Median sternotomy

The identifications are followed by a median and vertical incision and subcutaneous cauterization.

Tissue preparation
To assure a midline preparation, the jugulum and the xiphoid are located and prepared (Video 2). The midline can be easily developed with cautery between these two landmarks by dividing the subcutaneous tissue and the underlying pectoral fascia between the fibres of the pectoralis major muscle. Once the periosteum is reached and the midline identified by palpating the intercostal spaces and the sternochondral junctions at both sides of the sternum, it is marked with cautery along the whole bone (Video 3).

Identification and clipping of the transverse venous arch in the jugulum is recommended to avoid bleeding. The interclavicular ligament has to be carefully divided followed by digital dissection of the rear surface of the sternum from the underlying sternoclavicular ligament. The xiphoid is severed from the underlying tissue of the diaphragm by digital dissection.

The midline is identified by palpating the intercostal spaces and the sternochondral junctions at both sides of the sternum and is marked with the cautery.

Jugulum
While preparing the jugulum, it must be noted that most patients have a transverse venous arch, which can bleed heavily if not controlled beforehand (Video 2). It is recommended to clip it. The interclavicular ligament has to be carefully divided (with cautery or scissors) followed by digital dissection of the rear surface of the sternum from the underlying sternoclavicular ligament. This assures an undisturbed sawing of the bone, especially if it is performed from above downwards.

Xyphoid
The xiphoid is marked in the midline, and the linea alba is incised followed by digital dissection of the process from the underlying tissue of the diaphragm (Video 2). If the surgeon is sawing from down upwards, the xiphoid is split at the midline with scissors. There is always a vein crossing the cranial part of the xiphoid, which has to be cauterized to avoid excessive bleeding.

Osteotomy
After preparation of the jugulum, the xiphoid and the midline, the surgeon is prepared for sawing with either an electric or air-powered saw (Video 4). An oscillating saw is used in repeat sternotomy to control the depth of the bone incision without injuring the right ventricle behind it or in paediatric cases. Before sawing, the anaesthetist is asked to stop the ventilation in order to avoid accidental opening of the pleura with the saw. Depending on the surgeon's preference, the osteotomy can be either performed from above downwards (as shown here) or the other way around. While doing so, it is important to pull the saw upwards in order to avoid injury to underlying structures (pleura, pericardium, innominate vein, brachiocephalic artery and ectatic ascending aorta). If the sternum is not divided in the midline, it will be difficult to close it properly, which can result in healing complications with the need of subsequent osteosynthesis with plates.

Here, osteotomy is performed from above downwards. It is important to pull the saw upwards in order to avoid injury to underlying structures (pleura, pericardium, innominate vein, brachiocephalic artery and ectatic ascending aorta). Bleeding is controlled with pinpoint cautery of the periosteum and the use of bone wax to seal the bone marrow.

Bleeding control
The exposed periosteum results in bleeding from the arteries (Video 4). To have a clear operating field, we place a cloth between the pericardium and the sternal edges. Bleeding is controlled with pinpoint cautery to avoid continuous blood loss during surgery. It is important not to cauterize excessively because it leads to necrosis and can facilitate wound infection. Another possibility is the use of bone wax to seal the bone marrow, although it is a suspected risk factor for wound infection. It is prudent to use cautery and wax as limited as possible and only as much as needed. Some surgeons only use towels for bleeding control.

For hygienic reasons, we change gloves before continuing the operation at this point in order to avoid spreading of cutaneous germs into the mediastinum. Further bleeding control is achieved with towels placed around the sternal edges. The sternum is retracted slowly and progressively in order to avoid fractures or even a rupture of the innominate vein. The sternopericardial ligaments are freed from the posterior surface of the sternum using a towel.

Retraction
Towels are placed around the sternal edges for bleeding control (Video 5). The retractor is placed not too far cranially to avoid tension injury to the innominate vein and brachial plexus. The sternum has to be retracted progressively to avoid fractures of the bones with excessive postoperative pain due to costovertebral joint strain. The sternopericardial ligaments are freed from the posterior surface of the sternum using a towel. If the patient is too spastic, the anaesthetist can be asked for another dose of muscle relaxant.

Sternal closure

Chest tubes
After completion of the cardiac procedure, mediastinal and/or pleural tubes (24 F) are placed through stab incisions in the epigastrium (Video 6). A towel is placed between the heart and the sternal edges for protection. It is important to place the tubes below the fascia of the rectus muscle to avoid herniation and not too laterally to avoid injury of the epigastric pedicle. The tunnelling must be performed with care and not too deep because it can result in fatal colic, gastric or hepatic lesions.

The stab incisions for the mediastinal drains are made in the epigastrium. It is important to place them below the fascia of the rectus muscle in order to avoid herniation, not too laterally to avoid the epigastric pedicle and not too deep, which can result in colic, gastric or hepatic lesions.

Sternal closure
Before closure, we change the gloves once again. To protect the right ventricle, a towel is placed between the sternal halves (Video 7). Four to eight stainless steel wires are used for closure (either singular or figure of eight, as shown here). The wires can either be placed parasternally or through the sternal bone. The needle has to pass perpendicularly through the sternum to produce a small tunnel with minimal bleeding. Here, we apply one figure-of-eight wire through the manubrium and the second as a bridge over the manubrio-corporal joint. The others are placed through the corpus. The wires can also be placed through the intercostal spaces but with the risk of injuring the internal thoracic pedicle, resulting in major bleeding with haematothorax or tamponade. It is important to avoid an override or shift of the sternal edges by placing the wires at a proper distance from each other (Video 7). After all wires have been set, the towel is removed carefully while lifting the wires upwards. Extra care has to be applied in bypass surgery to avoid tearing the grafts by pulling the towel. Before closure, we rinse the mediastinum with saline and check both retrosternal halves to rule out bleeding (Video 8). Some surgeons even remove the initially used bone wax from the spongiosa to prevent healing complications. While approximating the sternal halves, it is important not to apply too much force and to pull the wires up and caudally to avoid horizontal fractures of the sternum (Video 9). If the patient is too spastic, the anaesthetist can be asked for another dose of muscle relaxant. After proper approximation, the wires are loosely twisted and cut. Then, the ends are twisted further until the sternal halves are tightly re-approximated. It is important not to over-twist the wires because they can easily brake, which makes a complete re-wiring necessary. A too tight approximation can cause malperfusion of the bone with the possibility of wound infection. The twisted ends must not be too long and have to be buried entirely into the presternal tissue especially in very thin patients, because they can cause skin erosion or perforation. Inappropriate sternal approximation can cause postoperative pain and dehiscence which is a risk factor for wound infection.

The stainless steel wires have to pass perpendicularly through the sternum in order to produce a small tunnel with minimal bleeding.

When all the wires are placed, the mediastinum is rinsed with saline and both retrosternal halves are checked to rule out bleeding.

While approximating the sternal halves, it is important not to apply too much force and to pull the wires up and caudally in order to avoid horizontal fractures of the sternum. The twisted ends must not be too long and have to be buried entirely into the presternal tissue especially in very thin patients because otherwise they can cause skin erosion or even perforation.

Tissue closure
The linea alba has to be properly re-approximated to avoid abdominal herniation (Video 10). The pectoral fascia is closed with one line of running suture followed by a second line for the subcutaneous tissue. The skin is closed either with an absorbable running suture or with clips. Especially in women with large breasts or obese patients, it is important to adapt the skin with extra care and stability to avoid dehiscence and subsequent wound infection. For these patients, we usually use clips but with the fact in mind that they prolong a fast re-thoracotomy in an emergency setting.

The linea alba is re-approximated to avoid herniation. The pectoral fascia is closed with one line of running suture followed by a second line for the subcutaneous tissue. The skin is closed at the surgeon's preference either with an absorbable running suture or with clips (as shown here).

Wound care
We clean the wound with iodine (Video 10) and cover it with a visible plaster, which will not be removed until 5 days postoperatively to avoid contamination.

Sternal care
All patients with risk for sternal wound infection and instability (body mass index >30, chronic obstructive pulmonary disease, bilateral mammary harvesting, >75 years of age and diabetes) receive a thoracic vest for stabilization for 4–6 weeks.