significant concussive effect; therefore, the prognosis for recovery is worse owing to the direct cord injury. This phenomenon may also explain the large percentage of civilian gunshot SCIs that present as complete myelopathies.

Penetrating Blast Injuries

Penetrating blast injuries have similar pathophysiology to high-velocity missiles. However, blast injuries are more likely to require surgical exploration as well as fixation for spinal instability. This is due both to the nature of the injury and the fact that blast fragments are more likely to be heavily contaminated, thus requiring fragment removal and surgical debridement.

Impalement Pathophysiology

A weapon (knife) that penetrates the spinal canal may damage the spinal cord directly or indirectly. The direct injury may range from a dural tear to a total cord transection. Indirectly, there may be spinal cord contusion from the weapon impacting the cord against the bony spinal canal. The anatomy of the spinal canal may protect the spinal cord from a complete transection ( Fig. 142-1 ). The weapon usually enters the spinal canal in the gutter between the spinous process and transverse process, leading to an incomplete SCI. Classically, the Brown-Séquard syndrome or a variant results.

Resuscitation

The initial management begins with advanced trauma life support measures. The airway should be evaluated and secured. If necessary, endotracheal intubation should be performed. Oral intubation using manual in-line traction has been shown to be both safe and effective in patients with suspected SCI. Tracheostomy is indicated if the injury involves the trachea or larynx. Chest radiographs and arterial blood gas analysis (if indicated) should be part of the initial evaluation. The incidence of associated visceral injuries may be as high as 25%. These injuries, such as pneumothorax or vascular injury, must be sought early, as their treatment takes priority over spinal cord or spinal column injury.

The patient’s early course may be complicated by hypotension, which may be due to blood loss (hypovolemia) or to neurogenic shock from the loss of sympathetic vasomotor tone. Determining the exact cause of the hypotension is often difficult in the acute setting. However, tachycardia and cool extremities are often observed with hypovolemia, whereas bradycardia is often observed with spinal shock. The treatment for either condition is aggressive volume resuscitation. A central venous catheter is often helpful for monitoring the volume resuscitation. If the hypotension persists despite adequate intravascular volume replacement, vasopressor agents such as phenylephrine or dopamine should be employed. Vagolytic agents such as atropine may also be used. An indwelling pulmonary artery catheter may be useful if hypotension persists despite the use of vasopressor agents. However, enthusiasm for the use of these catheters has waned lately.

A Foley catheter should be placed. This allows bladder decompression and assists with gauging of the effectiveness of volume resuscitation. It also decreases the likelihood of subsequent urologic complications.

Once the patient is stable from a cardiopulmonary standpoint, a more thorough history and physical examination should be performed. Information about the mechanism of injury and the caliber of the weapon should be obtained. The physical examination should note whether the patient has suffered a complete or incomplete myelopathy. If the injury is incomplete, the level of the SCI should be noted. The entry and exit sites should be inspected, and notation of cerebrospinal fluid (CSF) or foreign material should be made.

Treatment of non-neurologic injuries is of primary importance because such treatment is usually lifesaving (rather than function-preserving). Because the course that a penetrating object takes within the torso is unpredictable, there may be an associated visceral injury. A trauma surgeon should assist with the evaluation for such potential injuries. Explorations of the neck, chest, and abdomen take precedence over spine surgeries.

Some clinicians advocate exploration for wounds that penetrate the platysma, whereas others advocate the individualization of surgical planning. The two approaches appear equally effective if injuries to the great vessels, upper airway, and upper gastrointestinal tract can be ruled out via angiography, endoscopy, or swallowing studies.

Pharyngeal perforation carries the risk of osteomyelitis. There are divergent views on the appropriate management of pharyngeal perforation. Some authors advocate broad-spectrum antibiotics, debridement of bone and soft tissue, drainage, and immobilization. Others have reported a lower infection rate with neural decompression and debridement of the wound.

Penetrating thoracic injuries may damage the lungs or mediastinum. Chest radiography, computed tomography, or angiography may be used to define the extent of the injury. Tube thoracostomy or surgical exploration may be indicated.

Radiographic Evaluation

Initial evaluation should begin with routine radiographs. Fractures and bullet fragments may be seen ( Fig. 142-2 ). A computed tomography (CT) through the area of involvement should be performed next. This modality is generally superior to plain radiographs for the evaluation of the injury and for localizing the fracture or bullet fragments ( Fig. 142-3 ). Compressive lesions may be identified with routine CT imaging. Bone or bullet fragments compressing the thecal sac may be identified. The aforementioned will also give the surgeon a sense of spinal stability or instability. CT myelography may be used to assess or confirm neural compression. This modality may also aid in the evaluation of a CSF fistula. If there is a question of spinal instability, passive flexion/extension radiographs may be used, but only in an awake, alert patient in whom there is no neurologic deficit.

Magnetic resonance imaging (MRI) may also be used in the evaluation. There will be artifacts from the bullet fragments, but valuable information, such as the presence of extradural hematoma, disc herniation, or spinal cord contusion, may be gained. There is a risk of fragment migration in the magnetic field, so only patients for whom the information gained would have been difficult to obtain with other imaging modalities should undergo MRI.

Steroids and Antibiotics

Experience with large patient populations has shown no improvement in outcome from using steroids in patients with penetrating spine injuries. This lack of efficacy and the potential adverse effects on wound healing and infection suggest that steroids have no role in patients with penetrating spine injury.

The rate of infection in penetrating SCI during the Vietnam War was lower in comparison to the rates in prior conflicts. The reason for the lower incidence was predominantly the use of antibiotics. Therefore, one may reasonably conclude that prophylactic antibiotics are of benefit in penetrating SCI. At least 7 days of antibiotic treatment for penetrating abdominal wounds with accompanying involvement of the spine have been shown to result in fewer infectious complications than do shorter courses of antibiotic treatment. The antibiotic agents should be chosen on the basis of the region of the body injured and local hospital bacterial sensitivities.

There has been some concern regarding infection following associated visceral injury. Roffi and colleagues reviewed 42 patients with gunshot wounds to the spine involving bullets passing through the alimentary tract. The patients were treated with a 2-week course of broad-spectrum antibiotics, and no evidence of late infection or osteomyelitis was found. Waters and Sie confirmed these findings in more than 1000 cases of gunshot wounds to the spine. It may be concluded from these findings that it is not necessary to debride and remove bullet fragments following civilian gunshot wounds, even in the face of viscus perforation. This is not the case with high-velocity missile injuries, which pose a greater risk of contamination. Debriding the wound and removing the bullet fragments plus giving parenteral antibiotics are recommended.

Management

Protection of the integument, support of pulmonary function, and prophylaxis against deep vein thrombosis should be addressed immediately. Specialized nursing care is of the utmost importance and should begin immediately. The patient should be turned frequently, and an aggressive pulmonary toilet program should be instituted.

Surgical Indications

Missile Injuries

Surgery may be indicated in the following circumstances: (1) cord compression with an incomplete injury, (2) a discrepancy between the clinical examination and the missile trajectory with a complete myelopathy, (3) a migratory missile fragment, (4) spinal instability, (5) associated infection, and (6) persistent CSF leak ( Fig. 142-4 ). Consideration should be given to surgical exploration of lesions of the cauda equina regardless of neurologic status. Because such injuries involve nerve roots rather than the spinal cord proper, they have a better prognosis.