A mallet finger is a common injury caused by the tearing of a tendon at the tip joint of the finger. When this particular tendon tears, the tip of the finger droops down into a flexed position, simulating the appearance of a small hammer (or mallet). It is a frequent sports injury when a ball unexpectedly strikes the tip of a finger, but can occur under any circumstance where the fingertip is forcibly flexed.
The joint closest to the tip of the finger is known as the distal interphalangeal joint (DIP joint). There are two tendons that control the movement, a flexor tendon on the palm side and an extensor tendon on the back side. If the tip of the finger is flexed past its normal limit, the extensor tendon will either tear or detach. Once the tendon is disconnected, the fingertip cannot be held straight without support. Under certain circumstances, the tendon will sometimes detach along with a small piece of bone. The only way to know if this has happened is by x-ray.
The vast majority of mallet fingers can be treated with immobilization in a splint. Even when completely torn, the extensor tendon at this location does not retract away. The torn ends of the tendon can be brought back together by splinting the joint in full extension. Typically, over a period of 8-12 weeks the body lays down scar tissue to repair the tear. A physician, sometimes with the help of a hand therapist, chooses from a variety of splints to keep the DIP immobilized during healing. The key to proper healing is maintaining the splinted position without interruption, especially in the first six weeks. Allowing the joint to bend during this critical period causes the healing tissue to stretch or tear, prolonging the healing time and sometimes leading to persistent drooping.
In a minority of cases, simple splinting is not sufficient to keep the finger properly aligned. Surgery is occasionally considered to repair or tighten the torn tendon or to realign an associated bone fragment. This is done in an outpatient setting, usually without the need for general anesthesia.