Wht happen if lumbar fusion screws break?

Depends: What can happen after lumbar fusion screws break, depends on the status of the fusion. If the fusion is solid and well formed and there is a break of the screws, nothing will happen. If the fusion has not set up, then the construct will be at risk for failure. There will be movement and pain and the bones will not fuse and become solid and stable. Surgery may need to be redone to stabilize this.

Suggests that the : Fusion may not have fully taken well, at least at the time when the screws broke. Sometimes with time fusion still goes on and takes. You will need to see your spine surgeon, and follow their guidance. No need to do anything most of the time if there are no symptoms (even if the fusion did not take fully). Your surgeon will tell you what if anything he/she recommends for your particular situation.

Revise it: If the pedicle screws break, they can be revised. The screws do not commonly break. If they do, it is often due to a pseudoarthrosis (failed fusion).