A mallet finger describes deformity where there is an inability to straighten (extend) the last joint of the finger or thumb. This means that the last segment of the finger including the fingernail, droops. The deformity results from the tendon that straightens the joint tearing (avulsing) away from the base of the bone. Sometimes a small chip of bone can be pulled off. This happens when something strikes the tip of the finger and forces it into a bent (flexed) position, such as a cricket ball, but may also happen in a situation where the finger is accidentally driven into something more solid such as tucking the sheet in under a heavy mattress. The initial injury may be surprisingly pain free and may not even be noticed until the deformity becomes apparent.
Fortunately, this tendon does not retract and if the bone is kept in kept in contact with the tendon by splinting in extension for usually six weeks, it will re-attach and restore normal function. Occasionally surgery may be indicated to achieve this in specific circumstances, more often than not, involving fracture or where the diagnosis has been delayed. Your therapist will make a custom fitting thermoplastic splint which is easy to wear and supervise you through the process.