Acute Carpal Dislocations and Ligamentous Injuries

General Information

Acute carpal dislocations and acute ligamentous injuries of the wrist represent a spectrum of traumatic injuries to the wrist. Acute carpal dislocations are high-energy injuries to the wrist in which significant ligamentous injury occurs and either radiocarpal or midcarpal dislocation. These injuries may be associated with fracture(s) of the radial styloid, scaphoid, capitate, and/or the triquetrum.

Diagnostic Criteria

Acute Carpal Dislocations

Accurate recognition of the radiographic patterns of acute carpal dislocations leads to prompt diagnosis and elimination of other diagnostic considerations. It is important to recognize acute median nerve compromise when it occurs in the setting of this injury.

Acute Ligamentous Injuries

Early recognition of significant wrist ligament injuries may be difficult because of the subtle nature of radiographic findings. Further evaluation may be appropriate when initial x-rays are normal but clinical examination suggests the possibility of significant ligamentous injury. This may include reevaluation in several days as well as further imaging studies. Magnetic resonance imaging (MRI), arthrography, and MR arthrography may be extremely valuable tools in distinguishing these injuries from severe sprains. The differential diagnosis of acute ligamentous injury to the wrist includes a severe wrist sprain, an occult fracture of the distal radius or a carpal bone, and an acute exacerbation of a chronic ligamentous injury.

History

The mechanism of injury may be varied from severe to relatively minor because these injuries represent a spectrum of injury. Acute carpal dislocations typically are associated with a fall from a height, a motor vehicle accident, or a forceful extension of the wrist by a heavy object. Acute ligamentous injuries may occur by similar mechanisms, as well as by more minor falls and forceful torquing or twisting of the wrist. Acute carpal dislocations produce severe pain and/or visible deformity. Acute ligamentous injuries may produce less immediate pain and no deformity.

Physical Examination

Acute Carpal Dislocations

These injuries usually demonstrate significant deformity, marked soft-tissue swelling, marked limitation in wrist motion secondary to pain, and occasionally, decreased sensation. These injuries are rarely open. Two-point discrimination is diminished in the thumb, index, and long fingers if acute median nerve compromise is present. Carpal canal pressures should not be measured because of possible median nerve displacement.

Acute Ligamentous Injuries

Clinical findings in acute ligamentous injuries may be subtler. Although swelling may be present, it may not be all that impressive. Motion may be decreased secondary to pain during the first several days following injury; however, in the subacute setting, the patient may demonstrate near normal wrist motion but complain of pain at terminal flexion and/or extension. During the acute presentation, tenderness may be diffuse or localized to a specific region of the wrist (e.g., the scapholunate interval). Evaluation of the patient presenting in the subacute setting will more likely reveal focal tenderness. The specific areas to be evaluated for tenderness include the scapholunate interval, the lunotriquetral interval, and the foveal region on the ulnar aspect of the wrist. Specific tests to perform include the Scaphoid Stability test, the lunotriquetral shuck test, the Lichtman maneuver, and assessment of the stability of the distal radial ulnar joint.

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