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Mallet Finger

By

Danielle Campagne

, MD, University of San Francisco - Fresno

Last full review/revision Oct 2019| Content last modified Oct 2019

In Mallet finger, the fingertip curls down and cannot be straightened. It is usually caused by a tendon injury.

(See also Overview of Sprains and Other Soft-Tissue Injuries and Finger Fractures.)

Mallet finger usually results when the tendon that attaches bone to muscle in the fingertip is torn. This tendon (called the extensor tendon) is used to straighten the fingertip. Usually, the tendon is torn when a force causes the fingertip to bend more than it normally does. A common cause is a baseball that hits the fingertip and jams it. Thus, mallet finger is sometimes called baseball finger.

One or more fingers may be affected. Sometimes the joint is also dislocated.

When the tendon tears, it may pull a piece of bone from the finger (called an avulsion fracture). When an avulsion fracture occurs, the cartilage at the end of the affected bone (the joint surface) is also fractured.

Mallet Finger

People with Mallet finger cannot straighten the end of their finger.

Mallet Finger

Symptoms

The finger is usually painful, swollen, and bruised immediately after the injury. The joint remains bent. The person cannot straighten it. Occasionally, blood collects under the nail (called a subungual hematoma).

Diagnosis

  • Physical examination
  • X-rays to check for fractures

Doctors can usually diagnose mallet finger when they examine the finger.

X-rays are usually taken at several different angles to check for a fracture.

Treatment

  • A splint

Usually, doctors straighten the finger, then place a splint on it to hold it in a position that is bent slightly upward (in extension). The splint is worn for 6 to 8 weeks.

Rarely, when a fracture involves a large part of the joint surface or when the joint is dislocated, surgery is needed.

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