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Musculoskeletal Trauma
Musculoskeletal Systems of Children and Adults ------------------------------------------------------------------------------------------------------------------------------------------------
Differences in the musculoskeletal anatomy and biomechanics of children and adults determine the unique patterns of musculoskeletal injury seen in childhood. Injuries to growing bones are a double-edged sword: They can have a remarkable capacity for healing and remodeling, but they are also subject to the problems of overgrowth and growth disturbance, which can have lifelong consequences.
ANATOMY
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Musculoskeletal Trauma Richard S. Davidson and B. David Horn
Musculoskeletal trauma is the most common medical emergency in children. The number of cases continues to increase in association with the popularity of motor vehicles, all-terrain vehicles, and power lawn mowers. In a child with multiple injuries, optimal treatment requires a cooperating team of medical professionals with diverse specialties who understand the priorities of each team member. As in all other pediatric specialties, it is important to remember that children are not “little adults.” Priority management need not compromise complete patient management. This chapter reviews the important differences between the musculoskeletal systems of children and adults, and it highlights the principles of evaluation and management in children with musculoskeletal injuries. The treatment of high-priority musculoskeletal injuries is specifically discussed, including open fractures, compartment syndrome, femoral neck fractures, mangled extremities, spine trauma, and suspected child abuse. For details on the management of specific musculoskeletal fractures and injuries of childhood, readers should refer to textbooks on children’s fractures.1–3
The major anatomic distinctions of skeletally immature bones are the physis and the periosteum. Each long bone in a child consists of the epiphysis, physis, metaphysis, and diaphysis (Fig. 22-1). The epiphysis is the end of the bone beyond the physis, or growth plate, and contains the articular cartilage. The secondary center of ossification arises within the epiphysis and progressively enlarges as the cartilage ossifies during skeletal maturation. The physis, or growth plate, provides longitudinal growth of the bone by forming cartilage that is then converted into bone in the metaphysis. The diaphysis, or shaft, is surrounded by periosteum, which generates new bone and provides circumferential bone growth. In younger children, the periosteum also provides structural support to the bone. By adulthood, the growth plate closes, and there is limited potential for remodeling.
BIOMECHANICS Skeletally immature bones are more porous, less brittle, and better able to tolerate deformation than mature bones. The increased porosity of immature bones stops the progression of a fracture line but weakens the bone under a compressive force. As a result, a greater variety of fractures is seen in children than in adults. A child’s bone may undergo plastic deformation, where it bends without fracture; it can buckle under compression, resulting in a buckle or torus fracture; it can fracture like a “green stick,” with an incomplete crack on the tension side and a bend on the compression side; or it can fracture completely (Fig. 22-2). The thick periosteum that surrounds the diaphysis of the bone can minimize or prevent displacement of diaphyseal fractures. The periosteum tears on the tension side of a fracture but often remains intact on the compression side. The intact periosteum can then function as a hinge or a spring, increasing deformity. Depending on the injury, the periosteum may simplify or complicate reduction of a fracture (Fig. 22-3). In the complex of bone, ligaments, and cartilage in a child, the physis is the weakest part and therefore is the most likely site of failure. An angular force to a joint in a young child is most likely to cause a fracture along the growth plate, whereas in an adolescent or an adult, a ligamentous injury or dislocation would occur; so, it is not uncommon for growth plate fractures to be misdiagnosed as sprains. Frankel and Nordin4
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Articular cartilage Epiphysis Ossification center Growth plate
Physis
Primary and secondary spongiosa
Metaphysis
Cancellous bone Diaphysis Compact bone
FIGURE 22-1 Anatomy of a child’s bone.
Bend
Buckle
Greenstick
Complete FIGURE 22-2 Fracture types commonly seen in children. (From Rang M [ed]: Children’s Fractures. Philadelphia, JB Lippincott, 1974.)
The Salter-Harris classification system of fractures involving the physis can guide proper management (Fig. 22-4).5 Type 1 fractures extend along the entire physis. Type 2 fractures involve part of the growth plate and part of the metaphysis; these fractures are seldom associated with growth arrest except when they occur in the distal femur and proximal tibia. Type 3 fractures involve part of the physis and pass across the epiphysis into the joint. Because of the possibility of incongruity of the joint, type 3 fractures often require open reduction and fixation. Type 4 fractures occur longitudinally, crossing the physis from the metaphysis into the epiphysis. This type of fracture is commonly associated with subsequent formation of a bony bar across the physis, which causes partial growth arrest with subsequent angulation. Open reduction and internal fixation are usually required for type 4 fractures, because joint incongruity and fusion across the physis are common. Type 5 fractures are diagnosed retrospectively, when all or part of the physis fails to grow. It is hypothesized that injury to the physis results from direct compression or local vascular insult. Growth disturbance may result in loss of longitudinal growth or angular deformities. Damage to the physis in high-energy injuries can lead to asymmetric growth in any of the fracture types.
PHYSIOLOGY provide extensive information on the biomechanics of bone. In a fall on an outstretched hand, a young child is unlikely to sprain a wrist; more commonly, a child sustains a fracture through the growth plate of the distal radius. Similarly, instead of spraining an ankle, a child is more likely to sustain a physeal fracture of the distal fibula. Under low-energy forces, these injuries are unlikely to lead to growth disturbance.
Important physiologic differences between the musculoskeletal systems of children and adults are found in healing and remodeling. Growing bones are also at risk for the unique problems of overgrowth and growth disturbance. Healing in children is rapid and age-dependent. A newborn may achieve clinically stable union of a fracture in 1 week, whereas a similar fracture in an adolescent may take
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The bones of children have great potential for remodeling, but limitations must be understood. Remodeling potential is better in younger patients, in deformities closer to the physes, and where angulation is in the plane of motion of the nearest joint. Remodeling does not effectively correct angulation perpendicular to joint motion or rotation. These deformities should be reduced before healing begins (Fig. 22-5). Growth stimulation may follow fractures of long bones. This can be especially apparent in the lower extremity in children between 2 and 10 years of age. In this group, an average overgrowth of 1 cm can be expected in femur fractures.6–8 Although discrepancies in leg length are unpredictable, it is often possible to reduce the ultimate inequality by allowing the fracture to heal with a 1-cm overlap in an otherwise anatomic alignment. Most of the growth stimulation occurs within the first year after injury; so, follow-up visits for 1 year are recommended, even after uneventful healing. Damage to the physis can produce severe shortening, angular deformity, or both. Although this may be caused by the initial trauma, it can also result from failure to obtain anatomic reduction of a physeal fracture or from repeated or overzealous attempts at reduction (Fig. 22-6). Treatment depends on the amount of remaining skeletal growth and the projected difference in limb lengths and may involve timed ablation of the growth plate on the normal limb, shortening osteotomy of the normal limb, or lengthening of the short limb. Angular deformities can also be addressed, taking into consideration the patient’s skeletal age and the severity of the deformity.
6 weeks to heal. In children, the rapid healing process partially results from the thick periosteum, which may form its own bone bridge. Except for displaced intra-articular fractures or fractures with gross soft tissue interposition, nonunion of fractures is rare in children.
Periosteal hinge
A
Retracing the path
B Closing the hinge
Evaluation of Musculoskeletal Injuries
C
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CLINICAL ASSESSMENT The initial assessment of children with multiple injuries may be difficult. Details of the incident may be missing, and the patient’s history may be incomplete. The Advanced Trauma Life Support (ATLS) system of assessment involves a primary evaluation to identify and immediately address life-threatening injuries, followed by a secondary evaluation to find and treat other significant injuries. The injuries identified in the secondary evaluation must also be treated in a timely manner to prevent devastating lifelong consequences. Postponing the management of serious musculoskeletal injury for an extended period can be associated with a poor prognosis for return to normal function.
3-Point molding = closed hinge
D FIGURE 22-3 A, In children, the intact periosteum of a fracture prevents reduction by traction. B, By retracing the path of injury, the fracture can be reduced. C, Closing the hinge. D, A cast with three-point molding holds the hinge closed and keeps the fracture reduced. (From Rang M [ed]: Children’s Fractures. Philadelphia, JB Lippincott, 1974.)
1
2
3
4
5
FIGURE 22-4 Salter-Harris classification of epiphyseal fractures. Type 1 involves the entire physis. Type 2 involves part of the growth plate and part of the metaphysis. Type 3 involves part of the physis and passes across the epiphysis into the joint. Type 4 is longitudinal, crossing the physis from the metaphysis into the epiphysis. Type 5 is diagnosed retrospectively when the physis fails to grow. See text for clinical implications of each fracture type.
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A
B
C
D
E
F
FIGURE 22-5 Forearm radiographs of a 7-year-old boy demonstrating remodeling of a forearm fracture over a 9-month period. A to C, Anteroposterior plane. D to F, Lateral plane.
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FIGURE 22-6 Anteroposterior radiograph of the knees in a 13-year-old boy shows growth disturbance of the left distal femoral growth plate after a fracture (on right in photo).
The musculoskeletal examination begins with observation of the patient for sites of deformity, swelling, contusions, abnormal color, and open fractures. If a fracture is suspected, confirmatory diagnostic studies may be integrated into the complete physical examination. If such studies cannot be done, it must be assumed that a fracture exists, and the suspected site must be splinted until the fracture is confirmed or ruled out. Splinting may also reduce discomfort and limit further damage to soft tissue. A complete neurovascular examination is essential in any case of suspected limb or spine injury. When an uncooperative patient will not allow an adequate physical examination or, in the case of comatose patients or preverbal children, cannot provide a history, judicial use of special diagnostic studies can be critical.
RADIOGRAPHIC ASSESSMENT Plain radiography is the first and most widely used test to identify skeletal injury in children, but it can also be a major source of misdiagnosis in this age group. Cartilage, which makes up a large percentage of the child’s skeleton, is radiolucent but can fracture. Ossification centers appear at different ages in different locations. The timing of their appearance and their location vary greatly and can suggest fractures.
A
Confusion most frequently occurs in the elbow, knee, and cervical spine. Comparison of the injured and uninjured limbs can be useful. Plain radiographic soft tissue signs, such as the posterior fat pad sign in elbow injuries, are associated with a high likelihood of underlying fracture (Fig. 22-7).9 A number of imaging studies are available for the assessment of pediatric musculoskeletal injuries and are injury and age specific. Radiographs may confirm fractures. Ultrasonography is a readily available, noninvasive imaging test that can be used to evaluate the unossified epiphysis, especially in injuries about the elbow.10 Magnetic resonance imaging (MRI) may also be helpful, especially in evaluating the injured spine, but it may require general anesthesia in a young or uncooperative patient. Computed tomography (CT) scanning is useful in periarticular fractures in children approaching skeletal maturity. For example, ankle physeal fractures with articular extension in children with partially closed physes are best delineated with CT scan.11 Arteriography may be required to assess vascular injury associated with a fracture. Rarely, proximal tibial physeal fractures and distal humerus fractures through the supracondylar region can be associated with disruption of the blood supply to the distal limb. These injuries require emergent treatment, and an intraoperative arteriogram may be of value in diagnosis and treatment (although in
B
FIGURE 22-7 Lateral elbow radiographs of a 2-year-old boy with a mildly displaced supracondylar humerus fracture and arrow showing a posterior fat pad sign (A) and a normal age-matched elbow (B).
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most situations surgical treatment should not be delayed in order to obtain an arteriogram in the radiology suite).12 Joint aspiration can identify blood and fat, which indicate an intra-articular fracture that would not be identified on radiographs. Finally, arthrography and arthroscopy may define intra-articular injury to the cartilage and ligaments.
Median nerve
Brachial artery Radial nerve Ulnar nerve
Management of Musculoskeletal Injuries ------------------------------------------------------------------------------------------------------------------------------------------------
IMMEDIATE TREATMENT Priority treatment cannot interfere with complete treatment of an injured child. Proper timing and coordination of management with other disciplines are imperative. Traction or splinting often adequately stabilizes the musculoskeletal injury until other tests and treatments have been completed. Immobilization may also reduce the need for pain medications, which can mask the symptoms of other disorders, such as intra-abdominal injuries, and inhibit diagnosis. Although there are many types of splints, ranging from plaster to traction bows, the basic principles of fracture management remain the same. The injured part should be splinted as it is found, and the joints above and below the injury should be immobilized without compromising the circulation of the soft tissues. Portable traction splints or custommolded, well-padded plaster or fiberglass splints can be used in the initial management of fractures. Failure to immobilize the fracture can cause further soft tissue damage from sharp bone ends or the crushing of entrapped neurovascular elements.
DEFINITIVE FRACTURE MANAGEMENT Adequate stabilization of fracture fragments prevents further soft tissue injury, frequently decreases pain, and facilitates wound care and patient mobilization. Techniques of definitive stabilization in children include splinting, casting, skeletal traction, external fixation, pinning, flexible intramedullary nailing, and plating. The choice of fixation method depends on the child’s age, the location of the fracture, the presence and extent of soft tissue injury, and the presence of multitrauma. Metaphyseal undisplaced or impacted fractures are likely to heal faster than diaphyseal or displaced fractures. Fractures with devitalized bone or soft tissues take longer to heal. Radiographic evaluation in conjunction with clinical judgment and experience is needed when determining the healing time of fractures in children. Fragments of bone must be held together until they are sufficiently strong to withstand the forces specific to the bone. A satisfactory position must be obtained, without harming adjacent tissue, before the fracture becomes fixed. Fractures in newborns and infants begin to heal within a few days, but fractures in adolescents can be moved freely for 10 to 14 days. Excessive cast padding, resolution of swelling, or a poorly applied cast may permit progressive malposition within the cast. Fractures should be followed with frequent radiographs until union is secure, to avoid displacement. Unstable fractures should be imaged before
FIGURE 22-8 Supracondylar humerus fracture. Soft tissue and neurovascular structures may become entrapped between bone fragments in these types of fractures.
consolidation to evaluate for loss of alignment. This allows for easier repeat reduction. In children, the thick periosteum tears on the tension side of a fracture but often remains intact on the compression side. The intact periosteum can then function as a hinge, increasing the success of closed reduction of displaced fractures by threepoint molding (see Fig. 22-3). Reduction must be performed gently. Forceful and repeated manipulation of physeal fractures can produce iatrogenic damage and growth disturbances. Entrapment of soft tissue occasionally prevents reduction of an otherwise stable fracture (Fig. 22-8) and requires open reduction and stabilization with internal or external fixation or immobilization in a cast. In some cases, internal fixation with crossed pins, plates and screws, intramedullary nails, or external fixation with pins in metal outriggers or rods may be useful (Fig. 22-9). The benefits of each of these devices must be weighed against their risks, such as need for future operative removal and the possible disturbance to the growth plate, and should be individualized for each particular clinical scenario. Specific indications for internal and external fixation may include fractures with significant soft tissue injury, fractures in children with closed head injury, those associated with neurovascular injury, and fractures that fail nonoperative treatment. Comminuted and oblique fractures and those with complete tears of the periosteum may also prove to be too unstable for cast immobilization. In cases of intra-articular fractures, such as Salter-Harris types 3 and 4, open reduction and stable internal fixation are frequently necessary to avoid incongruity of the joint or growth disturbance. Fractures associated with neurovascular injury requiring repair should be stabilized first.
High-Priority Musculoskeletal Injuries ------------------------------------------------------------------------------------------------------------------------------------------------
Although many musculoskeletal injuries in children can be treated on an urgent rather than an emergent basis, the discussion of some high-priority musculoskeletal injuries in children is warranted. Even in nonurgent cases, it is important to remember that injuries to growing bones can have lifelong consequences.
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B
D
FIGURE 22-9 Anteroposterior radiographs of right femur fractures fixed with a variety of fixation methods. A, Salter-Harris type 2 fracture with crossed pins in a 9-year-old girl. B, Intertrochanteric fracture with screws and side plate in a 7-year-old boy. C, Transverse shaft fracture with elastic intramedullary nails in a 13-year-old boy. D, Subtrochanteric fracture with external fixator in an 8-year-old boy.
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OPEN FRACTURES AND TRAUMATIC ARTHROTOMIES Open fractures frequently result from high-energy trauma and communicate with the outside environment, and so are at increased risk for infection.13–14 The cornerstones of management include recognition, administration of appropriate antibiotics, stabilization of the fracture, and adequate irrigation and debridement of wounds. Open fractures may require multiple surgical procedures to achieve adequate soft tissue coverage and fracture healing. When a laceration or abrasion is noted in proximity to a fracture, an open fracture must be suspected. Radiographic evidence of air shadows around the fracture may confirm the diagnosis. A sharp fragment of bone can tear through the skin, and the elastic properties of a child’s bone can readily straighten the fracture fragments after the force is discontinued. The protruding point of bone can then draw back under the skin, taking debris and bacteria with it into the deep tissues. Minimal signs of injury do not necessarily mean a minimal chance of infection. Wounds should not be probed in the emergency department, where the risk of iatrogenic contamination is high and the likelihood of adequate debridement is low; if necessary, such procedures should be done in the operating room. The Gustilo system classifies open fractures according to the size and extent of soft tissue damage.13–15 Type I is an open fracture with a clean wound smaller than 1 cm. Type II is an open fracture with a laceration longer than 1 cm without extensive soft tissue damage, flaps, or avulsions. Type III is an open fracture with extensive soft tissue injury and is further divided into three subtypes: Type IIIA has adequate soft tissue coverage of a fractured bone despite extensive laceration of soft tissue, type IIIB involves extensive soft tissue injury with periosteal stripping that requires grafting or a flap for coverage, and type IIIC is an open fracture associated with arterial injury that requires repair. The risk of infection is related to the severity of the injury: 2% in type I open fractures, 2% to 10% in type II open fractures, and up to 50% in type III open fractures.15 Wounds should initially be dressed with sterile gauze soaked with antiseptic. Hemorrhage should be controlled by direct pressure. Patients should receive tetanus prophylaxis and antibiotics at recognition of the injury. First-generation cephalosporins cover the grampositive organisms found in type I and type II injuries. An aminoglycoside is added for type III injuries, and ampicillin or penicillin is added for farm injuries or other massively contaminated wounds to fight potential anaerobic infection. Each wound must be adequately debrided and copiously irrigated with the patient under general anesthesia. Current evidence suggests that this should be accomplished as soon as the patient is stable, and within 24 hours after injury if possible.16 Wounds may need to be re-evaluated after 2 or more days for additional debridement. Primary closure or delayed primary closure may be appropriate for some open fractures, whereas grafting or flap coverage is needed for larger soft tissue defects. The goal of debridement is removal of devitalized tissue to avoid the catastrophic consequences of an infection, which may include limb loss or chronic osteomyelitis. Adequate immobilization is necessary for soft tissue healing. For small lacerations, immobilization in a cast
that has been windowed for wound inspection may suffice. For larger lacerations, external or internal fixation is often necessary to provide stable fixation with access to the wound. Joint penetration by a foreign body can cause a diagnostic dilemma. Radiographs can be helpful if they reveal an “air arthrogram.” Injection of sterile normal saline into the joint, or saline load test, can also be diagnostic.17 If the saline load test results in the liquid exiting the wound or laceration, joint penetration has occurred and requires irrigation and debridement in the operating room.
COMPARTMENT SYNDROME Compartment syndrome occurs when pressure is elevated within a confined fascial space. This causes circulatory compromise and can progress to tissue necrosis. Closed fractures and crush injuries with associated edema may cause compartment syndrome. Forearm and leg compartments are most often involved. Ischemic injury starts when tissue pressure is 30 mm Hg less than mean arterial pressure.18–19 The pressure within the compartments surrounding a fracture should be measured if compartment syndrome is suspected. Commercially available tissue pressure monitors or other measuring devices, including electronic arterial pressure monitoring devices, can be used. The diagnosis of compartment syndrome in children can be difficult. Adults with compartment syndrome verbalize extreme pain and demonstrate pain with passive stretch of the muscles within the affected compartments, whereas children often have difficulty communicating their discomfort. The classical signs of compartment syndrome are the five Ps: pain, pallor, paresthesia, paralysis, and pulselessness. These signs are rather unreliable in children and may manifest late in the process. An increasing analgesia requirement is an important sign of compartment syndrome in children.20 With early recognition and timely management, full recovery can be achieved. All external compression is removed from the limb, compartment pressures are measured, and, if elevated, the compartments are surgically decompressed. In the forearm, volar and dorsal fasciotomies are required.19 In the leg, all four compartments (anterior, lateral, deep posterior, and superficial posterior) must be released. This can be accomplished with either a one- or two-incision technique.18 Without prompt intervention, the result is irreversible damage to soft tissues with loss of function, subsequent contractures, and deformity.18–19
FEMORAL NECK FRACTURE Although rare in children, fractures of the femoral neck and intertrochanteric region require attention (Fig. 22-10). These fractures frequently result from high-energy impact, including traffic accidents and falls from a height, and are associated with a high complication rate from avascular necrosis, coxa vara, nonunion, delayed union, and premature physeal closure.21 The upper end of the femur lies within the joint capsule. After roughly 4 years of age, blood is supplied primarily by retinacular vessels that course from distal in the neck to proximal in the head. Delay in treatment of a fracture at the
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or FIGURE 22-11 A pediatric backboard should have a torso mattress or an occiput recess to accommodate the child’s relatively large head and avoid potentially dangerous cervical spine flexion.
the skin. This is especially true of the fibula, tibia, and humerus and can necessitate cutting back the bone every few years.
SPINE TRAUMA
FIGURE 22-10 Anteroposterior pelvis radiograph of a 14-year-old boy shows a displaced left femoral neck fracture that required internal fixation.
neck is associated with increased risk of avascular necrosis of the head and destruction of the joint and can cause lifelong disability. Early decompression of the hip joint, reduction of the fracture, and internal fixation may minimize the complications.21
MANGLED EXTREMITIES Severely traumatized or mangled extremities in children must be assessed and treated through a multidisciplinary approach on a case-by-case basis. They may involve extensive injury to or segmental loss of skin, muscle, bone, and neurovascular structures. Some limbs may be unsalvageable owing to extensive damage, some can be reconstructed with a resulting dysfunctional limb, and others can be salvaged with a good outcome. The Mangled Extremity Severity Score rates injuries based on objective criteria at initial presentation, including skeletal and soft tissue injury, limb ischemia, shock, and patient age. Although originally developed in a primarily adult population,22 it can be a useful adjunct to managing lower extremity trauma in children.23 Segmental bone loss is rare in children and does not necessitate amputation. If periosteum can be preserved, the potential to reform bone is extensive. Proper techniques of debridement and stabilization, along with adequate time for healing, may produce good results in children. External fixation techniques can allow for bone transport and osteogenesis to replace lost bone and axial deformity. Power lawn mower injuries are uncommon, preventable injuries that cause significant morbidity in children.24–26 Direct contact with the blade leads to laceration of tissue, amputation, or devitalizing shredding of the extremity. Such injury can result in damage to the vasculature and growth plate, joint stiffness, infection, or amputation. If salvage is undertaken, treatment follows that of open fractures. In the case of amputation, preservation of bony length and retention of all viable soft tissue are important for the ultimate functional outcome. Amputation through the diaphysis of a child’s bone frequently results in overgrowth of the bony stump through
Injuries of the spine in children can be divided into those affecting the cervical spine and those in the thoracic and lumbar spine. Just as in other parts of the body, patterns of injury to the spine in children differ from those in adults. Radiographic imaging can be challenging. Principles of immobilization are different for children as well. Cervical spine injuries in children differ from those in adults.27–28 Children have greater ligamentous laxity and weaker neck musculature. In addition, they have large heads relative to body size; this effect is more pronounced in younger children. Cervical spine injuries in children tend to occur higher in the neck and can be primarily ligamentous or apophyseal without bony fracture.29 When immobilizing a child on a backboard, the relatively large head should be considered; a child’s backboard splint should have a recess for the occiput or a mattress for the torso to maintain the alignment of the cervical spine, avoiding flexion of the neck (Fig. 22-11).30 Radiographic evaluation of the pediatric cervical spine can be challenging. Pseudosubluxation, or the apparent forward displacement of C2 on C3 and, less commonly, C3 on C4, is a well-described plain radiographic finding in normal children younger than 8 years.27,31 Other sources of difficulty in interpreting radiographs include incomplete ossification, epiphyseal variation, and elasticity of the disks and vertebral bodies relative to the neural structures, which allows extensive injury to the soft tissues without evidence of abnormality on plain radiographs or SCIWORA (spinal cord injury without radiographic abnormality). MRI is helpful in evaluating soft tissues in cases of possible cervical spine ligamentous injury in children.27,32 Injuries to the thoracic and lumbar spine are rare in children. The growth of vertebral bodies occurs through the apophyses or growth centers on the cranial and caudal ends of the bodies. With compression injury, adolescents are at risk for traumatic displacement of the vertebral apophysis and the attached disk into the spinal canal, especially in the lumbar region.33 Symptoms are similar to those seen in central disk herniation, including muscle weakness and absent reflexes. This injury requires recognition and emergent surgical decompression. Lap-belt injuries are flexion-distraction injuries that typically occur in the thoracolumbar region when children violently flex over the seat belt.28,34 A fracture propagates from the posterior portions of the vertebra to the disks or vertebral body in the front (Fig. 22-12). In addition to the vertebral injury, children can sustain serious abdominal and aortic injuries, and these should be suspected when an abdominal contusion, or the telltale seat-belt sign, is evident in a trauma patient. Lap-belt injuries frequently require immobilization and possible internal fixation.28
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A
B
FIGURE 22-12 Lap-belt injury of L4 in a 15-year-old girl without neurologic injury. A, Lateral lumbar spine radiograph shows fracture of both the L4 body and the posterior spine. B, Sagittal magnetic resonance image of the lumbar spine shows the extensive bony and soft tissue injury.
CHILD ABUSE The maltreatment of children is a complex medical and social problem, and its recognition is key to management. Fractures before walking age in the absence of metabolic disease or child abuse are rare. Fractures are the second most common manifestation of child abuse after skin lesions.35 Suspicion of abuse must be raised when there is a discrepancy between
history and injury, when multiple fractures are present in different stages of healing, or when bruising, metaphyseal fractures, or long bone fractures appear in children younger than 1 year.35 The complete reference list is available online at www. expertconsult.com.
Differences in the musculoskeletal anatomy and biomechanics of children and adults determine the unique patterns of musculoskeletal injury seen in childhood. Injuries to growing bones are a double-edged sword: They can have a remarkable capacity for healing and remodeling, but they are also subject to the problems of overgrowth and growth disturbance, which can have lifelong consequences.
ANATOMY
CHAPTER 22
Musculoskeletal Trauma Richard S. Davidson and B. David Horn
Musculoskeletal trauma is the most common medical emergency in children. The number of cases continues to increase in association with the popularity of motor vehicles, all-terrain vehicles, and power lawn mowers. In a child with multiple injuries, optimal treatment requires a cooperating team of medical professionals with diverse specialties who understand the priorities of each team member. As in all other pediatric specialties, it is important to remember that children are not “little adults.” Priority management need not compromise complete patient management. This chapter reviews the important differences between the musculoskeletal systems of children and adults, and it highlights the principles of evaluation and management in children with musculoskeletal injuries. The treatment of high-priority musculoskeletal injuries is specifically discussed, including open fractures, compartment syndrome, femoral neck fractures, mangled extremities, spine trauma, and suspected child abuse. For details on the management of specific musculoskeletal fractures and injuries of childhood, readers should refer to textbooks on children’s fractures.1–3
The major anatomic distinctions of skeletally immature bones are the physis and the periosteum. Each long bone in a child consists of the epiphysis, physis, metaphysis, and diaphysis (Fig. 22-1). The epiphysis is the end of the bone beyond the physis, or growth plate, and contains the articular cartilage. The secondary center of ossification arises within the epiphysis and progressively enlarges as the cartilage ossifies during skeletal maturation. The physis, or growth plate, provides longitudinal growth of the bone by forming cartilage that is then converted into bone in the metaphysis. The diaphysis, or shaft, is surrounded by periosteum, which generates new bone and provides circumferential bone growth. In younger children, the periosteum also provides structural support to the bone. By adulthood, the growth plate closes, and there is limited potential for remodeling.
BIOMECHANICS Skeletally immature bones are more porous, less brittle, and better able to tolerate deformation than mature bones. The increased porosity of immature bones stops the progression of a fracture line but weakens the bone under a compressive force. As a result, a greater variety of fractures is seen in children than in adults. A child’s bone may undergo plastic deformation, where it bends without fracture; it can buckle under compression, resulting in a buckle or torus fracture; it can fracture like a “green stick,” with an incomplete crack on the tension side and a bend on the compression side; or it can fracture completely (Fig. 22-2). The thick periosteum that surrounds the diaphysis of the bone can minimize or prevent displacement of diaphyseal fractures. The periosteum tears on the tension side of a fracture but often remains intact on the compression side. The intact periosteum can then function as a hinge or a spring, increasing deformity. Depending on the injury, the periosteum may simplify or complicate reduction of a fracture (Fig. 22-3). In the complex of bone, ligaments, and cartilage in a child, the physis is the weakest part and therefore is the most likely site of failure. An angular force to a joint in a young child is most likely to cause a fracture along the growth plate, whereas in an adolescent or an adult, a ligamentous injury or dislocation would occur; so, it is not uncommon for growth plate fractures to be misdiagnosed as sprains. Frankel and Nordin4
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Articular cartilage Epiphysis Ossification center Growth plate
Physis
Primary and secondary spongiosa
Metaphysis
Cancellous bone Diaphysis Compact bone
FIGURE 22-1 Anatomy of a child’s bone.
Bend
Buckle
Greenstick
Complete FIGURE 22-2 Fracture types commonly seen in children. (From Rang M [ed]: Children’s Fractures. Philadelphia, JB Lippincott, 1974.)
The Salter-Harris classification system of fractures involving the physis can guide proper management (Fig. 22-4).5 Type 1 fractures extend along the entire physis. Type 2 fractures involve part of the growth plate and part of the metaphysis; these fractures are seldom associated with growth arrest except when they occur in the distal femur and proximal tibia. Type 3 fractures involve part of the physis and pass across the epiphysis into the joint. Because of the possibility of incongruity of the joint, type 3 fractures often require open reduction and fixation. Type 4 fractures occur longitudinally, crossing the physis from the metaphysis into the epiphysis. This type of fracture is commonly associated with subsequent formation of a bony bar across the physis, which causes partial growth arrest with subsequent angulation. Open reduction and internal fixation are usually required for type 4 fractures, because joint incongruity and fusion across the physis are common. Type 5 fractures are diagnosed retrospectively, when all or part of the physis fails to grow. It is hypothesized that injury to the physis results from direct compression or local vascular insult. Growth disturbance may result in loss of longitudinal growth or angular deformities. Damage to the physis in high-energy injuries can lead to asymmetric growth in any of the fracture types.
PHYSIOLOGY provide extensive information on the biomechanics of bone. In a fall on an outstretched hand, a young child is unlikely to sprain a wrist; more commonly, a child sustains a fracture through the growth plate of the distal radius. Similarly, instead of spraining an ankle, a child is more likely to sustain a physeal fracture of the distal fibula. Under low-energy forces, these injuries are unlikely to lead to growth disturbance.
Important physiologic differences between the musculoskeletal systems of children and adults are found in healing and remodeling. Growing bones are also at risk for the unique problems of overgrowth and growth disturbance. Healing in children is rapid and age-dependent. A newborn may achieve clinically stable union of a fracture in 1 week, whereas a similar fracture in an adolescent may take
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The bones of children have great potential for remodeling, but limitations must be understood. Remodeling potential is better in younger patients, in deformities closer to the physes, and where angulation is in the plane of motion of the nearest joint. Remodeling does not effectively correct angulation perpendicular to joint motion or rotation. These deformities should be reduced before healing begins (Fig. 22-5). Growth stimulation may follow fractures of long bones. This can be especially apparent in the lower extremity in children between 2 and 10 years of age. In this group, an average overgrowth of 1 cm can be expected in femur fractures.6–8 Although discrepancies in leg length are unpredictable, it is often possible to reduce the ultimate inequality by allowing the fracture to heal with a 1-cm overlap in an otherwise anatomic alignment. Most of the growth stimulation occurs within the first year after injury; so, follow-up visits for 1 year are recommended, even after uneventful healing. Damage to the physis can produce severe shortening, angular deformity, or both. Although this may be caused by the initial trauma, it can also result from failure to obtain anatomic reduction of a physeal fracture or from repeated or overzealous attempts at reduction (Fig. 22-6). Treatment depends on the amount of remaining skeletal growth and the projected difference in limb lengths and may involve timed ablation of the growth plate on the normal limb, shortening osteotomy of the normal limb, or lengthening of the short limb. Angular deformities can also be addressed, taking into consideration the patient’s skeletal age and the severity of the deformity.
6 weeks to heal. In children, the rapid healing process partially results from the thick periosteum, which may form its own bone bridge. Except for displaced intra-articular fractures or fractures with gross soft tissue interposition, nonunion of fractures is rare in children.
Periosteal hinge
A
Retracing the path
B Closing the hinge
Evaluation of Musculoskeletal Injuries
C
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CLINICAL ASSESSMENT The initial assessment of children with multiple injuries may be difficult. Details of the incident may be missing, and the patient’s history may be incomplete. The Advanced Trauma Life Support (ATLS) system of assessment involves a primary evaluation to identify and immediately address life-threatening injuries, followed by a secondary evaluation to find and treat other significant injuries. The injuries identified in the secondary evaluation must also be treated in a timely manner to prevent devastating lifelong consequences. Postponing the management of serious musculoskeletal injury for an extended period can be associated with a poor prognosis for return to normal function.
3-Point molding = closed hinge
D FIGURE 22-3 A, In children, the intact periosteum of a fracture prevents reduction by traction. B, By retracing the path of injury, the fracture can be reduced. C, Closing the hinge. D, A cast with three-point molding holds the hinge closed and keeps the fracture reduced. (From Rang M [ed]: Children’s Fractures. Philadelphia, JB Lippincott, 1974.)
1
2
3
4
5
FIGURE 22-4 Salter-Harris classification of epiphyseal fractures. Type 1 involves the entire physis. Type 2 involves part of the growth plate and part of the metaphysis. Type 3 involves part of the physis and passes across the epiphysis into the joint. Type 4 is longitudinal, crossing the physis from the metaphysis into the epiphysis. Type 5 is diagnosed retrospectively when the physis fails to grow. See text for clinical implications of each fracture type.
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A
B
C
D
E
F
FIGURE 22-5 Forearm radiographs of a 7-year-old boy demonstrating remodeling of a forearm fracture over a 9-month period. A to C, Anteroposterior plane. D to F, Lateral plane.
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FIGURE 22-6 Anteroposterior radiograph of the knees in a 13-year-old boy shows growth disturbance of the left distal femoral growth plate after a fracture (on right in photo).
The musculoskeletal examination begins with observation of the patient for sites of deformity, swelling, contusions, abnormal color, and open fractures. If a fracture is suspected, confirmatory diagnostic studies may be integrated into the complete physical examination. If such studies cannot be done, it must be assumed that a fracture exists, and the suspected site must be splinted until the fracture is confirmed or ruled out. Splinting may also reduce discomfort and limit further damage to soft tissue. A complete neurovascular examination is essential in any case of suspected limb or spine injury. When an uncooperative patient will not allow an adequate physical examination or, in the case of comatose patients or preverbal children, cannot provide a history, judicial use of special diagnostic studies can be critical.
RADIOGRAPHIC ASSESSMENT Plain radiography is the first and most widely used test to identify skeletal injury in children, but it can also be a major source of misdiagnosis in this age group. Cartilage, which makes up a large percentage of the child’s skeleton, is radiolucent but can fracture. Ossification centers appear at different ages in different locations. The timing of their appearance and their location vary greatly and can suggest fractures.
A
Confusion most frequently occurs in the elbow, knee, and cervical spine. Comparison of the injured and uninjured limbs can be useful. Plain radiographic soft tissue signs, such as the posterior fat pad sign in elbow injuries, are associated with a high likelihood of underlying fracture (Fig. 22-7).9 A number of imaging studies are available for the assessment of pediatric musculoskeletal injuries and are injury and age specific. Radiographs may confirm fractures. Ultrasonography is a readily available, noninvasive imaging test that can be used to evaluate the unossified epiphysis, especially in injuries about the elbow.10 Magnetic resonance imaging (MRI) may also be helpful, especially in evaluating the injured spine, but it may require general anesthesia in a young or uncooperative patient. Computed tomography (CT) scanning is useful in periarticular fractures in children approaching skeletal maturity. For example, ankle physeal fractures with articular extension in children with partially closed physes are best delineated with CT scan.11 Arteriography may be required to assess vascular injury associated with a fracture. Rarely, proximal tibial physeal fractures and distal humerus fractures through the supracondylar region can be associated with disruption of the blood supply to the distal limb. These injuries require emergent treatment, and an intraoperative arteriogram may be of value in diagnosis and treatment (although in
B
FIGURE 22-7 Lateral elbow radiographs of a 2-year-old boy with a mildly displaced supracondylar humerus fracture and arrow showing a posterior fat pad sign (A) and a normal age-matched elbow (B).
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most situations surgical treatment should not be delayed in order to obtain an arteriogram in the radiology suite).12 Joint aspiration can identify blood and fat, which indicate an intra-articular fracture that would not be identified on radiographs. Finally, arthrography and arthroscopy may define intra-articular injury to the cartilage and ligaments.
Median nerve
Brachial artery Radial nerve Ulnar nerve
Management of Musculoskeletal Injuries ------------------------------------------------------------------------------------------------------------------------------------------------
IMMEDIATE TREATMENT Priority treatment cannot interfere with complete treatment of an injured child. Proper timing and coordination of management with other disciplines are imperative. Traction or splinting often adequately stabilizes the musculoskeletal injury until other tests and treatments have been completed. Immobilization may also reduce the need for pain medications, which can mask the symptoms of other disorders, such as intra-abdominal injuries, and inhibit diagnosis. Although there are many types of splints, ranging from plaster to traction bows, the basic principles of fracture management remain the same. The injured part should be splinted as it is found, and the joints above and below the injury should be immobilized without compromising the circulation of the soft tissues. Portable traction splints or custommolded, well-padded plaster or fiberglass splints can be used in the initial management of fractures. Failure to immobilize the fracture can cause further soft tissue damage from sharp bone ends or the crushing of entrapped neurovascular elements.
DEFINITIVE FRACTURE MANAGEMENT Adequate stabilization of fracture fragments prevents further soft tissue injury, frequently decreases pain, and facilitates wound care and patient mobilization. Techniques of definitive stabilization in children include splinting, casting, skeletal traction, external fixation, pinning, flexible intramedullary nailing, and plating. The choice of fixation method depends on the child’s age, the location of the fracture, the presence and extent of soft tissue injury, and the presence of multitrauma. Metaphyseal undisplaced or impacted fractures are likely to heal faster than diaphyseal or displaced fractures. Fractures with devitalized bone or soft tissues take longer to heal. Radiographic evaluation in conjunction with clinical judgment and experience is needed when determining the healing time of fractures in children. Fragments of bone must be held together until they are sufficiently strong to withstand the forces specific to the bone. A satisfactory position must be obtained, without harming adjacent tissue, before the fracture becomes fixed. Fractures in newborns and infants begin to heal within a few days, but fractures in adolescents can be moved freely for 10 to 14 days. Excessive cast padding, resolution of swelling, or a poorly applied cast may permit progressive malposition within the cast. Fractures should be followed with frequent radiographs until union is secure, to avoid displacement. Unstable fractures should be imaged before
FIGURE 22-8 Supracondylar humerus fracture. Soft tissue and neurovascular structures may become entrapped between bone fragments in these types of fractures.
consolidation to evaluate for loss of alignment. This allows for easier repeat reduction. In children, the thick periosteum tears on the tension side of a fracture but often remains intact on the compression side. The intact periosteum can then function as a hinge, increasing the success of closed reduction of displaced fractures by threepoint molding (see Fig. 22-3). Reduction must be performed gently. Forceful and repeated manipulation of physeal fractures can produce iatrogenic damage and growth disturbances. Entrapment of soft tissue occasionally prevents reduction of an otherwise stable fracture (Fig. 22-8) and requires open reduction and stabilization with internal or external fixation or immobilization in a cast. In some cases, internal fixation with crossed pins, plates and screws, intramedullary nails, or external fixation with pins in metal outriggers or rods may be useful (Fig. 22-9). The benefits of each of these devices must be weighed against their risks, such as need for future operative removal and the possible disturbance to the growth plate, and should be individualized for each particular clinical scenario. Specific indications for internal and external fixation may include fractures with significant soft tissue injury, fractures in children with closed head injury, those associated with neurovascular injury, and fractures that fail nonoperative treatment. Comminuted and oblique fractures and those with complete tears of the periosteum may also prove to be too unstable for cast immobilization. In cases of intra-articular fractures, such as Salter-Harris types 3 and 4, open reduction and stable internal fixation are frequently necessary to avoid incongruity of the joint or growth disturbance. Fractures associated with neurovascular injury requiring repair should be stabilized first.
High-Priority Musculoskeletal Injuries ------------------------------------------------------------------------------------------------------------------------------------------------
Although many musculoskeletal injuries in children can be treated on an urgent rather than an emergent basis, the discussion of some high-priority musculoskeletal injuries in children is warranted. Even in nonurgent cases, it is important to remember that injuries to growing bones can have lifelong consequences.
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B
D
FIGURE 22-9 Anteroposterior radiographs of right femur fractures fixed with a variety of fixation methods. A, Salter-Harris type 2 fracture with crossed pins in a 9-year-old girl. B, Intertrochanteric fracture with screws and side plate in a 7-year-old boy. C, Transverse shaft fracture with elastic intramedullary nails in a 13-year-old boy. D, Subtrochanteric fracture with external fixator in an 8-year-old boy.
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OPEN FRACTURES AND TRAUMATIC ARTHROTOMIES Open fractures frequently result from high-energy trauma and communicate with the outside environment, and so are at increased risk for infection.13–14 The cornerstones of management include recognition, administration of appropriate antibiotics, stabilization of the fracture, and adequate irrigation and debridement of wounds. Open fractures may require multiple surgical procedures to achieve adequate soft tissue coverage and fracture healing. When a laceration or abrasion is noted in proximity to a fracture, an open fracture must be suspected. Radiographic evidence of air shadows around the fracture may confirm the diagnosis. A sharp fragment of bone can tear through the skin, and the elastic properties of a child’s bone can readily straighten the fracture fragments after the force is discontinued. The protruding point of bone can then draw back under the skin, taking debris and bacteria with it into the deep tissues. Minimal signs of injury do not necessarily mean a minimal chance of infection. Wounds should not be probed in the emergency department, where the risk of iatrogenic contamination is high and the likelihood of adequate debridement is low; if necessary, such procedures should be done in the operating room. The Gustilo system classifies open fractures according to the size and extent of soft tissue damage.13–15 Type I is an open fracture with a clean wound smaller than 1 cm. Type II is an open fracture with a laceration longer than 1 cm without extensive soft tissue damage, flaps, or avulsions. Type III is an open fracture with extensive soft tissue injury and is further divided into three subtypes: Type IIIA has adequate soft tissue coverage of a fractured bone despite extensive laceration of soft tissue, type IIIB involves extensive soft tissue injury with periosteal stripping that requires grafting or a flap for coverage, and type IIIC is an open fracture associated with arterial injury that requires repair. The risk of infection is related to the severity of the injury: 2% in type I open fractures, 2% to 10% in type II open fractures, and up to 50% in type III open fractures.15 Wounds should initially be dressed with sterile gauze soaked with antiseptic. Hemorrhage should be controlled by direct pressure. Patients should receive tetanus prophylaxis and antibiotics at recognition of the injury. First-generation cephalosporins cover the grampositive organisms found in type I and type II injuries. An aminoglycoside is added for type III injuries, and ampicillin or penicillin is added for farm injuries or other massively contaminated wounds to fight potential anaerobic infection. Each wound must be adequately debrided and copiously irrigated with the patient under general anesthesia. Current evidence suggests that this should be accomplished as soon as the patient is stable, and within 24 hours after injury if possible.16 Wounds may need to be re-evaluated after 2 or more days for additional debridement. Primary closure or delayed primary closure may be appropriate for some open fractures, whereas grafting or flap coverage is needed for larger soft tissue defects. The goal of debridement is removal of devitalized tissue to avoid the catastrophic consequences of an infection, which may include limb loss or chronic osteomyelitis. Adequate immobilization is necessary for soft tissue healing. For small lacerations, immobilization in a cast
that has been windowed for wound inspection may suffice. For larger lacerations, external or internal fixation is often necessary to provide stable fixation with access to the wound. Joint penetration by a foreign body can cause a diagnostic dilemma. Radiographs can be helpful if they reveal an “air arthrogram.” Injection of sterile normal saline into the joint, or saline load test, can also be diagnostic.17 If the saline load test results in the liquid exiting the wound or laceration, joint penetration has occurred and requires irrigation and debridement in the operating room.
COMPARTMENT SYNDROME Compartment syndrome occurs when pressure is elevated within a confined fascial space. This causes circulatory compromise and can progress to tissue necrosis. Closed fractures and crush injuries with associated edema may cause compartment syndrome. Forearm and leg compartments are most often involved. Ischemic injury starts when tissue pressure is 30 mm Hg less than mean arterial pressure.18–19 The pressure within the compartments surrounding a fracture should be measured if compartment syndrome is suspected. Commercially available tissue pressure monitors or other measuring devices, including electronic arterial pressure monitoring devices, can be used. The diagnosis of compartment syndrome in children can be difficult. Adults with compartment syndrome verbalize extreme pain and demonstrate pain with passive stretch of the muscles within the affected compartments, whereas children often have difficulty communicating their discomfort. The classical signs of compartment syndrome are the five Ps: pain, pallor, paresthesia, paralysis, and pulselessness. These signs are rather unreliable in children and may manifest late in the process. An increasing analgesia requirement is an important sign of compartment syndrome in children.20 With early recognition and timely management, full recovery can be achieved. All external compression is removed from the limb, compartment pressures are measured, and, if elevated, the compartments are surgically decompressed. In the forearm, volar and dorsal fasciotomies are required.19 In the leg, all four compartments (anterior, lateral, deep posterior, and superficial posterior) must be released. This can be accomplished with either a one- or two-incision technique.18 Without prompt intervention, the result is irreversible damage to soft tissues with loss of function, subsequent contractures, and deformity.18–19
FEMORAL NECK FRACTURE Although rare in children, fractures of the femoral neck and intertrochanteric region require attention (Fig. 22-10). These fractures frequently result from high-energy impact, including traffic accidents and falls from a height, and are associated with a high complication rate from avascular necrosis, coxa vara, nonunion, delayed union, and premature physeal closure.21 The upper end of the femur lies within the joint capsule. After roughly 4 years of age, blood is supplied primarily by retinacular vessels that course from distal in the neck to proximal in the head. Delay in treatment of a fracture at the
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or FIGURE 22-11 A pediatric backboard should have a torso mattress or an occiput recess to accommodate the child’s relatively large head and avoid potentially dangerous cervical spine flexion.
the skin. This is especially true of the fibula, tibia, and humerus and can necessitate cutting back the bone every few years.
SPINE TRAUMA
FIGURE 22-10 Anteroposterior pelvis radiograph of a 14-year-old boy shows a displaced left femoral neck fracture that required internal fixation.
neck is associated with increased risk of avascular necrosis of the head and destruction of the joint and can cause lifelong disability. Early decompression of the hip joint, reduction of the fracture, and internal fixation may minimize the complications.21
MANGLED EXTREMITIES Severely traumatized or mangled extremities in children must be assessed and treated through a multidisciplinary approach on a case-by-case basis. They may involve extensive injury to or segmental loss of skin, muscle, bone, and neurovascular structures. Some limbs may be unsalvageable owing to extensive damage, some can be reconstructed with a resulting dysfunctional limb, and others can be salvaged with a good outcome. The Mangled Extremity Severity Score rates injuries based on objective criteria at initial presentation, including skeletal and soft tissue injury, limb ischemia, shock, and patient age. Although originally developed in a primarily adult population,22 it can be a useful adjunct to managing lower extremity trauma in children.23 Segmental bone loss is rare in children and does not necessitate amputation. If periosteum can be preserved, the potential to reform bone is extensive. Proper techniques of debridement and stabilization, along with adequate time for healing, may produce good results in children. External fixation techniques can allow for bone transport and osteogenesis to replace lost bone and axial deformity. Power lawn mower injuries are uncommon, preventable injuries that cause significant morbidity in children.24–26 Direct contact with the blade leads to laceration of tissue, amputation, or devitalizing shredding of the extremity. Such injury can result in damage to the vasculature and growth plate, joint stiffness, infection, or amputation. If salvage is undertaken, treatment follows that of open fractures. In the case of amputation, preservation of bony length and retention of all viable soft tissue are important for the ultimate functional outcome. Amputation through the diaphysis of a child’s bone frequently results in overgrowth of the bony stump through
Injuries of the spine in children can be divided into those affecting the cervical spine and those in the thoracic and lumbar spine. Just as in other parts of the body, patterns of injury to the spine in children differ from those in adults. Radiographic imaging can be challenging. Principles of immobilization are different for children as well. Cervical spine injuries in children differ from those in adults.27–28 Children have greater ligamentous laxity and weaker neck musculature. In addition, they have large heads relative to body size; this effect is more pronounced in younger children. Cervical spine injuries in children tend to occur higher in the neck and can be primarily ligamentous or apophyseal without bony fracture.29 When immobilizing a child on a backboard, the relatively large head should be considered; a child’s backboard splint should have a recess for the occiput or a mattress for the torso to maintain the alignment of the cervical spine, avoiding flexion of the neck (Fig. 22-11).30 Radiographic evaluation of the pediatric cervical spine can be challenging. Pseudosubluxation, or the apparent forward displacement of C2 on C3 and, less commonly, C3 on C4, is a well-described plain radiographic finding in normal children younger than 8 years.27,31 Other sources of difficulty in interpreting radiographs include incomplete ossification, epiphyseal variation, and elasticity of the disks and vertebral bodies relative to the neural structures, which allows extensive injury to the soft tissues without evidence of abnormality on plain radiographs or SCIWORA (spinal cord injury without radiographic abnormality). MRI is helpful in evaluating soft tissues in cases of possible cervical spine ligamentous injury in children.27,32 Injuries to the thoracic and lumbar spine are rare in children. The growth of vertebral bodies occurs through the apophyses or growth centers on the cranial and caudal ends of the bodies. With compression injury, adolescents are at risk for traumatic displacement of the vertebral apophysis and the attached disk into the spinal canal, especially in the lumbar region.33 Symptoms are similar to those seen in central disk herniation, including muscle weakness and absent reflexes. This injury requires recognition and emergent surgical decompression. Lap-belt injuries are flexion-distraction injuries that typically occur in the thoracolumbar region when children violently flex over the seat belt.28,34 A fracture propagates from the posterior portions of the vertebra to the disks or vertebral body in the front (Fig. 22-12). In addition to the vertebral injury, children can sustain serious abdominal and aortic injuries, and these should be suspected when an abdominal contusion, or the telltale seat-belt sign, is evident in a trauma patient. Lap-belt injuries frequently require immobilization and possible internal fixation.28
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B
FIGURE 22-12 Lap-belt injury of L4 in a 15-year-old girl without neurologic injury. A, Lateral lumbar spine radiograph shows fracture of both the L4 body and the posterior spine. B, Sagittal magnetic resonance image of the lumbar spine shows the extensive bony and soft tissue injury.
CHILD ABUSE The maltreatment of children is a complex medical and social problem, and its recognition is key to management. Fractures before walking age in the absence of metabolic disease or child abuse are rare. Fractures are the second most common manifestation of child abuse after skin lesions.35 Suspicion of abuse must be raised when there is a discrepancy between
history and injury, when multiple fractures are present in different stages of healing, or when bruising, metaphyseal fractures, or long bone fractures appear in children younger than 1 year.35 The complete reference list is available online at www. expertconsult.com.