meat grinder for bones or bone meal?

My dog has been doing really well on the BARF diet for the last few months until recently when he experienced an extreme case of constipation that required hospitalization to remove the blockage non-surgically (even though I had been regularly feeding him mashed vegetables,greens, and fruit).   The blockage was rock hard and had pieces of undigested bone in it.  The bones he had eaten recently were from chicken thighs and some pork shoulder.  
This experience makes me hesitant to feed him anything but bones found in chicken wings. I'm wondering if I should purchase a meat grinder than can grind up the bones for him or go the bone meal route.  If it's that latter are there recommendations for which manufacturer to go with and how many mg per day?