Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
Gunshot Wounds and Blast Injuries
Introduction
Although violent crime continues to decline, approximately 74,000 nonfatal gunshot injuries were reported to the Centers for Disease Control and Prevention (CDC) in the United States in 2011, an increase of 10,000 compared with 2004. Estimates of total cost of injury indicate that firearm and gunshot injuries account for 9% or $41.4 billion per year. An unknown but substantial number involved the musculoskeletal system. Gunshot fractures are most common in urban areas and theaters of war but may be encountered in almost any region. In one retrospective study by Bartkiw and colleagues, 44% of all gunshot injuries treated at their urban trauma center involved fractures. The orthopaedic surgeon should therefore have a working knowledge of the various types of gunshot injuries and their treatment.
Ballistics
The purpose of a firearm projectile is to crush tissue. Secondary effects are laceration of structures and tissue stretching. When a projectile strikes the body, a permanent cavity, which is variable in size, is created in the tissues. This cavity is particular to the projectile type and represents the amount of crushed tissue. Some tissue, peripheral to the permanent cavity, will undergo elastic deformation (stretching) and is termed the temporary cavity . The amount of tissue damage is mainly related to the projectile velocity, projectile mass, tissue density, and projectile design.
The kinetic energy (KE) of a projectile is defined by KE = 1/2mv 2 . This equation shows that, in general, the velocity is more important than the mass since doubling the velocity quadruples the KE while doubling the mass only yields twice the kinetic energy. Bullets have been classified, based on muzzle velocity, into low velocity (<2000 fps) and high velocity (>2000 fps). Much of the previous literature focused on the velocity of the bullet as the most important determinant of tissue damage, but this factor is only one of several that must be considered. What appears to be more important is the degree of KE transmitted to the body tissues. The human body has many differing tissue densities. Low-density tissues include lung, fat, and muscle and are not so easily damaged by a projectile as the denser tissues of bone and solid organs.
High-velocity bullets may pass through certain low-density tissues such as lung or muscle with minimal damage owing to minimal transfer of the kinetic energy. A low-velocity bullet can produce considerable tissue injury if the majority of the KE is transmitted to the tissues.
The mass of the projectile also bears importance. An average 9-mm handgun may have a bullet weighing 150 grains; a 0.44 Magnum revolver, 230 grains; and a shotgun load as much as 650 grains. A large increase in mass yields substantially greater KE and the probability of greater tissue crush.
Design of projectiles has a profound effect on wounding potential. Bullets that deform on impact present a greater cross-sectional area capable of crushing more tissues. This is also true of bullets that fragment, resulting in many secondary “bullets” that scatter throughout the tissues, each creating its own path of destruction. Some bullets will oscillate or yaw before or after encountering the body, increasing the cross-sectional area of tissue contact and leading to more tissue crushing.
Low-velocity handguns cause most civilian gunshot wounds, with minimal soft tissue damage, and these are the most common that the orthopaedic surgeon will encounter. Direct hits onto bone may cause impressive comminution owing to the relatively high density of bone and its physical property of brittleness. The diaphysis is more prone to comminution than the metaphysis. Some types of higher power handguns, such as the 0.357 and 0.44 Magnum revolvers, have more destructive potential from larger bullet size and more propellant load.
Assault and hunting rifles with higher muzzle velocities and expanding or fragmenting bullets are designed to produce severe internal tissue damage with nearly complete retention of all bullet fragments, a measure of killing potential.
Shotguns can fire loads of either multiple small pellets or single large slugs. The muzzle velocity is classified as low (1200 fps), but the destructive power arises from the multiple or large and heavy projectiles that are used. Shotgun loads vary tremendously, but in general, the most tissue destruction occurs within a short barrel-to-target distance. At greater distances, the pellets spread out, and tissue damage will be minimized.
Close-range shotgun injuries have extensive wounds. The design of most shot shells incorporates some type of wadding between the lead load and the propellant. This wadding can be either plastic or fiber and will follow the pellets into the tissues. As part of the débridement process, the surgeon should explore for the retained wadding, because this material can become a focus of infection.
Diagnosis
The history of a gunshot injury may yield important clues that will assist in diagnosis and treatment. If possible, the type of weapon, number of rounds, and distance from the weapon to the victim should be elicited from the patient, first responders, or law enforcement officers. High- or intermediate-velocity or shotgun weapons may lead to more tissue injury, but this is not absolutely certain. Most handgun injuries occur within a few feet so the wounding potential of even small-caliber handguns can be significant.
Standard Advanced Trauma Life Support (ATLS) protocol should be followed for the initial physical examination and the treatment. Some special aspects of the physical examination in patients with gunshot wounds should be amplified. The skin should be searched for wounds of entrance and exit, and their location, size, and appearance documented. More than two wounds suggest multiple gunshots. An attempt should be made to match each entrance wound with its corresponding exit wound. Occasionally, bone fragments may be seen within the wound if the gunshot caused a comminuted fracture in a subcutaneous location. Pulsatile bleeding may be an early indication of a major vascular injury.
The gunshot pathway through the patient's body should be determined. All structures that could be violated require close evaluation. Detailed neurologic and vascular examination will detect any deficits. In the absence of obvious fracture, the extremities should be put through a full range of motion. Extremity joints that have been penetrated by the gunshot will typically be painful with an effusion.
After the initial physical examination is completed, the skin wounds should be sterilely dressed. The time-honored technique of securely placing a metallic marker (paper clip, coin) on the dressing surface can be helpful in determining the relationship of the skin wounds to the underlying anatomic structures on subsequent imaging studies ( Fig. 20.1 ). Immobilization via splinting or skeletal traction of all fractures is the next priority.
Plain extremity radiographs, two views at right angles, including the joints above and below, are obtained for all possible involved regions or extremities. Special radiographic views can be taken as needed to assess the pelvis or spine. The imaging studies are scrutinized for the location and number of all metallic gunshot fragments. Certain gunshots will leave an obvious trail of lead particles as they pass through the body tissues. In cases with only an entrance wound, there must be a retained gunshot fragment somewhere in the body. A gunshot fragment that is within the anatomic confines of a joint capsule on the two plain radiographs (perpendicular to each other) must be assumed to be intraarticular. In trauma situations, whole-body multidetector computed tomography (CT) scans will often be done and have been shown to be quite reliable in locating metallic fragments, although less effective at visualizing the path of the gunshot wound. Arthrocentesis and aspiration may reveal occult joint violation in suspicious cases. Standard musculoskeletal imaging studies should be done on the basis of the joint injury or fracture, regardless of the gunshot mechanism.
General Treatment Principles
Antibiotic Usage
As early as 1892 Lagarde demonstrated that bullets were not sterile, neither before nor after being fired from a gun. More recently Vennemann and colleagues have shown that skin particles and the subsequent bacteria adhering to them from the entrance and exit wounds can be found in the bullet tracks within the body. Therefore it is reasonable to believe that gunshot wounds are contaminated with bacteria and if associated with a fracture, the fracture should be classified as open. However, the majority of civilian gunshot wounds are small in size with limited tissue damage and would fit the criteria for a type I open fracture according to the classification of Gustilo and Anderson.
Howland and Ritchey studied nonsurgical management and antibiotic prophylaxis in patients with stable low-velocity gunshot fractures, and they concluded that it was not necessary to surgically débride the wounds or administer antibiotics. However, they did stress the importance of distinguishing between civilian and military gunshot fractures.
Dickey and associates treated 73 patients with gunshot fractures that did not require surgical repair and were randomized prospectively into two groups: intravenous antibiotics and no antibiotics. Two infections occurred, one in each group. They concluded that intravenous antibiotic prophylaxis was of no significant benefit.
Knapp and associates reported a series of 190 patients with 222 extraarticular long bone gunshot fractures that did not require operative fixation. They were randomized to both intravenous cephapirin and gentamicin for 72 hours or oral ciprofloxacin for 72 hours. Each group had two infections (2% for each), and it was concluded that these injuries could be treated with oral antibiotics.
Therefore it appears that the evidence for antibiotic prophylaxis of low-caliber (velocity) gunshot fractures not requiring surgical fixation is weak. Nevertheless, in the urban penetrating trauma population, a brief period, 24 to 48 hours, of antibiotics is often used. This protocol has been thought to be efficacious to treat the wound contamination characteristic of these injuries in these often nutritionally and medically compromised patients. Patients who require surgical fracture fixation should receive standard perioperative antibiotic prophylaxis according to the surgeon's discretion. Shotgun and high-velocity gunshot fractures benefit from intravenous antibiotic treatment for 24 to 48 hours and, in most situations, surgical débridement.
Wound Assessment
One problem facing the surgeon is the assessment of the character of the gunshot injury. The presence of a large wound is an obvious indicator of tissue damage. However, the skin wounds can be deceptive, with many significant injuries presenting with small entrance and exit wounds. In these cases, it is the intercalary tissue appearance and integrity that needs close scrutiny.
Extensive ecchymosis and severe local swelling are potential indications of the need to surgically explore a gunshot wound. Recent authors have stressed the importance of “treating the wound” and not treating the history of the wound mechanism. That is to say, gunshot velocity is only one factor in the decision for surgical exploration.
Some “low-velocity” gunshot tibial fractures can have extensive bone comminution with fracture fragments having been rendered avascular since most of the energy was transmitted to the bone. These fractures do require débridement and excision of nonviable fragments. Reconstruction of the skeleton may become necessary due to residual segmental defects.
Close-range shotgun injuries require thorough débridement and exploration for the retained wadding, which must be removed. Generally, it is futile to attempt removal of all retained pellets, since normal tissue will be violated in the process. Devitalized bone fragments are best excised unless they are intraarticular and possibly suitable for internal fixation ( Fig. 20.2 ). Longer distance shotgun wounds have multiple pellet entrance wounds without exit wounds. Pellet removal is indicated only if proven to be intraarticular.
High-power handguns, machine pistols, and assault rifles constitute the other end of the spectrum seen in civilian trauma. Some of the wounds associated with these weapons have a completely benign appearance. Large exit wounds are pathognomonic of severe soft tissue crush and laceration and are generally good indications for wound exploration and débridement ( Fig. 20.3 ).
Krebsbach and colleagues demonstrated in a gelatin extremity surrogate model that higher velocity projectiles tend to have greater bacterial contamination deeper into the projectile track and closer to the exit wound. This lends support for thorough exploration and débridement of the entire ballistic wound. Diaphyseal comminution is not uncommon, and judgment must be used if this is the only apparent criterion for exploration.
Upper Extremity
Proximal Humerus and Shoulder Joint
Vessel and Nerve Injury
When vascular injury near the shoulder is present, it is often accompanied by nerve injury. Hardin and associates reviewed 99 low-velocity, upper extremity vascular injuries. Eleven (52%) of the 21 patients with axillary artery lesions and 27 (63%) of the 43 limbs with brachial arterial injuries had concomitant nerve injury. At final follow-up, only one patient (9%) had complete return of function. Shotgun injuries produced the most extensive tissue destruction ( Fig. 20.4 ), almost always resulting in permanent functional impairment and often resulting in amputation of all or part of a limb. Borman and coworkers reported numerous successful arterial reconstructions but permanent and severe limitation of function when accompanying nerve or plexus injury was present.
There is no clear consensus about whether and when to explore brachial plexus injuries after a gunshot. Armine and Sugar recommended primary repair of the brachial plexus when there is an associated vascular injury requiring exploration and repair. However, if no vascular or pulmonary injury is present, Leffert recommended that initial management be conservative, with wound and fracture care and physical therapy as needed.
In a study of patients with brachial plexus injury during World War II, Brooks found only 4 of 25 who underwent surgical exploration for plexus lesions to have divided nerves. In an effort to relate the prognosis to the location of the nerve lesion, Brooks suggested three groups: (1) lesions of the roots and trunk of C5 and C6, (2) lesions of the posterior cord, and (3) lesions of C8 to T1 of the medial cord. The recovery in the first group was good; in the second, fair; and in the third, poor. Recovery in the small muscles of the hand did not occur if severance of the nerves occurred. Brooks therefore concluded that routine exploration of open wounds of the plexus was rarely indicated.
When managing nerve injuries nonoperatively, we have found that the most useful clinical indication of axonal regeneration in nerve injuries is evidence of an advancing Tinel sign. Percussion over the site of the nerve injury produces the sensation of radiating “electrical shocks” because of stimulation of the free nerve endings. If there is no recovery by 3 months, if the lesion is incomplete with a major area of neurologic deficit, or if a Tinel sign fails to advance for three consecutive monthly examinations, the nerve should be considered for exploration.
When exploration is performed, nerves found transected may be either repaired primarily or grafted. If a neuroma in continuity is found, either it may be resected and repaired or neurolysis may be performed. Whatever the finding at exploration, the outlook for a high nerve injury that fails to recover spontaneously is often poor, and tendon transfers may be an appropriate treatment.
Fracture
Low-energy gunshot injuries are treated with local wound care and intravenous or oral antibiotics. Formal irrigation and débridement are unnecessary; the surgeon should choose nonoperative or operative treatment as if the injury were closed. If surgery is selected, the bullet track remains unexplored unless it lies in the path of the surgical approach. In contrast, high-energy gunshot wounds are treated as grade III open fractures, with prompt irrigation and surgical débridement, frequent use of temporizing external fixation, and definitive fixation only if and when the condition of the soft tissues permits.
With low-energy gunshots, nondisplaced and minimally displaced proximal humeral fractures are treated nonoperatively. The indications for surgery of displaced fractures of the humeral head and neck are the same as those used for closed fractures—displacement of more than 1 cm of a “part” of the proximal humerus and angulation greater than 45 degrees are generally considered indications for operative treatment. Plate and screw fixation, closed or open intramedullary nailing, or closed reduction and percutaneous pinning may all be appropriate, according to the experience and preference of the surgeon. Comminution of the surgical neck without bone loss may be bridged with either a locked plate or an intramedullary nail. The proximal humerus is relatively tolerant of shortening, and when bone loss at the surgical neck is present, it may often be treated by simply shortening the humerus by 1 or 2 cm ( Fig. 20.5 ; see Fig. 20.4 ).
Although most low-velocity gunshot injuries to the shoulder girdle can be treated conservatively, if the gunshot wound involves the glenohumeral joint itself, the joint should be explored either arthroscopically or through a formal arthrotomy. The path of the bullet itself can sometimes be a useful portal into the joint. Intraarticular bullets should be removed, because lead may leach out into the joint and deposit within the synovial tissues, causing either periarticular fibrosis or toxic effects to the articular cartilage. Osteochondral fragments that are small and irreparable should be excised, but larger, more significant pieces of the joint surface should be repaired. Countersunk or headless screws are often useful in these unusual circumstances ( Figs. 20.6 and 20.7 ). In cases of extreme comminution of the articular surfaces, prosthetic replacement or resection arthroplasty may be the only options. Placing either vancomycin or tobramycin in cement used for the prosthesis may decrease the risk of infection.
External fixation is an option for both temporary and definitive treatment of proximal humerus fractures, especially when soft tissue injury or bony comminution is severe ( Fig. 20.8 ). Although we have little experience with it at most US centers, recent war experiences in the Balkans and Middle East have given us significant literature on the use of external fixation in high-energy gunshot injuries of the upper extremity reported as external fixation of severe gunshot and blast injuries. Surgeons were able to use the proximal humerus for pin placement in half of their patients but needed to use the scapula and/or clavicle for the most severe injuries. Large soft tissue defects around the shoulder can be covered by rotation of a latissimus dorsi myocutaneous flap on its vascular pedicle. Once a favorable soft tissue environment has been established, the temporizing fixator can be converted to a more elaborate, definitive frame or to internal fixation if desired. Because long-term use of pins or wires in the humeral head can cause soft tissue irritation or infection, if external fixation is to be used until fracture healing has occurred, pin care must be meticulous.
Humeral Shaft and Arm
Vessel and Nerve Injury
As in the shoulder, gunshot wounds in the upper arm frequently injure arteries and nerves in addition to the bone itself. If vascular injuries are treated promptly, critical limb ischemia is rare. Although some have advocated that a fracture be stabilized first if there is an associated vascular injury to protect the repair, others have found different results. McHenry and colleagues reviewed their upper and lower extremity fractures with associated vascular injuries. They definitively repaired five fractures first, shunted 13 of the 22 vascular injuries that were addressed before fracture repair, and repaired 9 of 22 vascular injuries definitively first. The need for fasciotomy and the length of hospitalization were both reduced when revascularization preceded care of the orthopaedic injury. Definitive fracture treatment, performed after the revascularization, did not disrupt the shunt or the definitive vascular repair in any case. Despite this, to maximize the safety of the vascular repair, our institution favors shunting of the vascular injury first, followed by either definitive fracture repair if the soft tissues allow or external fixation if not, and then definitive vascular repair. More recent reviews of the use of temporary vascular shunting in both the global War on Terrorism and in a civilian Level I trauma center have suggested benefit from the use of temporary shunts, particularly in cases requiring stabilization of high-grade open fractures.
When fracture and vascular injury are both present, complication rates for the vascular injury may increase. McNamara and coworkers found no amputations in 64 patients without humeral fracture who underwent brachial artery repair, but 10% of the 20 patients with humeral fractures had amputations. There was one failure of repair (2.3%) among the 44 patients without fracture, and there were two failures (10%) among those with fracture.
Humeral shaft fractures combined with ipsilateral brachial plexus injuries pose special problems. Of 19 patients with brachial plexus injuries and ipsilateral humeral shaft fractures treated at the Los Angeles County–University of Southern California Medical Center and Rancho Los Amigos Hospital, 3 were treated by compression plate, 4 by intramedullary nail, 2 with external fixation, and 10 with a cast or brace. All fractures treated by compression plating healed, but 4 of the 6 treated with intramedullary rods or external fixation and 4 of the 10 treated with a cast brace failed to unite. All of the nonunions required open repair with compression plating to achieve union.
The question of whether or not the presence of a nerve injury associated with a gunshot wound and fracture merits exploration has been controversial. A 4-year review of all gunshot fractures of the humerus at an urban trauma center identified three isolated single nerve palsies, which all resolved with observation. Three nerve injuries were associated with brachial artery lacerations, and all required secondary nerve procedures. Based on this, the authors recommended observation for nerve injury alone, with early exploration for nerve injury associated with vascular injury.
If the peripheral nerves traversing a high-energy gunshot wound in the upper arm are not functioning, and the wound is to be débrided because of the severity of the soft tissue injury, the nerves may be explored at the time of débridement. While repair can sometimes be carried out primarily, the extent of injury to the nerve is typically unclear, so the nerve ends are usually tagged for later repair. When fractures result from lower energy missiles, they can often be treated nonoperatively. In this case, peripheral nerve injuries are usually managed expectantly. Although some have found little benefit to exploration and repair of nerve injury in the upper arm, others have reported large series with better prognosis if the nerve injury is in the arm or more distal.
Fracture
Fractures of the humeral shaft, when not complicated by vascular injury, are often best treated with local wound care and plaster or cast-brace immobilization. Humeral fracture bracing may be started as soon as the wound permits. There is no significant difference in the rate of union between closed humeral fractures and uncomplicated humeral fractures caused by a low-velocity gunshot, even if appreciable comminution or displacement is present. When low- or even moderate-energy soft tissue injury is present, operative stabilization with either a nail or plate may be carried out both promptly and safely if the pattern of fracture merits. In cases of severe soft tissue injury, débridement and external fixation are almost always the initial treatments of choice for the fracture, facilitate subsequent wound and soft tissue care, and may provide definitive fixation. Half-pin frames in the arm often have pin track problems as the patient begins to mobilize the shoulder and elbow, and our preference is to convert to a plate when possible, or to an intramedullary nail, because the time required for healing is often prolonged, and the pins may be difficult to maintain for these long periods. However, with careful attention to the frame and appropriate treatment of the anticipated pin track problems, external fixation can certainly be used as definitive treatment.
In centers experienced with their use, Ilizarov type frames can also be used with good results. The care of these complex injuries is difficult, and decisions regarding care must be individualized to the patient, the fracture, and the injury ( Figs. 20.9 to 20.12 ).
In addition to neurovascular injury and soft tissue loss, high-energy gunshot wounds can also cause significant loss of diaphyseal bone. Although there are reports of spontaneous reconstitution of humeral bone loss, some type of surgical intervention is generally required to restore bony continuity. Numerous techniques have been proposed to deal with this challenging situation, including wave plating with cancellous grafting, interposition of a titanium mesh cage with bone graft, transposition of composite flap including the lateral border of the scapula, transfer of a segment of vascularized fibula, and bone transport using an Ilizarov type external fixator.
At present, there is no large series or body of evidence to suggest the superiority of any one method of reconstituting humeral bone loss.
Elbow
Because of its complex bony anatomy and propensity for stiffness after injury, gunshot wounds about the elbow are particularly difficult. After severe elbow injuries, the goal of achieving the flexion and extension and forearm rotation required for most activities of daily living is often not realized. Although secondary procedures, such as capsular release and resection of heterotopic bone, can sometimes help regain lost motion, articular injuries are sometimes so severe that achieving a stable and pain-free elbow with any motion at all may be a victory.
The brachial artery at the elbow is particularly vulnerable because of its location. In addition to trauma from the missile itself, displacement of fracture fragments about the elbow can lacerate or completely tear the artery as well. Compression or occlusion of the brachial artery can also result from entrapment between fracture fragments and from the edema that may follow restoration of arterial flow after prolonged ischemia, leading to forearm compartment syndrome. Six compartment syndromes that developed in association with isolated proximal ulna fractures have been reported. Five of the six developed in a delayed fashion; all five were associated with low-velocity gunshots. If a nerve injury is also present at the elbow, pain and paresthesias from forearm compartment syndrome may be absent, and the only reliable way to detect it is with a high degree of suspicion and direct compartment monitoring. In a review of vascular injuries about the elbow, Ashbell and colleagues reported that 86% of those who sustained arterial injury also had injury to muscle, nerve, or bone in the same area. Concomitant injuries to one or more major nerves in the arm occurred in 69% of patients, with muscle injuries next in frequency (66%). Combined injury to both nerve and muscle was seen in 45% of patients.
When there is severe soft tissue and muscle damage, we recommend initial external fixation across the elbow joint. This approach protects arterial repair and allows soft tissue management and recovery. If there is soft tissue loss, an intact soft tissue envelope must be reestablished before further reconstruction can occur. For smaller defects in the surrounding soft tissue, local flaps may be an option. For larger areas of bone and soft tissue loss around the elbow, a composite latissimus flap, such as that described by Evans and Luethke, offers an option for coverage and for osseous reconstruction as well. When soft tissues recover sufficiently to allow it, the surgeon may undertake fixation of the articular injury and reconstruction of any juxtaarticular bone loss. Although a significant loss of elbow motion often results if the fixator is left on for more than 4 to 6 weeks, there are times when the severity of the injury allows no other treatment.
You're Reading a Preview
Become a Clinical Tree membership for Full access and enjoy Unlimited articles
If you are a member. Log in here