Ernie went in for his operation today, and now he's back home doing well.
He went in at 8:30am and 8 hours later we picked up a little shaken up but happy to see us puppy. His tail wagged frantically when he was carried around the corner and placed in our arms, but I think he got a bit overwhelmed and started to cry. He soon calmed down and after the vet explained everything to us we took him home. He's on 3 different drugs for the next few weeks, and he needs plenty of crate rest. My mum took him out for the toilet and he did that with ease, so that's good. Over the next few days he might feel poorly and sad, but hopefully he should start recovering pretty soon.
The vet made an incision about 4cm long at the top of his leg, and cut away the bad part of the bone. He even showed it to us in a little pot, and you couldn't even tell it was meant to be bone! It was totally deformed and full of holes, so he knew it was definitely Legg–Calvé–Perthes disease. Below is his x-ray- left is before and right is after. You can see where the vet has cut across the bone, and he told us that after the physiotherapy the muscle should hold his leg bone back towards his hip.
He'll have about 90-100% use of his leg again once everything has healed, but it will take some time. He's having rest at home now, and even though he has the occasional whimper he seems pretty chilled out.