can 23 hour travel be handled in premier economy with bad trochanteric (hip)bursitis?

a) doable. Might cost extra on some airlines to guarantee an aisle seat, but even then no guarantee on where you end up sitting unfortunately.
b) Can't say as I don't sleep on airplanes no matter how much I want or need to.
c) as long as they work to help with the problem then good
d) gel packs will not make it through TSA security if you are flying out of the US. Old fashioned ice packs are useable and cabin crew would be happy to fill them or you could even just ask for a couple glasses of ice from a drink stand in the airport to put in them. Might need a replacement of the melted ice somewhere along the way.

e) biz seats are wider even more than economy plus or whatever your airline calls it. true they aren't the most comfortable seats and you can't roll over in most of them but they do have extra space. many are set up so you have direct aisle access from all the seats in that cabin so you don't have the guy next to you crawling all over you to get out when you are sleeping. often the airlines have biz on sale at not much more than the good economy seat. it just depends on where you are going.

If biz class is not financially feasible, can your MD do a cortisone injection shortly before you leave to minimize your symptoms?

Depending on the airline, premium economy seats may be a reasonable comprise of cost and comfort.
Some premium econ seats have foot rests of some sort, but some do not. Check carefully before you choose that option. All premium econ seats will have more space between the rows ( more leg room) but many premium econ seats are the same width as regular econ seats.

So much depends on the airline you are flying on. Some have many more amenities/options than others. Premium economy will usually give you more leg room, but not necessarily a wider seat.

I think most airlines will let you book your seat in advance, usually for an extra fee. But this feature may be included for premium economy on some airlines. You would pretty much have to have an aisle seat, since you would have to get up and walk around every couple of hours. And you would annoy the crap out of your seat mate if you had to climb over them to do so.

You could try to sleep in between walks. I usually take a Dramamine just before takeoff - that, plus the right music through my ear buds makes me drowsy enough to sleep a little.

As mentioned, gel type cold packs won't get through TSA. You'd have to request ice from the flight attendant. Bring along 2-3 ziplock bags to use as an ice pack. But double or triple bag it to prevent leaks. I agree with a PP that you could ask your Dr if a cortisone injection would be appropriate for you. Since it is a medication, topical gels or cremes would be allowed BY TSA. By all means use them if you find they are helpful.

Do have a look at the amenities offered in the business class cabin of the plane used by your airline. Have a read through the reviews for those flights on seatguru.com . The newer pod style setups are amazing, and very comfortable. No, the beds won't be as soft and cushy as your bed at home. But you would have a bed! You could actually lie down and stretch out instead of having to sit up! My daughter flew Emirates from Dubai to the US not long ago and remarked about just how comfortable the business class cabin was.

We deal with a similar problem. British Airways' Premium Economy seats are better than most others, have footrests and are in a separate cabin.

If you can afford it, go business class. Most airlines' business class seats are full flat meaning they are like a bed. And while they are not the size of a twin bed, they are usually around the same width as the seat. (It's still better than trying to sleep in a narrower premium economy seat that just reclines a bit.)

If this is not feasible, look to see which airlines fly to your destination. Then see what type of plane they fly. Go to seatguru.com and compare the different specs for each airline and plane's premium economy. Seatguru will give you the width of the seat, pitch (the distance between seatbacks), and a seating diagram. For business class seats, they give pitch and bed length if applicable

The other option would be to split the flight. Since you have to change anyway, why not spend the night at the intermediate stop to get some rest and stretch out before continuing on.

Thank you all so much for your replies, most appreciated.

It sounds like for carry-on, gel-packs are not likely to get through. I hadn't realised that and am glad to have found out now.
1. Are the gel packs allowed to be checked in then, so I can use them at the far end? especially in these times I would hate for TSA or other similar groups to have concerns and objections as to what I might have tried to check in.
2.besides ice cubes in layered ziplocs to avoid leaks (ive tried that. water usually finds a way out!) are the leak proof (usually for cosmetics..)travel sacks that llbean and other such sell any good for the same i wonder. Will experiment, but if anyone here has already had a go, please advise.
3. Might collapsible canes be checkable in also?

I hate to have to ask all this but on thinking it over it's not impossible i suppose that all of the above might be regarded as potentially dangerous. The last thing I want is to cause any of that sort of uncertainty.
thank you again,
W.

I like the idea of splitting the flights, if possible. It would make potential delays easier to deal with, as well.

Use an ice bag like this one. No leaks at all. Been using them for decades.
https://www.amazon.com/Mueller-Ice-Bag-Blue-Inch/dp/B000PD1EU2/ref=sr_1_4_a_it?ie=UTF8&qid=1506018184&sr=8-4&keywords=ice%2Bbag&th=1

You can carry your collapsible cane with you onto the plane.

Gel packs are allowed in checked baggage, at least by the TSA in the US.

1. Yes, if you want to bring gel cold packs with you to use at destination, you can pack them in your checked luggage. Put them in a plastic bag in case they get punctured.

2. The ice bag suggested by Mark would be ideal, snce it's made for that purpose. All you would have to do is ask the flight attendant for sufficient ice to fill it.

3. You could, of course, pack a foldable cane in your checked bag, but why? If you need to use a cane, then bring it onboard with you. I need a cane and never travel without one. And mine aren't foldable - I've never encountered a problem in airports or on a plane. If you prefer to use a foldable cane, then bring it and use it. Then fold it up and stow it in your carry-on once you've boarded, or just stow it in the overhead storage.

It is important to check the specific seats that each airline has in each class. Note that usually, Economy Plus is just a regular economy seat with more legroom, while Premium Economy is usually a wider seat, which will also have more legroom. For instance, on LOT Polish Air, regular economy is 2-3-2 seating, while Premium Economy is 2-2-2 seating, and the seat is nicer and fancier as well as wider than a regular economy seat.

I agree that with your pain issue, I'd plan to break up the trip with a layover of at least one night if at all possible, particularly if you can't afford lie flat business class seats. That way, even if the first flight aggravates your pain, you would get some sleep on a fully horizontal bed before having to get on the second plane.