I 100% agree with Terry. I'll add... General inquiry about support needs: "I just wanted to check in and see if there’s anything we can do to support you in your role here. We want to make sure you’re as comfortable as possible." Offer assistance without focusing on the hand: "As you get settled in, if there’s anything you find challenging or any adjustments we can make, please don’t hesitate to let me know. We're here to help however we can." Specific but open-ended: "I understand you might have some unique ways of doing things due to your hand. If there’s anything we can do to make your work easier or more comfortable, please let me know."

In my experience, it's helpful to ask questions that are more inclusive rather than pointing out a "disability." For example, "As with all of our employees, we want to make sure that the workplace is user-friendly. Do you have any requests to help accommodate your employment with us?" In this way, you facilitate the person being the expert on his needs, not you. I find that people with special needs often become quite comfortable talking about the scenario. They will let you know accordingly, most of the time.

You can't avoid being direct, and I assume that it is your responsibility to make these enquiries, so you are expected to be so. The usual way would be to tell him that you understand [ie. have been told] that he has a physical disability affecting his hand, and is there anything we [ie the employer] can do to make it easier for him to do his work ? It is then for him to let you know if there are certain tasks he may find difficult. If so, you can work together to find ways around the problem. You should maintain a positive approach if possible. My wife works in a nursery [for young children]. She does not have full use of her arms and hands due to arthritis, and the occupational health officer has informed her manager that she should not undertake duties involving lifting of heavy items, or lifting and carrying babies or children.

What do you know so far about the physical issue on his hand, and how did you come to learn that information?