Chest Wall and Sternal Reconstruction
The sternum or the breast-bone is an important component of the chest wall. First of all, it sits in front of the heart and protects it from injury. The sternum forms joints with the upper six ribs on both sides and allows them to move up and down, thereby aiding in breathing. The sternum by virtue of its location also helps in the movement of the upper arms through connections to the shoulder girdle. Its location in the midline meant decreased representation of pain nerve fibers and therefore decreased pain perception if the sternum is cut.
The midline sternotomy is the incision most commonly used in cardiac surgery and it is often denoted as the "cracking the chest". That in part is due to the fact that the sternum or the breast bone needs to be split down the middle to allow access to the heart. Fortunately, because this is an incision down the middle there is less perception of pain from the actual cut. The bone then needs to be closed at the end and typically, this gets done by using wire to wrap or circle the halves of the sternum together (more about that later).
This incision was first adapted by Julian in the late 1950s. It quickly became very popular because of the ease of access to all chambers of the heart. Another reason was that patients seemed to tolerate this incision and its aftermath very well.
The midline sternotomy propagated by Julian in the late 1950s proved to be a very versatile incision to allow for comprehensive access to all chambers of the heart. This was a great step forward compared to painful thoracotomy incisions of the day. However, it required the obligatory cut down the middle (from the base of the neck to just below the rib cage) and involved dividing the breastbone down the midline. At the conclusion of the procedure, the bone was typically closed by wire circlage (which was the prevalent custom of the day in helping get bony fragments to heal).
Over the intervening decades cardiac surgery has become a lot more common place and advances in medicine have made many important strides. In the meantime, other bone handling specialties ranging from orthopedics to plastic surgery and neurosurgery have changed the way they fix breaks of bone or fractures. The fundamental principle that underscores all bone healing is rigid fixation, which is best achieved by plates and screws. Just think of it, any of you that dabbles in carpentry would be horrified if you tried to lash a complex join of wood together with wire - especially, if you wanted that joint to withstand repeated stresses and regular movement.
Over the past 8 years, we have adapted used plates and screws to closure of the sternum in the high-risk patient. A patient is defined as high risk if there is an increased risk of the sternum not healing with "conventional" wire closure. The risk profile increases if the patient is diabetic, is undergoing repeat cardiac surgery, is taking steroid medication, has underlying osteoporosis, is likely to have a prolonged procedure, requires bilateral internal mammary artery grafts, etc..
Our experience with plate fixation of the sternum has been highly encouraging and has dramatically reduced our number of sternal complications. The most devastating complication after a sternotomy is deep sternal wound infection affecting the front of the chest, which is also known as mediastinitis. This carries a serious risk of morbidity and mortality. Despite having dramatically reduced our complication rate, improved patient satisfaction with their wounds, made sternal healing more secure, etc, we have had great difficulty in getting other groups and surgeons to change practice and use plates to close the sternum.
This may be partly due to the conservative nature of surgeons and also partly because wire closure of the sternum has been a relatively reliable technique in getting most sternal wounds to heal. The quality of the bony healing may not be as good but the complication rate in uncomplicated patients is low (at around 2 to 5%). The profile of cardiac surgery has changed over the past decade to now include older and sicker patients who have a higher risk profile for sternal wound complications and indeed survival. The evolution of this fairly simple concept from concept to practice was implemented by Dr Lawrence Gottlieb, a plastic surgeon at The University of Chicago. In the mid-1990s, he adapted plates used for fixing mandibles and used them to salvage sterna in infected sternotomy wounds, after the infection had been eradicated. Following the success of this concept, he proposed prophylactic plating of the sternum in high-risk patients to reduce the risk of sternal complications.
Dr Lawrence Gottlieb
Professor of Plastic Surgery
University of Chicago
Dr David Song, one of Dr Gottlieb’s trainees took this one step further and worked to prophylactically plate a group of high-risk patients at The University of Chicago in 2000. This was in response to an unacceptably high incidence of wound complications in some of these patients. Plate fixation almost eliminated sternal wound infections and dramatically reduced wound complications. This has since become standard of care.
Dr David Song
University of Chicago
Over the last 7 years, we have worked with industry to modify the plates and screws so that they are easy to use and the process of plating is not time consuming. We now have experience in plating over 1200 patients with a very low incidence of wound complications and a dramatic improvement in the patients’ perception of their wounds. Plating of the sternum provides secure closure and allows for quicker recovery of patients. Indeed, patients who have had previous cardiac surgery insist that their second procedure was associated with a lot less pain (presumably because there is less instability of the sternum).
This picture shows the body of the sternum fixed with 2 ‘X’ shaped plates. Note the wire at the left end of the picture which is at the manubrium of the sternum.
This diagram illustrates our most common plating confiruration - two figure of 8 wires (one in the manubrium and one at the xiphoid end) and 2 'X' plates in the body of the sternum.
he evolution of this system means that this plating procedure is now simple and easy to use with one session of training. Typically, in our hands, the plating procedure takes less time that wiring and causes less bleeding. This easy availability and adaptability of plating technology has allowed us to expand our capability in minimally invasive cardiac surgery (mini-sternotomy and mini-thoracotomy).