Iguana Tail Drop

Question
My iguana recently dropped it's tail, it then healed, but now it dropped it again... how far up the tail towards the body can it drop it's tail without being harmed? How short is too short?  

Answer
Hi Ryan:

Before I can answer this question, I have to know the reason for the tail drop?  There had to be something causing traums for the tail to pop and I can explain better if I know the reason.  Write back and I will get right back to you.

                        Later
                         Joel