Since cartilage has memory what is best approach if caudal septal cartilage is extremely bent? Does it need to be replaced?

There are a variety of techniques to try to address the bend. It really depends on how the bend happened (were you born with it? trauma? how long have you had it?) in terms of how best to treat it. Sometimes it is bent like that because the cartilage is too tall, so just trimming it down will allow it to bounce/flex back into the right position. Sometimes it is because of its attachments to the other cartilages so by releasing those, it will bounce back. Yes, cartilage has memory - so sometimes those maneuvers are not enough. Some surgeons will score parts of the cartilage or use special suture techniques to try to hold it straight. Another option is putting something such as cartilage graft or PDS plate next to it so that way it is encouraged to heal straight despite its memory. Good luck!