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}

MEDIAL CONDYLE

Fractures of the medial condyle^{83,84,86,87,102,108,109,148–156} are much less frequent (see Table 16-1) perhaps because of normal cubitus valgus and because of the projection of metaphyseal bone between the trochlea and medial epicondyle. They occur in children of all ages, with the peak age between 6 and 10 years in most series. Fractures of the medial condyle may result from a fall on the apex of the flexed elbow or from an avulsion valgus stress injury on an extended elbow.^67,153 Marked swelling on the medial side of the elbow is usually present (see Fig. 16-3). Some occur before the trochlea is ossified. Therefore, the displaced fragment consists of a portion of bone from the medial side of the lower humeral metaphysis, along with the cartilaginous trochlea and the ossified medial epicondyle. The unossified portion of the trochlea is not seen on the roentgenograph. Thus, if the fracture occurs before ossification of the trochlea, it may be mistaken for a fracture of the medial epicondyle. If the diagnosis is not made and the injury is treated nonoperatively as an avulsion fracture of the medial epicondyle, a poor functional result can be anticipated.^82,151

In addition to the factors of articular congruity and growth plate alignment, fractures of the medial condyle are important because of its proximity to the ulnar nerve. Anatomic reduction, therefore, is mandatory to avoid tardy ulnar palsy as well as nonunion or malunion. These fractures usually require open reduction and rigid internal fixation. Only if the fracture is undisplaced may this fracture be treated by cast immobilization alone.¹⁵⁰ The complication rate is high.¹⁵⁵

Fractures may involve both condyles, with a split through the center of the articular surface (Fig. 16-5D).¹⁶¹ These fractures are analogous to the adult T-intercondylar fracture, are frequently comminuted, and fortunately, are not common. They are often the result of direct force and therefore may be open fractures. This is an unstable situation that requires open reduction and internal fixation.⁹

FIGURE 16-5 Common distal humeral physeal fractures at ages 10 years to maturity. Normal distal humerus (A), type 5 injury of the lateral condyle (B), type 5 fracture of the medial condyle (C), type 5 fracture of both medial and lateral condyles (D).

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

MEDIAL EPICONDYLE

The medial epicondylar apophysis is extra-articular and is usually roentgenographically present (ossified) by age 5 years (see Fig. 16-1). Multicentric ossification centers have been demonstrated and give a fragmented appearance. Awareness of this normal variant may obviate misdiagnosis. The medial epicondyle matures slowly and is the last of the six epiphyses of the elbow to unite with its adjacent metaphysis; as late as the 19th year in men.⁴

The medial epicondyle is located slightly posteriorly, rather than strictly medially, which may cause confusion in roentgenographic interpretation.⁴ Oblique roentgenographs of both elbows are sometimes necessary to determine whether the epicondyle on the injured side is in an abnormal position.

Fractures of the medial epicondyle constitute nearly 10% of all fractures of the elbow region (see Table 16-1),⁴⁷ and usually occur between 9 and 15 years of age.^{6,165,166,173} The injury is unusual in younger children. The mechanism of injury is usually a valgus stress of the joint, which produces traction on the medial epicondyle through the flexor muscles. Arm wrestling is not a common activity among children but may result in this fracture.^172,173 The fracture is usually type 3, although types 2, 4, and 5 have been noted.^6,9 The epicondyle is always displaced distally because of the pull of the flexor muscle mass origin. It may be dislocated into and entrapped in the elbow joint, associated with opening of the joint by valgus stress. The entrapped epicondyle must be extracted from the joint and reduced. This is best done by open surgery, because manipulative maneuvers are unlikely to remove it from the joint, reduce it, and render it stable. About half of the cases are associated with partial or complete dislocation of the elbow,^{164,169,170,175} usually posterolateral dislocation.

Nowhere in the discussion of physeal injuries of the elbow is there a greater divergence of opinion concerning treatment than in medial epicondylar fractures. Recommendations range from performing open reduction in virtually all cases, to no surgical treatment for any case (other than for intra-articular epicondyle entrapment). The fear of painful pseudarthrosis following nonoperative treatment has been cited for using open reduction and internal fixation in nearly every case, even with minimal (1-mm) separation.⁹ Conversely, cases treated nonoperatively are reported to do relatively well for many years, despite a high rate of nonunion.^168,171

Any hypesthesia, paresthesia, or paralysis in the ulnar nerve distribution is an adequate reason for exploration, inspection of the nerve, and replacement of the fragment. If the ulnar nerve is found to be constricted or contused, it may be transposed anterior to the medial condyle.^85,91 This is rarely necessary.^153,167

In North America, 2 mm of displacement seems to be a commonly used criterion to determine treatment of physeal fractures in general. If the medial epicondyle is displaced 2 mm or less, the elbow may be immobilized for 3 weeks in a long arm cast, with the elbow in moderate flexion and the forearm in pronation. Oblique roentgenographs or comparison roentgenographs of the normal opposite elbow may be helpful in determining the degree of displacement. If the medial epicondyle is displaced more than 2 mm or rotated, or if the elbow joint is unstable on application of valgus stress, open reduction and internal fixation are indicated. The gravity stress test is a useful diagnostic test for acute medial instability.¹⁷⁹ Displaced fractures of the medial epicondyle, if left untreated, frequently progress to malunion or nonunion (Fig. 16-6). Tardy ulnar palsy is a common late problem despite relatively good elbow motion and freedom from symptoms for several years.¹⁷¹

FIGURE 16-6 A 15-year-and-8-month-old boy with tardy ulnar nerve palsy secondary to nonunion of a previous medial epicondyle fracture. Note hypertrophy of the epicondyle but lack of growth of the medial metaphysis.

The medial epicondyle can sometimes be reduced by closed means but cannot be held reduced. Percutaneous pinning is hazardous because of the proximity of the ulnar nerve. Therefore, open reduction and internal fixation with two smooth Kirschner wires, one screw, or absorbable rods and screws, is frequently performed.^168,174,178 It is usually not necessary to mobilize the ulnar nerve, although if the epicondyle is markedly displaced, this maneuver may be helpful in gaining exposure. Kirschner wires should be removed after 3 weeks and active motion begun. Potential complications after pinning, however, include pseudarthrosis, an ulnar sulcus, a double-contoured epicondyle, hypoplasia, or hyperplasia.¹⁷⁶

The physis of the epicondyle often closes after fracture, but because it does not contribute to longitudinal length⁴ and because the epiphysis does not articulate with the ulna, problems due to growth arrest are rare or nonexistent. This is particularly true because most of these children are near maturity and the other physes about the elbow have already closed.

Because of the proximity of the ulnar collateral ligament, elbow stability should be examined after fracture healing. Severe chronic medial instability, and even recurrent elbow dislocation, although rare, may occur after fibrous union of a displaced fracture.^177,179 Treatment options include osteosynthesis of the fragment to the condyle or excision of the fragment.

LATERAL EPICONDYLE

The ossification center of the lateral epicondyle appears at about age 10 years (see Figs. 16-1 and 16-8A) and fuses with the lateral condyle at 14 years of age.² Its ossification characteristics are prone to misinterpretation as an avulsion or chip fracture of the lateral metaphysis because (1) it ossifies as a smooth, thin, curved sliver of bone; (2) it is well separated from the humerus; and (3) the distal part usually fuses with the capitellum before the proximal part unites with the adjacent humeral shaft. As the epiphysis matures, its outline usually becomes smooth and well defined, but it may be irregular.²

Fracture of the lateral epicondyle is uncommon (see Table 16-1), and is usually associated with other elbow injuries. Separation fracture may accompany elbow dislocation.¹⁸⁰ Isolated fracture of the lateral epicondyle is rare.^9,65 In most cases, there is relatively little displacement of the fragment. Immobilization of the elbow for 3 to 4 weeks usually is sufficient. Open reduction and internal fixation are usually unnecessary because these injuries tend to occur only in children approaching the age of skeletal maturity. The risk of associated growth arrest is minimal or nonexistent. Tardy ulnar nerve palsy has been reported.⁹¹

PROXIMAL RADIUS

The epiphysis of the radial head begins to ossify at about the age of 5 years. Although it may appear first as a sphere, ossification soon advances into one or two ovoid, flat, or wedge-shaped nuclei, which may be eccentrically located on the radial metaphysis⁴⁵ and misinterpreted as an avulsion fracture of the epiphysis. Notches and clefts in the proximal radial metaphysis may closely resemble post-traumatic appearances.³

By definition, radial head fractures in children (age 0 through 16 years) are those that include the physis (Fig. 16-7). If these fractures appear in older children in whom physis is closed, they include the articular surface.^18,184 Radial neck fractures are metaphyseal, entirely distal to the physis. Physeal fractures 1, 2, 5, and 6 also involve the metaphysis, but because the major problem is physeal or articular cartilage involvement, they all qualify as fractures of the head. Of all pediatric elbow fractures, 10% to 15% involve the radial head and neck (see Table 16-1).^18,191 Of these head and neck fractures, approximately 50% involve the head and 50% the neck (Table 16-6).¹⁸ Proximal radial physeal fractures account for only 0.6% of all physeal fractures.^18,20

The normal valgus carrying angle of the elbow causes compression laterally during a fall on the outstretched arm. This drives the capitellum against the outer side of the head of the radius, tilting it and displacing it outward. The fracture may be, therefore, type 1, 2, 3, 4, or 5 (see Fig. 16-7), with type 1 being most common (Table 16-7). A second mechanism of injury is associated with posterior dislocation of the elbow with simultaneous compression of the capitellum on the anterior portion of the head of the radius.¹⁸⁷ This has the potential to produce the more serious type 4 and 5 fractures.

The joint capsule is attached to the radius in continuity with the annular ligament. Because the radial neck lies outside the joint capsule, fracture of the neck may not cause joint effusion or fat pad displacement. Fracture of the radial head, however, usually produces elbow effusion and a positive fat pad sign.³

Differentiating fractures that involve only the neck of the radius (metaphysis) from those that also involve the physis (head) can be difficult. Oblique roentgenographs and occasionally MRI can be helpful in making this differentiation.

The type 1 fracture is common (see Table 16-7), but may be difficult to diagnose. It is usually incorrectly called a neck fracture or type 2 fracture (Fig. 16-8). It is distinguished by a transmetaphyseal fracture with fracture extension to the physis. The transmetaphyseal fracture is often only a compression fracture that may not be visible on the initial roentgenographs. Transmetaphyseal sclerosis, however, is always present 3 to 6 weeks after fracture and verifies the compression component. The fracture line extending to the physis is also frequently difficult to visualize on routine anteroposterior and lateral views and is often best seen on oblique views. This may be only a fracture line, but often there is a displaced corner of metaphysis that may be called a “chip” fracture. Most importantly, however, is that there is no fracture transversely within the physis and the epiphysis is not displaced. Therefore, this is not a type 2 fracture. These fractures need only temporary external immobilization and invariably heal without sequelae.

If a type 2 or 3 fracture is minimally displaced or can be manually reduced, immobilization for 3 to 4 weeks will suffice.¹⁸³ A wire or a hook inserted percutaneously can be used to manipulate a mildly or moderately displaced head into position.^9,181 Occasionally, with a type 3 fracture, the entire epiphysis will be inverted or even displaced through the joint capsule, and closed reduction is not possible. In this instance, open reduction is necessary. After surgical reduction, the fracture is often stable, and no internal fixation is necessary.^9,189 Immobilization, with the elbow in 90 degrees of flexion and the forearm in neutral rotation, is satisfactory.

If the surgical reduction is unstable, internal fixation with two crossed Kirschner wires¹⁸⁸ or with one longitudinal wire through the capitellum ossification center extending across the radiocapitellar joint into the intramedullary cavity of the radial diaphysis can be considered.^9,186,189 Each method of internal fixation should be supplemented with a long arm cast. The wires may be removed in 3 weeks and gentle protected motion using a collar and cuff begun. If a single longitudinal wire is used, it should be stout enough to avoid wire breakage at the joint level.⁹ If this occurs, removal of the portion of wire embedded in the radius can be difficult, and it may be less damaging to leave the wire permanently in the radius.

Introducing a wire in the distal radius and passing it proximally up the intramedullary canal across the fracture site into the proximal fragment is an appropriate method for reducing or fixing a radial neck fracture, but this procedure is difficult to accomplish in a physeal fracture without further displacing the head.

Type 4 and 5 injuries require precise anatomic reduction to restore articular congruity. Open reduction and internal fixation with tiny transverse or oblique Kirschner wires will help prevent displacement of the fragments during healing. Premature closure of the physis nearly always occurs,^184,187,190 but because the proximal radius accounts for only 20% of the growth of the radius and because type 4 and 5 injuries often occur in older children, problems from growth arrest are rare.¹⁸² Functional impairment, however, particularly limited forearm rotation, is common after type 4 and 5 injuries.¹⁸⁴ The presence of associated fractures in the humerus and ulna reduces the chance of a favorable outcome.¹⁸⁵

Type 6 fracture (a part missing) (see Fig. 16-7) is always an open injury and usually results in functional impairment.^18,21 Regardless of how little physis is lost, the remaining physis always stops growing. Late reconstructive surgery is usually necessary.

Most radial head physeal fractures result in premature complete physeal closure and eccentric enlargement of the radial head.¹⁸⁵ Abnormal cam motion may occur during forearm rotation, and this may be painful. Excision of the radial head in a growing child will result in distal radial-ulnar length variance and should be avoided. After the patient reaches maturity and has joint pain or limited motion, the radial head may be excised with little risk of development of wrist deformity.⁸⁵ However, excision of the head rarely restores motion. Thus, the primary indication for excision of the radial head is pain.

The radial head blood supply is through the articular capsular and periosteal vessels. Although these structures are frequently damaged at the time of fracture, ischemic necrosis of the head is uncommon. Treatment considerations relate more to the degree of displacement and angulation, than to the fear of ischemic necrosis.

PROXIMAL ULNA

The proximal ulnar growth apparatus has features of both an epiphysis and an apophysis.¹⁹⁵ Because the proximal ulnar physis produces longitudinal growth and has articular involvement, it is included as an epiphysis.

The olecranon is the cartilage/bone projection of the proximal ulna. Its anterior aspect forms the articular surface with the humeral trochlea. As such, the olecranon includes the epiphysis, physis, and most of the metaphysis. Early in life, the physis is L-shaped, extending from the transverse metaphyseal-epiphyseal interface anteriorly and distally as part of the thick subchondral articular surface, to beneath the coracoid process (Fig. 16-9A). With growth, the epiphysis becomes a relatively smaller portion of the olecranon (see Fig. 16-9B, and C). In this sense, the physis “migrates” proximally, and has been called the “wandering physeal line.” The extent of this proximal migration varies among children.⁴⁷ In the majority of children, the physis continues to migrate proximally and obliquely until it is completely extra-articular (see Fig. 16-9C). This usually occurs by age 12 years. In the minority, the physis remains relatively transverse and closes while its anterior edge is still intra-articular (see Fig. 16-9D).

FIGURE 16-9 Proximal ulnar anatomy and growth. A, In infancy the physis is transverse and extends anteriorly and proximally beneath the coracoid. Almost the entire articular surface is part of the epiphysis. B, The ossification center first appears at age 9 years and is separated from the metaphysis more widely than in other epiphyses. The physis is now located relatively closer to the proximal end of the bone. This is called the “wandering physeal line.” The physis still extends anteriorly and distally beneath the entire joint surface. C, By age 12 years, the physis has “migrated” proximally to become entirely extra-articular in most people. In this case, the features of an apophysis now predominate. D, In the minority of individuals, the “migration” ceases while the anterior edge of the physis is still intra-articular. In this case, the features of an epiphysis still predominate.

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

The secondary center of ossification first appears at age 9 years in girls and 11 years in boys.⁴⁷ The epiphysis initially often has two, sometimes three, and occasionally several ossification centers.⁵ The physis is usually closed by the end of the 16th year.¹⁹⁵

Fractures of the proximal ulna account for 5% to 10% of children’s elbow fractures (see Table 16-1), and are often accompanied by other elbow fractures. Most fractures of the olecranon primarily involve metaphyseal bone distal to the physis (Fig. 16-10M).⁸⁵ Fractures of the proximal ulnar physis account for only 0.3% of all physeal fractures.^18,20 When the physis is involved, the fracture is usually a type 2 injury (see Fig. 16-10, 2a and 2b), occasionally a type 3 injury (see Fig. 16-10, 3). In type 2 injuries, the fracture line in the metaphysis may be oblique (as shown) or may enter the ulnar shaft more longitudinally. Because the proximal fragment contains articular surface, these fractures require anatomic reduction and maintenance of reduction until the fracture has united. Frequently, this can be accomplished by closed means, immobilizing the elbow in extension. However, if displacement is more than 3 mm, open reduction and internal fixation are advised.¹⁹³ Fixation may be accomplished by longitudinal Kirschner wire or a wire loop, or in older children, a tension band wire. A longitudinal screw should not be used in a young child if significant growth remains.⁹ However, growth arrest problems are rare.^196,199 Excision of the fragment, which is sometimes performed in adults, should be avoided, particularly in young children. In older children, who subject their upper extremities to excessive stress, delayed physeal closure can simulate a nonunion,^197,198 sometimes called a stress or chronic type 3 fracture. Fracture of the coronoid apophysis is rare.¹⁹²

FIGURE 16-10 Peterson classification of proximal ulnar physeal fractures in children.²² M, Fracture of the metaphysis. 1, Type 1 fracture with greenstick or longitudinal split fracture. There is a torus or transmetaphyseal fracture with extension of the fracture proximally to the physis. The arrow suggests compression force originates proximally from the epiphyseal side. However, this has not been proven and distally applied pressure could result in compression if the elbow is in full extension at the moment of impact. This fracture has been noted to occur only before ossification of the epiphysis. 2a, Type 2 fracture with anterior metaphyseal fragment. 2b, Type 2 fracture with posterior metaphyseal fragment. 3, Type 3 fracture.³⁸

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

Children with osteogenesis imperfecta are apparently prone to proximal ulnar type 2 anterior fracture-avulsions (see Fig. 16-10, 2a). Internal fixation is commonly used, and although fracture union is the rule, refracture can occur.^194,199

GROWTH ARREST

Growth arrest frequently occurs following any elbow physeal fracture. The older the child, the more likely its occurrence. The entire involved physis usually closes. Partial premature closure with resulting angular deformity is rare.

Because the elbow physes contribute only 20% of the longitudinal growth of the humerus and forearm, the growth arrest lines that usually occur after any significant bone injury are indistinct at best. Rarely can these lines be used as a measure of growth or as an indication of a growth arrest problem, as they are in other long bones.

Because each of the three elbow physes contribute only 10% of the entire upper extremity length, complete closure of any or all of these physes rarely, if ever, causes significant arm length discrepancy. Any resulting discrepancy is mild and causes no functional impairment and few, if any, cosmetic or clothes-fitting complaints. Even if complete closure of all physes about the elbow occurred in a young child, surgical lengthening of the involved humerus or forearm bones or surgical arrest of the contralateral elbow physes would rarely, if ever, be indicated.

Premature partial closure of the distal humerus, or proximal radius or ulna, is very rare. Premature partial closure of the medial or lateral humeral condyle theoretically may result in progressive cubitus varus or valgus, respectively. This could be determined only after many months of follow-up. In this rare occurrence, surgical closure of the remaining physis might be considered. Of 178 bar excisions for premature partial closure performed at Mayo Clinic between 1968 and 1997, none involved the elbow.¹⁸ Supracondylar osteotomy to correct angular growth is rarely necessary.

Premature closure of the central physis between the medial and lateral humeral condyles occurs occasionally and has been called a fishtail deformity.^18,84 The underlying cause of the arrest is multifactorial and may be due to a gap in reduction of an intracondylar fracture, avascular necrosis of the central or trochlear portion of the epiphysis, or central premature physeal arrest (bar formation) without a gap or avascular necrosis. This usually occurs in younger children and causes no pain and only minimal loss of motion. With growth, the deformity can, however, gradually progress to premature degenerative arthrosis and functional disability. The intercondylar notch may also predispose to subsequent intercondylar fracture. Thus, if the fishtail deformity is identified in a young child, surgical closure of the medial and lateral portions of the physis may prevent the deformity from progressing and result in only minimal additional humeral length discrepancy.

An occasional concern is damage to the physeal cells between the medial humeral metaphysis and the trochlea in young children. Because the trochlear ossification center has not ossified at this early age, this damage cannot be diagnosed by routine roentgenographs, tomographs, arthrograms, CT scan, or scintigraphy. In the future, MRI may have the ability to evaluate such an injury early. It is often necessary to observe these cases for months or years in order to make the diagnosis of premature partial physeal arrest.