Introduction

Injuries to the fingers are common including injuries to the distal interphalangeal, or DIP, joint of the finger. This joint is commonly injured during sporting activities such as baseball. If the tip of the finger is struck with the ball, the tendon that attaches to the small bone underneath can be injured. Untreated, this can cause the end of the finger to fail to straighten completely.

The main finger joint is the metacarpophalangeal joint (MCP). It is formed by the connection of the metacarpal bone in the palm of the hand with the first finger bone, or proximal phalanx. Each finger has three phalanges, or small bones, separated by two interphalangeal (IP) joints. The one closest to the MCP is called the PIP, or Proximal IP joint. The joint near the end of the finger is called the DIP, or Distal IP joint.

The extensor tendon is attached to the base of the distal phalanx. When it tightens, the finger straightens. Another tendon, the flexor tendon, is attached to the palm of the finger. When it pulls, the DIP bends.

Causes

A mallet finger results when the extensor tendon is torn from the bone. When this occurs, a small fragment of bone may be pulled, or avulsed, from the distal phalanx. The end of the finger droops down and cannot be straightened.
  
Symptoms

Initially, the finger is painful and swollen around the DIP joint. The end of the finger is bent and cannot be straightened voluntarily. The finger can be straightened easily with help from the other hand.

Diagnosis

Usually the diagnosis is evident from the physical examination. X-rays are required to see if there is an associated fracture since this may change the recommended treatment. No other tests are normally required.

Treatment

Conservative Treatment

Treatment for mallet finger is usually nonsurgical. If there is no fracture, then the assumption is that the end of the tendon has been ruptured, allowing the end of the finger to droop. Usually continuous splinting for six weeks followed by six weeks of nighttime splinting will result in satisfactory healing and allow the finger to extend.

The key is continuous splinting for the first six weeks. The splint holds the DIP joint in full extension and allows the ends of the tendon to move as close together as possible. As healing occurs, scar formation repairs the tendon. If the splint is removed and the finger is allowed to bend, the process is disrupted and must start all over again. The splint must remain on at all times, even in the shower.

There are many splints that have been designed to make it easier to wear at all times. In some extreme cases where the patient has to use the hands to continue working (such as a surgeon), a metal pin can be placed inside the bone across the DIP joint to act as an internal splint and allow the patient to continue to use the hand. The pin is removed at six weeks.

Splinting may even work when the injury is quite old. Most doctors will try a six-week trial of splinting to see if the drooping lessens to a tolerable limit before considering surgery.
 
Surgery

Surgical treatment is reserved for unique cases. The first is when the result of conservative treatment is intolerable. If your finger droops too much or the tip of your finger gets caught as you try to put your hand in a pocket, this can be quite a nuisance. If this occurs, the tendon can be repaired surgically, or the joint can be fused in a fixed position.

The other case is when there is a fracture associated with the mallet finger. If the fracture involves enough of the joint, it may need to be repaired. This may require pinning the fracture. If the damage is too severe, it may require fusing the joint in a fixed position.

Rehabilitation

Rehabilitation during and following treatment for a mallet finger focuses mainly on keeping the other joints mobile and preventing stiffness from disuse. A physical or occupational therapist may be consulted to teach you home exercises and make sure the other joints do not become stiff. Once the mallet finger has healed sufficiently, exercises may be instituted to strengthen the finger involved and increase flexibility.