Well, at last, we seem to have some good news regarding Max. I have studied the internet a lot, and I am quite certain that he had the right diagnosis (not that I am a vet!). Apparently these types of abcesses are very difficult to treat. Now, at last, he has finished with his anti-biotics, and is just taking a course of osteoporosis tablets. As you can see from the video, he is no longer lethargic, and Paddy has got his playmate back again.