A mallet finger is a deformity of the finger caused when the tendon that straightens your finger (the extensor tendon) is damaged.

The Anatomy of the Finger & Tendons

The terminal tendon – or part of the extensor tendon that attaches at the very end of the finger – is very thin and very susceptible to injury. When the end of the finger is loaded – or flexed – against a source of resistance, the extensor tendon may tear off of the left bone. This injury as known as a mallet finger. (Note that the tendon may also pull off of the distal phalanx. This injury is known as a mallet fracture.)

Tendon injuries of the fingers are sometimes referred to as “baseball finger”. We feel that a better nickname is “basketball finger” because of the high incidence of this injury in basketball players. Many patients involved in the sport described pushing with their finger against resistance on the court, only to have the finger suddenly flex (to the point of injury). The result of the sudden flexing was the mallet deformity where the left joint, or DIP joint, is flexed or droopy. 

The Diagnosis

An examination often reveals cases of mallet finger. During these exams, the finger is found to be drooped or flexed at the DIP joint, resulting in an inability to extend the finger against any resistance. The general ability to flex the finger, however, is usually still intact. 

X-rays may be needed to reveal the presence of a mallet fracture. In these cases, a small piece of bone is often retracted towards the hand along with the extensor tendon.

The Treatment

Conservative treatment is usually the first choice for mallet finger/mallet fracture injuries:

  • The finger is placed in a plastic stack splint, which holds the DIP joint straight. (In the case of mallet fractures, an x-ray is taken after straightening the finger in a splint to make sure that the fracture fragments are back in place.) 
  • It is important to maintain the DIP joint in the straight position for 6 to 8 weeks in order for the tendon or fracture to heal. If the splint is removed at all during that time, the DIP joint must be maintained in a straight position. 

With proper conservative treatment, success rates for recovery are approximately 80%. Some patients will have a minor droop at the DIP joint, but will maintain an amount of functionality in their finger(s) regardless.

If conservative treatment via a splint fails cannot adequately and properly position the joint (or in cases where the conservative treatment has not worked and there is a residual significant droop of the DIP joint), surgical repair is a necessary next step. 

  • This surgery is usually performed on an outpatient basis, under general anesthesia or regional block anesthesia. 
  • A small incision is made over the top (dorsum) of the finger near the attachment of the extensor tendon. 
  • The fracture is repaired (if the fragments are large enough) or the fragment attached to the extensor tendon is removed. Then the extensor tendon is repaired to the bone with a small anchor. 
  • A pin may be placed across the DIP joint to hold it in extension while the tendon heals.
  • The skin is closed and a protective dressing and splint are applied.
  • The pin, if used, is usually removed in the office at 6 weeks when the tendon or fracture is healed. 
  • Therapy is then initiated. 

Risks with the surgery are anesthesia-related risks, wound healing problems, infection, stiffness of the joint, or poor healing of the tendon/fracture post-op. 

Note that in a very small group of patients (where surgery does not lead to satisfactory results) the DIP joint may require surgical fusion to help a patient regain a functionally correct position of their finger(s).