Active pivot versus reactive pivot

[Yoda]

The dancer performing the horizontal eight dance certainly has hula hula flexibility.

What drill would you recommend for a golfer who has had spinal fusion surgery where all the lumbar vertebra were fused together preventing any rotary movement at the level of each lumbar vertebra?

I would recommend a seat directly opposite the dancer, a stiff drink -- just say "no" to the little umbrellas -- and an active #1 Accumulator (bending and straightening right elbow).