Extremity Trauma

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CHAPTER 4 Extremity Trauma

Medical imaging for evaluation of patients with orthopedic trauma has contributed to accurate diagnosis and subsequent management. In the era of modern medical technology, there is a wide range of imaging modalities for assessment of orthopedic trauma. Availability, invasiveness, cost-effectiveness, and image resolution dictate the use of each modality. Conventional radiography is the primary diagnostic modality for assessment of fractures and dislocations. Routine radiography includes two orthogonal views supplemented by additional projections. Most fractures and dislocations are sufficiently identified and managed with conventional radiographs alone. In addition, radiographs are useful for assessment of limb length, overall alignment, and monitoring of fracture healing. Computed tomography (CT) is helpful for evaluation of complex extremity fractures and spine injuries. Typical indications for CT of extremity trauma include fractures of the proximal humerus, scapula, pelvis, tibial plateau, tibial plafond, calcaneus, and midfoot. Postoperative evaluation of fracture reduction and monitoring of fracture healing are increasingly assessed by CT scan. Magnetic resonance (MR) imaging plays a leading role in the detection of soft tissue injuries, bone contusions, and occult fracture such as femoral neck and scaphoid fractures.

Knowing the important steps in interpretation of skeletal trauma is useful for increasing diagnostic accuracy (Box 4-1). Fracture terminology and a guide to fracture description are summarized in Box 4-2 and Box 4-3.

Besides direct visualization of the fracture line, indirect diagnostic clues to the presence of fractures include soft tissue swelling, obliteration or displacement of fat stripes, periosteal and endosteal reaction, joint effusion, lipohemarthrosis, double cortical line, and buckling of cortex.

UPPER EXTREMITY

The following diagram shows sites of common fractures of the upper extremity.

Fractures of the Scapula (Box 4-4)

The scapula provides a strong support to the upper extremity through its articulation with the humerus. At least 18 different muscles attach to this thin, broad bone. Therefore, fractures of the scapula often occur as a result of severe direct blunt trauma. Scapular fractures are associated with other significant injuries in up to 80% to 90% of cases, including trauma to the thoracic cage, glenohumeral joint, and brachial plexus, as well as axillary artery injuries. Attention is commonly diverted to these concomitant injuries, resulting in delayed diagnosis. Scapular fractures are classified according to their location: body, spine,

neck, glenoid, acromion process, and coracoid process. Approximately 80% of fractures of the scapula involve either the body (Fig. 4-1) or the neck. Glenoid and neck fractures have the potential to threaten the function of the shoulder girdle, as malalignment of these fractures can contribute to instability of the glenohumeral joint, arthrosis, and dysfunction of the rotator cuff and girdle musculatures. They may require open reduction and internal fixation. Fractures that pass through the suprascapular notch or spinoglenoid notch are at risk for neurovascular bundle injury. Early recognition may lead to a change in the type of therapy provided to polytrauma patients.

Fractures of the Clavicle

The primary mechanism causing fractures of the clavicle (Box 4-5) is a fall onto the superolateral shoulder. Because of the strength of the sternoclavicular ligament, the force exits the clavicle in the midshaft, resulting in the most common pattern of clavicle fracture: fracture of the middle third. The most widely used classification system (by Allman) divides clavicular fractures into three groups by location: group 1, middle third; group 2, lateral third; and group 3, medial third. Group 2 (or lateral third) fractures are further divided into three distinct types by Neer, depending on whether the coracoclavicular ligament is involved. The middle third of the clavicle (group 1) (Fig. 4-2A) is involved in 65% to 85% of all fractures. Complete fractures typically result in superior displacement of the medial fragment (due to pull of the sternocleidomastoid muscle) and inferior displacement of the lateral fragment (due to gravity pull by the shoulder joint). Overriding of fragments is common, with the lateral fragment underlying the medial fragment. The lateral third of the clavicle (group 2 fracture) is involved in 15% to 30% of cases. In this group, the integrity of the coracoclavicular ligaments influences the severity of displacement. The fracture may extend between the two portions of the coracoclavicular ligaments (medial conoid and lateral trapezoid ligaments) either without causing ligamentous disruption or involving the conoid ligament. The latter is a type II fracture that is more prone to delayed union and nonunion. A stress radiograph is often useful to make an accurate determination. Rarely, the fracture line involves only the joint margin and extends into the acromioclavicular joint. Fractures of the medial third of the clavicle (group 3) (Fig. 4-2B and C) are rare, accounting for only 5% of all clavicular fractures. These fractures are easily overlooked on conventional radiographs because of their lack of displacement and the overlapping ribs and spine. CT should be obtained when there is a question of injury to the medial third of the clavicle or the sternoclavicular joint. Unusual patterns of clavicular fractures include medial physeal separation and periosteal sleeve fracture that occur in the most medial and most lateral portions of the clavicle, respectively, in children and young adults.

Acromioclavicular Joint Injuries

Acromioclavicular (AC) injuries (Box 4-6) commonly result from a direct injury owing to a fall on the lateral aspect of the shoulder with an adducted arm during athletic activities. The initial trauma is directed at the AC joint capsule, and with greater force there is disruption of the coracoclavicular ligaments and detachment of the trapezius and deltoid muscles surrounding the joint. The name understates the importance of the status of the coracoclavicular ligaments, which are the most important structures maintaining alignment of the clavicle and scapula. Radiographic evaluation of the AC joint injury typically includes a standard anteroposterior view with the x-ray beam directed 15 degrees cephalad in the upright position. Both shoulders should be included in the same image. Stress radiographs may be performed with a patient holding a 10- to 15-pound weight if the initial radiograph without weight is normal. However, the increasing trend toward nonoperative management of even severe injuries has made stress radiographs less clinically relevant. There are six types of AC joint injuries. In type I injury (ligament sprain, intact coracoclavicular ligament), there is a normal AC joint space in radiographs obtained with and without weight bearing. In type II injury (Fig. 4-3A), the AC joint may be normal or slightly widened on nonstress radiographs. On the stress view (Fig. 4-3B), the AC joint is wide, which implies partial or complete ligament tear. In type III injury (Fig. 4-3C), there is a complete disruption of the acromioclavicular and coracoclavicular ligaments, resulting in widened acromioclavicular and coracoclavicular distances on nonstress radiographs. The distal clavicle is displaced superiorly. In type IV injury, the clavicle is displaced posteriorly; this is best visualized on the axillary projection. Type V and type VI injuries have associated separation of the sternoclavicular joint and are the result of severe trauma with other, accompanying fractures.

Subluxations and Dislocations About the Glenohumeral Joint

The glenohumeral joint (Box 4-7) is the most frequent site of dislocation of any joint in the body. Most commonly, these are post-traumatic dislocations. However, non-traumatic etiologies such as seizures and voluntary dislocations do occur. The type of dislocation is determined by the final resting place of the humeral head relative to the glenoid: anterior, posterior, superior, or inferior.

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.

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.

Fractures of the Proximal Segment and Shaft of the Humerus

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.

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.

Fractures and Dislocations Around the Elbow (Box 4-9)

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.

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.

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.

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.

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.

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.

Fractures of the Shafts and Distal Radius and Ulna (Box 4-10)

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.

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.

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.

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.

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

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