I have a inoperable back injury [annular tear in the L-5, S-1 & a couple of bulging discs (so most orthopedic surgeons I've been examined by have told me)]. I had bought a pro explorer for exercise purposes & found the twisting & digging (high angle paddling) was killing me & making my condition worse
. After a couple years of "lurking" on this site then joining, I have learned (at least in my instance) is that I can tolerate pedaling.
After reading about many members here with different back injuries & some simulated movement on an exercise machine I finally decided on a HOBIE Outback. About a month ago I dropped off my pro explorer @ OEX SSB for a trade-in and to accessorize my new Outback while there before leaving I asked "Andy" if I could test out a "Revo" just to see about stability issues compared to the Outback. It was equipped with standard fins & rudder but I found it comfortable and most of all painless after about 15 minutes of 'aggressive' pedaling!
This is just MY experience.
Not knowing exactly what back injury you're suffering from may be different to mine. Maybe consult with a orthopedic surgeon and if you can get him to view the "Mirage Drive" video maybe he can advise you. I was able to do that and got a Rx for mine which I hope to get reimbursed for!
My other best suggestion as given to me by members on this forum, is to try one out!
Otherwise it's the only way you'll know if you can do either.
Best of luck/prayers.
FFY.