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What is a mallet finger?

A mallet finger describes a condition in which the end of a finger is bent (flexed) towards the palm and cannot straighten.

The usual cause is an injury to the end of the finger. The injury tears the tendon that straightens (extends) the end of the finger.

It is sometimes called baseball finger, as it is a common injury when trying to catch a fast, hard ball. If the catch is missed slightly then the ball hits the straight finger. This may force the end of the finger to bend (flex) further than normal and tear the tendon. Without the use of this tendon, the finger stays bent (flexed).

Diagram of the hand showing mallet finger

Lesões esportivas are a common cause of mallet finger. However, any injury that forces the end joint of a finger to over-bend can cause it. (Sometimes the tendon does not tear but the injury causes a piece of bone to be pulled off the finger where the tendon is attached. This is called an avulsion fracture. The result is the same, as the tendon then cannot pull on the bone.)

After the injury, the end of your finger may:

• Be painful and swollen.

• Lie in a bent (flexed) position.

• Not be able to straighten (extend) at the end.

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  © Clappstar, CC BY-SA 4.0, via Wikimedia Commons

The clinician can usually diagnose a mallet finger from listening to how the injury occurred and how the finger looks and feels when examined. If there is any doubt they may request an x-ray.

Splint

A splint is worn for 6-8 weeks to keep the finger straight with the end joint bent backwards slightly (overextended). It must be worn all the time, day and night.

There are many different types of splints available. The type of splint given often depends on the size and shape of your finger. You must not take the splint off at any time during this treatment. If you have to take it off (for example, to wash) then you must keep that finger straight and not allow it to bend (flex).

Keeping the finger straight constantly allows the two ends of the torn tendon or bone to stay together and heal. About three in four cases heal well with this treatment.

Cirurgia

Surgery is needed to repair the torn tendon if the above fails. (Surgery may be advised straightaway if there is a cut to your finger; however, most injuries that cause mallet finger do not cut the skin.)

It may take several months for your finger to fully recover its function. Any redness, swelling and tenderness of your skin over the end of your finger may persist for the first few months after the injury. These symptoms will usually improve eventually.

As most mallet finger injuries occur during sports, taking care when playing with a hard ball is advisable but prevention may not always be possible. You can prevent the deformity returning by using the splint exactly as directed by your clinician.