Russians usually don't use any pronouns when talking about body parts (same goes with family members and relatives).
Ex: Я почистила зубы- I brushed (my) teeth. Вы вымыли руки?- Have you washed (your) hands?
I believe if they put pronouns such as его, её, etc, they brushed someone else's teeth or washed somebody else's hands. Either that, it would sound strange to them. I hope this helped! ^_^
DL gives "spine" on hover. However, as near as I can tell, that is not a good translation, despite the similarity of the sounds. .For "spine" I find позвоночник or спинной хревет, also хревет alone, but not срина alone, which seems to refer rather to the whole back. Why do they give the first (preferred?) translation as "spine"?