➢ Consider the injury level (cervical, lumbar, thoracic), spinal stability (substantial vertebral body collapse, facet disruption, and so forth), and neurological status (progressive neurological deficits) as well as high-energy compared with low-energy ballistic pattern (high energy is often associated with large, soft-tissue injury) when deciding between operative treatment and nonoperative treatment of gunshot injuries to the spine.
➢ The use of corticosteroid treatment for neurological injury resulting from a gunshot wound to the spine is not currently recommended given the risk of complications and the lack of evidence showing benefit.
➢ Antibiotic prophylaxis of gunshot injuries to the spine should include empiric treatment to cover skin flora for three days (for example, cefazolin, 2 g intravenously every eight hours, or equivalent). For injuries that first transverse the gastrointestinal tract, antibiotics that cover both skin and bowel flora are traditionally recommended for at least seven days (ampicillin and sulbactam, piperacillin and tazobactam, or clindamycin), although a shorter regimen may be sufficient.
➢ When gunshot injuries to the spine involve retained bullet fragments, clinical surveillance should be considered to avoid lead toxicity. Clinicians should be familiar with the common clinical signs and should obtain serum lead levels when present. Treatment with chelation therapy and/or surgical removal of retained fragments may be necessary.
➢ Magnetic resonance imaging (MRI) in the presence of retained bullet fragments near the spine may be safe in the case of bullets with a lead core and copper or alloy jacket, but not for bullets made of steel.
After experiencing a peak more than two decades ago, the incidence of gunshot injuries has recently stabilized1,2. Nevertheless, the effects of gunshot injuries to the spine and associated neurological sequelae continue to be substantial. In fact, approximately 14% of all civilian spinal cord injuries since 2010 are related to acts of violence, primarily gunshot wounds2. The number of minor gunshot injuries to the spine (i.e., those that cause no paralysis) are presumably much higher, although accurate data for this type of injury are not available nationwide.
As gunshot injuries to the spine and associated neurological sequelae remain a substantial clinical burden, the standardization of treatment regimens becomes more important. However, the literature regarding treatment for these injuries does not clearly define these standards. Additionally, many of the current treatment recommendations have their basis in the historic literature.
The purpose of this review is to provide an algorithm for the evaluation and treatment of gunshot injuries to the spine. We review the important factors related to wound ballistics, physical examination, spinal imaging, and use of antibiotics. The clinical decision-making process, including consideration of spinal stability, neurological status (including use of corticosteroids), and retained bullet fragments, is discussed in depth. Reported outcomes of recommended treatments with regard to neurological results and associated complications are also reviewed. Finally, special consideration is given to military or combat injuries.
Wound ballistics is described as the science of firearm projectile motion and impact, as it pertains to the human body or living tissue3. There are several factors involved in the ballistic pattern of a bullet projectile. The bullet mass, bullet velocity, and amount of bullet fragmentation each have an influence on the human tissues and may exert greater or lesser amounts of damage depending on each individual factor. In military-type firearms (i.e., high-powered rifles using large-caliber bullets), the bullet characteristics often involve a higher total mass and greater maximal velocity, which, in turn, cause greater tissue damage. Thus, military or combat gunshot injuries are considered high-energy, whereas civilian firearms injuries are most often low-energy. This is because civilian firearms injuries often involve pistols or small-caliber rifles. This distinction is very important, as it may guide the clinician in the diagnosis and treatment of these injuries, as described later. Also important in wound ballistics is the distinction between a permanent cavity and a temporary cavity. A permanent cavity represents the permanent disruption of the tissues resulting from the bullet passage. A temporary cavity is the stretching of the tissues as the bullet passes. The temporary cavity has different effects depending on the elasticity of the tissues. For example, muscle tissue is relatively resistant to this type of stretching related to bullet passage, whereas bone is more extensively damaged. This soft-tissue or osseous damage was traditionally considered the basis for aggressive surgical debridement to lessen the risk of infection. More recently, clinicians have considered this one of the common misconceptions of wound ballistics, which Fackler has discussed at length4. Instead of attributing the decrease in infection rate seen in gunshot injuries from World War I (5%) to those from the Korean War (0.8%) on surgical debridement techniques (which have not substantially changed during that time), he more accurately attributed this decrease in infection rate to the early administration of systemic antibiotics.
The initial evaluation and expeditious hemodynamic stabilization of the gunshot injury patient are crucial. Emphasis should be placed on the Basic Life Support guidelines of airway, breathing, and circulation. The evaluation should also include a thorough neurological examination to identify any motor or sensory deficits, as the findings may guide treatment recommendations and may provide a reference for future neurological examinations to document improvement or deterioration. Initial spinal stabilization with bracing should be utilized while the primary evaluation is performed. Once the patient is deemed hemodynamically stable, the secondary survey and spinal imaging studies may then be obtained.
Special consideration should be given to patients with gunshot injuries to the neck, as they often have substantial and potentially life-threatening airway and/or vascular injuries. Despite traditional Advanced Trauma Life Support (ATLS) recommendations for immediate cervical spine immobilization in the patient with trauma, cervical spine immobilization for presumed spinal instability in the setting of gunshot injury to the neck may further delay or may restrict the evaluation and treatment of airway or vascular compromise. Initial consideration should be given to the need for advanced airway management and computed tomographic angiogram or ultrasound for the identification of vascular injury, as Mohammed et al.5 reported that physical examination alone may not be a good predictor of vascular injury in the setting of penetrating trauma to the neck, although poor oxygen saturation and/or active bleeding from the wound are early signs of airway and/or vascular injury. If a vertebral artery injury is identified, these injuries can often be effectively managed with endovascular techniques6. Multiple studies have confirmed the importance of emergent airway and vascular injury management after gunshot injury to the neck, even at the (temporary) expense of cervical immobilization, as the likelihood of concomitant unstable cervical spine injury is relatively low7-9.
Although radiographs may easily identify bullet fragments within the spinal elements, the standard imaging for most major trauma centers is currently computed tomography (CT) with or without intravenous contrast. Fine-cut axial CT imaging, supplemented with sagittal reformatting, allows for a highly detailed evaluation of the exact location of bullet fragments, the tract or bullet trajectory, the probability of an associated vital structure injury, and any osseous injuries to the spinal column. However, CT imaging may not be beneficial in identifying injury to the neural elements or ligamentous structures. To visualize these structures, magnetic resonance imaging (MRI) is preferred. MRI should be considered in patients with neurological deficits to help determine if it is direct neural damage from the bullet fragment or indirect injury from the shock-wave effect. However, with MRI, there is concern for movement, heating, or artifact associated with metallic objects such as bullet fragments. A recent study by Dedini et al.10 confirmed that bullets composed of lead with copper or alloy jackets appear to be MRI-safe at 1.5-T, 3-T, and 7-T magnetic fields with regard to MRI-related movements compared with bullets containing steel, which exhibit strong magnetic field interactions and may pose a risk to critical structures. Their study also found no significant temperature increase with varying bullet composition during 3-T MRI. However, bullets containing steel did generate more artifacts than those composed of lead with copper or alloy jackets, which will decrease the usefulness of MRI in these patients.
Unfortunately, it is not possible to accurately determine the metallic composition of a bullet fragment on the basis of radiographic or CT imaging alone. However, if a bullet shell casing is available (i.e., from the crime scene or location where the shooting took place), the manufacturer and caliber of the bullet can be identified from markings on the shell casing itself. This manufacturer information can then be used to find the actual bullet composition.
Wound culture specimens taken from the bullet tract can be useful for the purpose of targeted antibiotic treatment. This is especially true if the bullet path traverses the pharynx, esophagus, or colon or if the wound is subsequently contaminated. Current recommendations include a three-day course of antibiotic treatment for routine, uncontaminated gunshot injuries, utilizing a second-generation cephalosporin (i.e., cefazolin, 2 g intravenously every eight hours) or other antibiotic with equivalent coverage, as suggested by Heary et al.11. When the bullet trajectory first penetrates the pharynx12,13, esophagus, or colon14, a different antibiotic regimen is recommended. If the bullet traverses the spine first and then penetrates a hollow viscus, this specialized antibiotic regimen is not clinically necessary. The traditional standard treatment for gunshot injuries that first perforate a contaminated viscus (i.e., colon) focuses on broad-spectrum antibiotics to cover organisms normally found in the viscus, which should be continued for seven to fourteen days (ampicillin and sulbactam, 3 g intravenously every six hours; piperacillin and tazobactam, 3.375 g intravenously every six hours; or clindamycin, 600 mg intravenously every six hours or 900 mg intravenously every eight hours)12,13,15, although a recent study by Rabinowitz et al.15 suggested that the aforementioned antibiotic regimen with a shorter duration may be sufficient. Roffi et al.14 were the first to recommend minimal or no spinal debridement and coverage with an extended course of the appropriate parenteral antibiotics. With this treatment regimen, the incidence of spine infections has been decreased to between 5% and 15% for injuries involving the pharynx, esophagus, or colon.
A review of the literature shows that a large majority of civilian gunshot wounds to the spine are stable8,16-19. However, a distinction must also be made between gunshot injuries to the cervical spine and gunshot injuries to the thoracic or lumbar spine. The stability of the cervical spine is determined by the anterior vertebral bodies and discs (anterior column) and by the facet joints and lateral masses (posterolateral columns), with the anterior column carrying 36% of the weight of the head and the two posterolateral columns each carrying 32% of the weight of the head20. No immobilization is needed if none of these columns are compromised. If one column alone is injured, immobilization with a rigid cervical collar is recommended. However, caution should be given when substantial osseous destruction of the cervical vertebral body (anterior column) is identified, as this could progress to focal kyphosis, which may be prevented by surgical intervention. If two or three columns are disrupted, operative treatment is recommended, or, in patients in whom operative intervention is otherwise contraindicated, halo vest immobilization may be considered instead.
As for the thoracic and lumbar spine, historical classifications systems such as the Denis three-column model have been applied in clinical practice, but with the understanding that this three-column model was designed to describe closed injuries from mechanisms much different from gunshot injuries21. The same is true of more contemporary thoracolumbar injury classification systems such as the Thoracolumbar Injury Classification and Severity Scale (TLICSS), which utilizes the assessment of injury morphology and the posterior ligamentous complex integrity to determine stability, both of which have a basis in the three-column model22. With this understanding, if the gunshot injury involves only one of the three columns, then no particular immobilization is needed. If two or three columns are injured, then either surgical treatment or nonoperative treatment with a thoracolumbar orthosis is typically indicated. Spinal immobilization is normally continued for six to eight weeks if treated nonoperatively. Subsequently, flexion and extension radiographs can help determine whether the spine injury has adequately healed and is stable. Unstable injuries are most commonly seen in small children and are related to the relative size of the vertebral body compared with the bullet. The rare cases of instability in adults after gunshot injuries to the spine have been most commonly seen as a result of aggressive surgical decompression17. Thus, there are few indications for surgical decompression in a neurologically intact patient. The appropriate indications include new-onset neurological deficit with proven neurological compression, documented lead toxicity from the bullet, and a possibly copper-jacketed bullet fragment that is in contact with neural elements7,17,23. Progressive loss of spinal alignment, which may be identified in the short or long term, should also be considered an indication for surgical treatment. A proposed treatment algorithm for gunshot injuries to the spine is shown in Figure 1.
Bullets can cause neurological deficits by direct injury to neural elements, by compression of the spinal cord or nerve roots as caused by a retained bullet in the spinal canal, or even by a shock-wave effect as the bullet passes near the neural elements24. Many authors have written about the consequences of bullets in the spinal canal25-33. The most recent prospective study34 showed that surgical decompression for intracanal bullets from the T12 to L4 levels yielded significant motor improvement (p < 0.004) compared with nonoperative treatment. Surgical removal and decompression at levels above T11 had no significant impact on neurological improvement, but the number of patients in this group was very small and, as a result, it would be difficult to find a significant difference.
In the case of progressive neurological deficits, surgical removal of the compressive bullet or osseous fragments, disc extrusion, or associated epidural hematoma may halt further neurological decline. Similarly, we recommend removal of bullets from the cervical spine even in complete spinal cord injuries to increase the chances of nerve root improvement at adjacent levels, analogous to the benefits of elective decompression on closed spinal cord injuries35,36.
The most current studies with regard to the use of corticosteroids in patients with neurological deficits after gunshot injury to the spine include those by Heary et al.11 and Levy et al.37. Both groups of authors found that routine use of intravenous corticosteroids after gunshot injuries to the spine of patients with neurological deficit did not improve the chances of neurological recovery, but did increase the risk of complications such as infection. Thus, the administration of corticosteroids for patients with neurological deficits and related gunshot injuries to the spine has been avoided at our institution.
Retained Bullet Fragments
For patients with retained bullet fragments within the spinal column (especially within the intervertebral disc space) but without other indications for acute fragment removal listed above, education and close clinical monitoring for signs of plumbism (lead toxicity), due to partial bullet fragment resorption, are recommended38,39. Figure 2 and Figure 3 describe two case examples of retained bullet fragments and discuss the treatment options. Figure 2, A, B, and C include CT images (sagittal, coronal, and axial) of a patient who sustained a gunshot injury to the lumbar spine, complicated by a retained bullet fragment within the spinal canal at the L3 level. Figure 2, D shows an intraoperative lateral fluoroscopic image just prior to surgical removal of the retained bullet fragment. This patient underwent a minimally invasive laminotomy for bullet removal and canal decompression with use of a 22-mm tubular retractor. No cerebrospinal fluid leak was noted.
Patients with plumbism can present with neurological symptoms such as neuropathic pain, extremity weakness, and/or paresthesias, but other nonspecific symptoms such as fatigue, insomnia, headache, abdominal pain, short-term memory loss, and even depression have been described40. Unfortunately, the timeline for these symptoms to become evident has not been clearly defined, which makes vigilance on the part of the clinician very important. Treatment in the form of bullet fragment removal and/or chelation therapy should be offered for patients with retained bullet fragments who are symptomatic with a serum lead level of >50 µg/dL or are asymptomatic but with a serum lead level of >80 µg/dL41. Chelation therapy typically involves administration of oral succimer (30 mg/kg/day), which functions by binding the lead ions to form nontoxic chelates42. For patients with retained bullet fragments but without any of the above symptoms and normal serum lead levels, close clinical monitoring is appropriate. Figure 3, A, B, C, and D show lumbar spine radiographs (anteroposterior and lateral) and CT myelogram images (sagittal and axial) of a patient who sustained a gunshot injury to the spine approximately ten years prior to presentation in our clinic, with a retained bullet fragment in the right L4-5 facet joint. Notice the dystrophic calcifications surrounding the retained bullet fragment. Her serum lead level was 59 µg/dL (normal, <10 µg/dL), but she displayed no signs of systemic lead toxicity. Treatment options were offered that included bullet fragment removal and/or chelation therapy.
A study by Tindel et al.43 found that copper bullet fragments cause local neural toxicity in an animal model compared with lead and aluminum, which had lesser effects on local neural tissues. These findings suggest that removal of copper bullet fragments within the spine may be indicated, even in the absence of neurological deficits. As mentioned previously, bullet composition can be identified by first obtaining a bullet shell casing, which allows identification of the manufacturer and caliber of the bullet, which can then be used to identify the metallic composition.
The rate of neurological recovery associated with gunshot injuries to the spine is different for complete spinal cord injuries compared with incomplete spinal cord injuries. Although complete spinal cord injuries may show improvement of nerve root function at one or two levels, incomplete spinal cord injuries can show dramatic improvement in spinal cord and nerve root function over time. The timeline for neurological improvement seems to mirror those seen with closed spinal cord injuries but may begin slightly later. Although there is a lack of studies directly comparing neurological recovery in patients who sustain low-energy gunshot injuries to the spine with those who sustain high-energy gunshot injuries to the spine, we suspect that the outcomes would favor low-energy injuries given the difference in ballistic patterns.
Waters et al. reported clinical outcomes of paralysis resulting from gunshot wounds to the spine44. The study population included a total of 135 patients, with 57% of them sustaining complete neurological injuries and 43% of them sustaining incomplete neurological injuries. After the one-year follow-up, 67% of the patients with complete spinal cord injury and 64% of the patients with incomplete spinal cord injury had no improvement in the neurological level of injury, meaning that the most caudal intact motor and sensory level did not change. Nevertheless, the overall results showed that the patients had a significant improvement (p < 0.0001) in the American Spinal Injury Association (ASIA) motor index score at the one-year mark45. Also, more improvement was seen in those with incomplete spinal cord injury than in those with complete spinal cord injury.
There have been reports of late neurological deterioration in patients with existing neurological deficit as a result of gunshot injury to the spine. Gellad et al.46 prospectively evaluated eleven such patients and found the following causes of late deterioration: syringomyelic cavity in seven patients, arachnoid cyst in three patients, and osteomyelitis in one patient.
Although there are instances of patients with gunshot injuries to the spine who are initially neurologically intact but experience late neurological decline, these are rare. This uncommon phenomenon has been reported as a result of bullet migration within the spinal canal, late development of spinal stenosis related to the bullet fragment and/or accelerated degenerative changes, or a combination of neural compression and local neurotoxic effects of retained bullet fragments. A high index of suspicion should be maintained when evaluating such a patient with a history of gunshot injury and new neurological findings. Although not reported in the literature, a substantial loss of spinal alignment (especially in the cervical spine) could also be cause of late neurological decline.
Gunshot injuries to the spinal cord can occasionally result in chronic dysesthetic pain described as burning or searing pain that radiates into the paralyzed extremities. Although this pain can be very debilitating, it often improves with time and conservative medical management, including use of nonsteroidal anti-inflammatory drugs combined with neuropathic medications such as gabapentin or amitriptyline. Persistent severe pain that is deemed out of proportion to what is normal should be evaluated further to rule out underlying infection.
Spine infections following gunshot injuries to the spine are uncommon, but they can occur following injuries to the esophagus, pharynx, or colon. They are rarely seen after injury to other organs, including the stomach or small intestines. Antibiotic prophylaxis, which has been discussed previously, may contribute to the minimization of this complication. Other associated sequelae include fistula formation related to contaminated viscus injury, which may require diversionary drainage and prolonged hyperalimentation. The surgical treatment of spinal infections is reserved for patients with progressive paralysis associated with the infection, progressive deformity, suspected foreign body associated with the infection, unknown infectious organism requiring surgical tissue biopsy, and failure of conservative treatment. Typically, spinal infections are not identified until weeks after the initial injury. At that time, we recommend a CT-guided needle biopsy of the spine and subsequent initiation of a six-week course of the appropriate antibiotics, with surgical debridement reserved for the cases mentioned above.
Cerebrospinal fluid leaks to cutaneous fistulae can occasionally be identified as a direct result of a gunshot wound to the spine but are more commonly seen after acute surgical treatment with laminectomy. Stauffer et al.25 reported on 185 patients with gunshot injuries to the spine and observed that cerebrospinal fluid-cutaneous fistulas did not occur in patients who had not undergone laminectomies. In those treated with laminectomy and bullet removal, the incidence was 6%. As most of these fistulas are seen following acute surgical treatment, consideration should be given to delayed removal of the bullet fragment for seven to ten days except when emergency surgical decompression is indicated, as discussed previously. If acute decompression is required, watertight closure of the dura, paraspinal muscles, fascia, and skin is necessary to minimize the chance of postoperative cerebrospinal fluid-cutaneous fistula formation. Other techniques utilizing synthetic or allograft dural patches have been developed for purposes of dural repair or reconstruction but have not yet been specifically studied in this clinical scenario, to our knowledge. In situations in which adequate dural repair and soft-tissue closure are not possible, a lumbar subarachnoid cutaneous drain should be placed to divert spinal fluid and decompress the dural sac to promote healing of the dura, which will prevent cerebrospinal fluid-cutaneous fistula formation and associated sequelae such as meningitis.
Special Considerations: Combat Injuries
As a result of the recent battles in Iraq and Afghanistan, there has been further opportunity to study combat gunshot injuries to the spine and to assess their outcomes. Combat gunshot injuries to the spine can often be associated with substantial collateral injuries given the high-energy ballistic patterns of military weapons. This difference in ballistics generally results in a difference in presentation and treatment. A recent study by Blair et al.47 confirmed this by noting that soldiers sustaining battle-related gunshot injuries to the spine underwent surgical intervention at a much higher rate than soldiers with non-battle gunshot injuries, likely related to the high-energy injury patterns typically seen with combat ballistics. The same authors also reported that soldiers who sustained penetrating spine injuries (i.e., gunshot injuries to the spine) also had higher rates of spinal cord injury and decreased neurological improvement compared with those with blunt spine injuries sustained in combat48. Patzkowski et al.49 studied a similar population of 598 soldiers who took part in Operation Enduring Freedom and Operation Iraqi Freedom and found that 78% of soldiers who sustained combat spine fractures had at least one non-spinal injury and 76% had multiple spine fractures, highlighting the need for a high index of suspicion for associated injuries and non-contiguous spine fractures in this population. Schoenfeld et al.50,51 reviewed recent publications on combat injuries during the Global War on Terror and noted the highest incidence of combat-related spinal injuries in American military history. The authors also noted an increased incidence of combat injuries related to sniper attacks, ambush, and improvised explosive devices that have contributed to an increasing number of spine injuries and new injury patterns. They recommend reexamination of the current clinical practice guidelines for the care of combat-related spinal injuries in light of these data.
With the persistence of gun-related violence in both the civilian and military settings, the clinical burden of gunshot injuries to the spine has also continued. Treatment recommendations have widely varied depending on bullet ballistics, neurological status, concomitant injuries, and infection risk. Given this persistence in violent crime and recent advances in weapons technology, we inquired about the current recommendations for the treatment of gunshot injuries to the spine for civilian and combat injuries with and without neurological deficits, the utility of corticosteroid use, and the length of antibiotic prophylaxis.
Although our review has found that most evaluation and treatment recommendations for gunshot injuries to the spine have not changed over the past ten years, there continue to be limitations in the literature. We identified two specific areas in which strong treatment recommendations are lacking. First, the literature on corticosteroid treatment for patients with neurological deficits as a result of gunshot injuries to the spine is equivocal with regard to benefit. Unequivocal data, as would be garnered from a randomized controlled trial, are thus far not available, to our knowledge. The second area in which we identified limitations in the literature is on the topic of antibiotic prophylaxis of gunshot injuries to the spine, especially where the projectile first traverses the gastrointestinal tract. Although it is clear that antibiotics should be chosen to cover the typical skin and bowel flora, the literature is not as clear when recommending the length of the antibiotic course. The trend in the recent literature has been to recommend a shorter overall course of treatment. However, these recommendations are based on data obtained from a small number of patients and without comparison groups. Certainly, larger studies with appropriate control groups would yield stronger recommendations.
Gunshot injuries to the spine have remained a substantial clinical problem whose treatment is built on a thorough understanding of bullet ballistics, typical physical examination findings, and the appropriate diagnostic testing. As indicated in the treatment algorithm, most injuries can be treated nonoperatively. However, the rare gunshot injuries that cause spinal instability or progressive neurological decline must be promptly identified and must be treated surgically. Antibiotic prophylaxis for gunshot wounds to the spine that pass through the gastrointestinal tract continues to be the standard of care. However, the length of antibiotic treatment remains controversial. Finally, there has yet to be a proven benefit to corticosteroid treatment, even in patients with neurological deficits.
Source of Funding: There was no external funding for this study.
Investigation performed at the Department of Orthopaedic Surgery, University of Miami Leonard Miller School of Medicine, Miami, Florida
Disclosure: None of the authors received payments or services, either directly or indirectly (i.e., via his or her institution), from a third party in support of any aspect of this work. One or more of the authors, or his or her institution, has had a financial relationship, in the thirty-six months prior to submission of this work, with an entity in the biomedical arena that could be perceived to influence or have the potential to influence what is written in this work. No author has had any other relationships, or has engaged in any other activities, that could be perceived to influence or have the potential to influence what is written in this work. The complete Disclosures of Potential Conflicts of Interest submitted by authors are always provided with the online version of the article.
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