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Dislocation, Wrist
Updated: Oct 20, 2008
Introduction
Background
Carpal dislocations represent a continuum of wrist injury that can lead to lunate or perilunate dislocation. The lunate cup commonly is directed in a volar direction in dislocation because of the mechanism of the injury. Perilunate dislocations result from dislocation of the distal carpal row. The capitate normally rests within the lunate cup, as seen on a lateral view. With perilunate dislocations, the capitate is seen most commonly as dorsal, but it also may be volar to the lunate on lateral x-ray evaluation. As a result of the stresses involved, scaphoid fractures often accompany perilunate dislocation. Carpal instability may take many forms and represents a spectrum of injury including scapholunate dissociation, lunate and perilunate dislocations, scaphoid fracture, and other intercarpal instabilities.
For more information, see Medscape's Orthopaedics Resource Center.
Pathophysiology
The mechanism of injury is usually a fall onto an outstretched hand with hand rotation, which may lead to a variety of injuries. These injuries range from scapholunate strain to carpal dislocation, with scaphoid fracture at the end of the spectrum. Unfortunately, most of these injuries are not diagnosed in the ED. The injury may lead to chronic pain and instability of the wrist.
Frequency
United States
Incidence of wrist injuries is estimated as 2.5% of ED visits. Wrist dislocations represent a very small portion of these visits. Because of this small proportion of wrist dislocations, they can be easily missed on initial presentation to the ED.
International
Same incidence as in the US.
Mortality/Morbidity
- The morbidity of wrist dislocations is tied to the frequently missed diagnosis of lunate or perilunate dislocation in the ED. Often, patients are not diagnosed with these injuries until weeks following the initial injury.
- Many patients with undiagnosed wrist dislocation have chronic pain.
- Carpal instability, including radiocarpal instability, is a frequent complication.
- Avascular necrosis of the lunate, Kienbock disease, is a potential complication of lunate dislocation.
Clinical
History
- Patients usually present to the ED fairly soon after a fall onto an outstretched hand.
- The mechanism of injury is ulnar deviation of the wrist coupled with dorsiflexion.
- The resulting intercarpal supination places great stress on the carpals. The result can be a lunate or perilunate dislocation.
- Often, the only symptom is wrist pain.
- Frequently, lunate and perilunate dislocations are not recognized at the time of the initial ED visit. This emphasizes the need to consider lunate or perilunate dislocation when a patient returns to the ED a second or third time for what appears to be chronic wrist pain following an injury.
Physical
The patient may have diffuse pain on palpation that is difficult to distinguish from other causes of wrist pain, including scapholunate strain, scaphoid fracture, triangular fibrocartilage complex tears, and other disorders.
Causes
- Carpal stability is based on the lunate as the central anchor for the proximal and distal carpal rows.
- The lunate is apposed to the radius, and the capitate rests within the lunate cup.
- The proximal row of carpals is connected by interosseous ligaments.
- Carpal stress is characterized as radial or ulnar, with some degree of axial loading. This stress is translated to all bones.
- Ligamentous injury results in a spectrum of injuries, including lunate and perilunate dislocations.
- The lunate-scaphoid ligaments may not be disrupted; if this is the case, scaphoid fracture may occur.
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References
Carter PR. Fractures and dislocations of the wrist. In: Common Hand Injuries and Infections. 1983:123-141.
Hayden SR. A case of peri-lunate dislocation. J Emerg Med. Mar-Apr 1995;13(2):241. [Medline].
Mital RC, Beeson M. The Wrist and Forearm. Emergency Radiology. 1999;47- 75.
Perron AD, Brady WJ, Keats TE, Hersh RE. Orthopedic pitfalls in the ED: lunate and perilunate injuries. Am J Emerg Med. Mar 2001;19(2):157-62. [Medline].
Rockwood CA, Jr, Green DP, Bucholz RW. Fractures and dislocations of the wrist. In: Fractures in Adults. Lippincott Williams & Wilkins Publishers; 1996:745-867.
Sochart DH, Birdsall PD, Paul AS. Perilunate fracture-dislocation: a continually missed injury. J Accid Emerg Med. May 1996;13(3):213-6. [Medline].
Further Reading
Keywords
wrist dislocation, carpal dislocations, lunate dislocations, perilunate dislocations, scaphoid fractures, wrist injuries, carpal instability, radiocarpal instability
