Practice Essentials
Wrist injuries are common among athletes. Emergency physicians and/or family practitioners frequently perform the initial evaluation of wrist injuries and determine the initial treatment. Recognizing wrist dislocations early and properly referring patients with wrist dislocations can prevent complications, including prolonged pain and discomfort, surgery, and lost time from sports participation. [1]
See the image below.
Perilunate dislocation. The lunate is in a normal anatomic position with respect to the radius. The rest of the carpal bones are displaced dorsally.
Signs and symptoms
Localized tenderness, especially over the dorsoradial aspect of the wrist, may be revealed. The tenderness is worse with dorsiflexion.
Crepitus or a click with movement and apprehension with radial or ulnar deviation are signals of instability.
Lunate dislocation can cause volar swelling on the median nerve. Perilunate dislocation can appear with considerable swelling. Scapholunate dislocation usually presents with a minimal amount of swelling, and pain is localized over the dorsal scapholunate region.
See Presentation for more detail.
Diagnosis
Plain radiographs are helpful. Magnetic resonance imaging (MRI) can be considered for patients with wrist pain or instability but who have normal radiographic findings.
See Workup for more detail.
Management
The goal of surgery and rehabilitation is to minimize the loss of motion in the athlete. Closed reduction of the wrist dislocation can be attempted after a complete neurovascular examination is performed and proper radiographs are obtained.
See Treatment and Medication for more detail.
Etiology
Repeated stress on carpal ligaments renders them more prone to injury, especially in athletes.
The carpal bones serve as a link between the hands and the upper body; a great deal of force is transmitted through them.
Sports with increased force vectors (height and speed), such as adult in-line skaters and football players, [2] commonly experience such injuries. Other examples of risks are falls from a height; these occur in athletes such as gymnasts, among others.
Although high energy is the most common cause of injury, some reports describe low-energy trauma as the cause of carpal dislocation. [3]
Epidemiology
United States statistics
In a study by Larsen and Lauritsen, as many as 2.5% of all emergency department visits were made by patients with wrist injuries. [4] A small number of those patients present with wrist dislocations. Subluxations and dislocations account for 10% of carpal injuries, with perilunate dislocation being the most common type of dislocation. [5]
Kerr et al concluded that dislocation/separation injuries represent a relatively small proportion of all injuries sustained by high school athletes in the United States; however, the severity of these injuries indicates a need for enhanced injury prevention efforts. [6]
Functional Anatomy
The wrist joint is composed of distal radial and ulnar surfaces, 8 carpal bones, and the proximal metacarpal bones. The distal carpal row consists of the following bones: hamate, capitate, trapezoid, and trapezium. The proximal row consists of the following bones: scaphoid, lunate, triquetrum, and pisiform.
The carpal bones are held together by a complex set of ligaments, including the interosseous, volar, and dorsal ligaments and a triangular fibrocartilage complex (TFC). The dorsal ligaments are weaker than the volar ligaments, making dorsal dislocation more common. [5]
Sport-Specific Biomechanics
The mechanism of injury for a wrist dislocation is usually a fall on an outstretched hand (ie, FOOSH injury) that results in a hyperextension type of injury to the wrist. High energy is a common characteristic feature in these injuries. [7] The distal row of carpal bones is commonly displaced dorsal to the proximal row. This displacement occurs as a result of a scaphoid fracture or a scapholunate dislocation, and if the force is severe, a perilunate dislocation occurs. [8] Trans-scaphoid perilunate fracture-dislocation is slightly more common than perilunate dislocation.
Different posttraumatic deformity patterns can cause the lunate to lose its linear relationship with the capitate and to tilt dorsally or volarly, resulting in a collapse deformity. The most common collapse deformity is caused by the lunate dorsiflexing on the radius. This is compensated by the capitate flexing volarly. This deformity is also known as the dorsiflexed intercalated segment instability (DISI) pattern. DISI normally occurs in unrecognized scaphoid subluxations or scaphoid fractures. The opposite type of deformity is known as the volar intercalated segment instability (VISI) pattern. Although VISI can be seen in healthy patients with lax ligaments, posttraumatically, it is a result of the lunate flexing volarly on the radius as the capitate tilts dorsally. [9, 10] VISI also is a sign of midcarpal instability or lunotriquetral injury.
Mayfield and coworkers have classified wrist dislocation as follows (see the image below) [11] :
Progressive perilunar instability pattern as reported by Mayfield et al. Stage I involves scaphoid instability; stage II, scaphoid and capitate instability; stage III, scaphoid, capitate, and triquetrum instability; and stage IV, lunate dislocation.
Wrist dislocations have been categorized into the following stages:
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Stage I – Scapholunate dislocation resulting from a tear in the scapholunate interosseous ligament and radiolunate ligament
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Stage II – Lunate-capitate subluxation resulting from injury to the capitolunate joint
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Stage III – Lunate-triquetral dislocation resulting from injury to the triquetrolunate interosseous ligament
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Stage IV – Lunate dislocation resulting from dorsal radiolunate ligament injury
Prognosis
If the diagnosis is established early (< 3 mo) and if the proper treatment is administered, the prognosis of wrist dislocations is excellent.
Complications
A missed or late diagnosis may lead to complications. Carpal tunnel syndrome may result.
Malunion or nonunion may occur. This is a misnomer because no fracture occurs; therefore, malunion or nonunion is not technically possible. Stiffness may be present. On rare occasions, late instability or apposition of the carpal bones may occur.
Degenerative joint disease is possible.
Undiagnosed lunate or perilunate dislocation can result in median nerve dysfunction, posttraumatic arthritis, and reduced functionality. Many patients with a missed diagnosis of wrist dislocation have chronic pain. Carpal instability, including radiocarpal instability, is a frequent complication. [12] About 25% of patients with perilunate dislocations have a delayed presentation. [13]
A study by Lameijer et al that assessed the long-term impact of perilunate dislocations found that patients with these injuries had decreased range of motion and physical functioning, pain, and lower general health status when compared with healthy control patients. [14]
Patient Education
Athletes should be educated about how to recognize wrist injuries. Seeking early medical attention for wrist injuries is important and should be emphasized to athletes. Proper technique, flexibility, and strengthening should also be emphasized.
For patient education resources, see WebMD's Wrist Injury Treatment.
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Lunate dislocation. Posteroanterior projection of the wrist showing the pie shape of the lunate.
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Perilunate dislocation. On the posteroanterior radiograph, crowding is evident between the proximal and distal carpal bones.
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Perilunate dislocation. The lunate is in a normal anatomic position with respect to the radius. The rest of the carpal bones are displaced dorsally.
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Scapholunate dislocation. The scapholunate space is usually greater than 4 mm, a scenario also known as the Terry-Thomas sign. Rotation of the scaphoid causes the scaphoid to be viewed end-on, producing the classic signet-ring sign.
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Progressive perilunar instability pattern as reported by Mayfield et al. Stage I involves scaphoid instability; stage II, scaphoid and capitate instability; stage III, scaphoid, capitate, and triquetrum instability; and stage IV, lunate dislocation.
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On a normal lateral radiograph, the 4 Cs should be easily visualized. The 4 Cs are the convexity of the distal radius, the convexity and the concavity of the lunate, and the convexity of the capitate. A longitudinal axis aligns the radius, the lunate, the capitate, and the third metacarpal bone. The scapholunate angle is normally 30-60 degrees.
