I’ve hunted antelope for 50+ years in 3 different States. As a guess I’d say 60% were taken prone, 35% taken sitting and 5% (Maybe less) were taken off hand or kneeling.
Depending on the terrain and height of sagebrush, prairie grass etc. shooting prone at times is not an option - you just can’t see your target.
Will your neck/back allow you to shoot off a backpack that is higher than bipod? How about using a bipod on a horizontal laid out pack which allows you to be higher?
If you just can’t shoot prone at all - sitting, kneeling and standing are your only options. I would try various methods until you find what works best for your neck-back and accuracy situation but I’d suggest you concentrate on the sitting and kneeling shooting position.
There are various bipods and tripods out there for the sitting-kneeling and standing position. I would look at those options. I personally always carry a backpack and a pair of carbon walking (trekking poles) sticks. I keep one stick on my backpack and walk with one. The one I walk with I use to stabilize my binoculars while sitting and glassing. Call it a mono pod for glassing. There is a company that makes an adapter that attaches to each hiking stick - complete adapter is maybe 3-4 oz. They have a male-female 1/4 turn quick attach that allows them to criss cross into the old style Buffalo shooting sticks.
Using these sticks while sitting and putting my backpack under the butt of the rifle gives me 2 points of stability. If you can sit with your back up against a rock or sage brush you’ve got 3 pts of stability. I know a guide that works for a ranch out here that takes out disabled vets on the ranch to hunt. They get into all types of situations and limitations. They flat get it done no matter what the vets disability is so don’t let a couple of fused vertebrae discourage you.
Antelope are fun to hunt. They can be as dumb and tame as a post but 98% of the time the second you peak your head over a rise one antelope will see the movement and start the whole bunch and head out.
Good luck - as I always tell my wife “I'm damn sure getting older every year but you can’t kill anything from our couch”.
If you have any specific questions feel free to give me a holler.