I posted a few days ago regarding a model that I was trying to retopologize in Zbrush. When I got to the hands the fingers would become all twisted and the polys randomly flipped. One suggestion that I found in a thread was to add another edge to each finger, but my reason for retopology is to make an animatable model amd to add those extra edges I would have to continue them into the model and rework the whole thing. I discovered by continuing to play with my retopology that if I left an edge incomplete on a finger by leaving two vertices on that finger unconnected it fixed the flipped polys when I previewed the new geo and Zbrush would complete the edge. I had to try each edge on each finger to get them to work and this is very time consuming. So my question is this: Is there a formula for how to determine which edge to leave incomplete to get a workable retopo?
It’s really hard to know,i’ve never experienced this on zb3.5 but,retopology in zb isn’t perfect anyway,I usualy tend to retopo all the body,export a level 2 subd to max and reduce the polys as needed. Its far more faster than doing the trial/error on zbrush.
For my part, I used to try to retopologize my fingers using 4 sides, and that’s when most of the problems happened.
I switched to using 6 edges, that cuts the hand in 2: inside palm side and top of the hand
It actually makes it easier to unwrap it as well 
so now I stick with the 6 edges thingie
what you can do to stick with the 4 sided fingers, is to add a diagonal edge in one of the messy side, you can remove it later in max or maya and it doesn’t mess the flow.
Thanks for the responses. If it is necessary to do the retopo outside of Zbrush how do I bring it back into Zbrush at the same scale? When I have tried this my model comes back in tiny and if I try to re-size it I lose symmetry.
clone the original sculpted model, then make sure that there is no subdivision level, then while the cloned original model is still selected as ztool, reimport your retopo model.
don’t retopologize the fingers, just make the hand, then when you have your adaptive skin done just extrude out the fingers using the edge loop function.