Mallet finger refers to an injury that causes the finger tip to droop. These are very common injuries that occur when the extensor tendon on the back of the finger tears off the small joint (the distal interphalangeal joint or DIJ) near the finger tip. Mallet fingers can occur with minimal trauma, such as banging your finger against a hard object or sometimes just pulling hard on something
Mallet fingers can be treated in a full-time splint for 6 weeks. That means ‘full-time’ in the strictest sense of the phrase, because any time the DIJ flexes down all of the scar that has formed to try to heal the tendon gets torn. The splint has to fit well in order to prevent this. Getting a good fitting splint is like getting a good fitting suit; if ‘off-the-rack’ works, that’s great. Otherwise, you need to have a custom splint made by a therapist. I always give patients two splints. The reason is because ‘full-time’ means that you even have to shower or bathe with the splint on. After the shower, place a dry washcloth down on a flat surface. Place your 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 your finger. Then place the 2nd (dry) splint on and tape it in place. The wet splint can be allowed to air dry, or a hair dryer can be used.
Except in rare cases, the DIJ 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 joint (PIJ) in the middle of your finger, gets stiff that’s a real problem. And the PIJ loves to get stiff. So make sure that you don’t tape over the PIJ and that you use the finger fairly normally to keep it moving.
The 6 weeks of full-time splinting is followed by 6 weeks of part-time splinting. The part-time protocol: wear the splint 3 hours on, 3 hours off, 3 hours on, 3 hours off, etc. during the day and then when asleep for 3 weeks. After that, just wear the splint at night for the next 3 weeks. Then you’re done. If the deformity recurs at any point during part-time splinting, then place the splint back on for one week of full-time splinting before resuming part-time splinting.
After all of this, the amount the finger tip droops (the ‘lag’) will be improved roughly 50%, although some peole do much better. There’s almost always some residual lag, but in the vast majority of cases it’s not worth surgery to fix the tendon.
There are certain exceptions. If the mallet injury occurs because the tendon got cut by a sharp object, then the tendon should be repaired surgically. Splinting can only work for roughly 3-6 months following injury. After 6 months, surgery may be required. If the thumb is involved, the tendon should be repaired in most patients. The 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 and 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.
If there is a fracture involved and the DIJ subluxes partially out of joint, these are often better treated surgically in young, active patients. These more severe injuries are often caused by a ball hitting the tip of the thumb. These injuries can often be treated in a minimally invasive manner without a surgical incision for up to roughly one month following injury. After one month, a formal open repair is usually required.