Carpal bone fractures are the most commonly missed wrist injuries. A careful examination is critical to recognize carpal bone fractures. The carpal fractures are in Table 269-2 listed in descending order of occurrence.
TABLE 269-2Summary of Carpal Bone Fractures and ED Management ||Download (.pdf) TABLE 269-2 Summary of Carpal Bone Fractures and ED Management
|Carpal Bone ||Mechanism of Injury ||Examination ||Initial ED Management |
|Scaphoid ||Fall on outstretched hand ||Snuffbox tenderness; pain with radial deviation and flexion ||Short arm thumb spica splint, in dorsiflexion with radial deviation |
|Triquetrum || |
Avulsion fracture—twisting of hand against resistance or hyperextension
Body fracture—direct trauma
|Tenderness at the dorsum of the wrist, distal to the ulnar styloid ||Short arm sugar tong splint |
|Lunate ||Fall on outstretched hand ||Tenderness at shallow indentation of the mid-dorsum of the wrist, ulnar and distal to Lister tubercle ||Short arm thumb spica splint |
|Trapezium ||Direct blow to thumb; force to wrist while dorsiflexed and radially deviated || |
Painful thumb movement and weak pinch strength
|Short arm thumb spica splint |
|Pisiform ||Fall directed on the hypothenar eminence ||Tender pisiform, prominent at the base of the hypothenar eminence ||Short arm volar splint in 30 degrees of flexion and ulnar deviation |
|Hamate ||Interrupted swing of a golf club, bat, or racquet ||Tenderness at the hook of the hamate, just distal and radial to the pisiform ||Short arm volar wrist splint with fourth and fifth metacarpal joints in flexion |
|Capitate ||Forceful dorsiflexion of the hand with radial impact ||Tenderness over the capitate just proximal to the third metacarpal ||Short arm volar wrist splint |
|Trapezoid ||Axial load onto the index metacarpal ||Tenderness over the radial aspect of the base of the index metacarpal ||Short arm thumb spica splint |
The scaphoid is the most common carpal bone fractured. Injuries result from a fall on either an outstretched dorsiflexed hand or from an axial load directed along the thumb's metacarpal. There is pain along the radial aspect of the wrist and localized tenderness in the anatomic snuffbox.24,25 Examination of the wrist in ulnar deviation exposes more of the scaphoid to direct palpation within the anatomic snuffbox. Eliciting pain in this area when the patient resists supination or pronation of the hand or pain with axial pressure directed along the thumb's metacarpal also suggests injury.
Radiographic evaluation includes both standard and scaphoid views for cortical disruption (Figure 269-11). The scaphoid view profiles the bone lengthwise and may assist in detecting subtle fractures. Distortion of a soft tissue fat stripe adjacent to the radial aspect of the scaphoid is suggestive of injury. Two thirds of the fractures occur at the waist or middle third of the bone, 16% to 28% in the proximal third, and 10% in the distal third. A scaphoid fracture may also have an associated injury in 12% of cases. Associated injuries may include the radius, neighboring carpal bones, a carpal instability pattern, or a dislocation. In patients with initial negative plain films, yet in whom a high index of suspicion remains for fracture, MRI is considered the gold standard for definitive diagnosis.26
Scaphoid fracture in the middle third or waist (arrow).
A scaphoid fracture can develop avascular necrosis of the proximal fracture segment that can lead to disabling arthritis.27 Because the vascular supply to the scaphoid enters the distal portion of the bone through small branches off the radial artery and palmar and superficial arteries, a fracture can easily disrupt the blood supply to the proximal segment. The more proximal, oblique, or displaced a fracture, the greater the risk of developing avascular necrosis. A scaphoid fracture is considered unsTable if it is oblique, if there is as little as 1 mm of displacement, if there is rotation or comminution, or if a carpal instability pattern is present. Two thirds of the scaphoid's surface is articular. This only adds to the scaphoid's problems because articular fractures are more difficult to heal. Thus, the main complications of improperly healed scaphoid fractures are avascular necrosis, delayed union, nonunion, malunion, and subsequent early degenerative arthritis.
Up to 10% of initial radiographs fail to detect a fracture, so initial treatment should be directed by clinical suspicion. Nondisplaced fractures and those that are only clinically suspected can be treated in a short arm thumb spica splint. Splinting in dorsiflexion and radial deviation helps to compress the fracture fragments. Patients with unsTable fractures should be placed in a long arm thumb spica splint and should be seen promptly by an orthopedic or hand surgeon for definitive treatment.
Triquetrum fractures are the second most common carpal bone injury, and occur as an avulsion or fracture through the body.23 Avulsion fractures are produced when a twisting motion of the hand is suddenly resisted or a hyperextension shear stress pushes the hamate or ulnar styloid against the triquetrum. Fractures of the body occur from direct trauma and are found in association with perilunate and lunate dislocations (part of the arc fractures). Localized tenderness is found over the dorsum of the wrist in the area immediately distal to the ulnar styloid. The dorsal avulsion fracture is best seen on the lateral radiograph or an oblique view in partial pronation. The fracture appears as a tiny flake of bone on the dorsum of the triquetrum best seen on lateral view (Figure 269-12). Triquetrum body fractures are usually nondisplaced because numerous ligaments encase the bone; these are best seen on the posteroanterior view. Nonunion is possible, but avascular necrosis has not been reported.
Triquetrum fracture seen at tip of arrow. [Photos contributed by: Brooke Beckett, MD, Department of Radiology, Oregon Health & Science University, Portland, OR.]
Refer triquetrum fractures to an orthopedist or hand surgeon. Patients with a dorsal avulsion fracture have an excellent prognosis for full recovery. Symptomatic patients are treated with a wrist splint for 1 to 2 weeks. Asymptomatic or minimally symptomatic patients may be treated with early range of motion. STable body fractures are treated in a cast for 6 weeks. UnsTable body fractures (>1 mm displacement) and those associated with perilunate/lunate dislocations may require internal fixation.28
Lunate fractures tend to occur with other carpal injuries. Isolated lunate injuries are rare. The mechanism of injury is commonly the result of a fall on the outstretched hand. The lunate is present in the shallow indentation on the mid-dorsum of the wrist. The lunate is easily palpable as it rises out of the floor of this indentation when the wrist is in a flexed position. Examination reveals tenderness at this point. Axial compression applied along the third metacarpal ray may also elicit pain in this area and is suggestive of injury. The lunate's blood supply enters through the distal end of the bone. A fracture subjects the lunate to risk for avascular necrosis of the proximal portion.
The lunate is seated in the middle of the wrist, so overlap with other carpal bones may make it difficult to identify an injury on a plain radiograph. On the lateral radiograph, the lunate, capitate, and distal radius should lie in the same vertical plane.
Refer suspected or actual lunate fractures to an orthopedist or hand surgeon. Clinical suspicion dictates the acute treatment. A short arm thumb spica splint should be applied when the diagnosis is unclear. MRI and CT may be used to identify occult fractures. The major complication is avascular necrosis (Kienböck's disease), leading to lunate collapse, osteoarthritis, chronic pain, and decreased grip strength.
The trapezium is a saddle-shaped bone that articulates with the thumb metacarpal. Injuries are produced by a direct blow to the thumb or from a dorsiflexion and radial deviation force. Fractures occur either at the trapezial ridge or body and are often intra-articular. Vertical fractures occur and are analogous to a Bennett's fracture (an intra-articular proximal thumb metacarpal fracture) (Figure 269-13). Examination reveals painful thumb movement and a weak pinch. There is tenderness at the apex of the anatomic snuffbox and at the base of the thenar eminence. This injury is best profiled on a 20-degree pronated oblique view. The major complication is nonunion.
Trapezium fracture seen at tip of arrow. [Photo contributed by: Brooke Beckett, MD, Department of Radiology, Oregon Health & Science University, Portland, OR.]
Refer to an orthopedist or hand surgeon. Initial ED stabilization of nondisplaced fractures is a short arm thumb spica splint. Displaced fractures >1 mm or diastases >2 mm require surgery.29
The pisiform is a sesamoid bone within the flexor carpi ulnaris tendon. It is positioned immediately volar to the triquetrum and is the palpable bony prominence at the base of the hypothenar eminence. Injuries usually result from a fall directed on the hypothenar eminence. There will be localized tenderness on the pisiform itself. If the wrist is flexed, the pisiform can be grasped and palpated between the examiner's fingers. This should elicit pain. The pisiform and hook of the hamate form the bony walls of Guyon's canal that contains the ulnar nerve and artery; therefore, it is important to exclude injury to them.30 Radiographs in partial supination, or the carpal tunnel view, are optimal because they remove the overlap with the triquetrum that is present on standard views (Figure 269-14).31 The pisiform is the last carpal bone to ossify, and it is usually complete by age 12 years old. Before the age of 12, multiple ossification centers in the pisiform may be confused with a fracture. The ossification centers differ in that they will have smoother margins and lack the perfect jigsaw-puzzle fit seen with fracture fragments. After age 12, any radiographic line is suggestive of fracture.
Pisiform fracture. [Photo contributed by: Brooke Beckett, MD, Department of Radiology, Oregon Health & Science University, Portland, OR.]
Refer to an orthopedist or hand surgeon. ED treatment is either a compression dressing or a splint in 30 degrees of flexion with ulnar deviation that relaxes the tension from the flexor carpi ulnaris. Pisiform fractures have an excellent prognosis.
Hamate fractures may involve the body of the hamate, the hook of the hamate, or any of its articular surfaces. Body fractures are rare and are generally associated with fracture dislocations of the fourth or fifth metacarpals (Figure 269-15). Most hamate fractures involve the hamate hook, which is a small bony prominence on its volar aspect. The classic mechanism is an interrupted swing with a golf club, bat, or racquet. The handle impacts against the hypothenar eminence and compresses the bone. Localized tenderness over the hook of the hamate is found by palpating the soft tissue of the hypothenar eminence, distal and radial to the pisiform. Standard and carpal tunnel views are necessary to visualize the fracture. Occult fractures may be identified by bone scan or CT. Physical examination should assess for injury to Guyon's canal (Figure 269-16), which houses the ulnar nerve and artery.
Hamate fracture (arrow) is best seen on posteroanterior view. [Photo contributed by: Brooke Beckett, MD, Department of Radiology, Oregon Health & Science University, Portland, OR.]
Refer to an orthopedist or hand surgeon. In the ED, treat hamate hook fractures with a compression dressing or splint. Nonunion is common, and excision of the bone may be necessary. Nondisplaced body fractures are treated by splint immobilization. Displaced body fractures or those with injury to Guyon's canal are surgically treated.
The capitate is the largest carpal bone. It is an elongated bone with a large proximal head that articulates with the lunate. The midportion of the bone is the neck, and the distal end, or body, articulates with the third metacarpal. Capitate fractures most often occur in the neck and usually occur in conjunction with a scaphoid fracture (Figure 269-17). The association of scaphoid and capitate fractures is called the scaphocapitate syndrome. Isolated capitate fractures are rare.32 Capitate fractures result from forceful dorsiflexion of the hand with impact on the radial side. The scaphoid fractures first, and then the neck of the capitate fractures. The fracture can continue around the lunate, creating other so-called arc fractures, eventually resulting in perilunate or lunate dislocation. The capitate's blood supply enters through the distal end. Thus, capitate fractures also share the same potential avascular necrosis of the proximal fracture segment as the lunate and scaphoid.
Capitate fracture (arrow) is seen best on posteroanterior view. [Photos contributed by: Brooke Beckett, MD, Department of Radiology, Oregon Health & Science University, Portland, OR.]
Physical examination reveals diffuse swelling and tenderness over the capitate, just proximal to the third metacarpal. Capitate neck fractures are best seen on the lateral radiograph. The head of the capitate should be carefully identified because it can rotate as much as 180 degrees. A capitate fracture is often overlooked because of the accompanying scaphoid fracture or perilunate/lunate dislocation that overshadows it. Complications include avascular necrosis, delayed union, nonunion, and malunion.
ED treatment of undisplaced, isolated capitate fractures is splint immobilization and early orthopedic/hand surgeon referral. Most capitate fractures, however, are displaced or associated with the scaphocapitate syndrome and require surgical treatment.33
Trapezoid fracture is extremely rare. The injury results from an axial load onto the index metacarpal. There will be tenderness on the radial aspect that is augmented by applying pressure along the index metacarpal ray. Fractures are difficult to visualize on standard radiographs, and CT or MRI may be necessary. ED treatment is with a thumb spica splint.