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 epiphyseal growth plate (the physis). With growth, the distal humerus develops four ossification centers^1,2,4; the proximal ulna, two⁵; and the proximal radius, one.³ 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 (Fig. 16-1). The two proximal ulna ossification centers unite to form one articulating epiphysis; its physis provides longitudinal growth, thereby qualifying it as a true epiphysis. 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.

FIGURE 16-1 Distal humerus epiphysis growth centers at various ages. At birth, the physis is transverse and the epiphysis is one cartilaginous mass. By age 2 years, the capitellar ossification center is usually present.¹ The physis still is relatively linear and transverse. At ages 5 to 7 years, there is mild obliquity of the epiphyseal growth plate to the longitudinal axis of humerus and beginning ossification of the medial epicondyle.⁴ Trochlear ossification begins at 8 to 9 years, is irregular with indistinct margins, and often appears as multiple fragments. At ages 10 to 12 years, a projection of metaphyseal bone separates the medial epicondyle from the major distal epiphysis, which now contains three ossification centers—capitellum, trochlea, and lateral epicondyle.² These three ossification centers unite with each other in the 13th year and to the humeral epiphysis by the 16th year, earlier in girls. There is wide variation of ages of these occurrences between genders and among children, but the sequence is constant.

(From Peterson, H. A.: Epiphyseal Growth Plate Fractures. Heidelberg, Springer, 2007, used with permission of Mayo Foundation for Medical Education and Research.)

The growth potential of these three physes is approximately 20% of their respective total bone length. This paucity of growth reduces the remodeling potential, requiring that fracture of any of these epiphyses be anatomically reduced.

EPIDEMIOLOGY

The incidence of fracture of physes of the elbow is unknown. Of all elbow fractures in children, slightly more than half are supracondylar fractures (Table 16-1). The vast majority of the remaining half are physeal fractures. When studying physeal fractures at all sites, the relative frequency of elbow fractures varies widely in different series.^{8,9,12,15–20} The only data available from a population-based study were gathered in Olmsted County, Minnesota, from 1979 to 1988.²⁰ 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; by the vagaries of ossification of the multiple secondary centers of ossification of the distal humerus^1,2,4; by the inclusion or exclusion of fractures of the medial epicondyle, which is an apophysis rather than an epiphysis; by imprecise definition between olecranon and physeal fractures of the proximal ulna, and by the difficulty in distinguishing radial neck fractures from those that involve the radial physis.

When physeal fractures of the elbow are considered as a separate category (excluding supracondylar fractures), 60 percent occur in the distal humerus. In one series,⁹ 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 young children), 2%.

CLASSIFICATION

Many classifications of physeal fractures have been proposed.^18,22 The classification of Salter-Harris²⁴ has been the most frequently used over the past four decades. There have been no case reports of acute physeal compression injury (Salter-Harris type V) of the distal humerus, proximal radius, or proximal ulna recorded in the literature. Speculation suggests that acute compression injury (type V) of any physis is unlikely and may not exist.²³ Supracondylar fractures of the distal humerus often have fracture lines extending distally into the physis, making them type 1 Peterson physeal fractures (Fig. 16-2).^18,88 Fractures of the proximal radius metaphysis (neck) (see Fig. 16-7M), and of the olecranon (see Fig. 16-8), frequently extend proximally into the physis,^18,184 also making them Peterson type 1 fractures. Therefore, the Peterson classification^18,22 is used in the remainder of this chapter.

FIGURE 16-2 Peterson classification of distal humeral physeal fractures in children.

(From Peterson, H. A.: Epiphyseal Growth Plate Fractures. Heidelberg, Springer, 2007, used with permission of Mayo Foundation for Medical Education and Research.)

FIGURE 16-7 Peterson classification of proximal radius physeal fractures in children. M, metaphyseal (neck) fracture. Fracture types 1 through 6, all of which involve the physis, are fractures of the head because the physis is part of the head.

(From Peterson, H. A.: Epiphyseal Growth Plate Fractures. Heidelberg, Springer, 2007, used with permission of Mayo Foundation for Medical Education and Research.)

FIGURE 16-8 A, An 11-year-and-6-month-old girl fell down six stairs and noted pain and swelling over the left radial head. Anteroposterior (A), lateral (B), and oblique (C) roentgenographs show a small “chip” fracture of the anterolateral proximal radius metaphysis and very slight increased sclerosis of the proximal neck but no displacement of the epiphysis. A posterior splint was applied. Three weeks after fracture (D), there is increased sclerosis of the proximal radial neck and faint new periosteal bone along the lateral border of the neck. Three months after fracture (E), there is mature subperiosteal new bone along the lateral neck, and the epiphysis and physis are normal. The patient is normally active and asymptomatic, and examination is normal. Note normal lateral epicondyle in A, C, D, and E.

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 neurolo-gic evaluation.^49–51 This will avoid the uncomfortable situation of finding a postreduction vascular or neurologic deficit without knowing the prereduction status.

Imaging possibilities of cartilage and osseous structures are numerous. True anteroposterior and lateral roentgenographs of good quality are essential for evaluation of the injured pediatric elbow. Soft tissue as well as osseous structures must be clearly discernible. An intra-articular hematoma may displace the posterior fat pad of the distal humerus (the fat pad sign), which may be the only demonstrable change in an undisplaced or spontaneously reduced intra-articular fracture.^26,47,94 Symmetric views of the contralateral elbow provide a valuable basis for comparison in assessing injury.⁴⁸ 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,^35,81,143 and oblique views of the injured or of both elbows are also helpful.⁴⁸

In younger children in whom the cartilaginous proportion of the epiphysis is high, arthrography,^{25,26,28,36,40,42,52,143} ultrasonography,^{29,31,32,44,53} and magnetic resonance imaging (MRI)^{33,34,41,44,46,119} play important roles in defining the injury. In older children, with predominantly osseous epiphyses, tomography³⁷ and computed tomography (CT)^27,30 may be of value.

Chapters 6 and 12 of this textbook also review imaging techniques that aid in evaluating anatomy, development, and pathology of children’s elbows.

MANAGEMENT

In a study of 698 childhood fractures in all bones, only 7.4% were treated operatively.⁶

However, fractures about the elbow were operated on 50% of the time. 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.

DISTAL HUMERUS

AGES 2 TO 6 YEARS

In early childhood, the growth plate gradually becomes more oblique distally and medially, from the lateral to the medial epicondyle (see Fig. 16-1). This obliquity of the epiphyseal line 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 as early as 6 months and always by 2 years of age (see Fig. 16-1).^1,83 This ossification center is initially oval and provides valuable orientation for alignment of the radial diaphysis. In the normal elbow roentgenograph, a line drawn through the radial diaphysis always 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 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.⁸⁰ As age increases, type 2 and 3 fractures are progressively less common, presumably due to a more irregular and stable physis.

Type 4 fractures are not common at this age but are a source of frequent complication, usually nonunion. They may occur on the medial condyle, which when not ossified makes diagnosis by routine roentgenographs very difficult (Fig. 16-3). 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.

FIGURE 16-3 A 5-year-and-1-month-old boy with type 4 fracture of right medial condyle (trochlea). A, Anteroposterior roentgenograph of both elbows (the right elbow is the image on the left). Patient had swelling and tenderness medially. There is mild medial displacement of the radius on the capitellum and of the ulna on the humerus on the right as compared with the left. B, Lateral view of both elbows (the right elbow is the image on the left) shows more soft tissue swelling and less joint congruity on the right elbow. The roentgenographs were interpreted as showing no osseous injury, and no treatment was given. C, Anteroposterior and lateral views at age 8 years. The patient had no pain or functional impairment. Note slight cubitus varus and beginning ossification of displaced, nonunited medial condyle. D, At age 18 years 1 month, the patient continues to have no pain or functional impairment. E, At age 31 years 5 months, 26 years after fracture, the patient returned with ulnar sensory neuropathy. The nonunion persists, and the cubitus varus is unchanged. F, Patient lacks the final 10 degrees extension and 30 degrees flexion. Note overgrowth of the head of the radius. At the time of the original injury, the presenting clinical findings and subtle roentgenographic changes were sufficient to warrant further evaluation. Better quality routine roentgenographs, varus-valgus stress views, or an arthrogram (and today magnetic resonance imaging) should have resulted in a diagnosis. Open reduction and internal fixation would have been indicated.

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. 16-4).^{71,75,78,102,107,110,112,123,130,137} Supplemental imaging, such as arthrography, ultrasonography, or MRI, should be considered. A coronal plane transcondylar fracture pattern has been described.⁹⁸ All displaced type 5 fractures require anatomic reduction and maintenance of reduction. 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 still only cartilage, closed reduction with percutaneous pinning is also not advised. 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 fracture at this age.

FIGURE 16-4 A right-dominant boy, age 2 years 7 months, fell off a bunk bed, injuring his left elbow. A, Oblique roentgenograph shows fracture of the lateral metaphysis. This was regarded to be a type 2 injury, with good prognosis for union and subsequent growth. Note, however, that this could be a type 5 injury, with intra-articular fracture and a poor prognosis. The best way to differentiate these injuries is by arthrography or magnetic resonance imaging. B, Lateral view shows excellent alignment. A cast was applied and multiple roentgenographs in the cast over the next month showed maintenance of position. C, Cast removal 6 weeks after injury. Motion was begun. The fragment was displaced. D, Fifteen months after injury: established nonunion. It now is obvious that this was an intra-articular type 5 injury, because the lateral condyle fragment is displaced proximally. E, Two years 9 months after injury, the patient was referred for treatment. The chief complaint is increasing valgus deformity. No pain or functional impairment. F, Five weeks after osteosynthesis. G, Age 6 years 10 months: union with persistent cubitus valgus. H, Three weeks postoperative arcuate varus osteotomy. Note fracture of the proximal two Crowe pins (arrows), probably from stress of pins holding the osteotomy. The pins were removed. A cast was applied for an additional 3 weeks. I, Age 10 years 3 months: union of lateral condyle with physeal closure, and relative overgrowth of medial epicondyle and proximal radius on left. J, Right elbow comparison. K, Lateral normal right elbow. L, Lateral left elbow. Elbow flexion right, 5 degrees hypertension to 145 degrees; left, 5 to 145 degrees.

An occasional complication of any distal humeral fracture at this age is the fishtail deformity.^43,60,84,87 This occurs most commonly after supracondylar, medial, or lateral condylar fractures and consists of an L-shaped distal humeral articular surface. It is caused by premature arrest of the central portion of the physis, which may be due to central longitudinal malunion, avascular necrosis, or central physeal arrest without malunion or avascular necrosis. The deformity is often mild, with no functional impairment, but at this age can be marked with significant consequences.^18,84

LATERAL CONDYLE

Fractures of the lateral condyle are relatively common, constituting approximately 10% to 15% of all fractures in the region of the elbow (see Table 16-1). They are the most common physeal fracture of the elbow. They occur in children between the ages of 2 and 16 years¹⁰⁴ but are most common between 6 and 10 years of age.^{90,103,117,133,139,142} The mechanism of injury is usually a varus stress with the elbow in extension.¹²² The lateral condyle may fracture during elbow dislocation.¹⁴³ Less commonly, pre-existing cubitus varus may predispose to fracture of the lateral condyle.¹⁰⁶

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 intra-articular and transphyseal. The epiphyseal portion of the fracture may traverse the ossification center of the capitellum but is often entirely through cartilage and therefore not visible on roentgenographs.

Because this fracture involves both the articular surface and the physis, anatomic reduction is necessary and must be maintained until the fracture has united. If the fracture is undisplaced and stable, external immobilization by a long arm cast with the elbow in 90 degrees of flexion for 4 weeks will suffice.^104,105 Frequent roentgenographic follow-up to assess maintenance of reduction is essential. If there is displacement, reduction and internal fixation will prevent redisplacement. If the fracture can be reduced or closed, pins inserted per-cutaneously may be used for fixation to prevent redisplacement.^92,105 Some authors¹²⁹ recommend arthrography to ensure a congruent joint surface before proceeding with percutaneous pinning. In most 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.^89,110,113 Smooth pins, small in diameter, are the standard.^{101,105,115,142} Screws are preferred by some authors^126,136 and biodegradable pins by others.⁹³ 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. Pins not crossing the physis should remain in situ until there is some roentgenographic evidence of fracture healing, which occurred after approximately 6 weeks in one study.¹⁰⁵ Fractures with early pin removal can be protected with additional long arm cast.¹⁰⁵ Threaded pins predispose to premature partial physeal arrest and should not be used across a physis. Skeletal traction for elbow physeal fractures should be used only temporarily in children with multiple injuries.

In one series of 33 lateral condylar fractures, four untreated cases all developed nonunion, 12 treated by closed reduction and immobilization had six with “poor results,” and 17 treated by open reduction and nailing had three with poor results.¹⁴

Untreated and inadequately treated cases are frequently complicated by malunion and nonunion, and these cause deformity, loss of motion, degenerative arthrosis, and tardy ulnar neuro-pathy.^{10,14,90,95,99–102,110,116,126,128,131,140,144,147,156,162} There is no agreement on the management of these complications, although many authors recommend osteosynthesis, combined with corrective osteotomy for significant deformity.^{89,98,99,108,112,121,125,128,134,145}

Lateral prominence of the elbow is common after lateral condyle fracture (Table 16-4). This rarely is trou blesome or requires treatment. Varus or valgus deformity is also common (Table 16-5) 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 fol-lowing successful management of a lateral condyle fracture.^{97,118,146,147} Although this may produce measurable cubitus varus, functional impairment is rare, and treatment is often for cosmetic improvement.

Premature physeal closure^113,146 has been noted in up to 20% of lateral humeral fractures. The premature fusion is more often complete than partial. Complete physeal closure causes no angular deformity, and the cessation of growth results in only minor relative shortening compared with the contralateral humerus. This usually results in no functional or cosmetic impairment. Premature partial lateral closure sufficient to cause progressive cubitus valgus is uncommon. Partial closure of the center of the physis, where a fracture crossed the physis and epiphysis, leads to a disturbance of growth referred to as a fishtail deformity.^{10,84,101,126,142}