GROWTH PLATES, APOPHYSIS, AND SECONDARY CENTERS OF OSSIFICATION

To a casual observer, the radiograph of a child’s elbow is an enigma—no two ever seem alike. The reason for this, of course, is that because the child is constantly growing, ossification centers are appearing and fusing, and cartilage is calcifying progressively until skeletal maturity is attained.

It is important to emphasize that there is usually a normal contralateral control that can be radiographed and compared with the radiograph of the injured elbow. This is not recommended as a routine practice, but sometimes it is necessary and useful, especially for those who treat elbow injuries in children only occasionally.

In general, the younger the child at the time of injury, the more difficult it is to assess the elbow, owing to the larger percentage of cartilage that is present about the elbow joint. Fortunately, new imaging modalities allow more accurate assessment.^7,8 Yet, in the newborn or infant, it may be very difficult to diagnose an elbow injury or to determine whether it is a transcondylar fracture or a dislocation of the elbow (the former being much more common at this age). The ossific nuclei about the elbow joint are helpful in radiologic interpretation of elbow dislocation (see Chapter 12). The capitellum, whose center of ossification should be present by 6 months of age, facilitates the interpretation of radial head alignment, because a line drawn through the radial head should always intersect the capitellum no matter what view is taken (Fig. 20-1). This interpretation is improved even further with the appearance of the radial head secondary center of ossification, at around 5 years of age. The secondary center of ossification of the olecranon, which appears at about 9 years of age, allows a more accurate assessment of the position of the proximal ulna in relation to the distal humerus, an important consideration in the management of dislocations of the elbow in young children.

FIGURE 20-1 A, A line drawn through the middle of the neck and head of the radius must always pass through the capitellum in every view. B, If it does not, dislocation of the radial head is present.

Both the medial and the lateral apophyses of the distal humerus may be injured in dislocations of the elbow in a child. Although many mnemonics have been devised by residents trying to remember the timing of ossification of the various centers about the elbow, the most important center to remember from a practical standpoint is the medial epicondylar apophysis of the distal humerus. This center is usually present by the age of 5 to 6 years, and because it is frequently entrapped within the joint following a dislocation of the elbow, it should always be searched for and identified after this age. Hence, if the center cannot be identified, it should be assumed that it is within the joint itself. In children younger than the age of 5 years, the diagnosis of entrapment must be clinical or by arthrography, because the apophysis is entirely cartilaginous.

The lateral epicondylar apophysis is injured less frequently. In posteromedial dislocations, it may suffer avulsion, owing to a severe varus strain on the elbow and may need to be repaired or fixed surgically.⁵

ELBOW FLEXIBILITY

In children younger than 10 years of age, elbow stability is provided almost entirely by cartilage. Because of this, there is considerable flexibility in the elbow joint in children. It is not unusual for a child to be able to hyperextend the elbow joint by 10 or 15 degrees and to have a much greater degree of laxity than is seen in an adult or even an adolescent. It is this combination of hyperflexibility and a lack of osseous stability in a joint subjected to considerable trauma that predisposes the elbow joint to dislocation. The major stabilizing ligaments on the medial and lateral sides are attached to the distal humerus through apophyses—structurally weak areas that are prone to avulsion with subsequent loss of joint integrity. In the many syndromes and conditions such as Ehlers-Danlos and cutis laxa syndromes,^111,119 ligamentous laxity is enhanced and stability is accentuated.

OLECRANON

The ulnohumeral joint provides the greatest articular stability in the elbow joint. In children, the coronoid process, which provides anterior stability resisting posterior dislocation of the ulna, is not well developed until about 12 years of age. Even at this age, the coronoid process is largely cartilaginous and, when stressed, is yielding and resilient. Similarly, the olecranon itself is a largely cartilaginous structure until the early teenage years. Neither the coronoid nor the olecranon fossa of the distal humerus is well developed until later in childhood, and they do not contribute as effectively to the “locking in” phenomenon in flexion and extension that occurs with well-ossified coronoid and olecranon processes.

RADIAL HEAD AND NECK

The radial head and neck in children are cartilaginous but have the same relative diameters as the radial head and neck in adults. Dislocation of the radial head, either as an isolated event or in association with a Monteggia fracture, or with dislocation of the elbow joint itself, is facilitated by the resiliency of the cartilaginous component. Children’s bones have plasticity and can be bent like the proverbial greenstick without fracturing. In the type A Monteggia lesion, for instance, it is conceivable that the ulna bends to the point of fracture, whereas the radius only bends to the point at which the radial head slips under the annular ligament and dislocates anteriorly (Fig. 20-2).

FIGURE 20-2 Annular ligament reconstruction using forearm fascia (Boyd technique).

It is of interest to note that in most cases requiring open reduction of the radial head, the annular ligament is actually intact. A similar situation may be found with the traumatic isolated dislocation of the radial head that occurs in very young children in which the radius bends just enough for the head and neck to slip under the annular ligament (called nursemaid’s elbow). When trauma is less severe, as in a pulled elbow, the head of the radius has simply slipped into the annular ligament, and there is no actual dislocation. A supination maneuver “screws” the radial head out of the annular ligament, usually with no actual damage to the ligament itself.

This combination of generalized laxity, the large cartilaginous component, the lack of osseous stability, and the presence of osseous plasticity as well as numerous secondary centers of ossification and apophyses all contribute to the anachronism of a greater tendency of dislocation of the pediatric elbow joint than seen with other joints.

CONGENITAL DISLOCATION

Congenital dislocation of the radial head is a controversial lesion, because some maintain this lesion does not exist at all and all such appearances are simply traumatic or developmental dislocations. This subject is discussed in more detail in Chapter 13. Here, I reserve the diagnosis of congenital dislocation for that entity in which congenital malformation of the extremity is obvious (Fig. 20-3). When isolated dislocation of the radial head is not accompanied by other congenital lesions, the congenital basis for the lesion cannot be substantiated. The long-standing nature of the dislocation can be inferred from the marked convexity of the radial head associated with elongation of the radial neck (Fig. 20-4).^27,28 Congenital dislocation of the radial head may be associated with radioulnar synostosis, the synostosis almost always occurring between the proximal radius and the ulna.^32–36

FIGURE 20-3 A and B, Congenital dislocation of the radial head associated with other congenital malformations of the forearm. Note the rounded convexity of the radial head.

FIGURE 20-4 Developmental or long-standing dislocation of the radial head. A, Note the rounded appearance of the head, convexity of the articular surface, and narrow neck typical of this deformity. B, Opposite normal elbow. C, Convexity of head develops if the radius is not in contact with the capitellum.

Hypoplasia of the capitellum associated with dislocation of the radial head strongly suggests that the dislocation is congenital. The radiologic appearance of congenital dislocations of the radial head has been emphasized by Miura.³⁷ In congenital dislocations, the posterior border of the ulna is usually concave rather than slightly convex, with the radial head being dome-shaped with no central depression (see Fig. 20-3). Posterior congenital dislocation, which constitutes about 40% of congenital dislocations of the radial head, is associated with an accentuation of the normal convexity of the posterior border of the ulna. In fact, because we have not been able to diagnose this pathology, at best, we consider this a developmental problem.²⁸

DEVELOPMENTAL DISLOCATION

Many instances of developmental or secondary dislocation of the radial head are misinterpreted as being congenital in origin.²⁸ Developmental dislocation is defined as any dislocation of the radial head that results from maldevelopment of the forearm. There are many inherited and acquired disease processes affecting the growth plate of the forearm bones that result in asymmetric growth between the radius and the ulna and subsequent dislocation of the radial head. These include the nail patella syndrome, Silver syndrome, arthrogryposis, Cornelia de Lange syndrome, and cleidocranial dysostosis. Asymmetric growth also occurs in multiple exostoses or diaphyseal aclasis. The ulna is most frequently affected at the distal ulnar growth plate; the radius then overgrows relative to the ulna (Fig. 20-5). Paralysis of the muscles innervated by the C5-6 nerve root, as in a nerve root palsy, also predisposes to a gradual dislocation of the radial head that occurs over a number of years of growth or occasionally in infancy.¹⁷ Cerebral palsy also may produce isolated dislocation of the radial head through marked spasticity of the muscles attached to the radius (Fig. 20-6).²¹ Trauma to the radius or the ulna, resulting in asymmetric growth, may also produce dislocation of the radial head. Fracture of the neck of the radius that has not been corrected adequately may result in the proximal radial epiphysis growing laterally instead of toward the capitellum (Fig. 20-7).^20–26

FIGURE 20-5 A to D, Dislocation of the radial head posterolaterally in a patient with multiple exostoses.

FIGURE 20-6 A and B, Long-standing dislocation of the radial head in a child with cerebral palsy. The elongation of the neck and convexity of the head indicate the presence of a prolonged dislocation. C, Spasticity or contraction of the biceps tendon may contribute to isolated dislocation of the radial head in children.

FIGURE 20-7 A and B, A child sustained a fracture of the ulna and neck of the radius that healed in malunion. Four years later, the radial head is dislocating laterally owing to malposition of the proximal radial epiphyseal plate.

A detailed developmental posterior study at the Mayo Clinic describes several grades, or types, of radial head dislocation with characteristic radiographic appearance (Fig. 20-8). Types II and III are complete dislocations and are more obvious cosmetically but have relatively little functional loss except forearm rotation.²⁸ Type I dislocations commonly are associated with late degenerative arthrosis and consist more of a subluxation than a frank dislocation. However, consistent with the definition of forearm maldevelopment, all types have a previous proximal ulnar bow.

FIGURE 20-8 The Mayo classification of posterior radial head instability. A, Type I is subluxation with characteristic radial head elongation and is associated with a poor functional result. B, Type II is complete dislocation but without subluxation. These patients typically have minimal pain but moderate loss of forearm rotation. Forearm prominence may be noticed C, Dislocation with posterior subluxation, type III, causes a marked cosmetic deformity but little functional impairment. Surgery is performed only for cosmetic reasons.

There are few indications for operative treatment of developmental dislocation of the radial head. For example, a malunion of the radius and the ulna that is obviously directing the head of the radius laterally, posteriorly, or anteriorly should be corrected with an osteotomy to redirect the proximal radius or the deformed ulna¹⁹; otherwise, excision of the radial head can be effective to improve motion, lessen pain, or to improve cosmesis.

In patients with cerebral palsy, if the bicipital tendon appears to be subluxating the radial head anteriorly, lengthening the biceps may prevent future dislocation. Once the dislocation is well established, attempts to relocate the radial head probably should not be made, and the dislocation should be accepted. Future resection of the radial head at skeletal maturity can be performed if the head is cosmetically or functionally a problem. The gradual nature of the dislocation and adjacent changes in the surrounding tissues and bone make this type of relocation of the radial head much more difficult than the acute traumatic injury.²⁶

Relocation of the radial head by shortening the radius and reconstitution of the annular ligament is ineffective.

TRAUMATIC DISLOCATION

Solitary dislocation of the radial head is uncommon but occurs much more frequently in younger children. It is essential to differentiate this entity from a developmental dislocation of the radial head that typically is diagnosed incidentally when assessing a minor elbow injury.

The history is of limited value in these cases because these children are often young, prone to frequent elbow injuries, and unable to make a reliable contribution to the history. The radiograph, however, is usually diagnostic because it shows the rounded concave appearance of the radial head in the congenital or developmental dislocation (see Fig. 20-4).^1–16

CLOSED REDUCTION

If the child is seen within 3 weeks of the injury, a closed reduction may be achieved. Direct pressure over the radial head with gradual flexion of the arm and immobilization in a flexed position of more than 100 degrees is usually successful.

If the radial head has been dislocated for several weeks and if the annular ligament has become entrapped, preventing adequate reduction, an open reduction may have to be performed.

If the radial head can be reduced but is not stable, a Kirschner wire fixation to the ulna may be effective. Driving a pin across the elbow joint through the capitellum and into the radial head is not recommended because these wires often break, making removal difficult. Breakage occurs because it is virtually impossible to immobilize the child’s elbow completely, and minor motion, even when in a cast, may result in a fatigue fracture of the wire. The elbow joint will then have to be opened unnecessarily to remove the fractured pin.

OPEN REDUCTION

Triceps Fascial Reconstruction

The technique of open reduction of an anterior dislocation of the radial head in children described by Lloyd-Roberts and Bucknill²⁰ is one I have used with success. This consists of using the lateral portion of the tendon of the triceps for reconstruction of the annular ligament (Fig. 20-9A).

FIGURE 20-9 A, Repair of radial head dislocation by reconstruction of annular ligament using triceps fascia (Lloyd Roberts-Bucknill technique). B, A Kirschner wire passed through the capitellum into the radial head (left) is not recommended owing to danger of pin fatigue and breakage. The radial head can be safely held in the reduced position by a pin across the radius and ulna (right).

A posterolateral incision is preferred rather than a posterior incision, which may disorient the surgeon to the position of the radial head. The triceps tendon is identified, and a long (10-cm) strip is removed from the lateral margin, ensuring attachment at the distal ulnar insertion. The tendon is increased in length by continuing the dissection through the periosteum to a point opposite the neck of the radius, where it is then passed around the neck and sutured to itself and the ulnar periosteum with enough tension to hold the radial head in place. A Kirschner wire is then passed through the ulna into the radius to ensure solid fixation until the tendon has healed (see Fig. 20-9B).¹⁸

The extremity is kept immobilized in an above-elbow plaster cast for 6 weeks; gradual mobilization is begun at 6 weeks after the Kirschner wire has been removed. If there is any difficulty in reducing the radial head, careful inspection of the joint capsule may reveal some infolding or tissue interposition, which may have to be excised.

Specific care must be exercised when exposing the neck of the radius in a child. Unlike the adult, the radial nerve may be only a fingerbreadth below the head of the radius rather than the classic two fingerbreadths that is often referenced.

UNTREATED ANTERIOR DISLOCATION OF THE RADIAL HEAD

A child with a long-standing anterior dislocation of the radial head actually may have good elbow function. The range of motion is usually functional, although the extremes of flexion and extension are usually limited by 20 or 30 degrees. In our experience, pain may develop at a later date, usually the fourth decade. The cosmetic deformity is also a concern, and the elbow may appear somewhat deformed, especially in a small, thin arm. Excision of the radial head at skeletal maturity is generally successful, and the radius does not migrate proximally.

ETIOLOGY

The most common cause of dislocation of the radial head associated with an ulnar fracture in childhood is a hyperextension injury,^44,62 followed by a hyperpronation injury.⁴⁵ In hyperpronation, Bado³⁹ pointed out that the bicipital tuberosity is posterior, thus predisposing the proximal radius to the greatest force during violent contraction of the bicipital tendon. In young children, the force generated by the biceps is less than that in the adult, and this mechanism probably is significant only in older children.

A direct blow over the posterior proximal ulna will produce a Monteggia lesion with anterior dislocation of the radial head, but this is an uncommon mechanism in children.

In our experience, this lesion is most frequently produced by a hyperextension injury. Further support for this theory is the observation that, in open type C injuries, the proximal ulnar fragment pierces the skin on the volar ulnar aspect of the forearm. This would not be possible if the arm were in full pronation because of imposition of the radius.

Because of the plasticity of the forearm bones, the radial head and neck may slip under the annular ligament and dislocate as the shaft of the radius bends. Indeed, many of the isolated traumatic dislocations of the radial head are undoubtedly variations of the Monteggia^46–48 (Monteggia equivalent), in which the ulna has simply bent but not fractured. The radial shaft is bent to the extent that the head and neck are slipped from within the annular ligament, resulting in an apparent isolated dislocation of the radial head.^30,43

CLASSIFICATIONS

Classifications of the Monteggia lesion are based largely on the injury in adults³⁹ (see Chapter 27). Because of differences in the configuration of the injury in childhood, the following pediatric classification is suggested to include dislocation of the radial head associated with the plasticity of the forearm bones in childhood (Fig. 20-10).

FIGURE 20-10 Classification of the pediatric Monteggia fracture dislocation: types A through E.

CLASSIFICATION OF PEDIATRIC MONTEGGIA LESIONS

Type A: Anterior dislocation of the radial head with anterior bowing of the ulna (Fig. 20-11).

FIGURE 20-11 A and B, Ulnar bend with lateral dislocation of the radial head, a type A Monteggia fracture dislocation.

Type B: Anterior dislocation of the radial head with greenstick fracture of the ulna (Fig. 20-12).

FIGURE 20-12 A and B, Type B Monteggia fracture associated with a greenstick fracture of the ulna and anterior dislocation of the radial head.

Type C: Anterior dislocation of the radial head with transverse fracture of the ulna (Fig. 20-13).

FIGURE 20-13 Anterior dislocation of the radial head with transverse fracture of ulna.

Type D: Posterior dislocation of the radial head with bending or fracture of the ulna (Fig. 20-14).

FIGURE 20-14 A and B, Posterior lateral dislocation of the radial head with bending or fracture of the ulna.

Type E: Lateral dislocation of the radial head with fracture of the ulna (Fig. 20-15).

FIGURE 20-15 Monteggia fracture with lateral dislocation of the radial head. A, Clinical appearance. B and C, Radiologic appearance.

Types B and C are the most commonly encountered Monteggia lesions in children.⁵¹

CLINICAL DIAGNOSIS

Like Monteggia himself, who described this injury initially in a young woman in 1814, long before the advent of radiography, most physicians today should be able to identify the clinical configuration in those seen early, before swelling has occurred (see Fig. 20-15). The dislocation of the radial head is often evident on inspection of the lateral aspect of the elbow joint. Angulation of the ulna, whether fractured or not, necessitates careful appraisal of the position of the radial head. Dislocation of the radial head is frequently missed by those who treat pediatric elbow injuries only occasionally.^52–58 A line drawn through the shaft and the neck of the radius should intersect the capitellum in all views taken (see Fig. 20-1). If it does not, dislocation of the radial head is highly suspect.

In contrast to the lesion in adults, overlap of the ulnar fragments is not a prerequisite for dislocation of the radial head in a child. Disruption of the forearm parallelogram may occur as a result of ulnar bend when the radial head slips out of the annular ligament. It is wise to obtain anteroposterior and lateral views of the elbow joint in all fractures of the ulna. The apex of the ulnar bend or angulation is always in the direction of the radial head dislocation.^51–65

TREATMENT

In contrast to the adult, the Monteggia injury in children usually can be treated by closed methods.³¹ Pressure directed over the dislocated radius usually will result in a stable ulnar reduction, provided that immobilization is imposed with the elbow flexed more than 90 degrees in types A, B, C, and E lesions. Supination assists in minimizing biceps pull. In the uncommon type D Monteggia lesion with posterior dislocation of the radial head, stability is obtained with extension, not flexion, of the elbow.

As long as the radial head is reduced and stable, angulation of the ulna of as much as 15 degrees can be accepted. Remodeling of this angulation will occur with further growth. In children, stable reduction of the radial head is the first priority. A supination-pronation maneuver may facilitate repositioning of the annular ligament, which is seldom completely torn.

If it is impossible to obtain a stable reduction of the radial head, I approach the radial head through a Kocher incision and reapproximate the annular ligament around the neck. If stability is still precarious or if the annular ligament has had to be reconstituted, I recommend internal fixation of the radius to the ulna with a Kirschner wire (Fig. 20-16A). As noted earlier, I would caution against maintenance of the reduction by a wire inserted through the capitellum and into the radial head. Fatigue fracture is always a possibility (see Fig. 20-8B).

FIGURE 20-16 A and B, Preferred radioulnar pinning to hold the radial head in place subsequent to late open reduction of a Monteggia fracture dislocation and annular ligament repair. C, Injury to the posterior interosseous nerve may occur in the Monteggia fracture with anterior dislocation of the radial head. D, Missed dislocation of the radial head in an unappreciated Monteggia fracture with greenstick fracture of the ulna.

If the ulna is unstable in the older child, an open reduction with plate fixation may be necessary, but in my experience, this is seldom required in those under 10 years of age.⁵⁸

NERVE INJURY ASSOCIATED WITH MONTEGGIA LESIONS

Anterior dislocation of the radial head may result in a traction injury to the posterior interosseous nerve as it passes dorsolaterally around the proximal radius to enter the substance of the supinator muscle mass between the superficial and deep layers (see Fig. 20-16B).^46,60 Compression of the posterior interosseous nerve also may be aggravated by the fibrous arcade of Frohse, a firm fibrous band at the proximal edge of the supinator muscle.⁵⁹

In children, nerve injury is less common than in adults, and recovery is the rule in closed injuries. In a large series of 102 Monteggia fractures, Olney and Menelaus⁵³ found a 10% incidence of nerve injuries, 6% involving the posterior interosseous nerve and 3% involving the radial nerve. All their nerve injuries healed completely within 6 months.

DISLOCATION-SUBLUXATION OF THE RADIAL HEAD FOLLOWING MALUNION OF A RADIAL NECK FRACTURE

Fractures of the radial neck in children that have occurred after the age of 6 or 7 years may, if unreduced, result in a subluxation (see Fig. 20-7). When neck angulation is more than 45 to 50 degrees, the growth plate becomes redirected laterally or posterolaterally. If there is not enough remodeling to allow the growth plate to reattain its normal transverse anatomy, increased prominence of the radial head ensues. As the child grows, pain may be experienced, as well as irritation, cosmetic deformity, and, to a lesser extent, limitation of supination and pronation. This can be avoided by ensuring that the angulation of the radial neck is reduced to less than 45 degrees by closed or open reduction.⁶³

When associated with malunion of the ulna radial head, instability may necessitate osteotomy of the ulna and open reduction of the radial head. It is of course always prudent to attempt a closed reduction of the radial head if the injury has occurred recently (i.e., within 2 months) because the ulna may still be straightened. Usually, however, in the missed Monteggia lesion, an open reduction of the radial head will be necessary, and in this instance, it will almost certainly be necessary to reconstitute the annular ligament—with the ligament itself, if possible, with fascia obtained from the triceps, or by using the Bell-Tawse procedure.^42,44,49 Shortening of the radius may be necessary to permit reduction. Internal fixation with Kirschner wires through the radius to the ulna is advisable. Relocation of the radial head should be attempted in children younger than 6 years of age.¹⁸ In older children in whom the lesion has been present for more than 1 year, it may be advisable to accept the dislocation because this is compatible with excellent function in most instances. A modified technique for reconstruction of the annular ligament has been reported by Peterson and Seel,⁵⁶ which appears effective in patients with long-standing radial head dislocations. If the radial head becomes cosmetically or functionally disabling, excision is performed as needed when skeletally mature. Removal of the radial head is avoided until skeletal maturity since 30% of radial growth occurs at the proximal radial epiphysis.

ETIOLOGY

Subsequent to a longitudinal pull on the forearm, the radial head is pulled down into the annular ligament (see Fig. 20-17B). This results in inability to rotate the radial head without considerable discomfort. Usually, the annular ligament is not torn; however, as the child becomes older, the annular ligament is undoubtedly partially torn, which accounts for the persistence of symptoms for several days even after the reduction. At one time, it was thought that the radial head in a child was smaller in relation to the neck than in adults or older children, and thus, subluxation of the radial head into the annular ligament was more common.¹²⁵ Studies by Salter and Zaltz¹²⁹ and Mehta¹²⁷ have shown that, even in infants, the relative proportion of radial head diameter to neck diameter is similar to that of adults.

The pulled elbow syndrome is most common between the ages of 6 months and 3 years, becoming less common as the radius grows in size and becomes more ossified.¹²⁶ A reasonable explanation for pulled elbow is simply the generalized ligamentous laxity of the elbow that exists at this age and the resiliency imparted to the radial head by the almost entirely cartilaginous structure.^122,123 A longitudinal pull with accompanying pronation of the forearm screws the radial head down into the annular ligament, and the larger head then becomes caught as if in a Chinese finger trap (see Fig. 20-17B).

CLINICAL APPEARANCE

A child with the pulled elbow syndrome complains primarily of pain and failure to move the elbow, and there may or may not be a typical history of a longitudinal pull. The infant may well go about his or her normal play activities and is comfortable as long as no one attempts to move the elbow. The child keeps the arm in pronation and expresses discomfort and anxiety if anyone attempts to move the elbow or to pronate or supinate the forearm. Radiographs are singularly nondiagnostic and are sometimes misinterpreted because it is impossible to position the limb properly.^124–129 However, the technicians, in attempting to obtain good anteroposterior and lateral films of the elbow, may inadvertently reduce the subluxation by supinating the forearm, and the child returns from the Radiology Department content and moving his or her elbow normally.

MANAGEMENT

Reduction of the pulled elbow is usually simple, consisting of a supination motion with the elbow flexed. A click is often felt and sometimes even heard. As the radial head is “screwed up” into the annular ligament, the ligament slips down over the head into its normal position around the neck with a snap. In younger children, resumption of normal activity often ensues in minutes; however, in the older child, the elbow may remain tender, probably owing to small tears within the annular ligament. If pain persists, immobilization of the arm in a plaster cast or splint for a week or so is curative.

Other than emotional upset, there are no long-term sequelae from the pulled elbow syndrome, because in some children, its frequent recurrence is a cause of concern to patient and family. In such a case, it is often worthwhile to explain precisely what is happening and demonstrate how to reduce the pulled elbow to avoid visits to the emergency department. Seldom is open repair of the annular ligament necessary, because even in the most recalcitrant circumstances, time and growth always cure this type of instability.

MECHANISM OF THE DISLOCATION

As discussed earlier, the elbow joint in a child is basically a ligamentous structure in which only a small portion of cartilaginous stability is imparted by the ulna. With a fall on the outstretched hand the downward force on the fixed forearm is considerable. An associated valgus or varus force created by the body falling over the fixed elbow occurs (Fig. 20-18). The forearm is typically in pronation during this time. The coronoid process may be fractured (Fig. 20-19). The valgus force of the body rotating over the fixed elbow accounts for the frequent avulsion of the medial epicondylar apophysis (Fig. 20-20).^71,83 If the body falls over the elbow medially instead of laterally, a varus force is exerted, and the lateral epicondyle of the humerus or the lateral condyle may be avulsed⁸⁴ (Fig. 20-21). Occasionally, as in a fall from a height, the forces may be such that the valgus force may disrupt the medial apophysis, and the posterolateral dislocation may also avulse the lateral epicondyle, resulting in elbow instability on both the ulnar and the radial sides of the joint. The radius and the ulna seldom separate owing to the strong interosseous membrane, although instances of divergent dislocations with tearing of the interosseous membrane have been reported.^75,81,86,96 Less commonly, traction injuries may result in elbow dislocation.⁸⁰

FIGURE 20-18 Mechanism of dislocation of the elbow in children.

FIGURE 20-19 A and B, Fracture of coronoid process of olecranon associated with posterior dislocation of the elbow.

FIGURE 20-20 A and B, Fracture of radial neck with avulsion of the medial epicondyle, which has remained intra-articular following spontaneous reduction of the elbow dislocation.

FIGURE 20-21 A and B, Dislocation of the elbow associated with fracture of the lateral condyle of the humerus. The radial head maintains its relationship with the displaced capitellum.

Occasionally, in falls from a height, the valgus force exerted on the elbow joint may result in a fracture of the neck of the radius and the olecranon process (Fig. 20-22). When the arm is in marked extension, the capitellum also may be fractured. Associated fractures of the distal radius and ulna occasionally occur (Fig. 20-23).

FIGURE 20-22 A and B, Dislocation of the elbow with valgus force resulting in fracture of the olecranon, radial neck, and medial epicondyle, which has remained intra-articular following spontaneous reduction.

FIGURE 20-23 A and B, Fracture of distal radius associated with dislocation of the elbow.

Along with the other associated trauma, capsular tearing is responsible for the prolonged stiffness that often follows dislocation of the elbow. The capsular attachment to the ulna and humerus is frequently torn.

SPONTANEOUS REDUCTION OF THE DISLOCATED ELBOW

Spontaneous reduction of a dislocated elbow in children is common. Often the child will present to the emergency department with a history of a fall, the only physical findings being a swollen, boggy elbow and no obvious radiographic evidence of any injury. However, if one looks carefully at the radiograph, signs of previous dislocation may be present (Fig. 20-24). Of particular note is fracture of the coronoid process (Fig. 20-25), which indicates that the elbow has been transiently subluxed.

FIGURE 20-24 Fractures about the elbow in children indicative of spontaneous reduction of an elbow dislocation.

FIGURE 20-25 A and B, Avulsion fracture of tip of coronoid process following dislocation of the elbow. The brachialis muscle often avulses a small portion of the coronoid process; when present, this is pathognomonic of a previous elbow dislocation.

Sometimes, at reduction the humerus may cause a type I or II fracture through the epiphyseal plate of the proximal radius, resulting in posterior displacement of the radial epiphysis on reduction (Fig. 20-26).

FIGURE 20-26 A, Type I fracture of the proximal radial epiphysis with posterior displacement occasionally occurs in posterior dislocation of the elbow if reduction is forceful. B, Fracture of neck of radius secondary to dislocation of the elbow with forceful spontaneous reduction.

DIFFERENTIAL DIAGNOSIS OF POSTERIOR DISLOCATION

The child with dislocation of the elbow is severely incapacitated with pain and deformity. The differential diagnosis basically consists of distinguishing a dislocation from a supracondylar fracture, a lateral condylar fracture, and, in the younger child, a transcondylar fracture of the humerus (Fig. 20-27).⁹² The elbow will be painful and swollen, and depending on how soon the child is seen after the injury, the posterior deformity may be either obvious or masked by swelling if several hours have passed. The child is always extremely apprehensive and will not allow anyone under any circumstances to move the joint.

FIGURE 20-27 Transcondylar fracture of the humerus in infancy may be misdiagnosed as a dislocation of the elbow. Arthrography or computed tomography scan is diagnostic.

In my experience, the commonly stated rules of lining up the triangular relationship among the medial epicondyle, lateral epicondyle, and olecranon are not of much practical value in this situation. One can sometimes feel a gap superior to the displaced olecranon, indicating that a posterior dislocation has occurred. The humeral condyles can also be palpated anteriorly. The supracondylar fracture is often difficult to differentiate from a posterior dislocation of the elbow, especially if presentation is late and considerable swelling has occurred to obscure the abnormal anatomy. Excessive examination and movement of such an elbow should be avoided because it serves only to make the child more apprehensive and less cooperative.

The neuromuscular examination of the extremity may be difficult but often can be performed simply by observation once the confidence and cooperation of the child have been obtained. Sensation then can be gently tested in the three major nerve distributions, including the anterior and posterior interosseous divisions. It is essential, of course, to assess the neurologic and vascular condition of the limb in the Emergency Department. The child should be encouraged to make the “O” sign with the index finger and thumb. If this cannot be done, injury to the anterior interosseous nerve has occurred, causing paralysis of the flexor pollicis longus. Images are diagnostic today. Dislocation of the elbow is very rare in children younger than the age of 2 years, and transcondylar fracture of the humerus should be suspected (see Fig. 20-25). This may be difficult to differentiate from a posterior dislocation, and confirmation may require special images.^{68–74,76,79,82}

Radiographs should be carefully examined for associated fractures aside from the dislocation. A careful appraisal of the coronoid process, the radial neck, the olecranon, and the medial and lateral epicondyles should be carried out.^67,77,78,84 If the child is over 5 years of age and the medial epicondyle is not present, a radiograph of the other elbow should be inspected to make sure that it is ossified. If the medial epicondyle cannot be found on the radiograph of the dislocated elbow, it must be assumed that it is obscured by its intra-articular position (see Fig. 20-20).^{66,71,89–95}

An injury to the radial epiphysis may occur when the elbow is forcibly reduced. This may even occur at the time of the injury; for example, when a direct blow to the elbow, following the original dislocation that was sustained by a fall on the outstretched hand, causes reduction. The direct force on the radial head results in a type I fracture through the proximal radial epiphysis with posterior displacement (see Fig. 20-26).

It is essential to emphasize that many children present to the emergency department with simply a swollen, boggy elbow joint and a history of a fall. In such cases, one can assume, especially if there is radiographic evidence of avulsion of the coronoid process or of the medial epicondyle, that this elbow has been dislocated and has spontaneously reduced.

TREATMENT OF POSTERIOR DISLOCATION

Posterior dislocation of the elbow is a painful, terrifying experience for a child, and the limb should be put at rest with a splint as soon as possible in the emergency department with minimal manipulation of the extremity. No child should ever be sent for radiographs without adequate splintage. The dislocation demands early treatment and, of course, if there is any vascular insufficiency, immediate treatment.

Occasionally, in a very cooperative older child, the elbow may be reduced in the emergency department. The instillation of local anesthetic into the joint itself often facilitates this maneuver. Turning the child prone with the arm dangling over the stretcher facilitates the application of some pressure over the olecranon, and this, combined with gravity or slight traction on the dangling limb, may allow the dislocation to be quickly and traumatically reduced.⁸⁷ If there is an associated fracture of the medial epicondyle, the radial neck, or the olecranon, this maneuver should be avoided.

In our experience with children younger than age 12, it is best to proceed with a general anesthetic for complete relaxation, ideally within 6 hours of the trauma. It is not appropriate to allow the child to wait overnight because massive edema may occur, which is extremely uncomfortable for the child and leads to stiffness.

Once the child has been anesthetized, it is usually a simple matter to reduce an uncomplicated posterior elbow dislocation. Gentle traction on the forearm combined with some anterior pressure over the prominent olecranon is usually successful, usually with an audible and palpable clunk (Fig. 20-28).

FIGURE 20-28 The author’s preferred technique for reducing a posterior dislocation of the elbow joint in children.

Occasionally, in older children, the coronoid process becomes locked behind the humerus. In this instance, the arm should be put in extension and a muscle relaxant administered; with traction and good firm thumb pressure over the olecranon, the elbow usually can be reduced. Hyperextension to free the coronoid is hazardous, especially if vascular insufficiency is already present, because it places more stress on the brachial artery, which may be tented over the distal end of the humerus. Once the elbow is reduced, the integrity of the medial and lateral collateral ligaments should be tested. Furthermore, a smooth arc of motion should be demonstrated to ensure no fragment, particularly the medial epicondyle, is caught within the joint. If the joint does not move freely or has a spongy feel to it, a mechanical problem with reduction exists. The reduction should always be checked radiographically, especially with any associated fracture.^85,94,97

Aspiration of the joint is recommended to assist in resolving the hematoma and improving joint motion after reduction. Using a local anesthetic may be helpful in the older patient.

MEDIAL EPICONDYLAR ENTRAPMENT

If it is known that the medial epicondyle is trapped within the joint, then during the reduction, a valgus strain is placed on the elbow. With flexion of the wrist this may allow the attached flexor muscle mass to pull the trapped fragment out of the joint. Occasionally, this may yield an anatomic or nearly anatomic position. If the medial epicondyle is displaced more than 1 cm, it should be pinned back in place because it will add stability to the elbow subsequent to the dislocation and allow stable elbow motion to occur within 3 to 4 weeks. In children younger than the age of 5, when the medial epicondyle is not ossified, any springiness in the elbow joint subsequent to the reduction indicates an intra-articular position of the medial epicondyle. Ultrasonographic evaluation of the elbow might be helpful in confirming the presence of an intra-articular fragment.⁷⁴ If the medial epicondyle cannot be removed from the joint with manipulation, it must be removed surgically. The elbow is approached through a medial incision. The flexor muscle mass initially appears to be anatomically intact as it disappears into the joint; however, with valgus force and gentle pull on the muscle mass, the attached fragment can be removed from the joint, and the capsule can be repaired. The fragment then should be reattached to the distal medial humerus. Care should be taken not to injure the ulnar nerve. If there is any concern about this, the nerve should be identified and retracted with tapes until the repair has been completed.^66,89,95,109

POSTOPERATIVE MANAGEMENT

Following reduction of the elbow, the joint should be immobilized at 90 degrees with slight forearm supination. Flexion is especially important if there has been a coronoid process avulsion. This allows the triceps to tighten posteriorly, acting as a dynamic splint for the elbow, and also helps prevent the ulna from slipping backward into the dislocated position.

OTHER TYPES OF ELBOW DISLOCATION

COMPLICATIONS OF ELBOW DISLOCATION

Complications from simple dislocations of the elbow are uncommon in children, especially when compared with this injury in the adult.

Joint Stiffness

As in adults, joint stiffness is the most common problem encountered after dislocation of the elbow in children. The child and his or her parents must be advised that joint motion may be lost as a result of the injury. In older children, fully complete extension may never be recovered, although the loss of the last 5 to 10 degrees of extension is not accompanied by any marked functional deficit. Elbows in children should not be immobilized longer than 4 weeks, and exercises after injury should be primarily active; passive motion should be avoided. Seldom is manipulation or passive physiotherapy required for joint stiffness after a dislocation of the elbow; this type of treatment often delays recovery because it is accompanied by further joint irritation, capsular tearing, and hematoma formation. A year may be required to regain full motion in the child’s elbow, the child being his or her own best physiotherapist. Management of the stiff elbow in the child is discussed in detail in Chapter 21.

Myositis Ossificans

Myositis ossificans is an uncommon complication of a simple dislocation of the elbow joint in children unless it is accompanied by a crush injury, head injury, major trauma, or multiple manipulations. Myositis ossificans may bridge the joint involving the brachialis muscle. The ossific lesion can be excised once it is mature, however, but recurrence is still possible.¹¹⁰

Nerve Injuries

Nerve injuries are uncommon in simple posterior elbow dislocations in children. The ulnar nerve is most frequently involved.^80,117 The common posterolateral dislocation of the elbow results in a stretch on the ulnar nerve. The median and, rarely, the radial nerves also may suffer neuropraxic injuries secondary to posterior dislocation of the elbow.

The median nerve may be vulnerable to entrapment within the joint subsequent to reduction of the elbow dislocation. Although rare, this type of entrapment has been reported only in children, and diagnosis is frequently delayed. It should be suspected when signs of median nerve injury or pain accompany avulsion of the medial epicondyle; in such instances, the nerve usually lies “posterior” to the medial epicondyle (Fig. 20-29).^{98,102,105,108}

FIGURE 20-29 Course of median nerve lying entrapped posterior to the medial epicondyle.

(Redrawn from Matev, I.: Radiological sign of entrapment of the median nerve in the elbow joint after posterior dislocation. J. Bone Joint Surg. 58:353, 1976.)

As emphasized by Green,¹⁰¹ in an excellent review of this subject, persistent pain or increasing median nerve dysfunction should alert one to the possibility of nerve entrapment. A late clinical sign of entrapment is persistent limitation of elbow motion; a late radiologic sign of median nerve entrapment is depression of the cortex of the distal humerus just proximal to the medial epicondyle, where the median nerve passes behind the humerus.^105,106 This is termed Matev’s sign (Fig. 20-30). Immediate exploration should be undertaken once the diagnosis of nerve entrapment has been made. If the nerve is functionally intact, as demonstrated by nerve stimulation, simple removal of the nerve from the joint is sufficient treatment. If the nerve is obviously severely damaged, crushed, or scarred and nonfunctional, resection of the damaged section with end-to-end reanastomosis is recommended.^99,107

FIGURE 20-30 Median nerve entrapment 3 months after injury. The arrow points to a cortical depression with interruption of periosteal reaction.

(From Matev, I.: Radiological sign of entrapment of the median nerve in the elbow joint after posterior dislocation. J. Bone Joint Surg. 58:353, 1976.)

Vascular Injury

Injury to the brachial artery to the extent of complete occlusion is not commonly observed in dislocations of the elbow in children. The brachial artery may be stretched over the distal humerus, and if the force is sufficient, damage to the artery may occur. This is evident by the usual signs of vascular impairment, which then demand exploration of the artery. The elbow should always be reduced before making a final assessment of the vascular status of the limb because it simply may be occluded subsequent to the elbow deformity.^{100,103,104,106}

In assessing vascular integrity in a child’s arm, caution must be advised in putting too much faith in capillary filling. Collateral circulation may be sufficient to provide excellent capillary filling but insufficient to adequately vascularize the extremity.

Recurrent Dislocation of the Elbow

Recurrent dislocation of the elbow in children is very uncommon, as is an unreduced dislocation.⁶⁹ Today, recurrent dislocation is known to occur with a deficient lateral ulnar collateral ligament.⁹³ Inadequate treatment, in which the elbow has been kept flexed at less than 90 degrees, especially when associated with a fracture of the coronoid process, may result in redislocation of the elbow and reinjury and recurrent dislocation.^111–121

It is uncommon to experience recurrent dislocation. Uncommonly, this may be secondary to severe generalized ligamentous laxity, as occurs in Ehlers-Danlos syndrome. In a review of the Ehlers-Danlos syndrome by Beighton and Horan,¹¹¹ 19 of 100 patients suffered dislocations of one or more joints, with three having dislocation of the elbow. Recurrent dislocations of the elbow were reported by Rames and Strecker¹²⁰ in a 9-year-old girl who subsequently required a repair of the lateral capsule and ligamentous structures with drill holes through the lateral epicondyle to firmly anchor the capsule, as described by Osborn and Cotterill.¹¹⁹

Recurrent subluxation of the elbow recently was described by O’Driscoll and Morrey,¹¹⁸ who noted the etiology as deficiency of the lateral ulnar collateral ligament. Of note, like the shoulder, recurrence of the elbow dislocation is greater in adolescents than in adults. This may be treated successfully with an orthosis designed to block the last 15 degrees of extension associated with muscle strengthening to protect and stabilize the elbow. If this fails, surgery to reconstruct the lateral collateral ligament complex is required.