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.[1] 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.[2, 3] 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. A lunate dislocation is shown in the radiograph below.
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Dislocations, wrist. Lateral view of a lunate dislocation, with the classic teacup sign.
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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.[4, 5, 6]
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.
Mortality/Morbidity
The morbidity of wrist dislocations is tied to the frequently missed diagnosis of lunate or perilunate dislocation in the ED.[7] 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.
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.[1]
Often, the only symptom is wrist pain.
Frequently, lunate and perilunate dislocations are not recognized at the time of the initial ED visit.[7] 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.
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.
Plain x-rays of the wrist, both anteroposterior (AP) and lateral views, are essential to diagnose wrist dislocations (as well as other carpal instabilities).
On an AP view (shown below), 2 arcs should be identified. The first arc consists of the radiocarpal row, which should be smooth and continuous. Disruption is suggestive of a lunate dislocation.
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Dislocations, wrist. Anteroposterior (AP) view of a lunate dislocation.
The second arc consists of the midcarpal row, which also should be smooth and continuous. Disruption of this arc is suggestive of a perilunate dislocation.
The appearance of the lunate is important on the AP view. Normally, the lunate is quadrangular. With lunate dislocations, it becomes triangular. This may be an additional clue to dislocation.
On the lateral view (shown below), visualize the column, which consists of the radius, lunate, and capitate. The lunate should lie within the radius cup and the capitate should rest within the lunate cup. Loss of this normal column implies lunate or perilunate dislocation.
View Image
Dislocations, wrist. Lateral view of a lunate dislocation, with the classic teacup sign.
Stress x-rays of the wrist may be necessary to demonstrate intercarpal ligamentous instability when no evidence of wrist dislocation is apparent on plain films.
Stress x-rays obtained with radial and ulnar deviation of the hand may demonstrate scapholunate dissociation.
Prehospital care includes assessment for other injuries that may accompany the wrist injury.
If no other injuries are identified, splint the wrist.
Patients may be transported in their private vehicles, but the prehospital provider must emphasize the potential seriousness of the injury.
Under no circumstances should a prehospital provider attempt a reduction of a suspected wrist dislocation. It may be a distal radius fracture, which requires significant care to reduce.
Patients in whom a wrist dislocation has been identified require referral to a hand specialist who is either an orthopedic or plastic surgeon, depending on local custom.
Wrist dislocations may be reduced by emergency physicians, but only after consulting with the hand specialist.
The patient's own primary care physician may follow up, but it is important to stress to the primary care physician the need for hand specialist referral.
Clinical Context:
DOC for pain in patients with documented hypersensitivity to aspirin or NSAIDs, those with upper GI disease, or those taking oral anticoagulants.
Pain control is essential to quality patient care. It ensures patient comfort, promotes pulmonary toilet, and aids physical therapy regimens. Many analgesics have sedating properties that benefit these patients.
Clinical Context:
DOC for treatment of mild to moderately severe pain if no contraindications. Inhibits inflammatory reactions and pain, probably by decreasing activity of enzyme cyclooxygenase, which inhibits prostaglandin synthesis.
Clinical Context:
Used for relief of mild to moderately severe pain and inflammation. Administer small dosages initially to patients with small body size, elderly persons, and those with renal or liver disease. Doses higher than 75 mg do not increase its therapeutic effects. Administer high doses with caution and closely observe patient.
Clinical Context:
Used for relief of mild to moderately severe pain. Inhibits inflammatory reactions and pain by decreasing activity of enzyme cyclooxygenase, decreasing prostaglandin synthesis.
These agents are used most commonly for the relief of mild to moderately severe pain. Although the effects of NSAIDs tend to be patient specific, ibuprofen is usually the DOC for initial therapy. Other options include flurbiprofen, ketoprofen, and naproxen.
Patients with lunate or perilunate dislocations, if reduced in the ED, may safely be discharged home with careful warnings of the potential for compartment syndrome, pain, and other postinjury conditions.
Close follow-up must be arranged with a hand specialist.
Many patients who sustain lunate or perilunate dislocation develop chronic wrist pain or wrist instability.
Remember that lunate and perilunate dislocations are part of a continuum of injury that arises from significant carpal ligamentous injury. This often results in chronic carpal instability.
Michael S Beeson, MD, MBA, FACEP, Professor of Emergency Medicine, Northeastern Ohio Universities College of Medicine and Pharmacy; Attending Faculty, Akron General Medical Center
Disclosure: Nothing to disclose.
Specialty Editors
Francisco Talavera, PharmD, PhD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference
Disclosure: Received salary from Medscape for employment. for: Medscape.
David B Levy, DO, FAAEM, Senior Consultant in Emergency Medicine, Waikato District Health Board, New Zealand; Associate Professor of Emergency Medicine, Northeastern Ohio Universities College of Medicine
Disclosure: Nothing to disclose.
Chief Editor
Trevor John Mills, MD, MPH, Chief of Emergency Medicine, Veterans Affairs Northern California Health Care System; Professor of Emergency Medicine, Department of Emergency Medicine, University of California, Davis, School of Medicine
Disclosure: Nothing to disclose.
Additional Contributors
James E Keany, MD, FACEP, Associate Medical Director, Emergency Services, Mission Hospital Regional Medical Center, Children's Hospital of Orange County at Mission
Carter PR. Fractures and dislocations of the wrist. Common Hand Injuries and Infections. 1983. 123-141.
Mital RC, Beeson M. The Wrist and Forearm. Emergency Radiology. 1999. 47- 75.
Rockwood CA, Jr, Green DP, Bucholz RW. Fractures and dislocations of the wrist. Fractures in Adults. Lippincott Williams & Wilkins Publishers; 1996. 745-867.
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