Dear Jonathan:

This is one of those issues that does not matter. Whether the nails were in the hands or wrists does not change the faith in any way.

From a forensic analysis, and historical analysis,  it is more likely that the nails were in the wrists. But, the Bible is not meant to be a book of history and science. It is a religious text and gives a religious message. The religious message is not affected in any way by this issue.

I am not sure at the moment about the Greek text here. The Greek for "hand" in the passage about Thomas' doubts is χείρ..,which seems to be somewhat vague, but then I really do not know Greek.

The wrist may be considered part of the hand to the first century people.

In any event, there is nothing problematic between the tradition of the nails in Jesus' hands as seen in art, nor even the stigmata phenomena, and the historical or medical forensics that indicates that the wrist was the most problable location of the nails.

These issues are not important any more than venerating a picture of Jesus with white skin and blue eyes. We know that he did not look like that. It doesn't matter. We are venerating Jesus not the accuracy of the painting.

As for an apparition, if Mary or Jesus is to appear to us, they will appear in a way that comforts us and does not challenge us. If a person believes that the nails were in the hands, Jesus will appear that way if the person will doubt the apparition because of this small point. The point of his appearance to us is not to correct history. 

I hope this helps.

God Bless,
Bro. Ignatius Mary