Mallet finger is an injury to the thin tendon that straightens the end joint of a finger or thumb. Although it is also known as "baseball finger," this injury can happen to anyone when an unyielding object (like a ball) strikes the tip of a finger or thumb and forces it to bend further than it is intended to go.

As a result, you are not able to straighten the tip of your finger or thumb on your own.

Classification
In a mallet injury, when an object hits the tip of the finger or thumb, the force of the blow tears the extensor tendon. Occasionally, a minor force such as tucking in a bed sheet will cause a mallet finger.

The injury may rupture the tendon or pull the tendon away from the place where it attaches to the finger bone (distal phalanx). In some cases, a small piece of bone is pulled away along with the tendon. This is called an avulsion injury.

History
In mallet finger, the patient’s history involves a forced distal interphalangeal (DIP) joint flexion injury, after which he or she notices an inability to actively extend the distal joint (although full passive extension remains intact). The dorsum of the joint may be slightly tender and swollen, but often the injury is painless or nearly painless.

Physical examination
Physical examination findings of mallet finger include localized swelling and tenderness to palpation at the affected DIP joint, as well as an inability to actively extend the injured joint.

Treatment
Mallet finger injuries that are not treated typically result in stiffness and deformity of the injured fingertip. The majority of mallet finger injuries can be treated without surgery.

Nonsurgical treatment
Mallet injuries, whether bony or tendinous, should be addressed with closed treatment. Splinting of the distal interphalangeal (DIP) joint in full extension allows healing of the injured structure and restoration of excellent function and appearance. To restore function to the finger, the splint must be worn full time for 8 weeks. This means that it must be worn while bathing, then carefully changed after bathing.

For 3 to 4 weeks after the initial splinting period, you will gradually wear the splint less frequently — perhaps only at night. Splinting treatment usually results in both acceptable function and appearance, however, many patients may not regain full fingertip extension.

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Surgical treatment
Your doctor may consider surgical repair if there is a large fracture fragment or the joint is out of line (subluxed). In these cases, surgery is done to repair the fracture using pins to hold the pieces of bone together while the injury heals.

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