Is there a way to undo an ABS joint? I have a break in a multidirectional elbow in a tough corner just below the floor In the corner of the basement. It's the main drain line.

Can you show us a couple pics of the broken fitting and all areas around it? If there is room, it really is best to just cut it out and install a new one. If we can see the room you have to work with, we will be able to give some ideas on the best way to fix this.