Not sure if sacrum fusion is the same as kyphoplasty, but mother went thru 2 a decade apart which helped immensely in getting around with a variety of walkers in physical therapy & then use of a cane. An elderly fishing friend also had spinal disc fusion, but the doctors did not inform of the high probability of repairing one might cause a fracture in the disc above or below; which resulted in him going thru another kyphoplasty within a year as he wouldn't slow down working in retirement.