Treating gunshot injuries to the spine

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By Jay M Zampini.

 

Perhaps one of the more inspiring patients I have treated is also one with a most devastating and poignant story. In contrast to the often unconvincing, “I don’t know what happened; I was minding my own business, on my way to church (and/or my grandmother’s house) and this dude just came up and shot me,” hers was a case of road rage turned violent. She was young and educated, working to get out of a bad neighbourhood in North Philadelphia, USA. She was involved in a minor motor vehicle collision. The other driver became enraged during the “discussion” following the event, and produced a handgun, shooting her in the back as she ran and tried to hide. She presented with a gunshot injury to the thoracolumbar junction with neurologic function that rapidly progressed to complete paraplegia.

Traumatic injury to the spinal cord is a life-changing event for any patient. Gunshot injuries currently represent the third most common cause of spinal cord injury (SCI) and produce approximately one in five of all SCIs in the USA. Both before and after injury, these patients represent an “at-risk” population. The average SCI patient is typically injured at an age of maximal fiscal productivity and half of the time is unmarried or unemployed, meaning that this is a population with socioeconomic disadvantages which are only likely to worsen following injury. Hospital readmission appears to be the rule, not the exception, and can contribute to a cost of care that approaches US$5m over the life of an SCI patient.

Treatment of spinal gunshot injuries can often seem something of an enigma, with very little high-quality evidence and contradictory conclusions to guide treatment decisions. Should retained bullets be removed? Are the injuries unstable? Can a patient undergo a magnetic resonance imaging (MRI) scan with retained bullets? Do patients really develop lead poisoning? My colleagues and I have recently reviewed the body of spinal literature to formulate an understanding of the key concepts surrounding spinal gunshot injuries. Piecing together data from several sources, we have made reasonably consistent conclusions about indications for surgical treatment and bullet removal, antibiotic prophylaxis, MRI safety, and metal toxicity.

The fundamentals of surgical treatment for spinal gunshot injuries are no different from those for any other spinal condition: decompress all compressed nerves and stabilise anything unstable. Empirical observation, however, has suggested that patients with injuries cranial to T12 and who present with complete and static cord injuries seldom recover function with surgical treatment. These patients often have more significant complications following surgery. A progressive loss of neurologic function, particularly at T12 and caudal, certainly represents a justifiable indication for surgical decompression. The osseous injuries are rarely unstable until overzealous decompression renders them so. Notable exceptions are bilateral pedicle fractures and vertebral body injuries caused by the so-called “high energy” firearms—those with a muzzle exit velocity of greater than 2,000ft per second. A computed tomography (CT) scan should be evaluated for the factors typically associated with vertebral instability including comminution and fragment displacement. High energy means high comminution and fragment spread. In these patients, the benefit of surgical decompression and stabilisation would outweigh the risk of additional complications and can lead to accelerated rehabilitation, if not frank neurologic improvement.

I can recall learning throughout my residency in orthopaedic surgery that all bullets should be removed from fluid-filled spaces in the body. The dissolution of the lead would lead to the ensuing lethargy, encephalopathy, anaemia, and possibly death from lead poisoning. What initially sounded like an old orthopaedic wives’ tale, if there is such a thing, is relatively well supported by several small case series and case reports of such toxicity from bullets in synovial fluid. In reports of spinal gunshot injuries, evidence for lead poisoning has been documented to result from retained bullets in cerebrospinal fluid (CSF) or the intervertebral disc, albeit even more rarely than with bullet exposure to synovial fluid. Urgent excision of the bullet fragments may not be necessary although the patient should be counselled about the symptoms that may develop even years in the future. Bullets should be removed from the spinal canal if the fragments are thought to be the cause of a progressive neurologic deficit or if migration leads to neurologic changes. Again, the best evidence suggests that bullets removed from segments cranial to T12 offer little chance of neurologic recovery.

Following the theme of sparse and contradictory evidence in spinal gunshot injury treatment, conclusions about antibiotic use for infection prophylaxis are equally mixed. Several authors have recommended up to fourteen days of antibiotics if the gunshot penetrated the abdominal cavity while others have noted that severe infections still occur in up to 10% of cases with a prolonged course of treatment. At this time, it appears that 24–48 hours of antibiotic treatment is sufficient to reduce the risk of infection in spinal gunshot injuries while minimising the potential for superinfections and drug resistance.

A final controversy encircles the use of MRI following spinal gunshot injuries with retained bullet fragments. The rationale for fear of the MRI follows this syllogism: bullets are metallic objects; MRIs displace metallic objects; therefore MRI is not safe for use with retained bullets. Materials typically used to manufacture bullets—copper and lead—are nonferromagnetic, though some ferromagnetic properties have been observed to result from metallic impurities. Several reports of up to 1.5 Tesla MRI scans performed on patients with retained bullets have repeatedly dismissed this fear, showing no displacement of the fragments or injury as a result of the scans. Of course, every patient should be considered individually, with a personal assessment of risk and benefit of the MRI. Missile fragments in the brain or eye, for example, may prove too risky and preclude MRI as with other metallic fragments. Certainly, this is a situation where the basic science and empirical observations suggest MRI to be safe, even though indoctrination and medicolegal fear seem to counterbalance the issue. The patient should be at the centre of any decision to perform MRI in this situation and should be duly educated in the consent process.

Spinal gunshot injuries comprise a startlingly common cause of one of the worst possible survivable effects of trauma. The decisions for treatment should be made with one part evidence and one part fundamental and basic science. So what, then, would be the best treatment for the patient I described above, whose imaging shows a stable spine with bullet fragments and bone in the spinal canal at T12 and a worsening exam? I took her to the operating room for decompression and repair of a traumatic CSF leak. Although she was never able to walk again, she did regain some meaningful lower sacral root function. The inspiring part of the story is the enlightened attitude she brought to each follow up; she worked hard to return to work and life, never showing anger or regret after what would otherwise devastate most of us.


Jay M Zampini is a spine surgeon in the Department of Orthopaedic Surgery at Harvard Medical School and a member of the Division of Spine Surgery at the Brigham and Women’s Hospital in Boston, USA

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