Mallet Finger refers to an injury that causes the tip of the finger to droop, or ‘lag’. Mallet Finger is a very common injury that occurs when the extensor tendon on the back of the finger tears off the small distal interphalangeal (DIP) joint near the finger tip. Mallet Fingers can occur with minimal trauma, such as banging or pressing the finger against a hard object.
If the Mallet Finger occurs because the extensor tendon was lacerated or cut by a sharp object, then the tendon should be repaired surgically. If the thumb is involved, the tendon should be repaired in most patients. The reason is because healing and ultimate function is not the same in the thumb as it is in the fingers; the thumb’s extensor muscle is stronger, causing the torn tendon to retract more and to not heal as well. In addition, lack of full thumb extension can result in a significant loss of dexterity, making it hard to pinch accurately.
Mallet Fingers can be treated in a full-time splint for 8 weeks (Figure 11). That means ‘full-time’ in the strictest sense of the phrase, because any time the DIP joint flexes down all of the scar that has formed to try to heal the tendon gets torn. ‘Full-time’ means that that splint needs to be worn during showering or bathing. After the shower, to dry off the finger without allowing it to bend: place a dry washcloth down on a flat surface. Place the wet finger, palm side down, on the wash cloth so that the flat surface supports the finger and prevents it from drooping. Then remove the splint and use the sides of the washcloth to dry the finger. A splint can be dried with a hair dryer before being replaced. Or a second dry splint can be used.
The splint has to fit well in order to maximize tendon healing. Getting a good fitting splint is like getting a good fitting suit; if ‘off-the-rack’ works, that’s great. Otherwise, a custom splint should be made by a hand therapist.
Except in rare cases, the DIP joint will not become permanently stiff from this splinting. Even if it did, it’s really not a functional issue. However, if the adjacent larger joint, the proximal interphalangeal (PIP) joint located in the middle of the finger, gets stiff that’s a real problem. And the PIP joint loves to get stiff. To avoid PIP joint stiffness, it is important to make sure that no tape is placed over the PIP joint’s creases on the palmar side of the digit and that the digit is moved and used fairly normally.
The 8 weeks of full-time splinting is followed by 4 weeks of night splinting, from the time work is done until the next morning. If work is potentially injurious, then the splint should also be worn during any hazardous activities that could reinjure the finger. If the droop (lag) recurs during night splinting, then place the splint back on for another week of full-time splinting before resuming night splinting.
After all of this, the amount the fingertip lags will usually be improved by roughly 50%. Although some people do much better. Some residual lag is not uncommon following splinting.
Splinting only works when started within 3-6 months following injury. If the Mallet Finger is over 6 months old, or if splinting does not successfully resolve the condition, outpatient surgery may be considered. This involves pinning the involved joint, removing the scarred portion of the extensor tendon, and then repairing the good extensor tendon back to itself.
The slight displacement of the fracture fragment is inconsequential, has no effect, and older techniques that attempted to treat this had unnecessarily high complication rates.
After surgery, the dressing should not be touched, and should be kept clean and dry until the first post-operative visit, at 2 weeks. After that, a smaller splint is placed, and therapy begun, to regain motion of all finger joints except the subluxated one that was pinned. At that point, the pin can get wet in the shower. After showering, use a Q-tip dipped in hydrogen peroxide to remove any blood that has dried around the skin; this is important to avoid infection. Do not get the pin dirty or submerge it under water until 24 hours after it is removed in clinic at 4-5 weeks after surgery (often 6 weeks in smokers). Pin removal is not very painful at all.