I have small arthritis-impaired hands, and I tried my sensei's advice to grasp sanko not on the hand or wrist/hand, but the distant part of the fingers. It makes it easy to find and control the chain of the lock.
True, actually I teach the kids how to do that for sankyo when working with adults. Their hands just aren't big enough or strong enough to grab the hand. Fingers work really well.
The problem I have is with taking sankyo on the hand with one hand, then using the palm of your other hand to push the fingers back. It simply adds more pain and people tend to rely on that rather than improving their overall technique. Just my own take on things fwiw.