I hope he is ok. It is so hard not to blame yourself when this happens, that is natural. This happened to us with our 6 year old cocker, the garden gate sprung back on him. It is such a horrible thing to see. I remember sobbing, shouting etc etc. It is horrible. You never know, with cage rest, some anti inflams it may settle. They are such crazy bouncy dogs, this is more common than you think. I hope for you they can do something. But I understand what a sad worrying time this is. Fingers crossed.