Physeal Fractures of the Elbow

Anatomy and Growth

The elbow joint consists of the articulating surfaces of three epiphyses: the distal humerus, the proximal ulna, and the proximal radius. At birth, each epiphysis is one mass of cartilage, each with its own growth plate (the physis). With growth, the distal humerus develops four ossification centers ( Fig. 29.1 ), the proximal ulna develops two, and the proximal radius develops one. The lateral three distal humeral ossification centers eventually unite into one bony epiphysis; the fourth, the medial epicondyle, gradually separates from the others, becomes an apophysis, and no longer participates in longitudinal growth or joint articulation. The two proximal ulna ossification centers unite to form one articulating epiphysis. Its physis provides longitudinal growth, thereby qualifying it as a true epiphysis, rather than an apophysis. Knowledge of the timing and pattern of ossification of these epiphyses, particularly the distal humerus, is essential in treating fractures of the elbow in children. The age of beginning ossification of each ossification center varies widely between and within each gender, but the sequence of ossification is always the same for both genders. Boys have an average delay of 2 years in each ossification center compared with girls.

Longitudinal growth potential of each of these three physes is approximately 20% of their respective total bone length. This paucity of growth reduces their remodeling potential, requiring that fracture of any of these epiphyses be anatomically reduced. This paucity of growth also reduces the likelihood of significant length discrepancy or angular deformity following physeal fracture, as is frequently seen in other long bones.

Knowledge of the elbow carrying angle and its variations is also important in the evaluation and treatment of pediatric elbow fractures and can conveniently be determined by examining the uninjured elbow. The carrying angle progressively increases up to age 15 years; overall the mean carrying angle for boys is 10.75 degrees and for girls is 12.88 degrees.

Epidemiology

The incidence of fractures of physes of the elbow is not well documented. Of all elbow fractures in children, slightly more than half are supracondylar fractures ( Table 29.1 ). The vast majority of the remaining elbow fractures are physeal fractures. When studying physeal fractures at all sites, the relative frequency of elbow fractures varies widely in different series. ^a

a References .

The only data available from a population-based study were gathered in Olmsted County, Minnesota, from 1979 to 1988. This study reported 951 cases of physeal fracture; 47 (5%) were in the elbow. Of these, 37 (3.9%) were in the distal humerus, 6 (0.6%) in the proximal radius, and 4 (0.4%) in the proximal ulna. Because elbow fractures in children are often referred to tertiary treatment centers, these percentages will be higher in nonpopulation-based studies.

Analyzing data of elbow fractures is further complicated by:

• difficulties in separating supracondylar fractures from physeal fractures of the distal humerus

• the late onset and vagaries of ossification of the multiple secondary centers of ossification of the distal humerus

• the inclusion or exclusion of fractures of the medial epicondyle, which is an apophysis rather than an epiphysis

• imprecise definition between olecranon and physeal fractures of the proximal ulna

• the difficulty in distinguishing radial neck fractures from those that involve the radial physis

• naming conventions at some institutions, which, for example, might code distal humeral fractures as trochlear, capitellar, or T-condylar, thereby omitting them from an electronic file search as a physeal fracture

When physeal fractures of the elbow are considered as a separate category (excluding supracondylar fractures), 60% occur in the distal humerus. In one series, fracture of the distal humeral lateral condyle was 26%, followed by radial head 23%, medial epicondyle 22%, proximal ulna 17%, T-intercondyle 4%, medial condyle 3%, lateral epicondyle 3%, and separation of the entire distal humeral epiphysis (typically occurring only in infants and very young children) 2%.

Classification

Many classifications of physeal fractures have been proposed. The physeal injury classification of Salter-Harris (S-H) has been the most frequently used over the past five decades. There have been no case reports of acute physeal compression injury (S-H type V) of the distal humerus, proximal radius, or proximal ulna recorded in the literature. In addition, speculation suggests that S-H type V injury of any physis is unlikely and may not exist. Distally located supracondylar fractures occasionally have fracture lines extending distally into the physis, making them type 1 Peterson physeal fractures ( Fig. 29.2A ). Fractures of the proximal radial metaphysis (neck) (see Figs. 29.7B and 29.8 ) and of the olecranon metaphysis (see Fig. 29.10B ) frequently extend proximally into the physis, also making them Peterson type 1 fractures. Therefore, the Peterson classification is used in the remainder of this chapter.

Evaluation

Any recent abnormality or change in a child's elbow, with or without a history of injury, deserves careful physical examination, including vascular and neurologic evaluation. This will avoid the uncomfortable situation of finding a postreduction vascular or neurologic deficit without knowing the prereduction status.

Imaging possibilities of osseous and cartilaginous structures are numerous. True anteroposterior and lateral roentgenographs of good quality are essential for evaluation of the injured pediatric elbow. Oblique views are helpful in nondisplaced or minimally displaced lateral condyle fractures. Soft tissue as well as osseous structures must be clearly discernible. An intraarticular hematoma may displace the posterior fat pad of the distal humerus (the posterior fat pad sign), which may be the only demonstrable change in an undisplaced or spontaneously reduced intraarticular fracture. Comparison radiographs of the uninjured elbow should be obtained if the presence or position of the epiphyseal or apophyseal ossification centers are in question or for comparison following manipulation of a fracture. This is particularly true in the pediatric elbow because of the wide variance in the ages at which the multiple ossification centers appear. Anteroposterior varus and valgus stress views can also be helpful.

In younger children in whom the ossification centers have not yet appeared, arthrography, ^b

b References .

ultrasonography, and magnetic resonance imaging (MRI) ^c

c References .

play important roles in defining the injury and determining the entry site for pin placement. In older children, with predominantly osseous epiphyses, tomography, computed tomography (CT), and multidirectional computed tomography, which lowers the radiation dose, may also be of value. However, these techniques are sometimes not available in the emergency room. In this case, drawing a line with a soft lead pencil on the radiograph longitudinally along the radius is helpful because in the normal elbow the line will always pass through the ossified capitellum regardless of the position in which the radiograph was taken. Drawing a line around the anticipated location of the unossified epiphysis can also be helpful.

Chapter 6 also reviews imaging techniques that aid in evaluating the anatomy, development, and pathology of children's elbows.

Management

In a 1952 study of 698 childhood fractures in all bones, only 7.4% were treated operatively. However, fractures about the elbow were operated 50% of the time. Since that time, there has been a gradual trend to treat more children's elbow fractures operatively. The goal is to restore articular congruity and angular alignment. The emphasis is to retain elbow function rather than growth. Because the distal humeral and proximal radial and ulnar physes contribute only 20% of the growth in these bones, the goal of restoring physeal continuity is less important than at other physes. Closed and open reduction with pin fixation is frequently done. Growth problems of either progressive angular deformity or relative bone length due to premature partial or complete physeal arrest are rare at the elbow. It is paramount that physicians both study each elbow fracture carefully and keep abreast of current literature to choose the best treatment for each fracture. Surgical exposures are discussed in Chapter 11 .

Distal Humerus

Ages 2 to 6 Years

After age 2 years, the physis gradually becomes more oblique, the medial side more distal (see Fig. 29.1 ). This obliquity of the physis may account in part for the frequent lateral displacement of the epiphysis and the difficulty of maintaining accurate reduction. The ossification center of the capitellum may appear radiographically as early as 6 months and always by 2 years of age (see Fig. 29.1 ). This ossification center is initially oval and provides valuable orientation for alignment with the radial diaphysis. In the normal elbow roentgenograph, a line drawn along the radial diaphysis normally passes through the capitellar ossification center in any projection. This aids in differentiating elbow dislocation from fracture. In a distal humeral epiphyseal separation, the capitellar ossification is aligned with the radius, regardless of the degree of displacement but is not properly positioned on the humerus. If the radius does not align with the capitellar ossification, there is radiohumeral subluxation or dislocation. Type 2 and 3 fractures are common. With increasing age, type 2 and 3 fractures become progressively less common, presumably due to a more irregular and stable physis. Dissolution of the trochlea 3 to 6 weeks post fracture, though rare, can result in permanent void of the trochlea.

Type 4 fractures are not common at this age but are a source of frequent complication, usually nonunion. They may occur in the medial condyle (trochlea), which when not ossified makes diagnosis by routine roentgenographs very difficult ( Fig. 29.3 ). When there is significant swelling medially and normal osseous contour, supplemental imaging is necessary. Soft tissue enhancement techniques and stress views are valuable, but if they are not diagnostic, ultrasonography, arthrography, or MRI should be considered.

Type 5 fractures are common at this age, and their differentiation from type 2 fractures is difficult and important because displaced type 5 fractures frequently develop nonunion if left untreated ( Fig. 29.4 ). ^h

h References .

Supplemental imaging, such as arthrography, ultrasonography, or MRI, should be considered. A coronal plane transcondylar fracture pattern has been described. All displaced type 5 fractures require anatomic reduction and maintenance of reduction, with the goal being to avoid nonunion, rather than to avoid premature physeal closure. Attempts to accomplish this with immobilization in a cast frequently lead to subsequent displacement of even nondisplaced or minimally displaced fractures of the lateral condyle. This contributes to significant complications. Because so much of the distal humerus is cartilaginous, closed reduction with percutaneous pinning is also not routinely advised for displaced fractures. The bone and pins can be visualized roentgenographically, whereas the cartilage cannot. Open reduction and internal fixation (usually smooth wires) should be considered for any displaced physeal fracture at this age.

Lateral Condyle Fracture

Fractures of the lateral condyle (capitellum) constitute 10% to 15% of all fractures in the region of the elbow (see Table 29.1 ). They are the most common physeal fracture of the elbow. They occur in children between the ages of 2 and 16 years but are most common between 6 and 10 years of age. ⁱ

i References .

The mechanism of injury is usually a fall with the elbow in extension, producing a valgus stress. The lateral condyle may also fracture during elbow dislocation. Less commonly, preexisting cubitus varus may predispose to fracture of the lateral condyle.

Type 5 fractures predominate in this age group (see Fig. 29.2 , Table 29.3 ). The portion of metaphyseal bone attached to the capitellar and lateral epicondylar epiphysis may be large or small. The most important consideration is that this fracture is both intraarticular and transphyseal. The epiphyseal portion of the fracture may traverse the ossification center of the capitellum but at a young age may be entirely through cartilage and therefore not visible roentgenographically. MRI is of great help in determining the nature and extent of the fracture.

Because this fracture involves both the articular surface and the physis, anatomic reduction is necessary and must be maintained until the fracture has united. Only the truly nondisplaced should be treated nonoperatively. If the fracture is undisplaced and stable, external immobilization by a long arm cast with the elbow in 90 degrees of flexion for 4 to 6 weeks will suffice. Closed reduction of significantly displaced fractures and a cast is occasionally successful. A percutaneous K wire can be used as a joystick to reposition the fragment followed by pinning. Frequent roentgenographic follow-up to assess maintenance of the reduction is essential. A radiograph taken out of cast within 5 days found a 10% incidence of displacement requiring open reduction internal fixation (ORIF) in one study. Further “late” displacement did not occur. If a displaced fracture can be reduced closed, pins inserted percutaneously may be used for fixation to prevent redisplacement. Arthrography or arthroscopy can be used to ensure a congruent joint surface before proceeding with percutaneous pinning. In many instances, however, open reduction and accurate replacement by direct vision is necessary. The reduction must be held by firm internal fixation, preferably metal rather than suture. Smooth metal pins, small in diameter, are the standard. ^j

j References .

The use of threaded wires and screws has some advocates. The use of biodegradable pins needs more review. Insertion of fixation devices from metaphysis to metaphysis and from epiphysis to epiphysis is preferred. However, because the trochlear cartilage is not ossified and not visible on roentgenographs, the pins may necessarily pass from epiphysis to metaphysis, crossing the physis obliquely. These pins should be removed within 3 weeks to prevent premature partial growth arrest, followed by a long arm cast for 3 weeks. Pins not crossing the physis should remain in situ until there is roentgenographic evidence of fracture healing, which occurred after approximately 6 weeks in one study. Fractures with early pin removal can be protected with an additional long arm cast. Threaded pins have a predisposition to premature partial physeal arrest and should not be used across a physis. Skeletal traction for elbow physeal fractures is used most advantageously only temporarily in children with multiple injuries.

Although there are more than 100 publications on the topic of lateral condyle fractures in children, evidence regarding the optimal surgical technique to treat displaced fractures remains limited to case series and expert opinion. Surgical approach and placement, number, and optimum configuration of pins varies considerably by author. A recent study states that “biomechanical stability of lateral condyle fractures is greater with divergent pin configurations and with three pins compared with two pins.”

Postoperatively an initial rapid recovery in elbow motion can be expected after lateral humeral condylar fracture in a child, regardless of whether the treatment was nonoperative, closed reduction and percutaneous pinning, or open reduction and internal fixation, with progressive improvements for up to 1 year after the injury.

Untreated and inadequately treated cases are frequently complicated by malunion or nonunion, which often cause deformity, loss of motion, degenerative arthrosis, and tardy ulnar neuropathy. ^k

k References .

The greater the initial displacement, the greater the risk of complication. There is no agreement on the management of these complications, although many authors recommend corrective osteotomy, combined with osteosynthesis, as early as possible for significant deformity. ^l

l References .

Lateral prominence and cubitus varus are the most common residual deformities. Lateral prominence (spurring, overgrowth) of the elbow occurs following half of all lateral condyle fractures ( Table 29.4 ). The development of a prominence correlates with initial displacement and treatment. Neither the presence nor the size of the lateral spur seems to influence the final outcome. Although frequently cosmetically visible, this rarely is troublesome and usually requires no treatment.

Varus or valgus deformity is also common ( Table 29.5 ) and may be due to malposition of the fragment or to true overgrowth of the capitellum and its physis. Overgrowth is an interesting phenomenon and occasionally occurs even following successful management of a lateral condyle fracture. Although this may produce measurable cubitus varus, functional impairment is rare, and treatment is often for cosmetic improvement. Treatment is a choice between wedge or dome osteotomy.

Premature physeal closure has been noted in up to 20% of lateral humeral fractures and is more often complete than partial. Complete physeal closure causes no angular deformity, and because the distal humeral physis provide only 20% of humeral growth, functional or cosmetic impairment is unusual. Premature partial lateral closure sufficient to cause progressive cubitus valgus is uncommon for the same reason.