I developed AVN after about 1.5 months of taking high dose steroids. It took out both of my hips and my right shoulder. I also developed cataracts from steroids. I am very sensitive to prednisone, probably more than most.
The pain of AVN usually falls into the joints, not so much up and down the spine, although I guess that is possible. For me the pain was most obvious when transferring from a seated position to standing or vice-versa. It was alleviated initially by walking and continuously moving.
The pain from AVN of the hips goes along the upper ridge of the pelvis on the back , and is also present along the pelvis along the inner thigh up to the hip bone.
I do hope that your father is not experiencing AVN as it is not fun, and may require some waiting until blood counts, especially whites and platelets are pretty normal, although my first surgery was done with about 80k platelets with no problems, and i experienced very good pain relief within about 1 week. It took a while to get full range of motion, but it wasn't as bad as one might think.
MDS RCMD w/grade 2-3 fibrosis. Allo-MUD Feb 26, 2014. Relapsed August 2014. Free and clear of MDS since November 2014 after treatment with Vidaza and Rituxan. Experiencing autoimmune attack on CNS thought to be GVHD, some gut, skin and ocular cGVHD. Neuropathy over 80% of body.