*3.2.3. Terminal ballistics*

Terminal ballistics is directly influenced by the internal and external ballistics, which delivered the bullet to meet its target in a certain condition. As discussed above, the energy entailed within the bullet upon the impact is the main characteristic that will influence its effect within the body and will determine the extent of the injury [66].

The other aspect that determines the amount of injury transferred to the body is the resistance to penetration of the body and the characteristics of the body surface and tissue. The ability of the body surface to resist penetration is influenced in turn by two factors—the presented area of the bullet, which increases with rising yaw up to a maximal impact surface when the yaw angle reaches 90°, and the bullet deformation upon impact, which has to do with its internal metal composition and structure [67].

As the bullet penetrates the skin, the energy transfer between the bullet and the tissue begins. As a result of the high level of resistance and drag that meets the bullet with its entrance, a high-pressure crushing effect develops in front of the bullet's tip, sometimes called the "shock wave," and together with the mechanical damage that occurs, while the bullet cuts through the tissue—these create one level of tissue damage [58, 68]. In contrast to the high pressure that develops in front of the bullet, as the bullet keeps on advancing, a vacuum is created in the back of the bullet, which in turn causes the tissue to collapse back.

This change of pressures causes the "cavitation" effect, which basically refers to the tissue's reaction to the very rapid change of pressures—the tissue first expands and then collapses back, leaving a tract within the tissue which is slightly larger in diameter than the bullet. The magnitude of the cavitation is directly related to the rate of energy transfer into the tissue and to the degree of yaw—the bigger the yaw, the bigger the cavitation [69].

The outer appearance of the body after the impact is not always suggestive of the true damage that lies within. With low-velocity handguns, the bullet usually does not cause cavitation, and the damage is usually due to the mechanical impact of the bullet. Sometimes, there is not even an exit wound and the bullet stays within the tissue. Alternatively, high-velocity rifles usually have an exit wound, and they leave behind them a distinct tract, usually very damaged and often contaminated because of the "suction" effect of the wound. One might find cloth fragments in a wound cavity [70].

#### **3.3. Initial evaluation and management**

[60] that might destabilize it and thereafter to the drag forces as it traverses the air, which

This combination of forces acting on the exiting bullet creates an overturning moment, which causes the bullet to diverge from its original line of trajectory. This divergence is called "yaw," and it is expressed by the angle between the bullet's axis and the velocity vector [36, 61]. Because of the bullet's spin, yawing results in complex spiral revolution of the tip about its center of mass. Eventually, if the distance the bullet travels is long enough, yawing becomes irreversible, and tumbling occurs—meaning the bullet advances base-forward [62, 63].

It is quite clear that as the distance between the firearm and the target is shortened, these are less so-called disturbances to the bullet's path, and hence it can deliver more energy upon the impact. Muzzle velocity decreases significantly after 45 m for most pistol bullets and after 100 m for rifle bullets [64]. Unfortunately, most civilian gunshot wounds (GSW) are inflicted

Terminal ballistics is directly influenced by the internal and external ballistics, which delivered the bullet to meet its target in a certain condition. As discussed above, the energy entailed within the bullet upon the impact is the main characteristic that will influence its effect within

The other aspect that determines the amount of injury transferred to the body is the resistance to penetration of the body and the characteristics of the body surface and tissue. The ability of the body surface to resist penetration is influenced in turn by two factors—the presented area of the bullet, which increases with rising yaw up to a maximal impact surface when the yaw angle reaches 90°, and the bullet deformation upon impact, which has to do with its internal

As the bullet penetrates the skin, the energy transfer between the bullet and the tissue begins. As a result of the high level of resistance and drag that meets the bullet with its entrance, a high-pressure crushing effect develops in front of the bullet's tip, sometimes called the "shock wave," and together with the mechanical damage that occurs, while the bullet cuts through the tissue—these create one level of tissue damage [58, 68]. In contrast to the high pressure that develops in front of the bullet, as the bullet keeps on advancing, a vacuum is created in

This change of pressures causes the "cavitation" effect, which basically refers to the tissue's reaction to the very rapid change of pressures—the tissue first expands and then collapses back, leaving a tract within the tissue which is slightly larger in diameter than the bullet. The magnitude of the cavitation is directly related to the rate of energy transfer into the tissue and

The outer appearance of the body after the impact is not always suggestive of the true damage that lies within. With low-velocity handguns, the bullet usually does not cause cavitation, and

increases with rising velocity [51].

76 Essentials of Spinal Cord Injury Medicine

from an average distance of only 10 m [65].

metal composition and structure [67].

the body and will determine the extent of the injury [66].

the back of the bullet, which in turn causes the tissue to collapse back.

to the degree of yaw—the bigger the yaw, the bigger the cavitation [69].

*3.2.3. Terminal ballistics*

As in any other trauma, MPSCI should be first treated according the ATLS principles [71]. This initial evaluation will reveal concomitant injuries. Rapid evacuation to a hospital is crucial. This is especially true for the military scenario, in which more than one injury is the rule. The Prehospital Trauma Life Support and the Military Trauma Life Support (PHTLS and the MTLS) emphasize the importance of rapid evacuation from the scene of injury. It recommends that only securing airway and breathing together with partial circulatory control (control external bleeding) are done at the scene, and, thus, instead of doing the whole "ABCDE" scheme, the team should perform stages A, B, and half C ("scoop and run").

After arrival to the hospital, these patients are initially evaluated in the trauma bay by a multidisciplinary team. Following initial resuscitations and stabilization, physical examination is undertaken. The sensitivity and specificity of this were shown to be high, in detecting spinal cord injury (100% and 87%, respectively) [72]. It should be emphasized that civilian and military scenarios are different. In the civilian, most injuries are inflicted by low-velocity weapons with a solitary injury and less comorbidity. The evacuation period is normally short, and most patients arrive conscious to the emergency room. Neurological examination in this setting is more feasible and accurate. The opposite is true for the military scenario where most injuries are of high-velocity nature, and usually there is more than one injury. Usually, since most of casualties have a longer period of evacuation, they are brought to the trauma bay intubated, and thus their neurologic assessment is limited. The clinician should rely mostly on the anamnestic report of the evacuation team that considering the circumstance might not always be accurate.

After securing airway, birthing, and circulation, and after an initial neurologic assessment was performed, the patient should be completely exposed to inspect the entire body. Documentation of the entry and exit wounds should be done. It should be kept in mind that in high-velocity weapons, more than one exit wound may be found. In a low-velocity weapon, no exit wound is usually the rule.

Treatment for associated injuries to other organs should be addressed.

Tetanus prophylaxis history should be inquired and treated accordingly. In cases of unknown immunization, tetanus immunoglobulin is required in addition to toxoid treatment.

Antibiotic treatment is usually given; however, no consensus for the type and duration of treatment exist. Evidence to support different antibiotic treatments in cases of organ perforation such as the larynx/esophagus in cervical injuries compared with abdominal viscera in thoracic injuries is low. There is, however, some evidence to support administration of a wide range of antibiotic treatments as prophylaxis [73]. Interestingly, a Cochrane review concluded that evidence exists for antibiotic treatment only for the first 24 h after initial debridement [74].

without further delay. In a stable patient, treatment should be guided by the presence of other factors such as neurological status, mechanical stability of the spine, CSF leak, risk for infec-

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There are no clear clinical guidelines to direct the treatment pathway in MPSCI, and hence each case should be treated individually. Some issues, however, should be considered:

Wound care: in high-velocity GSW, an extensive wound debridement and lavage should be performed in the OR given the expected large infected cavity and "wound suction effect" inserting debris into the wound [8, 45, 80]. A low-velocity, civilian-inflicted GSW (gunshot

Loss of neurologic function: progressive loss of neurologic function with radiographic evidence of neural tissue compression either by hematoma, bone fragment, or foreign body is an absolute indication for surgery [81–85]. There is no doubt that the initial neurological status will dictate the fate of the patient's neurological function [84]. There is only minor evidence that demonstrate neurological improvement following early (24–48 h) intervention. This is especially true if the insult occurs in the cauda equine area [82, 83, 86]. However, there is more evidence to show that there is no improvement following surgery, especially if the injury occurs between the levels of T1–T11 and definitely in complete injuries due to high-velocity GSW [49, 62]. In low-velocity civilian injuries, these types of injuries might have better prog-

Despite the above details, some subgroups of patients may benefit from surgical intervention, even in the presence of a complete or nonprogressing injury. This includes complete injuries of the cervical spine where a potential recovery of an affected level is anticipated or when the injury raises a mechanical issue that might be solved with surgery (**Figure 2**). When intervention is considered, one should remember that it has been shown to result in about 20% of complications compared to 7% for nonsurgical treatment [87]. Clinical discretion should be

Foreign body removal: foreign body, e.g., bullet fragments, shrapnel, and intact bullets, is considered an absolute indication for removal in cases of incomplete SCI, definitely when it is progressive. When there is imaging evidence of cord compression, early intervention has

Removal of bullets in cases of complete and static SCI is not efficient and will not restore any

Another possible indication for bullet removal from the spinal canal is the concern of fragment migration (**Figure 2**). This might happen early [89] or late [90, 91] in the course of injury, as shown in some sporadic cases. In both cases, neurologic deterioration had resolved following the surgery. That is why some surgeons suggest preventing this complication by surgically removing the foreign body, especially in cases with easy access and expectedly low complications.

tion, and other systemic injuries.

wound) can be treated locally in the ER and observed.

nosis, depending on what was the initial clinical presentation.

been shown to be beneficial in many studies [47, 51, 88].

*3.5.1. Indication for surgery*

used in all cases.

neurological function [47, 62, 86].

Most of the evidence exists for low-velocity injuries. There is less evidence guiding treatment recommendation in high-velocity injuries. We normally recommend empirically regimen of 3 days of prophylactic antibiotic which is discontinued if no sign of infection is observed.
