Anatomy and Physiology

Several factors distinguish the pediatric musculoskeletal system from that of the adult. The most striking difference is the presence of a physis or growth plate. The physis is made up of proliferating cartilage cells between the metaphysis and epiphysis. Because it is composed of cartilage, the growth plate is the weakest part of the bone and is more likely to separate before the adjacent tendon or ligament tears. Accordingly, sprains are less frequent in the pediatric population than in the adult population, and physeal injuries are common.

Another factor that influences pediatric musculoskeletal injuries is the presence of a thick, physiologically active periosteum that is easily stripped from the bony cortex. When injuries occur, the periosteum often is torn on the convex side (i.e., the reverse aspect of a bone subjected to a deforming force) while remaining intact on the concave side (the aspect directly incurring the force of injury). In any case, the periosteum acts as a tether to reduce the amount of fracture displacement and, when it remains intact, aids in fracture reduction. The great bone-forming potential of the periosteum also facilitates the healing process; callus formation is vigorous, and nonunion almost never occurs.

Growing bone is more porous, more pliable, and less dense than adult bone. These characteristics result in less strength, thus making children more susceptible to fractures. However, although it takes less force to cause deformation, pediatric bone is more likely to buckle when it is compressed or to bow when it is bent. Finally, because the bones are still growing, the potential for remodeling is greater with metaphyseal fractures. Growth can compensate for postreduction imperfections in both apposition and alignment, with deformities occurring in the plane of motion having the greatest potential for remodeling.

Fracture Patterns

As with fractures in adults, description of pediatric fractures includes the bone location (diaphysis, metaphysis, physis, or epiphysis), configuration, relationship of fracture fragments to one another (angulation and displacement), and relationship of fracture fragments to adjacent tissue (open or closed). The inherent differences between pediatric and adult bone result in fracture configurations that are not found in the adult population. Pediatric fractures can be classified as follows:

The relatively weak cartilaginous physis in growing bone makes physeal injury common in the skeletally immature. Although injuries to the physis can occur at any age, they are more common during rapid skeletal growth. The Salter-Harris classification system is the most frequently used tool to describe physeal injuries. This classification system is based on the extent of involvement of the physis, epiphysis, and joint (Table 176-1). Types I and II Salter-Harris injuries (Figs. 176-6 and 176-7) do not involve the germinal layer of the growth plate; therefore, the risk for growth arrest is small. In general, the higher the Salter-Harris classification (Salter-Harris types III to V), the greater the damage to the growth plate and the greater the likelihood of growth arrest or limb-length abnormalities (Figs. 176-8 to 176-10). Type II fractures are the most common Salter-Harris injury and account for approximately three fourths of all growth plate injuries.

Clavicle Fracture

The clavicle is one of the most frequently broken bones in children. The physis of the clavicle does not close until the age of 23 to 25 years and is at risk for injury until that time. Midshaft fractures account for approximately 85% of all clavicle fractures; distal and proximal fractures account for approximately 10% and 5%, respectively. The usual mechanism of injury is a fall on the shoulder or, less commonly, direct trauma to the bone itself. The child typically supports the affected side with the other hand and tilts the head toward the side of the fracture. Physical examination reveals point tenderness at the fracture site, with or without an obvious bone deformity. With a minimally displaced fracture, shoulder motion may be tolerated. Otherwise, range of motion of the shoulder is limited by pain. Although complications are rare, the proximity of the clavicle to the great vessels and brachial plexus calls for a thorough neurovascular evaluation; severe posterior sternoclavicular displacement can cause injury to the trachea, esophagus, and subclavian vessels; lateral clavicular displacement can result in injury to the brachial plexus. Middle third fractures have been associated with neurovascular bundle injuries, pulmonary injury, and pneumothorax.

An anteroposterior (AP) radiograph of the clavicle (Fig. 176-11) confirms the diagnosis. If clinical suspicion is high and the AP view does not reveal a fracture, a 30-degree cephalic view can be helpful. Specialized imaging studies are rarely needed, although computed tomography (CT) and duplex ultrasonography may be considered with proximal, posteriorly displaced fractures or dislocations to evaluate for the aforementioned complications.¹⁰

Clavicle fractures usually do not require anatomic reduction for healing or function; therefore, treatment is typically directed at maintenance of comfort with splinting, ice, and analgesics. Figure-of-eight splinting helps bring the clavicle out to length, relieves muscle spasm, and minimizes motion at the fracture site. Immobilization with the figure-of-eight splint, previously the treatment of choice, has fallen out of favor because of the risk for brachial plexus palsy with long-term use. Alternatively, a sling with or without a swath can be used to provide comfort by supporting the upper extremity and relieving the suspensory forces usually maintained by the clavicle. Most clavicle fractures heal without any problems, except for the development of bony callus at the fracture site; the younger the patient, the greater the potential for remodeling of this deformity. As the fracture stabilizes and the comfort level improves, range-of-motion exercises can be started, with gradual progression in intensity. Younger children generally require shorter periods of immobilization (2-4 weeks) than those used in adolescents and adults (4-8 weeks). Rehabilitation includes early range of motion and strengthening of the rotator cuff. Patients may return to contact sports when there is no tenderness at the fracture site or pain with range of motion and they have achieved normal strength.

Although surgical intervention is uncommon with clavicle fractures, immediate orthopedic consultation should be obtained for fractures that are open or associated with neurovascular compromise or for fractures that are associated with more than 100% displacement of the fracture fragment with severe skin tenting. In addition, distal clavicular fractures in general and middle clavicular fractures that are severely comminuted or displaced more than 20 mm may also require surgical management, and these patients should be seen by an orthopedic surgeon within 72 hours. High-level athletes should also be referred to an orthopedist for surgical evaluation as surgical repair may expedite their return to sports.

Clavicle fractures also can occur during childbirth and represent more than 90% of obstetric fractures. They occur equally in boys and in girls and on the right and on the left sides. Displaced clavicle fractures are identified by crepitus, edema, lack of movement of the affected extremity, asymmetrical bone contour, and crying with passive motion in the immediate period after delivery. Nondisplaced asymptomatic fractures may not be noticed until 10 days of age, when the bony callus becomes apparent. The diagnosis is made by radiographs of the chest, clavicle, and upper extremity; these radiographs help differentiate clavicle fractures from traumatic separation of the proximal humeral epiphysis, humeral shaft fractures, and dislocations of the shoulder, all of which may be manifested with similar findings. In addition, the presence of a clavicle fracture warrants further investigation for accompanying brachial plexus injury.

Supracondylar Fractures of the Humerus

Supracondylar fracture is the most common elbow fracture in the pediatric population. Most such fractures are sustained in children younger than 8 years. Until that age, the tensile strength of the ligaments and joint capsule is greater than that of the bone itself; the weaker bone therefore yields to the stronger ligament complex around the joint.

Supracondylar fractures are classified as flexion or extension according to mechanism of injury. The extension type of fracture constitutes 95% of all supracondylar fractures and typically results from a hyperextension injury to the elbow incurred in a fall onto the outstretched arm. In this injury, the olecranon is forcefully driven into the olecranon fossa, and the forces are concentrated in the supracondylar area. This mechanism results in failure of the anterior cortex and displacement of the distal fragment posteriorly. With extension-type supracondylar fractures, the degree of displacement and continuity of the cortex are further defined by the Gartland classification¹¹ (Table 176-2). In the less common flexion type of supracondylar fracture, the elbow is flexed when it hits the ground, and energy is transferred from the posterior aspect of the proximal end of the ulna to the distal end of the humerus. This mechanism results in a supracondylar fracture with anterior displacement of the distal fragment and failure of the cortex posteriorly.

Children with supracondylar humerus fractures may present with anything from mild swelling and elbow pain to a grossly displaced humerus. Gentle palpation is useful to determine the site of injury; however, manipulation should be avoided because movement may cause further neurovascular damage. Children with extension-type supracondylar fractures hold the affected arm in extension with an S-shaped configuration of the elbow and exhibit a prominence at the olecranon. Children with flexion-type supracondylar fractures hold the arm in flexion and exhibit an empty space where the olecranon should be. In all cases it is important to carefully assess distal neurovascular status. Motor and sensory function should be evaluated by assessment of the radial, ulnar, and median nerves (Table 176-3). Two-point discrimination on the fingers provides a sensitive means of assessing sensory status: an abnormal value (>5 mm) indicates a deficit. Vascular assessment should include evaluation of radial and brachial pulses and capillary refill of the hand. Patients with displaced fractures should have ongoing assessment for the development of compartment syndrome of the forearm. With pain on flexion or extension of the fingers, forearm swelling, tenseness or tenderness, or pain that is disproportionate to the injury, compartment pressures should be measured immediately. Unrecognized ischemic injury can result in Volkmann’s ischemic contracture, which is characterized by fixed elbow flexion, forearm pronation, wrist flexion, metacarpophalangeal joint extension, and interphalangeal flexion.

Radiographic evaluation of any elbow injury should include an AP view of the extended elbow and a lateral view of the flexed elbow. If these views do not show a fracture but clinical suspicion is high, oblique views are helpful. Even with proper radiographs, diagnosis of a pediatric elbow fracture can be difficult. The elbow is largely cartilaginous during early childhood, and the six secondary centers of ossification around the elbow can camouflage or be mistaken for fractures (Fig. 176-12). These ossification centers can be remembered by the mnemonic CRITOE: capitellum, radius, internal (medial) epicondyle, trochlea, olecranon, and external (lateral) epicondyle. The approximate ages at which these sites ossify may be estimated at 1, 3, 5, 7, 9, and 11 years, respectively (Table 176-4).

Bone relationships are helpful in evaluation of a radiograph for a supracondylar fracture (Fig. 176-13). A true lateral view should demonstrate a figure-of-eight appearance of the distal humerus with bisection of the capitellum by the anterior humeral line. If the capitellum falls posterior to this line, an extension-type supracondylar fracture is likely. In all views, the proximal end of the radius and radial neck should point to the capitellum. Baumann’s angle also is helpful in diagnosis of subtle supracondylar fractures¹² (Fig. 176-14). This angle is formed by a line drawn to follow the growth plate of the capitellum transected with a line that runs perpendicular to the axis of the humerus. The angle should be approximately 75 to 80 degrees. Baumann’s angle should be the same in both elbows, and differences between elbows can be used to detect subtle supracondylar fractures. In children younger than 3 years, difficult-to-distinguish bone landmarks limit the utility of Baumann’s angle. Postreduction alterations in Baumann’s angle reliably predict the final carrying angle.¹³

Fat pads also provide a means for detection of occult supracondylar fractures. A lateral radiograph with the elbow flexed at 90 degrees may show an anterior fat pad protruding from the coronoid fossa. This finding is normal unless the pad is bulging or in the shape of a ship’s sail. This “sail sign” may indicate fluid in the joint, although alone it may not be a reliable predictor of a fracture. The posterior fat pad, however, sits snugly within the olecranon fossa and should never be seen unless there is a fracture around the elbow. In this case, blood pushes the fat pad laterally, thereby making it visible on a lateral radiograph of the elbow. Accordingly, visualization of a posterior fat pad suggests the presence of an occult fracture around the elbow. The presence of a posterior fat pad without an obvious fracture warrants oblique views of the elbow (Fig. 176-15), splinting, and follow-up.

Plain radiographs usually are sufficient for diagnosis of supracondylar fractures. However, if the diagnosis remains in question after AP, lateral, and oblique radiographs are obtained, ultrasound imaging may be useful in infants,¹⁴ and magnetic resonance imaging (MRI) may be useful in older children.¹⁵

ED treatment of supracondylar humeral fractures is determined by displacement and neurovascular status. A pale, pulseless cold hand mandates emergency consultation with an orthopedic surgeon. If an orthopedic surgeon is unavailable and the vascular supply has not been restored, reduction should be attempted (Fig. 176-16). If necessary, reduction can be performed by a single operator. With the patient supine, the shoulder held in 90 degrees of forward flexion, and the elbow slightly flexed, both hands are placed on the arm proximal to the fracture, and both thumbs are placed on the posterior aspect of the fracture fragment. Then, while the thumbs are directed distally, the fragment is lifted onto the distal metaphysis. The return of blood supply is marked by the hand’s becoming warm and pink. If perfusion does not improve, another reduction may be attempted, with care taken to not entrap the brachial artery and median nerve. Multiple attempts at reduction increase the likelihood of neurovascular injury and swelling; therefore, no more than two reductions should be attempted. If perfusion is not reestablished, the child requires urgent operative intervention. A supracondylar fracture with a pulseless hand that is warm and pink does not need to be reduced immediately and should be splinted as it lies so that vascular status is not further compromised. The elbow should be splinted in relative extension because too much flexion in conjunction with swelling may obstruct the brachial artery and contribute to limb ischemia.

Gartland type I fractures can be splinted in the ED with the arm maintained in 90 degrees of flexion and neutral rotation. Hospital admission is not required, but these children do require urgent follow-up with an orthopedic surgeon. Gartland type III fractures require immediate orthopedic consultation and should be treated by either closed reduction and percutaneous pinning or open reduction and internal fixation in the operating room. Treatment of a partly displaced type II fracture is controversial. Some surgeons reduce and pin it in the operating room, whereas others perform closed reduction and keep the arm immobilized in a cast. Treatment of displaced supracondylar fractures by closed reduction and casting is associated with higher complication rates than is treatment by closed reduction and pinning; therefore, most such fractures are treated with pinning and casting for 3 to 4 weeks.

The primary complications of supracondylar fractures are related to neurovascular injury. Type III fractures are at greatest risk, with neurovascular compromise occurring in as many as 49% of patients.¹⁶ Neurovascular compromise, however, can occur with any displaced fracture. The median nerve is involved in half of the cases and is associated with posterolateral displacement. The radial nerve is involved in almost one third of patients and is associated with posteromedial displacement. Brachial artery injuries, including arterial entrapment, laceration, intimal tears, thrombosis, and compression from compartment syndrome, occur in approximately 40% of patients and are found with either type of displacement. Fortunately, the brachial artery has many branches around the elbow, and flow to the forearm and hand can be maintained even when the brachial artery is injured.

Despite the frequency of neurovascular deficits immediately after the injury, most nerve palsies are caused by stretching or contusion and resolve spontaneously. The typical course for nerve injuries is complete resolution. Although motor function usually returns within 12 weeks, sensory function may not return for 6 months or longer.¹⁷ If clinical or electromyographic evidence of nerve recovery is lacking after 5 months, exploration and neurolysis are indicated.¹⁸ Volkmann’s ischemic contracture (contracture deformity of the fingers, hand, and wrist) and permanent limb disability are the end result of untreated vascular injury. This complication is extremely rare and easily prevented by close observation and evaluation for the development of compartment syndrome. A few supracondylar fractures heal with a “gunstock” deformity; however, the combination of varus, hyperextension, and medial rotation of the limb is not a functional problem and, except in severe cases, requires no treatment. Severe cases can be corrected by humeral osteotomy.

Monteggia’s Fracture-Dislocation

Monteggia’s fracture-dislocations are characterized by a fracture of the proximal third of the ulna plus dislocation of the radial head. The radiographic evidence can be subtle, with only a minor greenstick fracture or bowing of the ulna. Isolated ulna fractures are rare in children; therefore, with all such fractures, AP and lateral radiographs of the elbow should be obtained to rule out dislocation of the radial head. The radial head should align with the capitellum on all radiographs of the elbow; if it does not, a Monteggia injury should be suspected (Fig. 176-17).

An orthopedic surgeon should be consulted promptly for closed reduction of the radial head dislocation and repair of the ulna fracture. Complications include permanent radial head dislocation, valgus deformity of the arm, loss of pronation, and late radial nerve palsy.

Nursemaid’s Elbow

In one study, radial head subluxation, or nursemaid’s elbow, was the most common upper extremity injury in children younger than 6 years presenting to a pediatric ED.¹⁹ It typically occurs when axial traction is placed on an extended and pronated arm, as when the child is pulled up or swung by the arms. It also may occur when the child falls onto the outstretched arm, sustains minor direct trauma to the elbow, or simply twists the arm. In infants, radial head subluxation can occur when an extended arm is caught beneath the infant’s body while being rolled over. In pathoanatomic terms, subluxation occurs when the annular ligament becomes loosened from the head of the radius and slips into the radiocapitellar joint, where it becomes entrapped (Fig. 176-18).

Nursemaid’s elbow occurs in children a few months to 5 years of age and has a peak incidence between 2 and 3 years of age.²⁰ It has been reported in children younger than 6 months²⁰ and has been seen in children as old as 9 years. This injury has a slight predilection for girls.

The history often includes an event involving a mechanism consistent with the injury followed by acute onset of arm pain that may or may not be localized to the elbow. The affected arm is held against the body, with the elbow slightly flexed and the arm pronated. Physical examination is significant for lack of swelling, erythema, ecchymosis, or deformity. Examination may reveal mild tenderness to palpation of the radial head. Pain is elicited with supination, pronation, and elbow flexion.

The diagnosis of nursemaid’s elbow is made clinically, and radiographs are not necessary. If, however, significant point tenderness, swelling, or ecchymosis is present or if the history suggests another injury, such as a supracondylar fracture, radiographs should be obtained. Although it is not commonly used as a diagnostic procedure, ultrasound imaging may demonstrate a widened space between the radial head and the capitellum.²¹

Radial head subluxation is an orthopedic injury that is easily reduced without sequelae. Classically, the affected elbow is gripped with the clinician’s thumb over the radial head, and with the other hand, the clinician flexes and supinates the patient’s arm. As the radial head relocates, the clinician feels it click or “clunk” under the thumb. Hyperpronation of the forearm also is effective in reducing radial head subluxation. As is done in the flexion-supination maneuver, the child’s affected elbow is held with the clinician’s thumb over the radial head, but then flexion-supination is replaced with hyperpronation of the forearm. Success rates range from 80²⁰ to 92%²² with supination and from 93²³ to 98%²⁴ with pronation. Pronation also may be less painful to the patient^24,25 and is the reduction method of choice.²⁴ After successful reduction, the child typically uses the arm normally within 10 minutes. This may be delayed in younger children and when the injury occurred more than 4 to 6 hours before reduction. Neither splinting nor orthopedic referral is required after a successful reduction.

Failure to reduce the subluxation of nursemaid’s elbow may result from improper reduction technique; swelling of the annular ligament as a result of edema, hemorrhage, or hematoma; or disruption of the annular ligament. Persistence of the subluxation also is more likely if reduction is attempted 12 hours or longer after the injury.

If two attempts at reduction fail to restore normal use of the arm, alternative diagnoses should be entertained. Because of the similarity in clinical findings, children also should be assessed for fractures of the clavicle and elbow. If no other pathologic process is found and the child is still not using the arm, a posterior splint should be applied with the elbow kept at 90 degrees and the forearm in supination. Follow-up evaluation with an orthopedic surgeon should be arranged for the next day.

Parents should be cautioned to avoid traction on the forearm and elbow because recurrence rates of radial head subluxation range from 5 to 39%, depending on the referral population studied.20,22,24 With recurrent subluxations, immobilization in a posterior splint with the elbow maintained at 90 degrees and the forearm supinated may be warranted. The need for open reduction or repair of the annular ligament is exceedingly rare.

Toddler’s Fracture

Toddler’s fractures are oblique nondisplaced fractures caused by low-energy torsional forces applied to the porous bone of infants and young children. Previously, it referred only to tibial fractures in children between 9 and 36 months of age, but the term is now applied more loosely. The mechanism of injury can be as mild as the child’s twisting on the leg while walking or a fall from an insignificant height. In some instances, the mechanism of injury may be unknown. The child will exhibit a limp or may refuse to walk on the affected leg. Some children will revert to crawling and can crawl without pain. Examination may show mild swelling of the leg and point tenderness. Gentle twisting of the lower part of the leg may elicit pain.

AP and lateral radiographs may reveal a spiral or oblique fracture extending downward and medially through the distal third of the tibia (Fig. 176-19). An internal oblique radiograph is helpful if evidence of fracture is absent on the AP or lateral view. If findings on all views are normal, consideration should be given to fractures elsewhere in the limb. If no fracture is apparent, the child should be splinted for comfort and radiographs repeated in 10 days, at which time periosteal new bone or sclerosis of the fracture edges will make the fracture visible. If findings on these radiographs are normal and the child is still limping, further evaluation should be undertaken to rule out osteomyelitis and malignant neoplasm. Bone scans often are helpful in the assessment of a limping toddler and are more sensitive than plain radiographs for detection of fractures. Ultrasonography is also emerging as an imaging option in the detection of occult fractures in toddlers as well as in older children.²⁶ Treatment of a toddler’s fracture consists of a below-knee walking cast for approximately 3 weeks.

The presence of a spiral fracture without an appropriate history may raise concern for nonaccidental trauma (i.e., child physical abuse). Midshaft fractures, which are more common in abused children, and tibial fractures in nonambulating children as well as other unexplained or frequent injuries should prompt further evaluation.

Skeletal Aspects of Nonaccidental Trauma