Humerus and Elbow

Perspective

Because injuries in the region of the elbow have a high potential for complications and residual disability, early recognition of neurovascular and soft tissue complications improves the outcome in many of these injuries. Coordination between the emergency physician and the treating orthopedist is essential, particularly because new options are emerging for many of these injuries.

Anatomy

The humerus is a long bone that articulates proximally at the shoulder with the glenoid of the scapula to form the glenohumeral joint and distally with the radius and ulna to form the three-way elbow joint. The upper end of the humerus, the humeral head, is shaped like a near hemisphere. Adjacent to the humeral head are two bony prominences, the greater and lesser tuberosities. Between these, on the anterolateral aspect of the humerus, runs the bicipital groove. The shaft of the humerus extends from the upper border of the insertion of the pectoralis major muscle superiorly to the supracondylar ridges inferiorly. The shaft is cylindrical on cross section in the upper half and tends to become flat in the distal portion in an anteroposterior direction. Three surfaces are described. The anterolateral surface presents the deltoid tuberosity for the insertion of the deltoid muscle, and below this is the radial soleus, which transmits the radial nerve and profunda artery. The anteromedial surface forms the floor of the intertubercular groove, but it normally has no outstanding surface markings. The posterior surface is the origin for the triceps and contains the spiral groove.

The bony anatomy of the distal humerus and elbow is diagrammed in Figure 52-1. The distal end of the humerus tapers into two columns of bone, the medial and lateral condyles. Between the condyles, the bone thins, and the recess created is the coronoid fossa. The more proximal nonarticular portions of the condyles are the epicondyles. Just proximal to the epicondyles, the supracondylar ridges run up each side of the humerus. Collectively, these areas serve as points of origin for the muscles of the forearm. The wrist flexors originate from the medial epicondyle, and the wrist extensors originate from the lateral epicondyle. Fractures of the distal humerus often result in fragment displacement because of the pull of these strong forearm muscles on attachment sites.

Figure 52-1 Bony anatomy of distal humerus and elbow region. A, Anterior view. B, Posterior view. C, Posterior view, 90 degrees flexion. D, Lateral view. Right elbow is shown. (Adapted from Connolly JF: DePalma’s Management of Fractures and Dislocations. Philadelphia, WB Saunders, 1981.)

The bony anatomy of the elbow allows for two complex motions: flexion-extension and pronation-supination. The elbow is composed of three articulations within a common joint cavity. The trochlea is the articular surface of the medial condyle and articulates with the deep trochlear notch of the ulna formed by the olecranon inferiorly and posteriorly and by the coronoid process anteriorly. This articulation permits hinged flexion and extension at the elbow. The articular surface of the lateral condyle is the capitellum, which permits the radius to hinge on the elbow. The proximal radius consists of a disklike head supported by the smooth narrow radial neck. The radial head articulates with the capitellum of the humerus and with the radial notch of the ulna.

Four ligamentous structures are important in evaluating elbow injuries (Fig. 52-2). The radial head is held in place by the annular ligament and the adjacent radial collateral ligament. Rotation of the radial head within the confines of the fibrous annular ligament permits pronation and supination. In addition, the ulnar collateral ligament and anterior capsule add stability to the joint. Fracture or dislocation of the joint may severely damage the ligamentous structures.

Figure 52-2 Ligamentous structures of elbow. (From Simon R, Koenigsknecht S: Emergency Orthopaedics: The Extremities, 2nd ed. Norwalk, Conn, Appleton & Lange, 1987.)

The soft tissues of the upper arm are divided into two compartments: anterior and posterior. The anterior compartment contains three muscles—the biceps brachii, the brachialis, and the coracobrachialis—and the brachial artery, median nerve, musculocutaneous nerve, and ulnar nerve. The only two structures contained in the posterior compartment are the triceps brachii muscle and the radial nerve.

The neurovascular structures of this area are shown in Figure 52-3. The brachial artery, which is the continuation of the axillary artery, travels with the median nerve in the anterior compartment of the upper arm. It enters the antecubital fossa and bifurcates into the radial and ulnar arteries.

Figure 52-3 Neurovascular structures of elbow region. Volar surface of left elbow is shown.

One important anatomic variation is the presence of a supracondylar process (in approximately 2.5% of cases) just proximal to the medial epicondyle (Fig. 52-4). When the supracondylar process is present, the median nerve and brachial artery must traverse behind this process, then forward between a fibrous band connecting the process to the epicondyle. Median nerve symptoms may develop if this process is fractured or if an injury causes swelling in the vicinity of the supracondylar process.

Figure 52-4 Supracondylar process of the humerus (arrow). Volar surface of right elbow is shown.

The radial nerve leaves the axilla and spirals posteriorly around the humerus between the heads of the triceps in the radial groove. It reenters the anterior compartment of the arm laterally, crossing the elbow anterior to the lateral epicondyle to innervate the extensors of the wrist and fingers. Because of its close relationship to the shaft of the humerus, the radial nerve is particularly susceptible to injury with midshaft humeral fractures. Fixed in position by the intermuscular septum, the nerve may become trapped between fracture fragments, particularly when reduction is attempted.

The ulnar nerve runs parallel to the median nerve. Halfway down the arm, it penetrates the intermuscular septum to run along the medial aspect of the triceps muscle in the posterior compartment. It enters the forearm by passing behind the medial condyle. Fractures in the vicinity of the medial condyle place this nerve at considerable risk for injury.

Three elbow bursae are clinically important. The olecranon bursa is located between the olecranon and the skin posterior to the joint. This bursa provides protective padding and allows smooth movement of the skin over the olecranon. Because of its position, it is often a site of traumatic or infectious bursitis. The radiohumeral bursa provides for smooth movement over the radial head with supination and pronation. A third bursa cushions the biceps tendon from the radius during flexion of the elbow. As evident by the descriptions of these structures, all are vulnerable when significant skeletal injury occurs in this region.

Clinical Features

History

A history detailing musculoskeletal complaints includes a description of any pain in terms of quality, duration, location, palliative and provocative activities, severity, and radiation. Past medical history and occupational factors are important in chronic problems. For traumatic injuries, a detailed account of the incident is important because it provides information about the mechanism of injury and some estimate of the energy delivered. Subjective complaints of numbness or weakness distal to the injury are important clues to possible neurovascular injury. In dealing with injuries in children, the possibility of nonaccidental trauma needs to be considered.

Physical Examination

Inspection of the upper extremity is important, but manipulation of the painful extremity should be minimized and postponed to the end of the examination whenever possible. This is especially important with children. A great deal of useful information can be gathered by simple inspection and comparison with the contralateral limb. The position in which the extremity is held should be noted. In children with extension-type supracondylar fractures, the arm is held at the side and has a characteristic S-shaped configuration, whereas with flexion-type supracondylar fractures, the forearm is supported with the opposite hand with the elbow flexed to 90 degrees. Patients with radial head subluxation have the elbow only slightly flexed and hold the forearm in pronation.

Deformity is evidence not only of significant injury, but also of the type of injury. Increased prominence of the olecranon suggests a posterior dislocation of the elbow or extension supracondylar fracture, whereas loss of the normal olecranon prominence indicates anterior dislocation or flexion supracondylar fracture. The extremity also should be inspected for wounds that may indicate an open fracture, evidence of swelling, and change in color of the distal extremity.

One special aspect of the elbow examination is the determination of the carrying angle, the normal outward angulation of the extended forearm at the elbow. This angle allows the long axes of the humerus and forearm to become superimposed when the elbow is flexed (Fig. 52-5). This angle varies from 5 to 20 degrees in adults, with men having less angulation than women. Measurement of the carrying angle is helpful in assessing subtle supracondylar fractures in children. As shown in Figure 52-6, lines drawn parallel to the shafts of the humerus and ulna intersect to form an angle with a mean measurement in children of 13 degrees, although this angle varies widely.¹ A difference in carrying angles of greater than 12 degrees (from one side to the other for a particular individual) is associated with fractures. However, the carrying angle is used primarily for assessing the adequacy of reduction or the results of fracture healing rather than for acute diagnosis, because it is difficult for children to fully extend the arm during the initial evaluation for this measurement to be obtained.

Figure 52-5 Carrying angle (3) is formed by intersection of lines drawn parallel to long axis of humerus (1) and ulna (2). (Adapted from Ruiz E, Cicero J: Emergency Management of Skeletal Injuries. St Louis: Mosby; 1995.)

Figure 52-6 A, The axis of the elbow joint bisects the angle formed by the long axes of the humerus and forearm. B, This allows these axes to become superimposed when the elbow is flexed. C, If the axis of the elbow joint was perpendicular to the long axis of the forearm, the respective axes would diverge when the elbow was flexed, as shown in D.

The vascular status of the extremity is of highest priority. Brachial, radial, and ulnar pulses should be palpated and documented. The ulnar pulse is not palpable in some normal people. Although brisk capillary refill suggests adequate tissue perfusion, a hand-held Doppler device often is required to evaluate major vessel flow if significant swelling is present or if the pulses are not palpable. Any suggestion of arterial injury requires immediate investigation. Poor perfusion may result from direct arterial injury, compression or kinking in the instance of significant displacement from a fracture or dislocation, or compartment syndrome. Passive extension of the fingers produces severe pain in the forearm in the presence of flexor (volar) compartment ischemia. Of the five Ps associated with arterial occlusion (pain, paresthesia, pallor, pulselessness, and paralysis), pain is the only dependable early sign of compartment syndrome. Orthopedic consultation and measurement of compartment pressures should be considered for patients who have pain disproportionate to their injury. Other modalities used to evaluate vascular status while the orthopedist is being called in include measurement of the ankle-brachial index and color flow Doppler.

Neurologic evaluation includes assessment of the radial, median, and ulnar nerves. After evaluation of neurovascular function, all bony prominences are palpated, and areas of tenderness are noted carefully and documented. Crepitus and bony deformities are unusual in the absence of fracture or dislocation. Bony crepitus associated with pain in an acutely injured limb is virtually diagnostic of a fracture. The radial head specifically should be palpated for tenderness, and any noticeable effusion should be noted.

The range of motion of the elbow in all planes (i.e., flexion-extension and pronation-supination) should be determined and documented. With the forearm supinated, the normal range of motion is 0 degrees in full extension to 150 degrees in full flexion. A mild degree of hyperextension is normal in some individuals and should be symmetrical. With the elbow flexed at 90 degrees and the thumb facing up, the forearm normally supinates and pronates 90 degrees. Range-of-motion testing may be impossible with severe injuries and can be postponed until after radiographic evaluation, avoiding manipulating fractures and dislocations. Any manipulation of the extremity is followed by reexamination because neurovascular injury has been reported with nearly every therapeutic procedure.

Radiographic Findings

Whereas most elbow and humerus injuries are evaluated radiographically, occasionally history and clinical examination alone are sufficient (e.g., radial head subluxations). Although clinical decision rules for the elbow have not been validated, it is reasonable to perform radiography when there is significant limitation in range of motion, obvious deformity, joint effusion, or significant tenderness over any of the bony prominences or the radial head. In the absence of these, radiographic studies are optional. The threshold for radiography should be much lower in pediatric populations owing to the presence of open growth plates and limitation in the physical examination with the exception of children with obvious nursemaid’s elbow (radial head subluxation).

Routine views of the elbow include at least the anteroposterior and lateral views, with consideration given to obtaining oblique views for certain injuries. Anteroposterior and oblique views are taken with the elbow extended. The lateral view is taken with the elbow in 90 degrees of flexion and the thumb pointing upward. Positioning of the elbow is important because anything but a true lateral view makes accurate interpretation of soft tissue findings and alignment difficult. Corresponding views of the opposite extremity may be helpful, especially for children, but should not be ordered routinely.

Many fractures in the elbow region are obvious on plain film, with cortical disruption, angulation, or displacement of fragments. Minor fractures can be subtle and may be missed. Special attention to the contour of the radial head and the fat pads reduces the risk of missing fractures. The normal cortex of the radius is smooth and has a gentle continuous concave sweep. If consistent with history and physical findings, any disruption of this smooth arc is considered evidence of fracture. Abnormalities within the soft tissues on elbow films are particularly important and may be the only radiographic sign of a fracture. Normally, fat surrounding the proximal elbow joint is hidden in the concavity of the olecranon and coronoid fossae. The normal elbow has only a narrow strip of lucency anteriorly (the anterior fat pad), and a posterior fat pad is not visible on radiographs. Injuries that produce intra-articular hemorrhage cause distention of the synovium and displace the fat out of the fossa, making the posterior fat pad visible on lateral radiographic views. The anterior fat pad also is altered by this swelling, becoming more prominent and taking the shape of a spinnaker sail from a boat: “sail sign” (Fig. 52-7). In the setting of trauma, more than 95% of patients with the “posterior fat pad” sign have intra-articular skeletal injury. These soft tissue findings occur even with subtle fractures, and when they are present in the setting of trauma, an occult fracture is considered to be present even when not visible on radiographs. In adults, a radial head fracture is implied, whereas in children a supracondylar fracture is the more likely underlying injury. In the absence of trauma, the presence of a fat pad suggests other causes of effusion (e.g., gout, infection, bursitis). The fat pad signs may be absent in fractures where the injury is severe enough to rupture the capsule.

Figure 52-7 A, Anterior and posterior fat pads on lateral study (arrows). B, The anterior fat pad is normally a thin radiolucent stripe; the posterior fat pad is now visible. C, An effusion displaces both fat pads. This posterior fat pad is now visible.

The anterior humeral line is a line drawn on a lateral radiograph along the anterior surface of the humerus through the elbow. Normally, this line transects the middle third of the capitellum (Fig. 52-8). With an extension supracondylar fracture, this line either transects the anterior third of the capitellum or passes entirely anterior to it. The abnormal relationship between the anterior-humeral line and capitellum may be the only evidence of a minimally displaced supracondylar fracture and is a presumptive finding of a fracture.

Figure 52-8 A, A line drawn down the anterior surface of the humerus on a lateral film should transect the middle of the capitellum. B, With an extension supracondylar fracture, the line passes more anteriorly. (From Simon R, Koenigsknecht S: Emergency Orthopaedics: The Extremities, 2nd ed. Norwalk, Conn, Appleton & Lange, 1987.)

Another diagnostic aid in evaluating radiographs of possible supracondylar fractures in children is the determination of Baumann’s angle. As shown in Figure 52-9, the intersection of a line drawn on the anteroposterior film through the midshaft of the humerus and the growth plate of the capitellum defines an angle of approximately 75 degrees. In normal children, Baumann’s angle is the same in both elbows, and it has been suggested that a comparison between the injured and uninjured sides be used to assess the accuracy of reduction. An increase in Baumann’s angle indicates medial tilting of the distal fragment. Alteration in Baumann’s angle is thought to predict the final carrying angle when the fracture heals, although there is controversy regarding its reliability.²

Figure 52-9 Baumann’s angle as measured on anteroposterior film. (From Worlock P: Supracondylar fractures of the humerus. J Bone Joint Surg [Br] 68:755, 1986.)

Radiographic evaluation of the elbow in children is difficult because of the presence of multiple ossification centers (Fig. 52-10). Table 52-1 lists the typical age of first appearance and fusion of ossification centers, which gives rise to the CRITOE acronym:

Table 52-1

Ossification Centers of the Elbow: CRITOE

OSSIFICATION CENTERS	AGE OF APPEARANCE
Capitellum	1-2
Radial head	4-5
Internal (medial) epicondyle	4-5
Trochlea	8-10
Olecranon	8-9
External (lateral) epicondyle	10-11

Figure 52-10 Secondary growth centers of the elbow. (1) Capitellum; (2) radial head; (3) medial epicondyle; (4) trochlea; (5) olecranon; (6) lateral epicondyle. (From Townsend DJ, Bassett GS: Common elbow fractures in children. Am Fam Physician 53:2031, 1996.)

• Capitellum

• Radial head

• Internal (medial) epicondyle

• Trochlea

• Olecranon

• External (lateral) epicondyle

Comparison views of the uninjured elbow are often helpful in distinguishing fractures from the normal epiphyses and ossification centers.

Management

General management principles for humerus and elbow injuries are similar to those for other orthopedic injuries. Limb-threatening conditions, such as vascular injury, are addressed immediately by reduction of fractures or surgical exploration. The limb should be splinted in a position of comfort, and appropriate analgesia should be provided. Antibiotics are administered for suggested open fractures. Prolonged immobilization of the elbow frequently results in stiffness of the joint that requires extensive physiotherapy to restore normal function. For this reason, range-of-motion exercises are begun early in the convalescent period, often before a fracture has healed completely.

Fractures

Injuries in the region of the shaft of the humerus and about the elbow fall into several categories (Box 52-1). Emergency department (ED) management varies with location and type of fracture or dislocation. Supracondylar fractures of the humerus in children are usually described according to the Gartland classification (Box 52-2).

BOX 52-1 Classification of Fractures

I Humerus fracture

A Shaft of the humerus fractures

B Distal humerus fractures

c. Separated and rotated

d. Combination with articular surfaces

II Radial head fracture

BOX 52-2 Gartland Classification for Supracondylar Fractures in Children

Type I—Minimal or no displacement

Type II—Displacement of the fracture, but with the posterior cortex intact

Type III—Displaced, no cortical contact

Type IIIA—No rotation of the fracture

Type IIIB—Rotation present

Fractures of the Shaft of the Humerus

Pathophysiology

Fractures of the humeral shaft commonly result from a direct blow to the arm, such as occurs during a fall or motor vehicle collision. Severe twisting of the arm or a fall on an outstretched hand can also produce this type of fracture. Fractures produced by violent muscle contraction, such as occurs when a javelin or baseball is thrown, also are reported.³ Motion of the humerus is controlled by several muscle groups, which also influence the fracture pattern of the humeral shaft. If the fracture is located proximal to the attachment of the pectoralis major, the proximal fragment of the humerus abducts and rotates internally owing to the action of the rotator cuff, whereas the distal fragment is displaced medially by the pectoralis major (Fig. 52-11A). If the fracture occurs below the pectoralis major insertion but above the deltoid insertion, the distal fragment is displaced laterally by the deltoid muscle, and the proximal fragment is displaced medially by the pull of the pectoralis major, latissimus dorsi, and teres major muscles (Fig. 52-11B). In fractures occurring distal to the deltoid insertion, the proximal fragment is abducted by the deltoid, and the distal fragment is proximally displaced (Fig. 52-11C). The shaft of the humerus most commonly fractures in the middle third in a transverse fashion (Fig. 52-12).

Figure 52-11 Influence of muscles on displacement of humeral shaft fractures based on fracture location. A, Fracture is proximal to the attachment of the pectoralis major muscle. B, Fracture is between insertion of the pectoralis major and deltoid muscles. C, Fracture is distal to the deltoid insertion.

Figure 52-12 Pathologic fracture of proximal humerus.

Clinical Features

The patient reports localized pain, often severe in nature. The arm is visibly swollen and cannot be used. When a fracture is complete, bony crepitus is felt in the shaft of the humerus with any manipulation of the arm. The arm may be shortened or rotated, depending on the displacement of the fracture fragments. When the fracture is incomplete, the skeleton is tender to palpation and swollen, but not otherwise deformed. A complete neurovascular examination is indicated. Attention should be directed to radial nerve function because injury to this nerve is the most common complication associated with humeral shaft fractures.

Radiographic findings are confirmatory. Studies routinely should include the shoulder and elbow joints. The humerus is a common site for benign tumors, unicameral cysts, and primary bone malignancies. The humeral shaft also is a common site for metastatic disease. Thinning of the cortex and abnormal osteoblastic or osteoclastic activity are evidence of a pathologic fracture (see Fig. 52-12). These fractures do not heal without concomitant treatment of the underlying pathologic condition.

Management

Closed fractures that are isolated injuries are treated conservatively with a high degree of success. Elaborate attempts at fracture reduction and external immobilization are unnecessary and sometimes detrimental to healing. Humeral shaft fractures remain surrounded by a richly vascularized envelope of muscle so that fracture reduction is accomplished most easily with the aid of gravity and muscle balance. Fractures that are nondisplaced or minimally displaced are immobilized by adding a coaptation, or “sugar-tong,” splint, to the sling and swathe (Fig. 52-13). This is accomplished by first padding the extremity, then carrying a long plaster splint from the lateral side of the shoulder, down the lateral aspect of the upper arm, around the elbow with the elbow flexed, and then up the inner aspect of the arm to the axilla. The sugar tong is wrapped in an elastic bandage, and a sling is used to support the arm in 90 degrees or less of flexion. The weight of the splint aided by gravity applies traction while it immobilizes the fracture. Some authorities use the coaptation splint for only the first 10 to 14 days of treatment, followed by a functional brace.

Figure 52-13 Sugar-tong splint for humeral shaft fractures. Gentle traction is applied (1) as the splint is placed (2) from over the deltoid laterally, under the elbow, and up into the axilla. An elastic wrap holds the splint in place (3). The axilla must be padded (4), and a sling is used (5). (Adapted from Connolly JF: DePalma’s Management of Fractures and Dislocations. Philadelphia, WB Saunders, 1981.)

If the fracture is grossly displaced or comminuted, the hanging cast technique sometimes is used. This technique is especially effective with spiral fractures. The cast is lightweight, applied at least 1 inch proximal to the fracture site, and extends to the distal palmar crease of the hand. The elbow is flexed 90 degrees, and the wrist is placed in the neutral position. The sling is attached through a loop at the wrist. Angulation is corrected by placing the plaster loop on the dorsal aspect of the cast (to reduce lateral angulation) or on the volar side of the cast (to reduce medial angulation). Anterior or posterior angulation is corrected by altering the length of the sling apparatus (Fig. 52-14). Care is taken not to make the cast too heavy because this would distract fracture fragments. The hanging cast has the disadvantage of requiring gravity for traction and requires that the patient remain upright at all times, including during sleep, a situation that many patients find intolerable. Neurovascular examination should be repeated and documented after the application of any splint or cast, because loss of nerve function from entrapment of the nerve between fragments can occur after these interventions.

Figure 52-14 Hanging cast technique.

The use of open reduction and internal fixation (Fig. 52-15) has been more frequent recently and is necessary in certain circumstances, including open fractures, presence of multiple injuries that preclude mobilization, bilateral fractures, poor reduction, poor patient compliance, failure of closed treatment, and fractures through pathologic bone.^4,5 Isolated radial nerve palsy usually is assumed to be a neurapraxia and is managed nonoperatively. Exploration and internal fixation are indicated, however, if the radial nerve palsy develops after manipulation because this is highly suggestive of nerve entrapment.⁴

Figure 52-15 Midshaft humerus fracture: A, before and B, after open reduction and internal fixation.

All patients with humeral shaft fractures should be referred to an orthopedic surgeon for close follow-up monitoring. When dependency casting is used, follow-up evaluation within 24 to 48 hours is recommended to be certain that the alignment has been maintained. Emergent referral to an orthopedist is recommended for patients with evidence of radial nerve injury, severely displaced or comminuted fractures, open fractures, or fractures associated with forearm fractures in the same extremity.

Complications

The most common complication, radial nerve injury, occurs in 20% of humerus fractures. This nerve injury is most often a benign neurapraxia that resolves spontaneously in most patients, although recovery may take several months. Patients should be advised of this possible complication, with instructions to contact their orthopedist or return to the ED for evaluation if this occurs. Radial nerve injuries associated with penetrating trauma or open fractures are likely to be permanent and usually warrant operative exploration. Median and ulnar nerve injuries are rarely seen, usually in the presence of penetrating trauma. Injuries to the brachial artery occur rarely, and, if clinically suggested, angiography or other vascular studies should be considered.

Fractures of the Distal Humerus

Supracondylar Fractures

Distal humerus fractures that occur proximal to the epicondyles are called supracondylar fractures. This type of fracture is almost exclusively an injury of the immature skeleton, with a peak incidence in children 5 to 10 years old ⁶ This injury rarely occurs after age 15 and accounts for approximately one half of all elbow fractures and one third of pediatric limb fractures. In children, the tensile strength of the collateral ligaments and joint capsule of the elbow is greater than that of bone. In adults, the reverse is true, and a posterior elbow dislocation is sustained instead. Supracondylar fractures are classified as either extension or flexion fractures, depending on the mechanism of injury and the displacement of the distal fragment. Of these injuries, 98% are of the extension type.

Extension Supracondylar Fractures:

Pathophysiology.: Extension supracondylar fractures occur as a consequence of a fall on the outstretched arm when the elbow is either fully extended or hyperextended (e.g., a fall off the “monkey bars”). The elbow is likely to be in the latter position at the time of the fall because ligamentous laxity, with hyperextension of the joints, is a normal phenomenon in younger children. With the forearm acting as a lever,⁷ the ground reaction produces a moment of force at the elbow (Fig. 52-16). Ultimately the distal humerus fails anteriorly in the supracondylar area. The strong action of the triceps tends to pull and displace the distal fragment in a posterior and proximal direction. There may be anterior angulation of the sharp distal end of the proximal fragment into the antecubital fossa, endangering the brachial artery and median nerve (Fig. 52-17). In most cases, however, the brachialis muscle protects the anterior neurovascular structures from injury.