Dr C, this is the summary of my CAT scan:(clearly much more written, but this is the part that discussed the fusion issue)
L4 L5 interbody fusion device shows incomplete bony fusion. There is also increased mild L4/5 end plate sclerosis and mild deformity and depression of the upper L5 vertebral end-plate. Finding compatible with subsidence. There is minimal anterolisthesis L4/5.
I hope you can assist and i will be going for a second opinion.
Thanks
Steven