A mallet finger is an injury to the last finger joint only. If left untreated, or poorly treated, a mallet finger can progress to a swan neck deformity affecting the whole finger. In a swan neck deformity, the middle finger joint gradually bends backwards as the muscles and ligaments adjust to the fingertip bending forwards. This looks unusual, and most importantly, leads to difficulty bending the finger in day-to-day activities. The first signs of this will be an uncomfortable snapping of the tendons as you try to bend the finger.
Mallet finger occurs when the tendon that holds the fingertip straight is torn, pulled away from the bone or cut through the skin. The tendon (terminal extensor) is often torn or pulled away from the bone when the tip of the finger is forced bent by a ball or when the fingertip is caught in the bedsheets, as an example.
A cut or laceration to the back of the finger can go straight through the tendon, which will also cause mallet finger. Mallet finger occurs more easily in people with weakened tendons, from rheumatoid arthritis, for example.
Mallet finger may be painful or swollen, but is sometimes neither. The tip of the finger will drop down because the tendon or bone is no longer connected. When the actual tendon is ruptured, the condition can be relatively painless. If a piece of the bone is pulled off, it is normally a bit more swollen and sore.
A mallet finger can be diagnosed by the appearance of the finger with the drop of the fingertip and your history of how the injury occurred. An X-ray may be taken, which will show if the injury is an avulsion fracture or a tendon rupture. It will also show if there is a fractured bone, which could also cause the finger to look like a mallet.
Your physiotherapist will assist you by making a moulded thermoplastic splint to extend the finger. This will be worn full time for 6–8 weeks to allow the tendon or bone to heal back together. Your physiotherapist will show how you can clean and look after your finger while wearing the splint during that time. If the finger bends during this time, it will damage the healing, so you need to be comfortable in the splint and be shown how to take care of the skin for that period of time.
After the first eight weeks, you will continue the splint part time, often overnight while you regain your movement. For a further month or two, a splint should be worn during sport.
Surgery to repair a mallet finger is required when the bone fragment is large, when the fingertip has moved position a little or when the cause is a laceration.
It’s important to note that not all physiotherapists are specialised in the area of hand therapy. For the best treatment outcome, find a physio who specialises in this area.
Splinting treatment usually allows the tendon or bone to heal effectively. Most patients regain full movement and strength at the completion of treatment, but some patients will not get their finger perfectly straight. The results are best when splinting is commenced early, when the splint is holding the finger in exactly the right position and is worn for the right amount of time.
It’s quite important that the finger is dead straight or bent a little bit backwards in the splint. If your finger is sitting in the splint in a slightly bent position, then the finger will heal up bent.
A properly moulded splint worn continuously is the best treatment. It is important to follow the instructions of your physiotherapist during the splinting phase to get the best result. This may include regular appointments to check you are managing well with your splinting and your skin is in good condition.
When the tendon is strong enough to hold the fingertip straight, you will be given a schedule to gradually wean out of the splint safely. If you are playing sport with your splint on, you need to strap it on firmly with sports tape to make sure it doesn’t fly off.
