Are ham bones safe for dogs?

I'm scared to give anything anymore to my dogs after the whole "greenies" thing and watching the emergency vet show on Animal Planet and seeing how easily things like bone fragments either get lodged in their throats or impacted in their insides! These bones came sealed and the dogs are crazy about them! I hate to deprive them of such a treat! The packaging says to supervize them which I do. They just rip off tiny bits of ham still stuck to the bone but when they start trying to actually gnaw off segments of the bone, should I throw it away? We used to give our dogs butcher bones growing up and we never had any problems so am I just being paranoid? Oh, they are Shetland Sheepdogs so they don't tend to gulp things down like breeds like Labs do (I had a Lab and a Golden and they ate cell phones, remote controls, Christmas Ornaments, basically anything!).