The ribs are comprised of 12 pairs, all of which have a bony and cartilage component. The ratio of cartilage to bone depends on what rib it is and whether it attaches to the sternum or not. The first ten ribs do attach to the sternum and have varying cartilages in those attachments as it descend higher in number. The higher the rib number the more cartilage that exists along its length, with the exception of ribs 9 and 10.
The largest amount of cartilage in ribs is evident in the subcostal rib margins where the confluence of ribs 7 through 10 meet to create the anterior lower ribcage. This is also a ribcage area that is frequently exposed to trauma in which dislocation injuries can occur in which variable amounts of separation of the costochondral junction can occur. These junctional disruptions can result in prominences over the disrupted bone-cartilage area that may or may not result in residual discomfort as well.
Whether it is to reduce the rib protrusion and/or help reduce any discomfort associated with it, direct reduction can be done. This requires a small linear incision directly over it with exposure of the underlying prominence. This is usually composed of cartilage but in older patients such cartilage can be partially calcified and acts more like bone.
The most effective method of reduction is to use a high speed drill and burr. This can be done very quickly with a large carbide burr. But to do so through the smallest incision possible the burr should be used as a spot technique rather than in a side to side motion. In doing so it is important to protect the skin edges and deeper tissues from the trauma of the rotating shaft of the burr. This is done by placing a plastic guard fitted over the shaft of the burr. In this way the risk of inadvertent tissue injury is reduced.
Spot burring reduction of prominent rib dislocations can be effectively done whether it is cartilage or bone. Keeping the incision small, particularly when the reason for the reduction is aesthetic in intent, is an important part of the procedure.
Dr. Barry Eppley