The incision is a transverse sub-mammary incision. It is useful to mark with ink the mid line, the upper and lower limits of the defect and the incision itself half way between these limits. As ink is frequently smudged during the operation I scratch two or three lines across the incision for later alignment. The defect is rarely fully symmetrical so the incision should be carefully marked with the eventual alignment in mind.
Incision lines

The incision need not extend as far as the nipples in boys. In girls it is important not to cut cross developing breast tissue. In girls I perform a more formal sub-mammary incision below the developing breasts.

The outer dermis is cut with the skin knife. Thereafter the cautery is used on a coagulation setting to complete the dermal incision, and on down through the subcutaneous tissue to the muscle fascia.

Subcutaneous flaps are fashioned to allow full movement of the later muscle flaps. Stay outside the muscle fascia to avoid bleeding.They do not need to be quite as extensive as the muscle flaps. Keep in mind that you do not want to de-vascularise the skin completely. Avoid button holing the skin. Placement of retractors superiorly and inferiorly in the corners of the incision will allow the skin to be undermined laterally to allow full rectus incisions.
Subcutaneous flap

Muscle flaps
Bilateral pectoral flaps will be raised as well as raising the rectus abdominis muscles as an inferiorly based flap. The incision in the muscles makes a three pointed “Mercedes Benz” star. A mid line incision starting at the sternal notch divides the pectoral muscles down to the top of the xiphisternum where the muscle is little more than fascia and periosteum. Two cuts are brought out infero-laterally, rather artificially dividing the inter-digitations of the rectus and pectoral muscles.
A corner of the pectoralis is raised being careful to cauterise each perforating branch of the IMA before it bleeds. (They can be a nuisance to stop if you miss one!) The flaps are continued superiorly to at least the level of the second rib and laterally to the costo-chondral junctions.
Pectoral muscle flap

The rectus is lifted off the lower ribs with cautery. Care should be taken not to enter the peritoneal cavity but usually there is enough fat for this not to be a problem. For carinatum defects I usually excise the xiphisternum at this stage leaving it attached to the rectus muscles for later suturing over the sternum. In an excavatum defect it is usually too deep and retroflexed. There is frequently a lot of bleeding as one lifts the rectus flap so go slowly and carefully, first one side then the other as you retract down towards the inferior extent of the defect. As the costal margins can later be pulled up into the incision it is not necessary to lift the flap to the full extent of the defect.

[Some surgeons do not raise flaps, preferring to cut directly through pectoralis over each cartilage in line with its fibres. This does cut down bleeding from perforating vessels but denervates at least some muscle fibres. I like to keep as much muscle to provide bulk over my repair.]

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