'Thanks, I do keep him quiet, but if I don't help him 'sit up' he tries to do it by himself and then falls over, which is causing him even more stress and pain'
I think it's unhelpful to say anything except that this is a v. v. serious situation. The emu yearling I tried to save, found in a fence -- very similar circumstances -- wouldn't sit still, to rest and heal, because it was terrified of me. Watching it thrash about was heart-rending.
If I had to do it again -- I lost the chick -- I'd literally immobilise it: bind its wound (I used a poultice of herbs), then bind its legs in the familiar sitting position, put it in a box of straw, put food and water in front of it, and see what happens!
Even three or four days of this, providing the 'swaddling' is not injurious, is not gonna do more damage. The bird may be hungry, thirsty, and stressed; but it gives the leg some small chance of beginning to heal.
Here’s the only way you can subdue a mid-sized ratite while you treat it. Have done it three times in a decade. Lost two of the birds.
Swoop down from above. Ya gotta get hold of its upper leg – with your thumbs pointing downward – right up the top, where the ‘drumstick’ begins. Not higher. Not lower. This keeps the body pulled back holus bolus into your own body.
I’d wear safety glasses, though I wasn’t pecked by the emu yearlings in question.
And then your assistant comes in from your right or left, to minister.
DON’T shift your grip.
Keep the two legs pulled just a little apart.
Overall then, the bird can only frantically wave its legs from the knee down, and your assistant won’t have trouble controlling the lower limb.
The chick will certainly behave in a ‘cycle’: it’ll struggle like HELL for a few seconds, then go perfectly still. But in ten seconds or thirty, it’ll launch almighty powerful heaves to try to escape. That's exactly when you must have an iron grip of its legs.
So long as you stubbornly and powerfully subdue its upper legs, it can hardly hurt itself further.
The two eight-month-olds I examined – as you know, much less bird under the feathers than you think – astounded me with the strength they showed, even though injured.