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A mallet finger is a deformity of the finger caused when the tendon that straightens your finger is damaged, commonly caused by a direct blow to the fingertip.
What is mallet finger?
The extensor tendon found on the backside of the hand, and the flexor tendon, found on the palm side, work together to extend the fingertip. Mallet finger is an injury to the extensor tendon that causes an inability to extend the fingertip. It is commonly caused by a direct blow to the fingertip, such as while trying to catch a ball.
The major symptom of mallet finger is an inability to actively extend the fingertip as well as pain and swelling.
Mallet finger may be treated with or without surgery. Non-surgical treatment consists of placing a splint with the fingertip extended. Flexion of the fingertip at any point during the treatment period will delay healing. More complex injuries, or cases where there is a persistent deformity after non-operative treatment, will require surgical management.
You should see your primary care doctor or visit an urgent care clinic within 24 hours. Diagnosis involves x-rays to determine severity of injury. Treatment is splinting. If the bone is poking through the skin, go to the emergency room immediately.
Mallet finger symptoms
Usually, mallet finger is caused by a blow to the extended fingertip. Athletes are at the highest risk, as the injury can involve a ball, another player, or hitting the ground. The diagnosis of mallet finger is made based on physical examination and X-rays.
The main symptoms of mallet finger include:
- Limited motion: Rupture of the extensor tendon causes the fingertip to drop, and the person will be unable to actively straighten the finger. In most cases, it will be possible for another person to extend the fingertip (passive extension), but in severe cases where there is an injury to additional structures other than the extensor tendon, the fingertip will be stuck in a flexed position.
- Pain: The fingertip will usually be painful, particularly when it is palpated (pushed on).
Often the fingertip will appear normal other than being flexed, but sometimes it may have an abnormal appearance, such as:
- Blood collection under the fingernail: If the fingertip injury also involves the fingernail, a collection of blood beneath the fingernail may be visible as a dark spot.
- A detached fingernail: The fingernail may start to detach from the finger.
What causes mallet finger?
Each finger other than the thumb has three bones (phalanges), creating two joints where the finger can bend. The joint between the middle bone and the bone at the tip of the finger is called the distal interphalangeal joint. The flexor tendon (running over the joint on the same side as the palm) flexes the tip of the finger, while the extensor tendon (running over the joint on the backside of the hand) extends the tip of the finger. Injury to the extensor tendon results in mallet finger and is commonly caused by a blow to the fingertip or some other injury.
Blow to the fingertip
One common mechanism of mallet finger is a blow from a ball during a sports event, such as football or baseball. Mallet finger usually occurs via a direct blow to the extended fingertip, and the injury can be described by:
- The finger was straight rather than bent: The flexor tendon is relaxed and the extensor tendon was pulled tight.
- The blow caused sudden bending: This can stretch or tear the extensor tendon, resulting in mallet finger.
- Bone injury: In some cases, a piece of bone gets torn off along with the extensor tendon.
Less commonly, mallet finger can be caused by a direct injury to the extensor tendon, such as when the finger is:
- Forcefully hyperextended
Who is most likely to be affected
The individuals at the highest risk for mallet finger or further complications are:
- Athletes: Those in sports like rugby and football, or that involve direct contact and have fast-moving balls.
- Those who do not seek care promptly: People who present for treatment long after the injury occurred.
- Those who fail to follow instructions: This includes failing to use a provided splint or moving the finger prematurely.
Treatment options and prevention for mallet finger
Mallet finger is diagnosed by the presence of characteristic findings on physical exam and X-rays for confirmation. Surgical and non-surgical management can both have good outcomes, so the type of treatment should be chosen based on particular characteristics of the injury as well as individual factors.
Mallet finger is typically treated by splinting the fingertip in an extended position for six to 12 weeks and keeping the following in mind:
- Factors for successful treatment: This is highly dependent on keeping the finger straight at all times, even when changing the splint. If the fingertip is flexed, the treatment period may need to be restarted.
- Using the splint at proper times: You can continue playing sports while the finger is still in the splint. Eventually, the splint is worn only at night and during sports, and then it can be removed altogether.
Surgery is typically preferred in more complex injuries, such as with a large bone fragment or dislocated joint, although there is evidence showing that non-operative management can still be effective in these cases.
- Pinning: One option for operative management is pinning the joint in an extended position.
- Open surgery: If it is not possible to straighten the finger, open surgery will be required.
When to seek further consultation for mallet finger
It is important to seek care if you suspect you have a mallet finger injury in order to restore function and prevent further complications.
You should seek medical attention any time you injure your finger to the point that it is impaired or you experience:
- Immobility: You are unable to move your finger normally after an injury, particularly if it is stuck in one position.
- A deep cut: Get emergency medical care if you have a deep laceration to the finger with the tendon exposed.
Though treatment for mallet finger is usually successful, complications can occur during and/or after the splinting period and require evaluation if you experience:
- An abnormal fingertip appearance: Splinting can lead to skin damage and/or loss of blood supply to the fingertip (causing the skin to turn white), often due to overextending the finger. Your medical provider can provide guidance on how to prevent further damage by splinting properly.
- Difficulty with splinting: Keeping the finger straight at all times, even during splint changes, can be challenging. Given how important it is to prevent flexion during the treatment period, your medical provider may recommend coming to the office for splint changes.
- Persistent abnormalities: Delayed presentation or failure to keep the finger straight throughout the full treatment period can prevent normal healing. Seek medical attention if you are still unable to actively extend the fingertip after treatment, or if you develop a "swan-neck" deformity where the first joint in the finger is hyperextended and the distal joint is flexed. In these cases, operative management will likely be necessary.
Questions your doctor may ask to determine mallet finger
- How would you describe what happened to your finger?
- How severe is your finger pain?
- Can you move your injured finger fully?
- Where exactly is your hand pain?
- Do you have a rash?
Self-diagnose with our free Buoy Assistant if you answer yes on any of these questions.
Lauren is a resident physician in family medicine at the University of Illinois at Chicago. She earned her medical degree at the University of Pennsylvania and her undergraduate degree at Oberlin College. Lauren also has an interest in teaching as well as experience with college tutoring and writing MCAT preparatory materials. She believes family medicine challenges her to maintain a broad field of medical knowledge and she hopes to work in an academic setting in the future. In her free time, Lauren enjoys running, reading, and visiting historic sites.
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