I have seen one bird missing part of its keel bone one time as a congenital defect. It didnt cause the bird any problems thankfully but the owners had to be very careful with him! No flying or jumping off of things as hitting the chest area could have damaged the vital organs below. My case I saw it in was a congo african grey. As for hernias I have seen many many hernias. It possible there could be a hernia associated with the malformed keel in your bird but I would have to see it to say if that was the case. In my african grey patient there was no hernia. Most of the hernia patients I have seen, have hernias associated with egg laying and hormones.
Dr. Stephanie Lamb