My neck is shorter than others. am i at risk for neck arthritis or injury with age?

Most likely no: Anatomical differences are well known from one person to another. Unless you have had trauma or other problems, you should be fine. It is rare to be born with a less bones in the neck then say another person. If you are having pain, then have a physician look at you.

No: I have never read any medical literature implicating a short neck with higher risk of neck arthritis or injury.