Lunate Dislocation

A lunate dislocation is an injury to one of the small bones of the wrist. Lunate dislocations usually occur as part of a major injury such as a fall from a height or an automobile collision. When a lunate dislocation occurs, one of the small bones of the wrist, called the carpal bones, comes out of its normal position.

What are the symptoms of a lunate dislocation?
The typical symptoms a lunate dislocation are:

• Significant pain in the wrist and palm of hand

• Swelling of the hand

• Limited motion of the wrist and hand

• Tingling and numbness of the fingers

The reason tingling and numbness are common in patients with a lunate dislocation is that the bone pushes into the carpal tunnel. The carpal tunnel contains the median nerve. This nerve is pinched in carpal tunnel syndrome. A lunate dislocation can be the cause of acute onset carpal tunnel syndrome.

What tests are needed to diagnose a lunate dislocation?
A lunate dislocation can be seen on a regular x-ray. However, the appearance of a lunate dislocation can be subtle, especially if the x-rays are done with the hand slightly rotated. When people have severe injuries, getting good x-rays can be uncomfortable and difficult. However, it is important to have proper x-rays to evaluate for injuries such as a lunate dislocation.

A CT scan or MRI can be helpful if there is a question of the diagnosis. Furthermore, lunate dislocations can occur as part of a group of injuries including fractures and ligament tears. Further studies may be performed to evaluate for other injuries in the wrist.

What is the treatment of a lunate dislocation?
It is important to reposition the lunate bone so that it is properly oriented. Sometimes this can be done in the emergency room, but often this needs to be treated surgically. Even if the lunate dislocation can be repositioned nonsurgically, a surgical procedure is usually required to stabilize the bones to allow for proper healing.

Lunate dislocations are usually held in place using pins that come through the skin for later removal in the office. A carpal tunnel release may be performed at the time of surgery if there were symptoms of carpal tunnel syndrome. Additionally, surgery may address other fractures and ligament tears that occurred at the time of the injury.

Complications are common after sustaining a lunate dislocation. These can include wrist arthritis, persistent pain, and instability of the wrist joint. Prompt treatment helps to lower the chance of these complications, but they are still common. Recovery from a lunate dislocation will take a minimum of 6 months, if not longer.

_Sources:

SH Kozin "Perilunate injuries: diagnosis and treatment" J. Am. Acad. Ortho. Surg., Mar 1998; 6: 114 - 120.