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Mallet finger is a common tendon injury that occurs in everyday life, so termed due to the classic presentation of a finger deformity that resembles a “hammer” or ”mallet”.

 

You are playing a friendly game of basketball with your friends on the weekend and you reach overhead to catch a ball thrown to you. However, instead of getting a firm grip on the ball, it hits you on the finger and bounces off. You feel a “pop” in your finger as this happens and when you look at the finger, something does not look right. The last joint of the finger seems to be jammed in a bent position and try as you might, you are not able to straighten it on your own. There is also some pain and swelling over the last joint of your finger, but not too much to cause immediate concern. “Maybe it’s just a mild sprain and it’ll get better on its own in a few days”, you think. After a few days, the pain and swelling seems better, but you are still unable to straighten the last joint of your finger. What is happening here? Will you be able to straighten your finger ever again? If this sounds like a familiar scenario, it is likely that you have sustained a mallet finger injury.

What is a mallet finger?

Mallet finger is a common tendon injury that occurs in everyday life, so termed due to the classic presentation of a finger deformity that resembles a “hammer” or ” mallet”. Also known as a “baseball finger”, this finger deformity results from the disruption of a muscle tendon, called the extensor tendon, which helps to straighten the last joint of your finger or thumb. The extensor tendon travels along the back of the finger or thumb and attaches to the last bone of the digit. Its main function is to assist in the straightening of the thumb or finger.

During injury, this tendon is torn from its attachment site on the bone (called a tendinous mallet finger). But, there are also cases whereby the force of impact causes a small fracture at the base of bone where the tendon is attached to (called a bony mallet finger). In both cases, the tendon is no longer attached to the last bone of the digit and is thus unable to pull the end joint into a straightened position, resulting in a fingertip that droops.

How common is a mallet finger injury?

The prevalence of mallet finger is relatively high, accounting for 9.3% of all tendon and ligament lesions in the body. Injury trends indicate that it is more common among young to middle-aged men and occasionally in older women. 74% of mallet injuries occur in the dominant hand, and >90% of the injuries involve the middle, ring and/or little fingers.

How does a mallet finger occur?

Common injury mechanisms include (clockwise from right to left): (a) stubbing the finger against a hard surface while cleaning, (b) injuring the finger while removing a sock forcefully, (c) injuring the finger while tucking in bedsheets, and (d) the hand/finger is hit by a ball during sports activities.

A tendinous mallet injury (only the tendon is ruptured) usually occurs from a traumatic blow, which results in the sudden forceful bending of the end joint of the finger (e.g. the hand is hit by a ball during sports activities, the finger is injured after a fall, stubbing of the finger against a hard surface while cleaning furniture). This force tears the tendon at the back of the finger from its attachment site on the bone. Occasionally, the force of the impact may be strong enough to break off a piece of bone (fracture) together with the tendon, resulting in the aforementioned bony mallet finger. Finally, a crush injury over the fingertips (e.g. having a finger caught in a door) or a deep cut over the back of the fingertip can also result in detachment of the tendon.

What are the signs and symptoms of mallet finger?

In the initial stages following the injury, you may experience pain, swelling and bruising over the end joint of your finger or thumb. The end joint of your finger stays in a bent position and there is an inability to straighten the joint on your own, unless helped by your other hand.

How can mallet finger be treated?

It is important to seek early treatment for mallet finger as treatment success rates tend to decrease as more time passes by before the start of treatment.

Non-surgical Treatment Options

Most mallet finger cases can be treated successfully without surgery. Generally, the doctor will refer you to an occupational therapist, who will fabricate a customised splint for your finger. This splint will help to support your fingertip in a straight position so that the ends of the ruptured tendon are positioned close to each other, allowing for healing to take place. It is therefore of utmost importance that this splint is worn at all times for a period of at least 6 to 8 weeks. There should be no movement of the end joint of the finger during this period as bending of the joint during can lead to a re-rupture of the tendon.

After this period of immobilisation, if your finger has regained the ability to straighten on its own, your therapist will advise you on gentle exercises that will help you gradually regain the movement and strength of the finger. The amount of time required for splint wear will also be gradually reduced according to your progress. It usually takes around 4 to 6 weeks of therapy after immobilisation to regain maximal movement and strength of the injured finger.

Surgical Treatment Options

Surgery may be needed for mallet injuries under the following circumstances:
– Bony mallet injuries where the bone fragment that broke off is of a larger size
– The presence of joint misalignment
– The tendon has been injured via a cut by a sharp object
– Previous non-surgical management by splinting has been unsuccessful

Surgical procedures may include the use of wires or small screws/metal plates to help realign the joint or re-attach the fracture fragment onto the original bone, as well as the repair or reconstruction of the cut tendon. Regular therapy sessions are usually required after surgery to help in regaining movement and strength of the injured finger/thumb.

Why is it important seek early treatment for mallet finger?

Without early treatment of a mallet finger, the extensor tendon will not be able to re-attach itself onto the bone and heal, leading to a permanent deformity of the finger. Over time, this may continue to worsen due to the imbalance in muscle tendon forces, resulting in a swan-neck deformity of the finger, where the middle joint becomes hyperextended in addition to the end joint being in a permanently bent position. Swan-neck deformities can cause difficulties in finger bending, as well as a snapping sensation during finger movements.

OT Joanna Lim is a senior hands specialist in the Lifeweavers team. She is passionate about ergonomics and rehabilitation of hand and fingers injuries, often writing specialised articles like this on her blog and contributes to the Lifeweavers Magazine.

Sources:
American Society for Surgery of the Hand. (2020). Mallet finger: Symptoms & Treatment: The hand society. Retrieved April 13, 2021, from https://www.assh.org/handcare/condition/mallet-finger

Physiopedia. (2021). Mallet finger. Retrieved April 13, 2021, from https://www.physio-pedia.com/Mallet_Finger

Salazar Botero, S., Hidalgo Diaz, J., Benaïda, A., Collon, S., Facca, S., & Liverneaux, P. (2016, March 18). Review of acute traumatic closed mallet finger injuries in adults. Retrieved April 13, 2021, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4807168/

Sheth, U. (2019). Mallet finger. Retrieved April 13, 2021, from https://www.orthobullets.com/hand/6014/mallet-finger

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