Hi,
Welcome to HealthCareMagic.com I am Dr.J.Mariano Anto Bruno Mascarenhas. I have gone through your query with diligence and would like you to know that I am here to help you.
Fusion of C4 and C5 is done (that is fusion of fourth bone and fifth bone in your neck) and Fusion of L4 and L5 (fourth and fifth bone of your lower spine) too is common
I have not seen some one with Fusion of disk. Can you please specify whether the
Vertebral Bodies have been fused or whether the disc has been fused.
If it is fusion of bone
Then
it can be commonly due to injuries or infections or degenerative diseases
If you need any clarification / have doubts / have additional questions / have follow up questions, then please do not hesitate in asking again. I will be happy to answer your questions.
In the future, for continuity of care, I encourage you to contact me directly in HealthCareMagic at http://bit.ly/askdrbruno
Best Wishes for Speedy Recovery
Let me know if I can assist you further.
Take care.