INTRODUCTION

Supracondylar humerus fractures are the most common fracture about the elbow in children and have the highest complication rate for elbow fractures in this age group.^8,16,39 These compelling facts continue to pique the interest and hold the attention of orthopedists who treat pediatric patients. Since the last edition of this text, issues that have generated the most discussion regarding supracondylar fracture treatment concern timing of reduction and treatment as well as pin configuration used for fracture stabilization. Both issues are addressed in the body of this chapter.

INCIDENCE AND ETIOLOGY

Supracondylar humerus fractures almost exclusively affect the immature skeleton.^41,50 Eliason²⁵ reported that 84% of supracondylar fractures occurred in patients younger than 10 years. The peak age for supracondylar humerus fracture has been reported to be between ages 6 and 7 years, and the left arm is injured more frequently than the right.^* Previous reports have suggested that supracondylar fractures are common in boys, but more recent studies have documented an equal sex distribution.^†

Traditional teaching has held that the peak incidence for extension-type supracondylar humerus fractures occurs at approximately age 7 because that is the age of maximum elbow flexibility and hyperextension. This mechanism has been confirmed by research suggesting that a fall on a hyperextended elbow produces a supracondylar humerus fracture, whereas a fall on an outstretched arm without elbow hyperextension is more likely to cause a distal radius fracture.⁶⁰ Hyperextension converts what would be an axial loading force to the elbow into a bending moment. The tip of the olecranon acts as a fulcrum, causing the fracture to occur through the relatively thin bone of the olecranon fossa (Fig. 14-1). The distinctive shape of the humeral metaphysis with the medial and lateral condyles and columns, and the narrow midpoint of the olecranon fossa, adds to the instability of the fracture, particularly when there is rotation and tilting of the distal fragment.^62,63

FIGURE 14-1 A, Transverse and sagittal sections of the distal humerus. The shaft diameter is large above the supracondylar foramen. B, However, if a cut is made through the supracondylar foramen, the “bicolumnar” nature of this region becomes evident, looking proximally (C) and distally (D).

(From Ogden, J.: Skeletal Injury in the Child. Philadelphia, Lea & Febiger, 1983.)

Knowledge of elbow anatomy is important to understanding the cause of the injury, and to understanding effective treatment principles (see Chapters 2 and 3). The stability of the elbow derives from bony and soft tissue structures.^33,61,66 Soft tissue stability on the lateral aspect of the elbow is provided by an expansion of the triceps, anconeus, brachioradialis, and extensor carpi radialis longus. The thickened periosteum of a young child, both medially and laterally, is an important additional stabilizer of the fracture fragment and provides a medial or lateral hinge during attempted reduction (Fig. 14-2). Research by Khare et al⁴⁵ has confirmed the importance of the triceps tendon’s acting as a tension band to achieve fracture stability in the flexed elbow.

FIGURE 14-2 An experimentally produced fracture shows the medial periosteal hinge and offers a glimpse of the posterior hinge. After reduction, the soft tissues hold the fragments in place. The better the reduction, the greater the security.

(From Rang, M.: Children’s Fractures, 2nd ed. Philadelphia, J. B. Lippincott, 1983.)

Because angular deformity is a common complication of these fractures, the normal variations in pediatric anatomy should be understood. The carrying angle of the elbow joint is the angle formed by the intersection of the longitudinal axis of the arm and the forearm (Fig. 14-3). The normal elbow is usually in slight valgus alignment, but this feature varies among children.^1,17,77 Smith⁷⁷ noted that, of 150 children aged 3 to 11, the carrying angle in boys averaged 5.4 degrees and ranged from 0 to 11 degrees, whereas in girls, it averaged 6 degrees and ranged from 0 to 12 degrees. Aebi¹ observed that the measurements were not constant and changed as the child matured, tending to decrease in magnitude and in variation between children.

FIGURE 14-3 A, Change in the carrying angle cannot be detected when the flexed elbows are examined from in front. B, Change in the carrying angle is apparent, however, when the flexed elbows are examined posteriorly. On the right, the bone prominences (black dots) can be seen to have tilted medially. C, With the arms extended, a 25-degree varus deformity of the right arm can be seen in a 9-year-old boy 2 years after a supracondylar fracture of the right arm. There is no limitation of motion. Note that the normal carrying angle of the left arm is 0 degrees. D, When the varus elbow is acutely flexed, the hand points laterally, away from the shoulder joint. This view also demonstrates the medial tilt of the bone prominences.

(From Smith, L.: Deformity following supracondylar fractures. J. Bone Joint Surg. 42A:236, 1960.)

Although not commonly associated with abuse in the past, a recent report found that 36% of patients younger than age 15 months at the time of their supracondylar fracture sustained the fracture as a result of abuse.⁷⁹ Clinicians must exclude “nonaccidental trauma” as a potential cause of injury whenever an infant presents with a supracondylar humerus fracture.

CLASSIFICATION

A classification system should guide treatment, provide information on prognosis, and facilitate research by ensuring that similar injuries are compared in the literature. The vast majority of supracondylar humerus fractures can be classified as either flexion or extension injuries, a distinction based on the radiographic appearance and the mechanism of injury. The distinction is important for treatment because the reduction maneuvers are essentially opposite for the two fracture types and flexion-type fractures are significantly more difficult to reduce by closed means. A small minority of fractures exhibit multidirectional instability and do not fit into either flexion or extension types.⁴⁹ Recognition of multidirectional instability is helpful in formulating an effective treatment strategy.

FLEXION-TYPE FRACTURES

Flexion-type fractures are the result of a direct fall onto a flexed elbow in which a powerful flexion force is applied to the distal humerus, usually through the olecranon. The distal humeral fragment is displaced anteriorly, and the fracture line crosses the humerus from the distal posterior to the proximal anterior aspect (Fig. 14-4). Flexion-type fractures are frequently completely displaced and are difficult to reduce by closed means. The reduction maneuver for flexion-type fractures involves elbow extension or involves using the forearm to apply a posterior-directed force to the anteriorly displaced distal fracture fragment.

FIGURE 14-4 A, Flexion-type supracondylar fracture with anterior and medial angulation. B, Lateral view. Note also that what appears to be an avulsion of the medial epicondyle is really due to the rotation of the distal humerus and the oblique orientation of the film.

TYPE I

Type I fractures are nondisplaced (Fig. 14-5). In many patients, the fracture line may not be visible on injury radiographs, but the posterior fat pad sign, palpable tenderness in the supracondylar region, and an appropriate mechanism of injury allows the physician to establish a correct diagnosis. The diagnosis is often confirmed when periosteal callus is seen on radiographs taken 3 weeks after the injury. If recognized and treated appropriately, type I fractures should never be associated with neurovascular injury or malunion.

FIGURE 14-5 A and B, Type I supracondylar fracture with an indistinct fracture line but markedly positive anterior and posterior fat pad signs. C and D, After 3 weeks of cast immobilization, fracture callus confirms the presence of a nondisplaced fracture.

TYPE II

In type II fractures, there is displacement or angulation at the fracture site, but a hinge of bone crossing the fracture keeps the fragments in continuity. The distal fragment is most often displaced posteriorly, and apex anterior angulation at the fracture site results in a hyperextension deformity (Fig. 14-6). Variations of type II fractures have also been described that involve medial impaction or rotation, which can result in cubitus varus if unrecognized (Fig. 14-7). Although there are reports of neurovascular injury associated with type II fractures, such injuries are rare.⁶⁹

FIGURE 14-6 A, Type II supracondylar fracture with apex anterior angulation. B, When treated with flexion of the elbow and casting, the injury shows excellent early alignment.

FIGURE 14-7 A, Schematic view of greenstick type II fracture that is causing medial trabecular-cortical compression leading to cubitus varus. This condition must be corrected with manipulation. B, Acute cubitus varus in a 5-year-old child with a type II fracture that was not corrected. C, Mild cubitus varus can be seen 2 years later.

(From Ogden, J. A.: Skeletal Injury in the Child. Philadelphia, Lea & Febiger, 1982.)

TYPE III

Type III fractures are completely displaced fractures in which there is no continuity between fracture fragments (Fig. 14-8). The distal fragment is displaced posteriorly and may be displaced medially or laterally as well. There is a much higher incidence of neurovascular complications with type III fractures, and soft tissue is usually interposed between fracture fragments. The brachialis muscle is most often interposed, but the median nerve, radial nerve, or brachial artery may also be entrapped.

FIGURE 14-8 A and B, Severe type III fracture with rotation and posterior and lateral displacement with associated neurovascular compromise.

DIAGNOSIS AND RADIOGRAPHIC EVALUATION

We define a supracondylar humerus fracture to be a transverse fracture crossing the entire width of the distal humeral metaphysis without involving the distal humeral physis. The primary challenge in establishing this diagnosis is to rule out other fractures of the distal humerus that do not meet these criteria. Fractures that can sometimes be confused with supracondylar humerus fractures include lateral condyle fractures, medial condyle fractures, and transphyseal fractures. Establishing the correct diagnosis is most difficult in patients younger than 4 years, whose ossific nuclei of the distal humerus are yet unossified.

Routine anteroposterior and lateral radiographs should be taken at 90 degrees to each other whenever a supracondylar humerus fracture is suspected. If the examiner is certain of the presence of a distal humerus fracture, because of focal point tenderness, mechanism of injury, and positive posterior fat pad sign, but is unable to identify the specific fracture pattern, 45-degree oblique radiographs often provide adequate visualization to establish the definitive diagnosis. On the other hand, if what may be a pathologic abnormality could possibly be a normal variant in a partially ossified distal humerus, comparison films of the opposite elbow allow identification of normal anatomy and determination of whether or not a fracture is present. Once a fracture is identified, the radiographic fracture classification system described earlier may be applied.

The anterior and posterior fat pad signs are often helpful in diagnosing intra-articular elbow fractures such as supracondylar humerus fractures (see Chapter 15). Although it is very sensitive, the anterior fat pad sign is not very specific for intra-articular elbow fractures because the coronoid fossa of the humerus (occupied by the anterior fat pad) is much more shallow than the olecranon fossa (occupied by the posterior fat pad). Any insult that causes a joint effusion may cause the anterior fat pad to become visible on the lateral radiograph. A larger intra-articular fluid collection such as fracture hemarthrosis is necessary to displace the posterior fat pad enough for it to become visible on lateral radiographs; therefore, the posterior fat pad sign is much more reliable.

Additional radiographic measurements have been described to assess fracture alignment before and after reduction. The most commonly used measurement is Baumann’s angle, the intersection of a line drawn along the longitudinal axis of the humerus and a line drawn along the physis between capitellum and distal lateral humeral metaphysis. The normal angle varies in magnitude but averages approximately 72 degrees, and it should always be compared with the uninjured contralateral elbow (Fig. 14-9).⁸⁸ A second useful radiographic reference line is the anterior humeral line (Fig. 14-10). If the capitellar ossific nucleus is displaced posterior to the anterior humeral line, fracture reduction should be considered. Fracture reduction should restore Baumann’s angle to a measurement similar to that of the opposite elbow on the anteroposterior view, and on the lateral view, it should restore the capitellum to a position in which the central third is bisected by the anterior humeral line.

FIGURE 14-9 Baumann’s angle is the angle formed by a line perpendicular to the axis of the humerus and a line tangential to the straight epiphyseal border of the lateral part of the distal metaphysis. In the case illustrated, Baumann’s angle is 80 degrees on the fractured left side and 70 degrees on the normal right side, indicating varus angulation of 10 degrees. The same holds true for lateral tilt and valgus angulation.

(From Dodge, H. S.: Displaced supracondylar fractures of the humerus in children: treatment by dental extraction. J. Bone Joint Surg. 54A:1411, 1972.)

FIGURE 14-10 The anterior humeral line (AHL). A, A line is drawn down the anterior humeral cortex. B, A second line is drawn perpendicular to the AHL from the anterior to the posterior extent of the capitellum and is divided into thirds. In normal cases, the AHL passes through the middle third of the capitellum.

(From Rogers, L. F., Malave, S. Jr., White, H., and Tachdjian, M. O.: Plastic bowing, torus and greenstick supracondylar fractures of the humerus: radiographic clues to obscure fractures of the elbow in children. Radiology 128:146, 1978.)

For all patients with supracondylar humerus fractures, the entire extremity should be examined and radiographs obtained of all areas where associated injuries might be present. Approximately 15% of patients with supracondylar fractures have an associated fracture in the ipsilateral extremity.⁸⁶ Supracondylar fracture associated with a Montaggia lesion has also been reported.^3,65

TREATMENT

The goal of treatment is to obtain and safely maintain anatomic fracture alignment, promote rapid healing, and return to full and unlimited function with minimal risk of complications. Injury severity determines the ease with which this goal is attained and the most appropriate method of treatment. For extension-type supracondylar fractures, Gartland’s radiographic classification system is a helpful guide to injury severity and optimal treatment.