CHAPTER 12 Surgical Treatment of Chest Wall Deformities
Open Repair
Step 1: Surgical Anatomy
♦ The severity and configuration of the pectus excavatum deformity vary widely. The depression involves posterior displacement of the sternum as well as the costal cartilages. The depression may also be linked with a protrusion of one side creating a “mixed” deformity.
♦ In teenagers, the posterior curvature of the ribs often involves part of the bony ribs as well as the cartilaginous portion.
♦ Another key consideration for these patients is the degree of asymmetry of the excavatum configuration. In some patients there is a marked asymmetry, often with a much shorter anteroposterior (AP) diameter of the chest on the right than on the left side. The sternum in these patients is often rotated with the right side down, and the ribs may actually take off at almost a right angle from the sternum. Surgical repair should address all of these anatomic components.
♦ The severity of the depression is often assessed using the Haller index, in which the transverse diameter of the chest (Fig. 12-1 A–B) is divided by the shortest distance between the sternum and the spine (Fig. 12-1 C–D). Indices greater than 3.25 are generally considered significant and appropriate for repair.
Step 2: Preoperative Considerations
Step 3: Operative Steps
Positioning
Incision
♦ In females, the incision is placed in the inframammary crease. I mark this with the patient sitting in the preoperative area to ensure that it is correctly identified. The incision must not extend onto the breast, which can produce “tethering” of the scar between the breasts.
♦ Skin flaps are then developed superiorly to the level of the highest cartilage to be resected and inferiorly to allow exposure of the triangular insertion of the rectus muscle onto the base of the sternum.
♦ The pectoral muscles are mobilized off the sternum beginning at their insertion on the sternum, and care is taken to avoid injury of the periosteum, which in teenagers can result in significant bleeding (see Fig. 12-2). The muscle flaps are elevated to the lateral extent of the deformity. Ellis (1997) has described performing this flap elevation mobilizing the pectoral muscles with the skin flap rather than as separate layers.
♦ This step is facilitated by first developing the plane directly anterior to one of the costal cartilages; electrocautery is used to divide the insertion of the pectoral muscles onto the sternum and then inserting an empty knife handle in the more lateral areolar plane just anterior to the costal cartilage, followed by a right angle retractor. I then repeat the process to the space in front of the costal cartilage either superior or inferior to this site and then retract the muscle flap anteriorly with two right-angle retractors. With electrocautery, one can then divide the salmon-colored muscle between the two retractors off from its insertion on the intercostal muscles, developing a plane laterally. One should avoid injury to the silvery fascia overlying the intercostal muscles to avoid hemorrhage and entry into the pleural cavity.
♦ Once the pectoral muscle flaps are mobilized, resection of the deformed costal cartilages is performed. This is achieved by placing a transverse incision directly over the midportion of the costal cartilages passing just through the perichondrium (Fig. 12-3).
♦ Perichondrial elevation is achieved using a perichondrial elevator defining the plane between the costal cartilage and the perichondrium. This is facilitated by incising the perichondrium with electrocautery at its anterior junction with the sternum, which allows the perichondrial sheath then to be reflected either superiorly or inferiorly to enhance exposure of the perichondrium on the posterior aspect of the rib.
♦ In children in their early teens, the growth plate for the rib at the costochondral junction is preserved by leaving a segment of the cartilage attached to the rib to allow continued growth (Fig. 12-4).
♦ In older teenagers who have completed most or all of their growth, the most anterior portion of the osseous ribs is often involved in the posterior depression, at least on the right side. In this situation, I extend the excision of the rib out onto the osseous portion and divide the rib with an angled bone cutter at the point where the rib is at the apex of its height. Dissection of the perichondrial sheath is facilitated by remembering that ribs 2 and 3 are fairly flat with a narrow depth, ribs 4 and 5 are almost circular in their transverse configuration, and ribs 6 and 7 are narrow and deeper (see Fig. 12-4). Fonkalsrud and Mendoza (2006) described a method of repair in which only segments of the deformed costal cartilages are removed.
♦ After the costal cartilages have been resected on each side, a transverse osteotomy is created at the superior aspect of the deformity on the sternum. I perform this using a Hall air drill to perforate the anterior plate of the sternum with two osteotomies approximately 3 to 5 mm apart or wider for larger teenagers (Fig. 12-5).
♦ The underlying cancellous bone is then mobilized with a perichondrial elevator or osteotome so that the segment of bone can then be elevated anteriorly.
♦ The base of the sternum is then elevated to fracture the posterior plate of the sternum. This maximizes the flexibility of the sternum and the ability to obtain a complete correction.
♦ The lowest portion of the sternal depression is then identified. This is generally the point of insertion of the 4th or 5th ribs. A tunnel is created at this site posterior to the sternum to allow passage of the retrosternal strut. At this time, the sternum is elevated anteriorly with a large towel clip to increase the distance between the posterior aspect of the sternum and the pericardium.
♦ Using electrocautery, the perichondrial sheath at the selected 4th or 5th space is then divided from its junction with the sternum. A Schnidt clamp is used to dissect bluntly between the sternum and the pericardium until the retrosternal space is traversed. On the opposite side of the sternum, the perichondrial sheath is again divided from the sternum to allow the Schnidt to come through that opening. The sternum is then elevated, placing the Schnidt on the anterior surface of the bony ribs on each side.
♦ The retrosternal strut is then configured into a “gull-wing” configuration so that the sternum will sit in the posterior depression of the strut as shown in Fig. 12-6. The strut is passed behind the sternum in a concave up position and with the strut flat relative to the sternum. After it is in position on each side on top of the ribs, it is then grasped with Kelly clamps and rotated 180 degrees. This should achieve an optimal correction for the sternum. If additional anterior elevation is required, the strut can be removed and repassed after altering its configuration or it can be bent further using handheld plate benders.
♦ To prevent lateral motion, the strut is secured with a heavy absorbable suture traversing a portion of the periosteum of the underlying rib and coming through one of the holes on the end of the strut. I secure the strut at both ends (see Fig. 12-6). Care is taken at this point to ensure that the ends of the strut are flush with the chest wall and not protruding into the skin, which will cause discomfort.
Closure
♦ Once hemostasis is confirmed, the wound is then closed, bringing the pectoral muscle flaps over the strut and sternum, joining them in the midline attached to the underlying periosteum of the sternum. At the inferior end of the sternum, it is important to join the muscle flaps to the rectus muscle fascia to achieve a water-tight closure.
Step 4: Postoperative Care
Step 5: Pearls and Pitfalls
♦ When the subcutaneous flaps are mobilized, the pectoral muscle fascia should be preserved intact with the muscle to maintain the strength and integrity of the muscle flap for closure. This is important because the flap will often be under some tension when it is stretched over the anteriorly displaced sternum.
♦ When sharply incising the perichondrium of the costal cartilages, stay in the middle of the cartilage. It is much easier to start the plane of dissection on the flat surface of the cartilage than on the side. Use a knife to make the perichondrium incision because it allows easier dissection of the perichondrium from the cartilage than if electrocautery is used for the incision.
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