I had a hand injury during my freshman year of college and couldn't play piano at all for a couple years. BTW, the injury happened *while* playing piano due to bad self-taught technique! Then for over a decade I only played with three fingers on my right hand, eventually able to add my 4th and 5th fingers held together for strength. Only in the last few years have I been able to play octaves and have independent movement of my 4th and 5th fingers when playing piano. Ligament and tendon stabilizer injuries take a LONG time to heal or learn to compensate for using muscle support instead.
Back in the late 80's / early 90's, a hand surgeon wanted to do three surgeries to fuse bones in my right hand to form a false arch to make up for the damage, but said it only had a 20% chance of improving things and 20% chance it would make things worse. I decided against the surgery. So far, so good
I still have a collapsed arch in my right hand. I have to be very careful and pay attention to any slight pain while playing and stop whatever I'm doing immediately to avoid re-injuring it. My pinky has never felt normal since the initial injury. I'm still constantly aware that something doesn't feel right inside of my hand. Oh well. That's life.
Oh, the song I was playing when my ligaments snapped? David Foster's "Winter Games". There are a lot of parallel sixths in that tune and I was pounding way too hard. I've been trying to learn better technique for many years now. Still learning.