Anterior Dislocation

The vast majority of glenohumeral joint dislocations are anterior dislocations (Fig. 4-4A). This usually occurs as a result of indirect force applied to the arm in abduction, extension, and external rotation. Subcoracoid anterior dislocation is the most common subtype, followed by subglenoid, subclavicular, and intrathoracic. It is readily diagnosed on clinical exam and frontal radiographs as a medially and inferiorly located humeral head relative to the glenoid. The common associated injuries are Hill-Sachs fracture and Bankart lesion as a result of impaction of the humeral head against the glenoid during the movement of dislocation. The Hill-Sachs fracture (Fig. 4-4B) is a large defect or groove in the posterolateral aspect of the humeral head, best visualized in the internally rotated anteroposterior (AP) projection. Bankart lesions (Fig. 4-4B and C) may be composed of soft tissue (fibro-cartilaginous, cartilaginous labrum) or a piece of bone avulsed from the anteroinferior portion of the glenoid rim. They are less common than Hill-Sachs fractures. Neither one of these lesions is a sign of recurrent or previous dislocations, because they do occur at the initial dislocation.

Figure 4-4 Anterior shoulder dislocation. A, Anteroposterior radiograph of the shoulder demonstrates a classic subcoracoid anterior shoulder dislocation. The humeral head is located medial to the glenoid fossa and inferior to the corocoid process. B, Postreduction radiograph reveals an impacted fracture of the posterolateral aspect of the humeral head, consistent with a Hill-Sachs fracture (arrow). A linear lucency at the anterior glenoid rim is a bony Bankart fracture (arrowhead). C, Volumetric (3D) CT image confirms the Bankart fracture (arrowhead).

Posterior Dislocation

Posterior dislocations of the glenohumeral joint (Fig. 4-5) usually occur with violent muscle contractions, as seen with seizures, or electric shocks. The dislocation can be either subacromial, subglenoid, or subspinous. It is an uncommon injury that frequently coexists with an impacted fracture of the anterior humeral head due to trauma to the humeral head on the glenoid fossa during dislocation. It is difficult to detect clinically, especially in obese or muscular individuals. On frontal radiographs, posterior dislocations may go unrecognized in up to 50% of cases. Multiple signs have been described as helpful for detection of this subtle injury on frontal projections. The “positive rim” sign is an increase in the distance between the articular cortex of the humeral head and the anterior glenoid rim to more than 6 mm. The “light bulb” sign is a humeral head fixed in internal rotation, resembling a light bulb. The “trough line” is a curvilinear dense line parallel to the articular margin of the humeral head, representing an impacted fracture of the anterior aspect of the humeral head that coexists with the dislocation.

Figure 4-5 Posterior shoulder dislocation. A, Chest radiograph shows increased distance between the articular cortex of the humeral head and the anterior glenoid rim (double-headed arrow). Anteroposterior shoulder radiograph (B) of the same patient shows a “trough line” sign as a curvilinear density (arrowheads) consistent with an impacted reverse Hill-Sachs fracture (arrow), confirmed in the axillary projection (C, arrow).

Inferior Subluxation (Luxatio Erecta)

Luxatio erecta is a rare type of subglenoid inferior dislocation; the arm is severely hyperabducted, and the humerus is directed superiorly so that the long axis of the humeral shaft is perpendicular to the lateral chest wall. This rare entity is associated with Hill-Sachs fractures, other humeral head fractures, and occlusion of the axillary artery.

Pseudosubluxation

Pseudosubluxation describes the drooping of the humeral head with respect to the glenoid, and is usually apparent only in erect examinations. It is secondary to joint distension of traumatic or non-traumatic etiologies, for example, hemarthrosis, lipohemarthrosis, disruption of the joint capsule in chronic or recurrent dislocation, and others.

Fractures of the Proximal Humerus

The proximal humerus consists of the humeral head, anatomical neck, greater tuberosity, lesser tuberosity, surgical neck, and proximal shaft. Fractures of the proximal humerus (Box 4-8) are associated with osteoporosis. The majority of fractures are the result of indirect forces such as a fall onto an outstretched arm. Patterns of fracture and displacement are dictated by the position of the humerus at the time of injury, by bone quality, and by the direction of muscular pull on humeral fracture fragments. By counting the number of major displaced fragments and defining specific parts of involvement (head, greater tuberosity, lesser tuberosity, and shaft), Neer classified fractures of the proximal humerus into one-, two-, three-, and four-part fractures. Each of the four fracture sites results in a potential fragment, or “part.” A fragment is considered a “part” if it is displaced more than 1 cm or rotated more than 45 degrees. Regardless of the number of fracture lines, a lesser degree of displacement is considered to be minimal. One-part fractures (Fig. 4-6A) are nondisplaced or minimally displaced fractures. Muscles inserting on the proximal humerus influence the direction of fragment displacement fragments. The pectoralis major pulls the humeral shaft anteromedially. The supraspinatous and infraspinatous pull the greater tuberosity posterosuperiorly, and the subscapularis pulls the lesser tuberosity medially. When describing fractures of the proximal humerus, it is important to specify the type (one-, two-, three-, or four-part; surgical or anatomical neck) and the involved fragments (shaft, greater, lesser tuberosity). According to Neer’s description, 80% of fractures of the proximal humerus are one-part fractures and the majority of them are fractures of the surgical neck. Nondisplaced surgical neck fractures usually have a good prognosis because blood supply to the humeral head is preserved. On the contrary, fractures of the anatomical neck heal poorly because of the completely disrupted vascular supply that results in avascular necrosis and secondary osteoarthritis. Two-part fractures (Fig. 4-6B and C) account for 10% of all fractures of the proximal humerus. Displaced fractures of the surgical neck may injure the brachial plexus or axillary artery because these structures lie immediately anterior to the humeral head and surgical neck. Isolated fractures of the lesser tuberosity are unusual. A four-part fracture (Fig. 4-6D and E) is one in which the articular segment is isolated from both tuberosities and the humeral shaft. A “classic” four-part fracture is a fracture-dislocation, in which the articular segment dislocates anteriorly with no remaining soft tissue attachments. This results in an increased risk of osteonecrosis. Another important variant of a four-part fracture is the “valgus-impacted” fracture, which has a better prognosis due to maintained residual vascularity.

Figure 4-6 Fracture of the proximal humerus. A, Anteroposterior radiograph of the shoulder demonstrates a nondisplaced (“one-part”) fracture of the surgical neck of the humerus. B and C, Anteroposterior radiograph and volumetric (3D) CT reformation of the shoulder reveal a comminuted fracture of the surgical neck. This is a “two-part” fracture (proximal articulating part, and shaft): only two fragments are considered “parts” because they are displaced more than 1 cm. In addition, there is a nondisplaced fracture of the acromion process (B, arrowheads). D and E, Four-part fracture with valgus impaction is shown in an anteroposterior radiograph and a volumetric (3D) CT reformation. The greater tuberosity (G) and articulating part of the humeral head (white arrowheads) and shaft are separated from each other by more than 1 cm. The “L” indicates that this is the left shoulder.

Fractures of the Shaft of the Humerus

A humeral shaft fracture (see Box 4-8) is defined when the main fracture line is distal to the surgical neck of the proximal humerus, and proximal to the supracondylar ridge. Fractures of the humeral shaft are common. They are classified according to their location: above or below the pectoralis major insertion and above or below the deltoid insertion. Location of the fracture line affects the way the fragments are displaced. With fractures occurring above the pectoralis major insertion, the distal fragment is displaced anteromedially by the pull of the pectoralis major. Fractures occurring between the insertions of the pectoralis and deltoid muscles (Fig. 4-7) are associated with lateral displacement of the distal fragment. Fractures occurring distal to the deltoid insertion result in abduction of the proximal fragment by the deltoid and shortening of the arm by the pull of the brachialis and biceps muscles, which remain attached to the distal fragment. Associated injuries of the radial nerve are common, especially with fractures located at the junction of the mid and distal thirds. Pathologic fractures of the humerus are common in adults as a result of metastatic disease. In children, this usually occurs through a simple bone cyst of the proximal humerus.

Figure 4-7 Fracture of the shaft of the humerus. A and B, Anteroposterior and lateral radiographs demonstrate a comminuted fracture of the distal third of the humerus with a large butterfly fragment (arrows). The butterfly fragment is pulled medially and posteriorly, while the distal fragment (arrowheads) is retracted proximally due to the pull by the deltoid muscle.

The Fat Pad Sign

Normal thin layers of fat lie between the synovium and the joint capsule of the elbow anteriorly and posteriorly. In a normal flexed elbow, the anterior fat pad is visible, while the posterior fat pad is hidden in the intercondylar depression on the posterior surface of the humerus. In the presence of a joint effusion, the posterior fat pad (Fig. 4-8) becomes visible on the lateral radiograph of the flexed elbow because it is displaced posteriorly and the anterior fat pad becomes more elevated. In the acute trauma setting, elbow joint effusions can be a result of an intra-articular fracture or traumatic synovitis. This sign is usually present in children and adolescents, where 70% to 90% of patients with a posterior fat pad sign prove to have a fracture on initial or subsequent examinations. In adults, the sign is less frequently seen, and its absence cannot be used to exclude a fracture. This sign is not present in elbow dislocations, displaced intra-articular fractures with a torn joint capsule, and fracture-dislocations because it requires an intact synovium to prevent blood from mixing with extrasynovial fat. An optimal-quality lateral radiograph of the elbow is essential for evaluation of the fat pad sign. The image is taken when the elbow is flexed at 90 degrees with the hand in a lateral position. On the radiograph, three concentric arcs of the distal humerus (trochlear groove, capitellum, and medial trochlea) should be visualized.

Figure 4-8 Supracondylar fracture in children. A, Lateral radiograph of the elbow demonstrates a posterior fat pad sign (curved arrow), indicating presence of an intra-articular fracture. A subtle cortical break is seen on this view (arrow). B, Anteroposterior view confirms the fracture line (arrows).

Fractures Around the Elbow in Children

Supracondylar fractures are the most common type of fracture of the distal humerus. They are frequently seen in children aged 9 to12 years and occur as a hyperextension injury in which the olecranon acts as a fulcrum. When displaced, the fracture is easily recognized and characteristically displaced posteriorly. The brachial artery and median nerve may be stretched or interposed between fragments. Presence of abnormal cubitus valgus or varus should be assessed because either of these findings may alter the choice of therapy. Volkmann’s ischemic contracture is the most serious complication of this type of fracture and is caused by diminished blood flow to the rest of the arm. Subtle fractures are difficult to visualize directly; presence of a posterior fat pad sign and an abnormal anterior humeral line are important clues in this circumstance.

Lateral condylar fracture (Fig. 4-9) is the second most common type of fracture occurring around the elbow in children. This fracture is caused by a lateral blow to the forearm, resulting in varus stress across the elbow. Typically, the fracture line runs across or along the physis, with or without a small metaphyseal fragment. Fractures may terminate in the physis (incomplete) or extend beyond the physis through the ossified capitellum or unossified cartilage (complete). Differentiation between incomplete and complete fractures can be difficult because most of the fractures extend through the unossified cartilage. Additional imaging with magnetic resonance imaging (MRI) or intraoperative assessment with arthrography is often needed.

Figure 4-9 Lateral condylar fracture in children. Anteroposterior and lateral radiographs (A and B, respectively) of the elbow demonstrate a displaced lateral condylar fracture (arrows), which is the second most common fracture around the elbow in children.

Fractures of the Distal Humerus

The distal humerus consists of two columns of medial and lateral epicondylar ridges located at the distal humeral metaphysis and a central articulating axis (trochlea). The most distal part of the lateral column is the capitellum, and that of the medial column is the nonarticular medial epicondyle. Between the two columns lies the trochlea, which serves as a “tie-arch.” Although the column anatomy is not important for stability of the elbow, it is essential for determining the type of surgical reconstruction. An increasing trend toward operative treatment of these fractures requires a more comprehensive classification system. The AO/OTA (Orthopedic Trauma Association) classified distal humeral fractures into three types. Type A is an extra-articular fracture, type B is a partial articular fracture, and type C is a complete articular fracture. Ninety-five percent of distal humeral fractures in adults are intra-articular.

Type A extra-articular fractures (Fig. 4-10A and B) include apophyseal avulsion fractures (avulsion of the lateral epicondyle, medial epicondyle) and simple and complex nonarticular metaphyseal transcolumn fractures. Type B partial articular fractures (Fig. 4-10C and D) are intra-articular fractures that involve only one column (either medial or lateral) with one or more sites of intra-articular extension (capitellum, trochlea, or both). They are subtyped into lateral sagittal fractures, medial sagittal fractures, and frontal fractures. Sagittal fractures are either transcapitellar or transtrochlear fractures depending on the fracture line involvement. Frontal fractures are isolated fractures of the capitellum, trochlea, or both, without metaphyseal extension. Fractures of the capitellum account for 10% of all distal humeral fractures in adults. A shearing force transmitted by the radial head or trochlear groove results in this type of injury. The fragment is visualized on the lateral radiograph of the elbow and is characteristically displaced proximally above the radial head and coronoid process.

Figure 4-10 Fractures of distal humerus. A and B, Anteroposterior and lateral radiographs of the elbow show a comminuted transverse extra-articular metaphyseal fracture (type A) (arrows) with medial and volar displacement of the distal fragment. C and D, Transtrochlear fracture (partial articular, type B) (arrows) with mild displacement. The fracture extends from the trochlea to the lateral column of the distal humerus. E and F, Complete articular fracture (type C) with marked displacement. The fracture lines extend to both medial and lateral columns (arrows) of the distal humerus, as well as to the articular surface of the elbow (arrowhead). Distinction between type B and type C is based on the number of columns involved.

Type C, complete articular fractures (Fig. 4-10E and F), are fractures that involve both the medial and lateral columns, with articular extension. These fractures are further subclassified according to the nature (simple or complex) of the column fracture and the presence of intra-articular extension.

Fractures of the Proximal Radius

A radial head fracture (Fig. 4-11A and B) is the most common elbow injury in adults. It is intra-articular and usually produces hemarthrosis. It can be very subtle due to minimal cortical disruption and is usually not seen on all projections. Two patterns of fractures are usually seen: a single longitudinal fracture through the proximal articular surface, and impaction of the intact radial head into the radial neck. The former presents as a step-off or abrupt angulation of the joint surface, or depression of the fragment (double line of cortical bone). The latter creates an abrupt step-off between the normally gentle concave curve of the radial head and neck. Three types of radial head fractures were described by Mason, and later modified by Morrey to include a type IV fracture. Type I is a nondisplaced fracture, which accounts for 50% of cases. Type II is a displaced fracture without comminution, and type III is a comminuted fracture. Type IV is a radial head fracture-dislocation. The fracture is considered displaced if a fragment involves 30% or more of the articular surface and is displaced more than 2 mm. Open reduction with internal fixation is sometimes used to correct this fracture, especially with a large displaced fragment.

Figure 4-11 Fractures of the radial head and olecranon process. A, Lateral radiograph of the elbow demonstrates a classic posterior fat pad sign (arrows) produced by posterior bulge of the extrasynovial fat. In addition, there is an elevated anterior fat pad (white arrowheads). The cause of the joint effusion is a radial head fracture (black arrowhead). B, The black arrowhead demonstrates a nondisplaced fracture of the radial head. C, Lateral radiograph of the elbow shows a transverse fracture of the olecranon process (black arrowhead), a posterior fat pad sign (arrows), and elevated anterior fat pad (white arrowheads).

Presence of comminuted radial head and neck fractures due to high-energy trauma should raise suspicion for additional elbow and forearm injuries, such as capitellar and coronoid process fractures, elbow dislocation, and the Essex-Lopresti fracture. The latter consists of an unstable, comminuted fracture of the radial head and neck, and proximal migration or subluxation of the distal radioulnar joint that leads to an acute tear of the interosseous ligament of the forearm. Fractures of the olecranon (Fig. 4-11C) are the second most common type of elbow fractures in adults. They can be caused by a direct injury to the olecranon itself, which usually presents with comminution and distracted fragments, or by an indirect injury (e.g., a fall on the forearm) that results in simple fractures. If the periosteum is completely torn, traction by the triceps will displace the proximal fragment proximally resulting in a wide fracture gap. Although the fractures are usually obvious on lateral radiographs, soft tissue swelling in the olecranon bursa is an important clue to the presence of a subtle fracture.

Fractures of the coronoid process (Fig. 4-12) are usually oriented in the coronal plane and are caused by a shearing mechanism, most commonly from a posterior elbow dislocation. These fractures are pathognomonic of an episode of elbow instability. In every posterior dislocation, the coronoid process should be examined closely to exclude a fracture. A free intra-articular bone fragment within the elbow joint of an adult with posterior dislocation is most likely a displaced coronoid process fracture.

Figure 4-12 Elbow dislocation and fracture of the coronoid process. Lateral radiograph of the elbow demonstrates a posterior dislocation of the radius and ulna with respect to the distal humerus. A coronoid process fracture is noted (arrowheads).

Dislocations of the Elbow

The elbow is one of the most commonly dislocated joints of the body. Elbow dislocations usually occur in young people, with a peak in individuals between 5 and 25 years of age. Dislocations of both the radius and ulna, with respect to the distal end of the humerus, are the most frequently seen type. More than 80% are posterior or posterolateral dislocations (see Fig. 4-12). Less commonly, the radius and ulna dislocate in divergent directions. Common associated injuries include fractures of the coronoid process, radial head, and medial epicondyle of the humerus. “Terrible triad” fracture-dislocations describe the combination of elbow dislocation with radial head and coronoid process fractures. This condition is prone to early recurrent instability and post-traumatic arthritis.

Abnormal Pronator Quadratus Sign

The pronator quadratus is a thin flat muscle located on the volar aspect of the interosseous membrane at the level of the distal radioulnar joint. It is normally seen on lateral radiographs, outlined by a thin radiolucent fat stripe. When there is hemorrhage beneath the muscle, the contour of the muscle bulges anteriorly. This could present as a volar bulge of the thin fat stripe superficial to the muscle, or as a loss of definition of the lucent fat stripe overlying the muscle itself. It is usually caused by injuries to the distal third of the radius and ulna.

Monteggia Fracture-Dislocation

Monteggia fracture-dislocation is a combination of a fracture of the proximal ulnar shaft and subluxation or dislocation of the radial head. The term “Monteggia lesion” describes a number of traumatic lesions that have in common disruption of the radial head and fracture of the ulna at any level. Four types of Monteggia fracture-dislocation (Bado classification) are described according to the direction of the displaced ulnar fracture and the dislocated radial head. Type I is the most common; it is a fracture-dislocation with volar angulation at the fracture site and volar dislocation of the radial head. Type II, or reverse Monteggia fracture-dislocation (Fig. 4-13), is more likely to be seen in adults. This type has dorsal angulation at the fracture site and dorsal dislocation of the radial head. Type III is the most severe of all Monteggia fracture-dislocations. The fracture fragments are laterally displaced, with lateral or anterolateral dislocation of the radial head. Type IV is a fracture-dislocation that includes fractures of the proximal radius and proximal ulna along with volar dislocation of the radial head. In the presence of an isolated fracture of the shaft of a forearm bone, one must always anticipate the possibility of injuries to other bones.

Figure 4-13 Monteggia fracture-dislocation. A, Lateral radiograph of the forearm demonstrates dorsal dislocation of the radial head (black arrowheads), along with an angulated comminuted fracture of the proximal third of the ulna (arrows). Soft tissue gas indicates an open injury. This is a type II Monteggia fracture-dislocation. B, Volumetric (3D) CT reformation reveals an impacted fracture of the radial head (white arrowhead) along with the Monteggia fracture-dislocation.

Galeazzi Fracture-Dislocation

Galeazzi fracture-dislocations (Fig. 4-14) are uncommon, accounting for 3% to 6% of all forearm fractures. They consist of a fracture of the distal third of the radial shaft and dislocation or subluxation of the distal radioulnar joint (DRUJ). When one is faced with an isolated radial shaft fracture, injury of the DRUJ should be sought. The following signs suggest traumatic disruption of the DRUJ: fracture of the ulnar styloid at its base, widened DRUJ space on a frontal radiograph, dislocation of the radius relative to the ulna on a lateral radiograph, and radial foreshortening.

Figure 4-14 Galeazzi fracture-dislocation. A and B, Lateral and anteroposterior radiographs of the forearm show a displaced transverse fracture of the radial shaft at the junction of the middle and distal thirds, along with dislocation of the distal radioulnar joint (DRUJ). Dislocation of the radius relative to the ulna on the lateral radiograph and radial foreshortening (double-headed arrow) are clues suggesting DRUJ disruption.

Fractures of the Distal Radius

Fractures of the distal radius are exceedingly common and usually the result of low-energy trauma. They affect women more than men and their incidence increases with advancing age. Although the classification of these fractures as Colles’, Smith, or Barton types continues to be used in practice, most distal radial fractures do not fall into one of these categories. The more clinically useful way to describe the fractures of the distal radius is to use the number of fracture “parts” and to define whether the fracture is intra- or extra-articular. Extra-articular fractures do not affect either the radiocarpal joint or the DRUJ. They characteristically occur in the distal 3 to 4 cm of the radius and are composed of two parts. Intra-articular fractures can have two, three, four, or more parts. They extend into the radiocarpal joint or DRUJ. Barton and Chauffeur’s fractures fall into this category. The degree of intra-articular incongruity is the most clinically significant predictor of functional outcome and future degenerative changes of the radiocarpal joint, especially if there are 2 mm or more incongruity. Stability of these fractures is determined by the degree of angulation, comminution of the dorsal metaphysis, presence of intra-articular extension, and the patient’s age.

Colles’ fracture (Fig. 4-15A and B) is a transverse extra-articular fracture of the distal radius with dorsal displacement of the distal fragment along with the bones of the wrist and hand. It usually occurs as a result of a fall on the outstretched hand. It is commonly associated with an ulnar styloid process avulsion fracture, scapholunate dissociation, and other carpal dislocations or fractures.

Figure 4-15 Fractures of the distal radius. A and B, Posteroanterior and lateral wrist radiographs demonstrate a transverse extra-articular fracture of the distal end of the radius (arrows) with dorsal displacement of the distal fracture fragment, producing a “dinner fork” deformity. This is a classic Colles’ fracture. C and D, Smith, or reverse Colles’, fracture is demonstrated and characterized by volar displacement of the distal fracture fragment.

Fractures of the ulnar styloid occur in approximately 60% to 70% of distal radial fractures. The majority of them are small avulsions involving the tip of the ulnar styloid. Choice of treatment remains controversial, although the injury may well produce symptoms owing to the fracture itself or to associated injury to the triangular fibrocartilage complex. Treatment may be indicated if the fracture involves the base of the ulnar styloid with significant displacement and/or gross translation of the radius relative to the ulna.

The Smith fracture (Fig. 4-15C and D) is a transverse fracture of the distal radius with volar displacement of the distal fragment together with the carpus and hand; therefore the term “reverse Colles’ fracture” has been used.

The Barton fracture (Fig. 4-16A and B) is an oblique coronal fracture of the dorsal or volar margins of the distal radius with intra-articular extension. If the fracture line extends to the volar aspect of the distal radius, it is called a volar Barton fracture. The volar Barton fracture is more common than its counterpart, the dorsal Barton fracture, in which the fracture line extends to the dorsal aspect of the distal radius.

Figure 4-16 Fractures of the distal radius. A and B, Frontal and lateral radiographs of the wrist demonstrate an oblique coronal fracture of the distal radius with intra-articular extension. The fracture line extends to the volar aspect of the distal radius (volar Barton fracture). C, Frontal radiograph of the wrist shows a nondisplaced transverse fracture of the radial styloid process, or a Chauffeur’s fracture. D and E, Torus fracture. Posteroanterior and lateral radiographs of the wrist of a child reveal a subtle undulation in the distal radial metaphysis (arrows). This is a classic location for a fracture of the dorsal cortex of the distal radial metaphysis.

Chauffeur’s fracture (Hutchinson fracture) (Fig. 4-16C) is an intra-articular fracture of the base of the radial styloid process. The name comes from the era when hand cranking was needed to start motor vehicles. At present, it is most frequently caused by a fall on an outstretched hand, resulting in an avulsion of the radial collateral ligament, or a direct blow to the radial styloid process.

Torus fracture (buckle fracture) (Fig. 4-16