Gunshot wounds to the spine. (NM) - Department of Neurosurgery

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C.M. Bono and R.F. Heary / The Spine Journal 4 (2004) 230–240 231rifles, such as the AK-47 and M-16. In contrast, shotgunsare low-velocity weapons that incur high-energy wounds becauseof the combined mass of the numerous fired pellets.In addition, shotgun wounds are further complicated by thepresence of large pieces of “wadding” that are a gross contaminantand require prompt surgical debridement [8].In general, civilian gunshot wounds are considered lowenergy. However, an increasing frequency of high-energyinjuries is being reported in the nonmilitary population [9].Greater availability of military-type firearms, especiallyamong the criminal element, is a contributing factor. In1995, assaults with high-energy weapons accounted for 16%of homicides in New York City [10]. Close-range gunshotslose less energy during transit and therefore transfer moreenergy to the victim. Differentiation between high- and lowenergyinjuries is crucial, because treatments are distinct.In vivo experiments in monkeys have demonstrated thelocal necrotic effect of copper on brain tissue [12]. Similarstudies have been performed on the spinal cord. Tindelet al. [13] demonstrated spinal cord necrosis around copperfragments implanted within the dura of rabbit spinal cords.Whereas lead fragments caused less axonal necrosis thancopper, aluminum resulted in minimal pathologic changes.Importantly, extradural fragments, regardless of the metaltype, did not cause appreciable pathologic changes within theneural tissue. The authors extrapolated that these effectswould be similar to those in the human spinal cord. Althoughthese findings might support removal of intradural copperbullet fragments [14], the clinical challenge is determiningthe material of the bullet, which in many instances is notknown, as well as avoiding further neurologic injury duringexplantation. The clinical benefits of bullet removal to avoidthe neurotoxic effects of copper remain unclear.Bullet material and designThe bullet energy is not the sole determinant of the extentof injury. Fragmentation of the missile can increase thezone of tissue destruction. Hollow-point bullets explode onimpact, leading to multiple fragments that deviate from initiallinear path. The phenomenon of yaw refers to the tumblingof a bullet along its longitudinal axis. Longer bulletshave a tendency for greater yaw, which can further increasethe zone of destruction. In its mid-path, one can imaginethe bullet turned 90 degrees to its long axis so that it is ineffect being pulled through the tissues sideways.Bullets can be nonjacketed, partially jacketed or fullyjacketed. The “jacket” refers to a thin metallic layer coveringthe surface of the bullet. Fully jacketed bullets exhibit littledeformation with firing and are designed for accuracy to hitlong-range targets. They are highly precise and incur cleanexit and entrance wounds. Partially or nonjacketed missilesexpand on tissue impact and, like hollow-point bullets, exponentiallyextend the circumference of tissue damage. Suchdesigns are intended for close-range targets.Various materials have been used to produce bullets. Mostbullets are composed of a lead core, which may be combinedwith a number of different metals to achieve a desiredhardness. Similarly, the jacketing material can be copper,brass or nickel. These substances can have both systemicand local toxicities on tissues. More common in synovialjoints, lead poisoning has been reported with bullets lodged inthe intervertebral disc [11]. Although cerebrospinal fluidwould intuitively be an effective solvent, systemic lead elutionwith intramedullary bullets is uncommon. In cases ofretained lead bullets, lead levels can be measured periodically.Notwithstanding other clinical factors, significant increasesin lead levels and characteristic hematopoieticchanges on bone marrow biopsy can be an indication forbullet removal. In actual clinical practice, bullets very rarelyneed to be removed from the spine to treat or preventlead toxicity.EvaluationAcute examinationThe initial evaluation of the gunshot victim must addressall life-threatening injuries. Maintenance of airway, breathingand circulation (ABCs) is paramount. The region of injuryshould be considered. Gunshot wounds to the neck arefrequently complicated by airway injuries that can necessitateemergent intubation [15]. Action should not be delayedfor radiographic “clearance” of the cervical spine, becausegunshot fractures are usually inherently stable [5,16–18].Carotid and vertebral artery perforations should be suspectedwith pulsatile neck bleeding. Immediate vascular consultationto restore cerebral blood flow is important, as temporarystents placed emergently can enable definitive repair at alater time. Pharyngeal and esophageal wounds must also bedetected and evaluated, because they are often associatedwith infections. In particular, large hypopharyngeal lacerationsare associated with a higher rate of contaminationbecause of the pooling of secretions in this area. Endoscopictechniques can be used effectively and expediently for surveillancein the acute setting. Open surgical exploration ismandatory to repair any documented tears.The thoracic spine is the most commonly affected withgunshots [4]. The lungs, heart and great vessels are at riskwith such injuries. Careful chest auscultation can detectasymmetric breath sounds indicating hemothorax or pneumothorax.Cardiac monitoring, including distal pulses, cansuggest heart perforation, aortic disruption or tamponade.Until stabilization of ventilation and hemodynamics, theevaluation of any spinal injury remains secondary. Similarly,the examination of the abdomen is focused on suspectedvascular or viscus injuries. In particular, colonic perforationsthat occur before the missile passing through the spine mustbe recognized, because they are associated with a high rateof spinal infection if not treated with an appropriate antibioticregimen [19–22]. In paraplegic or quadriplegic patients, the
232C.M. Bono and R.F. Heary / The Spine Journal 4 (2004) 230–240abdominal examination may be less reliable because of lossof visceral sensation. This may lower the threshold for obtainingadvanced diagnostics, such as peritoneal lavage orabdominal computerized tomography, to rule out injuries.Although numerous organs exist in the pelvic area, sacralgunshot wounds are most often complicated by hemorrhage[23]. After posterior gunshot wounds, sterile packing ofthe posterior bullet hole using methyl cellulose and bone waxhas been reported effective in facilitating tamponade [23].Likewise, emergent angiographic embolization can diminishor halt severe bleeding, with the risk of possible devascularizationof the neural structures [23].Evaluation of the spinal injuryAfter patient stabilization by the trauma team, focus isturned toward the spinal injury. Witnesses, emergency medicaltechnicians and law enforcement officers can offer usefulinformation about the direction of the injury, the type ofweapon or bullet and the proximity of the shot. Often thealert and awake patient can account for the number of shotsfired. The cervical spine should be immobilized with a hardcervical collar until initial radiographs are complete.The patient must be stripped of all clothing while logrolling the patient to protect the spine from further harm.Entrance and exit wounds should be examined thoroughly.Often, only an entrance hole can be found if the bullet islodged in tissue. The entrance hole may be differentiatedfrom the exit wound. As a bullet pierces the skin fromthe outside, the margins of the wound are cleaner and moredefined. Upon exit, the bullet can take a more random path(fragmentation) and has more of a “blown out” appearance.In the abdomen, it is critical to determine if the bullettraveled from front to back. Although deep probing is notrecommended, superficial inspection for imbedded pieces ofclothing or foreign materials is useful. After sterile woundcare and dressing, radiopaque markers (eg, electrocardiogramleads) are placed over all wounds. This facilitatesroentgenographic deduction of the gunshot path.The physical examination should proceed as for othertypes of spinal trauma. Each spinous process must be palpatedfor tenderness and crepitus. An in-depth neurologicexamination, including motor, sensory, reflexes and analsphincter tone is mandatory and must be documented precisely.In the intubated or unconscious patient, neurologictesting is limited. However, if paralytic agents have not beenadministered, deep tendon and bulbocavernosus reflexesmay still be elicited.this path. Fragments can be located in soft tissue, intervertebraldisc, bone or the spinal canal. Such parameters as vertebralbody height, interpedicular distance and segmentalkyphosis can be measured. In the awake, neurologicallyintact patient in whom spinal stability is in question, dynamicactive flexion-extension views may be obtained. This is bestdelayed until 2 weeks after injury when pain and spasmhave sufficiently subsided.The necessity of radiographically clearing the cervicalspine after gunshot wounds to the head and face has beenquestioned in a number of recent articles. In a series of 53consecutive patients sustaining gunshots to the cranium,none had cervical spine fractures [24]. Similarly, Kennedyet al. [17] found wounds limited to the calvaria had noconcomitant cervical spine trauma in 105 cases. However,with gunshot wounds extending outside the calvaria, 10%sustained a cervical spine fracture. Kihtir et al. [16] studiedthe association of cervical injuries with gunshots to the face.Dividing the face into three zones, spinal fractures were notedin 10% and 20% of mid-face (maxillary) and orbital injuries,respectively, whereas surprisingly none were noted aftergunshots to the lower face (mandibular region). From thesedata, it would appear that gunshots to the maxilla and orbitscarry the highest risk for concomitant cervical spine injuryand that radiographic imaging should be pursued more aggressivelyafter such incidents. Clearing the cervical spineafter calvarial injuries is probably not necessary.After plain films have determined the level of the bulletand/or fracture, computed tomography (CT) should besought. Currently, this is the advanced modality of choice forspinal gunshot trauma. CT images allow better localizationof the bullet within the vertebral segment and can moreclearly demonstrate foreign bodies in the spinal canal. Thinslices (1 to 3 mm) are used to evaluate the integrity of thebony elements. Of note, images are often obscured by artifactwhen metallic bullet fragments are present (Fig. 1). Thiscan limit the amount of detail appreciable.ImagingTwo orthogonal plain radiographic views of the spine canhelp detect gunshot fractures and locate bullet fragments.Using radiopaque bullet hole markers, the bullet path canbe deduced. Damage must be suspected to structures alongFig. 1. Computed tomography images are highly useful in evaluating thelocation of bullet and bone fragments. However, their utility can sometimeslimited by metallic artifact.
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