I haven't had this on my lurabar spine but had something similar on my cervical spine. It's to put the curve back in your lurabar spine. You have something called "flat back syndrome" and is not uncommon after laminectomies.
In the neck, it involves taking off pieces of the bone and fusing the entire area with pre-shaped titanium roRAB. I'm fused from C3 to T1 but they had to take off so much bone off of C6 that it didn't even have enough bone to put any screws in so it's just squeezed into place with the bone grafts. But I can hold my head up again.
Yeah, they are tough surgeries but necessary. Otherwise you end up looking down for the rest of your life and eventually, it would affect your breathing, I imagine. For me, it was looking down and severe pain and headaches.
Good luck...............Jenny