I have what's called a Boutonniere deformity of the index finger on the left hand. Fortunately, I'm right-handed, so it doesn't affect me too much. But if I wanted to do something about it, what else is there? I've used a splint with no change. I can pull the finger straight but unless the splint is on, it doesn't hold.
The boutonniere deformity affects the extensor tendon(s) of the finger so they no longer work properly. The injured area of the tendon is called the central slip. Damage occurs where the extensor tendon attaches to the middle phalanx (bone) of the finger. Tightening of the tendon from injury or scarring can lead to a permanently crooked finger. The proximal interphalangeal (PIP or middle joint of the finger) gets stuck in a flexed (bent) position. At the same time, the distal interphalangeal (DIP) joint (moves the tip of the finger) is pulled up into too much extension (hyperextension). The PIP joint may not straighten out completely under its own power. The finger can usually be straightened easily with help from the other hand. Eventually, the imbalance leads to the typical shape of the finger with a boutonniere deformity (tip of the finger extended too much, middle knuckle stuck in flexion). Sounds like that is your situation. If conservative care has not helped (splinting, exercises), then surgery may be an option. We say 'maybe' because loss of motion, stiffness, and the inability to use the finger in a normal way are often long-term problems even with surgery. A hand surgeon is the best one to assess your finger/hand and see if you are a good candidate for surgery. There is some evidence that for fingers that won't extend (straighten) but the loss is less than 30-degrees, the tendon can be cut. If the lag is more than 30-degrees, another surgery may be needed to repair the central slip and restore normal tension. Again, the surgeon will make a determination as to which procedure will be most helpful for you after completing an examination of the area.