Wrist Fracture in Emergency Medicine

Updated: Feb 14, 2015
  • Author: Bryan C Hoynak, MD, FACEP, FAAEM; Chief Editor: Trevor John Mills, MD, MPH  more...
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Overview

Background

The wrist is the most commonly injured region of the upper extremity. Fractures of the distal radius and ulna account for three fourths of wrist injuries. The carpal bones themselves are injured much less frequently but account for up to 10% of injuries to the structures of the hand. Not only are these injuries frequently encountered in the emergency department setting, but the mobility and delicate functional requirements of the hand make accurate diagnosis and treatment crucial to avoiding long-term loss of function and disability.

Volar dislocation of the lunate is shown in the image below.

Lateral radiograph of the wrist illustrating volar Lateral radiograph of the wrist illustrating volar dislocation of the lunate.
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Pathophysiology

Anatomic considerations

The wrist or carpus is a highly mobile structure composed of a large number of small bones and joints. This complex system of articulations works in unison to provide a global range of motion for the wrist joint. Motion at the wrist joint occurs between the radius and the carpal bones, which function as a single unit, and between the carpals and metacarpals.

Carpal bones

The 8 carpal bones are arranged in 2 rows to form a compact, powerful unit. Each is cuboid with 6 surfaces; 4 are covered with cartilage to articulate with the adjacent bones, and 2 are roughened for ligamentous attachment. The proximal carpal row contains the scaphoid (also called the navicular), lunate, triquetrum, and pisiform. It articulates proximally with the radius and the triangular cartilage. The ulna does not articulate directly with the carpus but is separated from the triquetrum by a triangular fibrocartilage, which acts as a stabilizing structure. The distal carpal row contains the trapezium, trapezoid, capitate, and hamate and articulates with the 5 metacarpals.

Joints and ligaments

The wrist includes 5 large joint cavities in addition to the intercarpal joint spaces: the radiocarpal joint, the distal radio-ulnar joint (DRUJ), the midcarpal joint, the large carpometacarpal joint (between the carpus and the second, third, fourth, and fifth metacarpals), and the small carpometacarpal joint (between the first metacarpal and the trapezium).

The strength of the wrist is dependent on the integrity of the ligamentous network, which links the carpus together. The volar carpal ligament extends from the trapezium to the hook of the hamate and forms the anterior roof of the osseous/fibrous tunnel. Within this tunnel lie the tendons for the finger flexors and the median nerve. Encroachment on this space results in median nerve compression. The second and third metacarpals are fixed at their bases and are immobile.

The muscles of the hand originate primarily in the forearm and pass over the wrist. The only muscle with insertion into the wrist is the flexor carpi ulnaris, which inserts into the pisiform, a small sesamoid bone.

Movement of the wrist is 80° in flexion, 70° in extension, 30° in ulnar deviation, and 20° in radial deviation. Pronation and supination occur at the radial-ulnar articulation in the forearm not at the wrist.

Neurovascular anatomy

The wrist comprises several important neurovascular structures. The deep branches of the ulnar nerve and the ulnar artery run deep to the flexor carpi ulnaris tendon through the Guyon canal. They pass near the hamate and capitate and can be involved with injuries to these structures. The ulnar nerve innervates the intrinsic muscles of the hand, including the hypothenar muscles, interossei, ulnar lumbricals, and adductor pollicis.

The median nerve lies between the flexor carpi radialis and the palmaris longus tendon in the carpal tunnel. The median nerve innervates the thenar compartment and provides sensation to the radial portion of the hand. Any displacement of the normal anatomic alignment of the wrist can injure this nerve.

The blood supply to the hand is via the radial and ulnar arteries, which form the dorsal palmar arch. The scaphoid bone receives its blood supply from the distal part of this arch, which is prone to injury.

Surface anatomy

Several anatomic landmarks are important to recognize when performing an accurate and thorough examination of an injured wrist. The anatomic snuffbox lies on the radial aspect of the dorsum of the wrist. It is defined in the ulnar aspect by the tendon of the extensor pollicis longus and radially by the tendons of the extensor pollicis brevis and abductor pollicis longus. The floor is composed of the scaphoid proximally and the trapezium distally. The anatomic snuffbox is most easily observed with the thumb held in a position of extension with the wrist slightly deviated in the radial aspect.

The next landmark is the Lister tubercle, a bony prominence over the dorsum of the distal radius. With the hand held in neutral, a line drawn between the third metacarpal and the Lister tubercle will cut through the capitate distally and the lunate proximally. Just distal to the ulnar styloid, the triquetrum can be palpated. At the base of the hypothenar eminence on the volar aspect of the wrist lies the pisiform. The hook of the hamate can be felt with deep palpation of the palm approximately 1 cm distant from the pisiform along a line pointing to the index metacarpophalangeal (MCP) joint.

Carpal fractures and dislocations

Scaphoid fracture

The scaphoid bone is based in the proximal row of carpal bones but extends into the distal row, making it more vulnerable to injury than the other carpal bones. It is the most frequently injured carpal bone, accounting for 60-70% of all carpal fractures. It is also a frequently missed injury, as approximately 10-15% of fractures are not demonstrated on routine radiographs. More than three fourths of all fractures occur at the narrow midportion or waist of the scaphoid. Because blood is supplied to the scaphoid along its dorsal surface near its waist, fractures at this location potentially compromise flow to the proximal portion of the bone. As a result, avascular necrosis is a serious complication of this injury.

Hyperextension of the wrist is the most common mechanism of scaphoid fracture either by a fall on an outstretched hand or by a direct blow to the palm. Often, the wrist has some degree of radial deviation. Hyperextension causes the radial styloid to impinge on the waist of the scaphoid as it crosses between the 2 rows of carpal bones. Scaphoid fractures are often associated with other injuries of the wrist, including dislocation of the radiocarpal joint, dislocation between the 2 rows of carpal bones, fracture-dislocation of the distal end of the radius, fracture at the base of the thumb metacarpal, and dislocation of the lunate.

Lunate fracture

Although a relatively uncommon injury, fracture of the lunate is the third most frequent carpal bone fracture. The lunate is located in the center of the proximal carpal row and articulates with the radius. Fractures can occur in any orientation, and diagnosis often requires a high degree of clinical suspicion.

Fractures of the lunate most often result from hyperextension of the wrist or impact of the heel of the hand on a hard surface. This injury can also occur from a fall on the outstretched hand. Patients usually present with weakness of the wrist and pain aggravated with compression along the third digital ray.

Triquetrum fracture

The triquetrum is one of the more commonly injured carpal bones. The triquetrum is the second most injured carpal bone associated with sports injuries. [1] It lies on the ulnar aspect of the proximal row of carpal bones. Strong ligaments attach the triquetrum to the lunate, which adjoins its radial aspect. In addition, the triquetrum is connected to the distal ulna by a triangular fibrocartilage complex.

The most common mechanism of injury is forced hyperextension of the wrist with ulnar deviation. In this position, the triquetrum is forced against the ulnar styloid, generating a shearing force that results in avulsion of ligaments and a dorsal chip fracture of the triquetrum. A second, less common, mechanism is a direct blow to the dorsum of the hand, which causes a transverse fracture through the body of the triquetrum. This is a high-energy injury and is frequently associated with injury to other carpal bones.

Capitate fracture

The capitate is the largest carpal bone and articulates with 7 other bones, including the second, third, and fourth metacarpals. It is located in the center of the distal row of carpal bones. Axial motion of the third metacarpal depends on a functional articulation with the capitate. These fractures account for fewer than 10% of carpal bone injuries and usually are transversely oriented. Blood supply to the capitate enters its dorsal segment and is often disrupted following fracture, resulting in avascular necrosis.

Two mechanisms of injury are common in capitate fractures. Like most carpal bones, the capitate can be injured by a fall on an outstretched hand with forced dorsiflexion and a degree of radial deviation of the wrist. In this position, the dorsal lip of the radius is able to strike the body of the capitate. A second mechanism is a direct blow or crush injury to the dorsum of the wrist

Hamate fracture

The hamate occupies the ulnar aspect of the distal row of carpal bones. It is an unusually shaped bone, with a hook that protrudes toward the palmar surface and serves as an attachment site for several ligaments. The most common injury pattern is a fracture through the base of this hook. This is an uncommon injury. Clinical examination is very important as plain radiographs often miss this fracture. The hook of the hamate is found by palpating the pisiform bone and then moving in an oblique line toward the index finger metacarpophalangeal joint about 2 cm. Reproducible pain indicates a suspected hamate fracture. [1] If plain films are normal, a CT scan has 100% sensitivity, 94.4% specificity, and 97.2% accuracy. [2, 3]

The hook of the hamate is typically fractured by a direct blow when the hand is held slightly dorsiflexed and with some degree of ulnar deviation. A common history is that a golf club, racket, or bat struck a stationary object during full swing, resulting in immediate pain over the hypothenar eminence. This pain is exacerbated by any type of gripping activity.

Trapezium fracture

Fractures of the trapezium are rare, comprising no more than 5% of fractures of the carpal bones. Fractures of the body of the trapezium result when an adducted thumb is forced onto the articular surface of the carpal bone. In addition, forced radial deviation of the thumb may result in small avulsion fractures due to capsular strain.

Trapezoid fracture

Fractures of the trapezoid are rare, accounting for fewer than 1% of carpal bone fractures. The mechanism of injury is axial loading along the line of the second metacarpal.

Pisiform fracture

The pisiform is a sesamoid bone within the tendon of the flexor carpi ulnaris. It articulates only with the triquetrum and lies near the deep ulnar nerve and artery. Fractures are rare. The pisiform is typically injured by a fall on an outstretched hand in a dorsiflexed position, with the impact on the hypothenar eminence.

Lunate and perilunate dislocation

Dislocations of the carpal bones are usually the result of extreme flexion or extension of the wrist. The type of dislocation or fracture-dislocation produced by these mechanisms depends on the direction and intensity of the injuring force and the position of the hand in relation to the forearm at the moment of impact. The integrity of the lunate-capitate relationship is the most crucial factor in all dislocations of the wrist. The resulting lesions are related directly to disruption or preservation of this articulation.

These rare injuries may have a poor outcome if not recognized in a timely fashion. The exact diagnosis can often be difficult to determine by radiography. Four specific projections can help when taking comparison radiographs: anteroposterior (AP), lateral, 45° of pronation, and 45° of supination. An accurate history can be a clue to the diagnosis. Knowledge of the exact mechanism of injury can allow prediction of the resulting dislocation.

Extension injuries

Dorsal perilunate or volar lunate dislocation is caused when the hand is forced into extension such as in a fall on the outstretched hand. Commonly, a fracture or fracture-dislocation of the scaphoid complicates the dorsal perilunate dislocation.

Flexion injuries

Dorsal dislocation of the lunate can occur when the hand and carpus are hyperflexed, as occurs with a fall onto the back of the hand. The upward force generated when the hand contacts the ground, together with the downward force acting through the radius, forces the capitate to rotate anteriorly and drive the lunate backward into a dorsal position.

With a volar perilunate dislocation, the lunate remains in its normal position relative to the radius and the rest of the carpus dislocates anteriorly. This dislocation is often associated with a scaphoid fracture.

Fractures of the distal radius and ulna

Fractures of the distal radius, ulna, or both account for approximately three quarters of bony injuries of the wrist. The radius articulates directly with the carpal bones; the ulna has attachments to the triangular fibrocartilage, which is interposed between the distal ulna and the triquetrum in the proximal row of carpal bones. The radius and ulna themselves articulate at the DRUJ, about which occurs the movements of supination and pronation at the wrist. They are enveloped in a common joint capsule and share multiple ligamentous attachments. Along the midshaft of both bones is the interosseus membrane. Several muscle groups attach on the distal aspect of both bones and contribute to the displacement of fracture fragments.

Extension fractures of the distal radius

Multiple classification schemes have been developed for extension injuries of the distal radius. These tend to be complex and cumbersome. In general, however, the greater the degree of displacement and comminution, the more severe the injury. Extension of a fracture into the radiocarpal or the DRUJ is also a marker for a more severe injury. More complex fractures tend to be more unstable.

Extension fractures result from a fall on an outstretched pronated hand with the impact on the palm and subsequent forced dorsiflexion or hyperextension. On striking a hard surface, the hand becomes fixed while the momentum of the body produces the following 2 forces: twisting force that causes excessive supination of the forearm, and compression force that acts vertically through the carpus to the radius.

The lunate acts as the apex of a wedge against the articular surface of the radius and causes injuries that vary by the age of the patient. Very young children usually sustain a greenstick fracture of the distal radius, with or without an associated fracture of the distal ulna. In adolescents, the lower epiphysis separates, with dorsal displacement or crushing. In adults, fracture occurs within 1 inch of the carpus. The distal fragment is usually displaced upward and backward. In all age groups, the fracture may be complicated by injury to the median nerve or the sensory branch of the radial nerve, by fracture of the scaphoid or dislocation of the lunate, or both.

If a concomitant supinating force is applied, often the distal ulna also fractures. Approximately 60% of distal radius fractures are associated with fracture of the ulnar styloid. Approximately 60% of ulnar styloid fractures also have an associated fracture of the ulnar neck.

Colles fracture is the most common extension fracture pattern. The term is classically used to describe a fracture through the distal metaphysis approximately 4 cm proximal to the articular surface of the radius. However, now the term tends to be used loosely to describe any fracture of the distal radius, with or without involvement of the ulna, that has dorsal displacement of the fracture fragments.

Colles fractures occur in all age groups, although certain patterns follow an age distribution. In elderly individuals, because of the relatively weaker cortex, the fracture is more often extra-articular. Younger individuals tend to require a relatively higher-energy force to cause the fracture and tend to have more complex intra-articular fractures. In children with open physes, an equivalent fracture is the epiphyseal slip. This is a Salter I or II fracture with the deforming forces directed through the weaker epiphyseal plate.

Flexion fractures of the distal radius (reverse Colles fracture/Smith fracture)

A Smith fracture is relatively uncommon compared with the Colles fracture. This term is used loosely to refer to any fracture of the distal radius, with or without involvement of the ulna, that has volar displacement of the distal fragments. A true Smith fracture comprises a fracture of the entire thickness of the distal radius, 1-2 cm above the wrist. The lower end of the radius is displaced forward and upward.

This fracture is typically caused by a fall onto a supinated forearm or hand with generation of a hyperflexion force. On striking the ground, the hand locks in supination while the body's momentum forces the hand into hyperpronation. A direct blow to the dorsum of the wrist with the hand in flexion and forearm pronated can also produce a similar fracture pattern. Another mechanism is punching with the wrist in a slightly flexed position.

Pseudocarpal injuries

Pseudocarpal injuries are those that involve the distal end of the radius and ulna just proximal to the carpus and manifest with clinical signs that mimic carpal bone injuries. Specifically, these include articular disk injuries of the wrist, dislocations of the inferior radioulnar joint, and traumatic dislocation of the distal end of the ulna. These are rare injuries and require orthopedic consultation for definitive management. Recognition of these injuries in the ED is important if functional outcome is to be optimized.

Wrist articular injuries

Injury to the articular disk of the wrist occurs from multiple mechanisms. It usually coexists with other more common injuries, but isolated injuries to the articular disk can occur. The most common pathologic defect is tearing of the disk from its attachment at the margin of the ulnar notch of the radius. The primary function of the triangular disk of the wrist is to prevent lateral displacement of the ulna. The most common mechanism of injury is dorsiflexion and pronation of the hand. Less frequently, extreme hyperextension and supination may cause injury. Volar or dorsal dislocation of the head of the radius may coexist.

The Barton or push-off fracture is an intra-articular injury involving the dorsal or volar articular surface of the radius. It is an uncommon fracture pattern. This type of fracture is generally observed with extreme dorsiflexion of the wrist with concomitant exertion of a pronating force.

Traumatic dislocation of the distal ulna

Dislocation or subluxation of the distal ulna is most often associated with fractures of the radius. However, acute traumatic dislocation/subluxation of the head of the ulna without fracture can occur and often is not recognized in the ED.

The ulnar head may be displaced anteriorly or posteriorly, depending on the mechanism of injury. Extreme extension and pronation of the hand produces a dorsal dislocation of the head of the ulna. Extreme extension and supination of the hand produces a volar dislocation of the ulnar head.

Radial styloid fracture

A Hutchinson fracture, an isolated fracture of the radial styloid, is typically caused by a direct blow to the radial aspect of the wrist. It may also be referred to as "chauffeur's fracture" or "backfire fracture," as it initially was described in individuals struck by the hand crank on early automobiles when the engine suddenly backfired during starting.

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Epidemiology

Frequency

United States

Fractures of the distal radius account for one sixth of all fractures seen and treated in the ED.

Mortality/Morbidity

Little or no risk of death is associated with isolated wrist fractures. The potential does exist for substantial morbidity, including primarily arthritis, chronic pain, limitation of motion, and physical deformity. Morbidity also may be related to associated injuries, including those of the median and ulnar nerves and the radial and ulnar arteries.

Age

Patients aged 6-10 years and those aged 60-69 years have the greatest frequency of distal radius fractures. Injuries to the carpal bones are common in all age groups but are more common in adolescents.

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