According to Dr. Barry Eppley, a plastic surgeon in Indianapolis, his preference is the 7th, 8th, and free floater 9th rib for harvesting. He claims it " is easier and provides plentiful options of shape and configurations. A small subcostal incision can be moved around to provide good visibiity and the underlying rectus muscle is split vertically for access rather than transecting it." See link below (exploreplasticsurgery).
He continues, "One of the major concerns about rib harvesting is the risk of pneumothorax as the lung pleura is close by underneath. But at the level of the 7th ribs and lower, the lower apex of the lung is higher so this is not going to happen. In over 65 cases of rib harvest at this chest wall level, the pleura has never been violated. It becomes evident at the level of the 7th and most certainly at the 6th rib." So for those seeking revision rhinoplasty and need rib grafts, don't forget to ask the surgeon at time of consult which rib he uses, how many has he done like that, and has he/she had any complications with it.
Another nose revision surgeon , Dr. Anil Shah in Chicago prefers to use the 5th, and 6th rib. He says "either the 5th or 6th rib are most commonly used. The 5th rib has the advantage of being straighter and not really connected to any of the other ribs. The disadvantage is it tends to be smaller. The 6th rib tends to be longer but more curved than the 5th rib. In addition, it tends to connect to other ribs." See link below (shahfacial plastics).
How about calcification of the ribs as we age?
According to Dr. Shah, "as we age, the cartilage portion of the rib cage becomes calcified and eventually actually turns to bone. This process is typically complete at age 55, but I operated on patients well over fifty who have had substantial cartilage remaining in their ribs". When your over the age of 40 there is normally more calcification which makes the costal graft harder to shape, however the upside to this is there is less chance of warping over the years.
Dr. Eppley mentions "one can always find enough cartilage to use. I have done rib grafts up to age 65 and adequate cartilage has always been found".