Spondylolisthesis: single-segment reduction

That it has lost its alignment with the one below and moved forward. In isthmic spondylolisthesis this happens because the pars has broken — the bridge of bone joining the front of the vertebra to the back — while in the degenerative form the slip comes from wear.

No. Not every case needs surgery. In the isthmic form I consider it when there is poorly controlled pain or compression of the nerve roots. And in the degenerative form fusion is not even mandatory: it depends on the stenosis, the foraminal narrowing and the intensity of the back pain.

Only the affected one, and I am insistent about this. I favour reduction with a cantilever manoeuvre over a single fulcrum, together with an interbody implant, without dragging a healthy second segment into the fixation. It can also be done minimally invasively.

It can be reduced, that is, repositioned, and that is what I favour when surgery is indicated: recovering the position and fixing it there, rather than simply consolidating the slip.