Can you explain the surgery for herniated disks in their neck where it had to be fused?

Yes. Standard approach for cervical disc surgery is to remove it through the front of neck excavating it from the spinal cord allowing for safe approach & excellent decompression but now you have to stabilize the spine by fusing it. An alternative to a fusion is an artificial disc. Occasionally, disc herniation can be fixed from posterior approach without fusion if it is very lateral or to the side.