Interesting, so I can't help myself...
It is far more common for a spider to get stuck in a moult. This can be at the onset of the process, or any time during the process. This can, and is fatal in more cases than not.
It also happens that a spider "bleeds" to death after a moult due to hemolymph "leaking" from the joints, but this does not happen often.
What happened to your P irminia is far less common. I have never seen this condition as severe as this. There are obviously more questions than answers, so allow me to hypothesise.
The spider had a successful moult. It was able to escape the old exuvium, then things went south from there. Because the spider would have extracted perfectly formed limbs from the old exuvium, the problem must have occurred AFTER the moult. (Common sense tells me that it would not be able to extract skew limbs from the old exuvium. Because the entire NEW exuvium is soft, it must have been perfect when it completed its' moult.)
So what happened?
I am of the opinion that the new exuvium had various consistency issues. It is possible that the exuvium of the new limbs "hardened" at a different rate. Example: If you stick glue or sellotape to one side of a balloon and then inflate, the resulting inflated balloon would appear skew.
Bacause the spider "pumps" hemolymph into the new limbs shortly after the moult, it is my theory that the limbs were deformed due to varying thickness or consistency of the new skin, thus "pulling" them into this abnormal shape.
I doubt it would survive on it's own, so I think you did the right thing. It would probably starve to death had you not intervened.
Most people are like clouds. The sun comes out when they f*ck off...