A "mallet finger" is a finger that has lost the ability to axtively extend the tip as a consequence of the rupture of the terminal part of the extensor tendon.
Standard treatment for a mallet finger is splinting for a minimum of 2 months in extension. The finger must be kept straight with the splint on 24/7. The splint is not to be removed for washing or for any other reason. If the finger tip is allowed to bend before the month is over, the clock starts from zero and the finger must be kept straight in a splint for another full month.
A typical mallet finger injury does not require surgery, and surgery can be counterproductive.
In a bony mallet injury, the extensor tendon detaches together with a piece of bone. Depending on the size of the bony piece, it may cause subluxation of the DIP joint. A bony mallet injury may be amenable to surgical treatment.
Here is the case of a teenager who presented about 3 weeks after the injury. The xray all the way to the right shows the injury best. The DIP joint is subluxed.
This injury was amenable to surgical treatment.
During surgery, I debrided the fracture site, I reduced and stabilized the fracture with a tiny 1mm screw. The finger was placed in a split holding the DIP extended.
Treatment was successful.
I took the following xray a year later.
And here is the clinical appearance.