There are no vitamins, no Omega Fatty Acids in BONE, no digestive enzymes, and only scant amounts of poorly digestible amino acids locked up in the collagen. Even if stomach acids could leach out all the collagen locked up in the bone fragments the collagen would yield minimal nutritional value. Finely ground bone is a good source of Calcium and Phosphorus. Finely ground bone presents no risk whatsoever to the canine or feline digestive tract. Other than being a great source of Calcium and Phosphorus, the chemical composition of raw bones is such that minimal nutritional benefits are obtained from their ingestion.
Marrow does have some nutritional value but is composed mainly of fat.
Take a look at the following photos. The shards and splinters were collected and placed on the dish in front of the fractured bone. The images speak for themselves. Click on a photo to see the full sized image. It would be unlikely that a dog could break open a large beef bone such as this.