Shrapnel injuries were once confined to the battlefield. Today, these wounds are more frequently being seen in noncombatants because of the increase in terrorist acts worldwide. Explosive devices are the preferred weapon in terrorism because they are relatively cheap and can cause a large number of casualties. Musculoskeletal injuries are the most common modern warfare wounds, accounting for 60% to 70% of all wounds.1,2 Most penetrating injuries are inflicted by shrapnel, not bullets. The high speed of chemical decomposition of the explosive into gas (detonation) generates primary blast waves, which cause primary insult to gas-containing organs. Secondary blast injuries are inflicted by objects that have been energized by the explosion and thus have become projectiles. This shrapnel most often affects the musculoskeletal system; it is driven into both soft and osseous tissues, causing local damage or infection.3 The debate continues as to why, when, and how shrapnel should be removed.
Imaging techniques are used for patient diagnosis, shrapnel localization, and determining the timing and extent of treatment. Shrapnel management/removal is chronologically divided into acute, subacute, and late phases. In the acute phase, the victim is treated according to Advanced Trauma Life Support (ATLS) guidelines.4 Depending on the amount of energy of the blast, anatomic site, and related injuries, specific wound care and thorough débridement is performed with or without shrapnel removal. In general, shrapnel is left inert in the tissue and is removed at a later (subacute) stage only when absolutely necessary, such as in cases of systemic toxicity or local tissue complications (eg, abscess, foreign body granuloma)5,6 (Figure 1).
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Figure 1:
Metallic shrapnel in the tibia of a patient who was asymptomatic for 36 years. A, Anteroposterior plain radiograph of the left tibia demonstrating shrapnel in the diaphysis. B, Axial computed tomography scan demonstrating shrapnel in the cortex of the tibia. Note the wide reactive bone around the metal shard. C, Bone scan demonstrating high uptake around the shrapnel, indicating active bony process.
Diagnosis and Imaging
In recent years, radiology has played an important role in the medical workup of victims of terrorist attack. Imaging technology, including plain radiography, computed tomography (CT), ultrasound, and angiography, is used to assess the site and extent of injury. These examinations also are important in determining the timing of surgery (immediate versus late).7
Plain radiographs, which are routinely obtained in patients with skeletal trauma, usually are sufficient to determine the presence and location of shrapnel as well as the diagnosis of bone fractures; generally, no additional studies are needed. With abdominal, chest, pelvic, head, or spinal involvement, additional studies often are needed to distinguish the location and proximity to vital organs.
CT is useful in identifying the precise anatomic location of most shrapnel that is metallic in nature. Because it is a static study, however, it does not contribute to understanding the dynamic relation of the shrapnel to other structures.
In contrast, ultrasound is useful not only in diagnosing shrapnel in soft tissues but also in demonstrating the dynamic relationship with other structures, such as proximity to tendons or movement within a joint. In addition, ultrasound can detect nonmetal shrapnel. Anecdotally, ultrasound has been reported as a useful tool in the rapid detection of shrapnel composition (eg, depleted uranium).8 Ultrasound equipment is portable and available for intraoperative localization.
Fluoroscopy is useful in diagnosis and localization, especially intraoperatively. The multiple projections of the image intensifier enable threedimensional localization of the shrapnel, based on two-dimensional projections. In mass casualty events, there is an overwhelming exhaustion of imaging resources;9 the availability of fluoroscopy both reduces the need for other imaging resources and facilitates case handling.
The constant trade-off between tissue damage as a complication of surgery and the benefits of nonacute shrapnel removal led to the search for minimally invasive approaches for removal. As a result, other high-tech modalities have been added to the armamentarium of intraoperative imaging and detection, such as computerized surgical navigation based on real-time acquisition of fluoroscopic data. In this technique, several fluoroscopic images of the specific anatomic site are obtained. Accurate spatial location of the foreign object is seen on images displayed on the computer screen, with no further fluoroscopic radiation necessary. During surgery, an infrared camera tracks the position of a surgical probe on the image of the patient's anatomy and continuously updates the probe's three-dimensional position simultaneously on all displayed images until the location of the shrapnel is reached.10
Iso-C 3D (Siemens, Iselin, NJ) is a relatively new intraoperative technology. This intraoperative CT scan mounted on a C-arm allows exact anatomic localization of shrapnel.11 Coupled with computerized navigation, Iso-C 3D enables tracking based on axial, coronal, sagittal, and threedimensional reconstructions (Figure 2). This technology is especially valuable in the patient with spinal or deep organ involvement.
Figure 2 A,:
Shrapnel in the hip joint. B, The surgeon removes the shrapnel through a small incision, using Iso-C 3D navigation. C, Tracked grasper holding the shrapnel.
Initial Management
Per ATLS guidelines, plain radiographs, CT, and ultrasound should be obtained as appropriate during the early phase of shrapnel injury management in order to assess concomitant visceral damage. In the patient with multiple shrapnel wounds (eg, caused by a blast), extensive bleeding may occur through the entrance sites; therefore, modification of the ATLS guidelines is suggested. Multiple entrance wounds are predominantly found in the back of the patient. The patient with such wounds who is taken to the operating room for emergency laparotomy or thoracotomy should be placed on his or her side while the entrance wounds are packed by more than one surgeon. This will significantly minimize bleeding.4
The surgeon should attempt to identify the likely path of the projectile. The path is more easily identifiable when there is a direct line connecting the entry point and the exit wound. It is generally assumed that any structure in the path between these two points is affected. When the exit wound does not correspond with the entrance point or is remote, however, the path becomes much less certain.2
The physician should be aware of the possibility of penetrating injury caused by foreign human tissues or blood carried by the shrapnel from suicide bombers or innocent bystanders. Mass casualty event treatment protocols should address the potential for infection from blood-borne pathogens in any patient who may have come in contact with tissues or body fluids.12 Because these are not bacterial infections, shrapnel removal to avoid contamination generally is not an issue. In these cases, immunologic treatment is necessary.
Shrapnel Management/Removal
Shrapnel management/removal is chronologically divided into acute, subacute, and late phases.
Acute Phase
The acute phase involves shrapnel removal at the time of injury. The fundamental principles guiding shrapnel wound management are proper evaluation and excision of necrotic or contaminated tissue. Although war surgery literature stresses the need for complete wound débridement, this task is not an easy one; frequently, it is inadequately performed.13
High-velocity (>1,800 m/s) projectiles are thought to cause more tissue damage than low-velocity projectiles. It is presumed that the higher velocity results in much greater energy being absorbed by the victim, as illustrated by the physics equation E = ½mv2. This is not exactly true, however. Many bullets do not efficiently impart all of their velocity into the victim.14-16 In fact, high-velocity military bullets are less damaging to soft tissue, in particular, when exiting the body.
Bowyer et al17 indicated that most casualties who reach surgical facilities alive were struck by fragments with initial velocity <600 m/s. The aerodynamic drag of these irregularly shaped projectiles results in deceleration outward from the point of detonation.18-20 Depending on the distance from the blast, fragments that strike the body can range from high to low velocity. In addition to their lack of streamlining, as with bullets fired through a rifle barrel, there are other ways in which lowvelocity fragments from explosive ammunition behave differently from low-velocity bullets. Upon striking tissues, even at low velocities, these fragments may exhibit the tumbling or so-called shimmy effect, which can increase the amount of tissue damage. Additionally, these shrapnel usually carry environmental debris into the wound, frequently causing more severe tissue injury than do low-velocity bullets. For these reasons, mandatory wide débridement of high-velocity wounds is no longer recommended. This information has not yet entered the mainstream surgical literature, however.21,22
Shrapnel wounds should be treated on a case-by-case basis using this fundamental principle to guide management: evaluate and excise necrotic or contaminated tissues. The four C's of muscle viability (color, consistency, capacity to bleed, contractility) are used to assess what needs to be excised. This is subjective, however, and greatly depends on surgeon experience.23 Serial débridement is often necessary in high-risk injuries (eg, excision of muscle that is merely questionable at first assessment but may become necrotic at a later stage). Shrapnel in the wound tract is usually removed during the acute stage; other shrapnel is either left for delayed removal or retained in the tissue for life.
It can be difficult to predict whether a shrapnel injury has a high potential for infection and thus requires débridement. Experienced clinical judgment is necessary to make that determination. Factors that help the surgeon determine whether the wound is high- or lowrisk include time to treatment, path of the projectile, bone involvement, and the number of projectiles.23
In the acute phase, damage control principles are applied. Only lifesaving procedures are performed to hemodynamically stabilize the patient.4 Once the patient is stabilized, shrapnel should be left in the tissue until the emergency condition has subsided.
Subacute Phase
In the subacute phase, retained shrapnel removal is indicated in several instances: when infection is suspected, in the presence of periarticular involvement, in weight-bearing areas, with superficially located shrapnel, or in proximity to neurovascular structures.24 In addition, significant large fragments that affect normal functioning should be removed.
Periarticular Involvement
High-energy projectiles are likely to carry foreign material into the joint. The surgeon should not hesitate to surgically explore the wound. Apart from posing an infection hazard, any foreign material in the joint may cause mechanical abrasion and joint destruction, and fragments passing through the joint may cause ligamentous or meniscal injury.23,25,26 Fragments in the periarticular area (eg, the bursae) also should be removed. Another indication for removal is in the presence of superficial shrapnel under the skin and in patients whose weight-bearing surfaces become painful to the touch and to external pressure.
Nerve Involvement
Nerve palsy is a common finding with shrapnel injury. Because it is usually temporary, neurapraxia in itself is not an indication for exploration. When shrapnel is located near nerve structures and there is irritation of the nerve with progressive neurologic signs or symptoms, however, nerve exploration with shrapnel removal is indicated. Omer27 reported a recovery rate of up to 70%, usually within 6 to 9 months of injury, for gunshot wounds with neurologic symptoms. A transected nerve should be repaired after the inflammatory phase has subsided and when there are no signs of infection. Shrapnel removal is indicated whenever exposure of the nerve is performed. Recovery after nerve repair is reported to be 25%.27
Late Phase
Retained fragments are usually benign, and the surgeon should not attempt to remove them.26 After recovery from the preliminary injury, most patients are asymptomatic. The shrapnel gradually becomes encased in fibrous tissue and is considered inert.25,28 Rarely, however, shrapnel causes harm in the long term, either in the form of systemic damage as a result of shrapnel degradation or because of a local foreignbody reaction. For example, large lead shrapnel retained in soft tissue can cause plumbism.5 Chronic plumbism (lead toxicity) should be considered in patients with retained lead shrapnel, and a history should be taken to assess the presence of symptoms attributable to plumbism. These patients may require long-term follow-up to assess the development of elevated blood lead levels and lead toxicity.5 The first widespread use of depleted uranium was seen in the early 1990s during the Gulf War. The kidney uranium concentration in some individuals reached its peak 6 years after the war.29 Depleted uranium degradation causes multi-organ toxicity.29
Malignant processes have been reported in conjunction with the prolonged presence of shrapnel.15,30 Cases of delayed aneurysm and abscess at the site of a retained foreign body6,31 as well as foreign-body granulomas and reactions have been described. Nevertheless, considering the morbidity involved in surgical removal, these rare incidents do not justify the surgical removal of shrapnel in all cases.26
A relatively new reason for shrapnel removal is the clinical indication for a magnetic resonance imaging (MRI) study. This examination cannot be safely performed on patients with retained shrapnel because patients who undergo MRI examination may suffer from magnetic effects on the shrapnel (eg, pain, bruises, injury to nerves or blood vessels in the vicinity of the shrapnel). Thus, shrapnel removal is indicated before performing an MRI study.28
Summary
The increase in terrorism worldwide makes it crucial for surgeons to understand the major role of shrapnel injuries in mass casualty events. Proper diagnosis, understanding the indications for and the timing of shrapnel removal, and careful follow-up may improve event management and patient outcome, and may reduce the number of unnecessary procedures.
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