1) According to the Halacha it is quite possible to eat the hind quarters. One has to be very careful to remove the Gid Hanasheh;sciatic nerve; and all the forbidden fats, before eating the rest of the meat. Up to the time of Dayan Yechezkel Abramsky porging of the hind quarters was carried out in England. Dayan Abramsky disallowed this because of the difficulty, in World War 2 conditions, of finding porgers who were sufficiently expert in the Halachos about what must be removed. In some parts of Eretz Yisrael the hindquarters are still used after the forbidden parts have been removed.

2) Some people do make bone soup, or bone broth. That aside, I am not sure where one sees in the Gemara that it is referring to bones.

Gmar Chasimah Tovah

Dovid Bloom

Follow-up reply:

I see that Tosfos above 2a DH Magbihin does not agree with my idea about the bone soup, since Tosfos there writes that bones are not fit for human consumption, which suggests that bone soup is not a sufficiently normal way of usage to take away the issur of Muktzeh.

However, Chidushei Rabbi Akiva Eiger here seems to say that bones are considered to be "Oichel Odom" for a different reason; they are connected to the meat when Shabbos starts in Bein HaShmoshos and since the meat is edible the bones are also considered Muchan l'Odom.

Dovid Bloom