Hi, If I were your treating Doctor for this case of pain after L4-L5 fusion, I would ask for imaging study of your lumbar spine
because you may have developed discal hernia
at the upper level of fusion (L2/L3), or the level below it ( L5/S1) with compressive elements. You should have a CT scan
or MR ( if the hardware is compatible) scan of your lumbar column. The decision how to treat your problems should become clear after this. Hope this answers your question. If you have additional questions or follow up questions then please do not hesitate in writing to us. I will be happy to answer your questions.