When I began having lower back issues I had to re approach everything I did from my day to day posture to how I played jiujitsu. Just as an example, I had to rely on my upper back and shoulders both for a lot of my hip movement and for defending the stack sparingly spinning on the small of my lower back. During most movement I try to keep my lower back locked out in an S curve in order to protect it.
This video sort of shows a variation of what I'm talking about. In a Standard arm bar you pivot off the small of your back to gain the optimum angle. In this variation, taught by Pedro Sauer, you actually pivot off of your upper back. The difference here is subtle, but try this no handed arm bar and you'll feel what I mean.