Hi Volfan
I had these two procedures explained to me by my Othropod as I understand it the cage is pretty majour surgery I think they might have to enter fron the back and also the front and they basically put a cage around the degenerated spinal area and secure with screws as for movement afterwards I think it is very limited but could be wrong it is pretty majour operation due to entering fvrom the front and the back to completely access the spine
The rods and screws type fusion I believe they can access from the back only and two rods are placed on either side of the affected spinal area and secured with screws, As for mobility of this area I do not know for sure I would expect limited the spine segments above and possible below the site depending where it is fused take up all the movement and after a period of time also wear out and must be fused and so on and on
The4 screws and even the rods can snap/break or the screws can pull out causing additional surgery to try to fix
A lot of the people I have known who had the fusion wish they never had it done but that is just their opinion all cases are different
When I was at my Orthapedic surgeons office he had a model their that had been fused with rods and screws to illustrate the procedure to his patients as I was looking at this model it really looked like a majour procedure pretty intimidating lookind and I noticed that the screws used on the model had come out or broken off a piece of the vertabra but it was only a model
I would advise to think very very carefully before getting any of these done It would be a very last choice for me before I would go through any of them I had a 3 level Laminectomy done and it was bad enough and offered me very little to NO relief or improvement in pain and it took 7 hours
I am sure others will chime in who know more or more accurate info for you or maybe had one of them done from my knowledge the caging of the spine is the worst and most severe spinal surgery
Best of Luck
Bob