Mallet Finger

Mechanism of Injury

As described above, a ball or object forcefully contacts the tip of an athlete's finger. The trauma results in a sharp movement of the distal interphalangeal (DIP) joint or the last joint of the finger from extension to flexion. This sharp movement results in a tearing of the extensor tendon on the dorsal (top) part of the finger (see Figure 1). The extensor tendon is very thin at this point of the finger, so it is easily damaged. If the resultant force is a slower blow, then an avulsion injury (chip fracture with the tendon intact) can occur. The athlete would exhibit swelling, bruising, or inability to extend the distal part of the finger. Typically, passive extension remains, and the athlete may think it is only a sprain.

Symptoms

The athlete may experience pain at the tip of the finger; however, the main symptom remains the inability to actively extend the distal portion of the finger. Blood may be present below the nail bed. If a patient notices blood under the nail bed, he or she should seek immediate medical attention as a detached nail bed signifies an open fracture.

Figure 1 Mallet Finger

Notes: Mallet finger is a traumatic injury to the distal finger, resulting in tearing of the extensor tendon. Often a small portion of bone comes off, too, making it a tendon avulsion injury.

Diagnosis

A sports medicine physician will examine the finger for active and passive range of motion. In addition, palpation of the dorsal aspect of the distal finger may result in pain or a palpable defect (i.e., a hardened bump or divot). An X-ray of the finger may be taken to discern whether it is an isolated tendon injury or an avulsion injury. An avulsion injury signifies that a piece of the distal finger bone has become dislodged with the tendon.

Treatment

The majority of mallet finger injuries are treated nonoperatively. The key to healing remains early detection and compliance with the treatment. The patient should apply ice for the first 4 days after the injury to decrease the swelling. The patient needs to be splinted in full extension for 6 to 8 weeks at all times. Two types of splints exist. First, the sports medicine physician may use an aluminum splint. The aluminum splint is placed on the dorsal aspect of the finger past the DIP joint to incorporate the distal and middle phalanges. Athletic tape is used to affix the splint to the finger. The second type of splint is called a “stack” splint. The stack splint is plastic in nature and surrounds the middle and distal portions of the finger. The advantages of the stack splint include increased compliance secondary to comfort and ease of use. The splint affixes to the finger with tape and sits under the finger, as opposed to over it like the aluminum splint. (The aluminum splint can occasionally fall off due to the taping.) On follow-up visitation during the 6 weeks of splinting, a repeat X-ray may be taken. If the physician removes the splint during one of the follow-up visits, the finger should not be manipulated as this movement could reinjure the finger.

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