40 

When Is Surgery Indicated for Patients with Gunshot Wounds to the Spine?

Robert F. Heary and Christopher M. Bono

BRIEF ANSWER

Question 1: Does Spinal Decompression Improve Neurologic Recovery After Gunshot Wound to the Spine?

Background

GSWSs often result in SCI. More than half of these cases result in paraplegia or tetraplegia (class III data).¹ Compared with blunt trauma, gunshot injuries to the spine are more likely to produce complete injuries and are usually associated with stable fracture patterns that do not require surgical stabilization (class III data).^2–4

Controversy

Although the beneficial effect of neural decompression for canal compromise after blunt spinal trauma is becoming increasingly accepted, the effectiveness of decompression after gunshot wounds is less clear. Both class II (prospective, nonrandomized) and class III (retrospective) evidence suggests that surgical decompression of cervical and thoracic gunshot wounds has no beneficial effect on the likelihood of neurologic recovery. However, class II evidence supports operative decompression for gunshot wounds at the T12 to L4 levels when a bullet remains in the spinal canal. No class I studies have investigated the surgical treatment of gunshot wounds to the spine.

Stauffer et al2 retrospectively reviewed 185 cases of GSWS, half of which were treated with laminectomy and half with observation only (class III data). For complete lesions, the authors documented no appreciable return of neurologic function after either surgery or nonoperative management. With incomplete injuries, 71% of the decompressed spines and 76% of the nonoperated spines improved neurologically. Injuries near the thoracolumbar junction, which tended to be incomplete, were associated with better neurologic recovery than injuries to more cranial levels, which were more likely to be complete. Although the antibiotic regimen was not documented, four wound infections, six CSF fistulas, and six cases of late spinal instability were reported in the operative group. There were no cases of infection, CSF fistula, or spinal instability in the patients treated without surgery. Both groups had a high incidence of causalgia (19% and 13% for operative and non-operative groups, respectively).

Further support of a nonoperative approach was provided by Robertson and Simpson,⁵ who reported no increase in neurologic improvement after lumbar laminectomy versus nonsurgical treatment in 33 patients with gunshot wounds to the cauda equina region (class III data). They documented a high rate of postoperative complications. In no case did the authors report a bullet within the spinal canal.

In a prospective study, Waters and Adkins⁶ demonstrated statistically significant motor improvement after surgical decompression between the T12 and L4 levels compared with nonoperatively treated GSWSs (class II data). Importantly, only patients with bullets lodged within the spinal canal were included. At more rostral sites in the thoracic and cervical regions, surgical removal of the bullet and decompression of the neural elements were not found to have a significant effect. No infections were reported in either group.

An important consideration is the timing of surgery. Cybulski et al⁷ reported rates of occult abscess and arachnoiditis of 17% and 15%, respectively, if decompressive laminectomy of the lumbar spine was performed more than 2 weeks from the time of injury (class III data). In other reports, however, the majority of reported cutaneous CSF fistulas and spine infections have occurred after early surgical exploration (class III data).^2,8 Regardless of the level of injury, most authors agree that documented progression of a neurologic deficit, although quite rare, is an indication for urgent surgical decompression and possibly removal of the bullet. In the acute setting, a progressive neurologic deficit can result from an expanding subdural or extradural hematoma (class III data).⁹

Late bullet migration can cause neurologic deficits months to years after the initial injury. Kuijlen and associates¹⁰ reported a case of neurogenic claudication 11 years after a gunshot wound to the abdomen (class III data). The bullet had migrated from the paraspinal muscles at the L3 level into the spinal canal, where it had disintegrated into multiple fragments that had caused a diffuse inflammatory reaction. The patient responded favorably to decompressive laminectomy and removal of the inflammatory mass. Conway et al¹¹ reported a case of cauda equina syndrome after a bullet previously lodged in an intervertebral disk migrated into the spinal canal 9 years after injury (class III data). Again, decompressive laminectomy and removal of the bullet and associated inflammatory mass were effective. Bullet migration within the spinal canal has been documented in numerous other cases.^12,13 However, because bullet migration or entry into the spinal canal is not always associated with neurologic deficit,¹⁴ the advisability of bullet removal must be assessed on an individual basis.

Disk herniation after a GSWS is a rare but potentially significant cause of neurologic compromise (class III data).¹⁵ Entry of a bullet into the intervertebral space is postulated to increase the pressure in the nucleus pulposus. If a defect exists in the posterior or posterolateral annulus, the disk material can be expelled into the canal or foramen, compressing the spinal cord or nerve root. Treatment recommendations are similar to those for other acute disk herniations. Significant and acute neurologic deficits may improve after disk excision. A disk herniation causing cauda equina syndrome is widely regarded to be a surgical emergency. Bullet removal is neither necessary nor indicated unless it can be accomplished easily, without further jeopardizing surrounding neural or bony supporting structures.

Recommendations

For low-energy civilian GSWSs to the spine, most authors agree that surgical decompression of the cervical and thoracic spinal canal has little utility (level II). Substantial rates of postoperative complications with no demonstrable improvement in neurologic outcome lead to the general conclusion that surgery is not indicated in these regions. However, in the specific situation in which a neurologic deficit is associated with an intracanalicular bullet at the conus medullaris or cauda equina level, surgical decompression may be beneficial (level II).

In the terminology of the three-column spine model of Denis,16 disruption of two or more columns of the spine may indicate spinal instability. In contrast to blunt trauma, two- or even three-column disruption from a GSWS is less likely to result in instability. In Denis’s original work, the proposed mechanisms of injury implied an abrupt acceleration/deceleration of the body/spine in space. In the case of gunshot wounds, the body/spine can be considered stationary, and the bullet is the directional force. In the best-case scenario, a through-and-through bullet wound will only damage those structures that lie directly in its effective path. Low-energy gunshots have a narrower circumference of damage than high-energy wounds. These factors influence the amount of spinal instability after GSWSs. These concepts can be likened to a magician pulling a tablecloth from underneath a table that has been set with glasses and plates. The bullet acts as the tablecloth. If the tablecloth is pulled very quickly, the glasses and plates (i.e., the spinal elements) stay in place. If the table is pushed abruptly (i.e., motor vehicle accident), the contents will surely fall and break.

Controversy

Most spine fractures after gunshot wounds are stable injuries (class III data).³ Interestingly, most cases of spinal instability after gunshot wounds may be associated with overly aggressive decompression (class III data).²

Literature

In the retrospective review by Stauffer et al,² 185 patients were treated either operatively or nonoperatively for GSWSs (class III data). The only cases of spinal instability occurred in the operative group (6%). These were attributed to removal of the posterior elements during laminectomy. Similarly, Kupcha and associates³ reported no cases of instability from the GSWS itself in a retrospective review of 28 patients who sustained cervical gunshot wounds (class III data). Again, the only case of late instability occurred after decompressive laminectomy.

Recommendations

In general, the majority of gunshot wounds are stable injuries and do not require surgical stabilization (level III). If stability is questionable, careful flexion and extension radiographs of the spine can demonstrate pathologic mobility of adjacent spinal segments in an awake, cooperative, neurologically intact patient. For the cervical spine, commonly used criteria for radiographic instability are angulatory change exceeding 11 degrees or translation exceeding 3.5 mm between flexion and extension views (class III data).¹⁷ In cases of instability, the affected segments can be stabilized with a variety of instrumentation and fusion constructs, detailed discussion of which is beyond the scope of this chapter.

Surgical decompression of spinal gunshot injuries can lead to vertebral instability (level III). Aggressive laminectomy with substantial removal of the facet joints and posterior elements can destabilize the spine. Laboratory studies suggest that instrumentation and fusion should be contemplated if total facetectomy has occurred, even if only unilateral.¹⁸