I don't believe you need the saran wrap all the time once you apply the cream. An hour or so is enough to drive the product into the skin. If the vehicle base is transdermal in type, it would penetrate faster, but I don't know what they use etc.

The Lidoderm patches have an aqueous adhesive impregnated with lidocaine that releases continuously thru the skin. The cream you use is a one time thing with no reservoir drug to be continually available. When using Emla for before surgery, the wrap is used for about 1 hr prior.

I would think using Lidoderm patches on the sacral area would be the way to go since you believe that is where your compression issues are. You would wear the patch there for 12 continuous hours, with 12 hrs off, and repeat.
It is also possible you have developed some spinal stenosis, and it would be prudent to see if that is happening. An MRI and Xrays would be a good idea so you could understand what is happening. It is always possible to have more than one thing going on and fixating on that "adjustment" in the past only, may be only part of a larger back problem.