Dude, that was nuthin'. If I was trying I could have gotten the first knuckle the middle finger of my right hand to 90 degrees... prolly the rest too for that matter. The thums do almost the same thing. I can get the line from thumb to pinky to 180 deg and from pointer to thumb nearly there too (as you can see). Better yey if I could be arseI could bend both thumbs back BEHIND the knuckles of the other fingers on the same hand. Joints in shoulder, elbow, and wrist are so flexible that I used to be able to do a full 360 with my palm on the table (will need to practice to do that again), and I can scratchs my chin with my right hand for example from the LEFT side (all the way behind head and back around) it really looks like someone reaching around from behind me with their left hand to scratch the right side of me face.
I could go on....