Mallet Finger

A mallet finger is a deformity of the finger typically caused by injury. After the fingertip gets jammed, the end joint just before the fingernail droops and looks crooked, giving the finger the appearance of a mallet or hammer.

Causes

The cause of this condition is an injury to the extensor tendon, which straightens the end joint just before the fingernail. There are two types of mallet finger. The first type is an injury to the extensor tendon itself called a rupture. This can happen quickly from jamming or cutting the finger, and it can happen slowly from arthritis stretching out the tendon over time.

The second type is a broken bone at the extensor tendon’s attachment site that prevents the tendon from pulling on the whole bone. The tendon itself is intact, but the bone it attaches to breaks off. In children, the fracture may happen in the growth plate of the distal phalanx.

Mallet fingers can happen when an object, such as a ball, strikes the tip of the finger or thumb. This condition is sometimes called “baseball finger” because it can happen when catching a baseball bare-handed.

This condition can also happen when the small joint is forcefully bent during use, such as lifting heavy objects that force the joint into a bent position. Sometimes, the tendon can rupture from only a little force exerted at just the wrong angle, such as scrubbing dishes or bumping an object when putting clothes into a drawer.

A mallet finger can also result from a deep cut from a knife or sharp object on the back of the finger. This cut can go down to the bone and divide the extensor tendon away from the bone.

Symptoms

In a mallet finger, the fingertip droops and cannot straighten on its own. At first, it may look like just a “jammed finger.” The finger may be painful, swollen, or bruised. A bump may appear just below the nail on the back of the finger.

Blood can collect beneath the nail, and the nail can even become detached at the base. This occurs most commonly with the broken-bone type of mallet finger.

An “open” mallet finger starts with a sharp cut or laceration, which goes through the tendon and down to the bone over the last joint of the finger.

Sometimes, mild drooping of the last joint in all fingers is seen normally in some people because of tissue laxity or flexibility rather than injury.

Diagnosis and Treatment

Medical attention should be sought within the first few days after the injury, especially if there is blood beneath the nail or if the nail is detached at the base. This may be a sign of a nail bed injury or an open fracture. Injuries with even a little swelling or bruising may have a fracture.

X-rays or ultrasound images can be used to show whether there is a fracture causing the finger deformity. CT scans may be ordered if there are many fracture fragments. In children, the fracture may involve the growth part of the bone.

Mallet fingers with exposed bone or with a cut tendon should be treated urgently to prevent infection. If a mallet finger is not treated promptly, the finger may not function properly and may cause pain.

Non-Surgical Treatment

Most mallet finger injuries can be treated without surgery. Many are treated with non-removable finger splinting until the tendon heals itself or the bone seals the fracture.

If there is no cut or laceration, ice can be applied to help decrease swelling, and the hand can be elevated. A temporary splint can be used to keep the fingertip straight until medical evaluation. Tape should be loose enough to allow sensation and blood flow to the fingertip.

After diagnosis and reduction in swelling, there are many types of splints and casts for mallet fingers. The goal is to keep the finger straight at the small joint until it is fully healed. A splint is commonly worn at all times for about eight weeks. If the joint flexes even briefly while the splint is off, healing can be disrupted and the process may take longer.

After the tendon or bone has healed, the splint may be worn only during sleep and sporting activity for additional weeks or months to prevent re-injury. Your surgeon or hand therapist will provide specific instructions and exercises.

Surgical Treatment

Surgery may be considered for closed mallet fingers when the skin is open and the nail is injured, the joint is not properly aligned because the bone fragment is too large, or it is not possible to wear a splint at all times or keep the finger and splint dry.

Surgery may involve inserting a wire, pin, or screw into the finger to keep it straight, making a new tendon if the original injury is too severe, or permanently straightening the joint so that it stays fixed and does not bend with grasp. Permanent straightening is irreversible and is usually done for arthritis.

In summary, mallet fingers are “jammed” fingertips that appear drooped or crooked at the end joint. Prompt care should result in a full recovery. Your hand surgeon will help recommend the proper treatment specific to your injury.

Disclaimer: This mobile-friendly version is adapted from patient education content originally provided by the American Society for Surgery of the Hand.