Anatomy of the abdominal wall and aesthetic classification

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Chapter 19 Anatomy of the abdominal wall and aesthetic classification

Anatomy of the Anterior Abdominal Wall and its Surgical Implications on Abdominoplasty

Subcutaneous Anatomy of the Anterior Abdominal Wall

The subcutaneous tissue of the anterior abdomen is divided into two layers: the superficial (areolar) and the deep (lamellar) layer. The superficial fascia, also called Scarpa’s fascia, separates these two planes. Adipose tissue is thick and dense in the superficial layer, which is evenly distributed over the whole abdomen. The fat tissue in the deep layer is loose. In the infraumbilical area, these layers are very well defined, whereas in the supraumbilical region this separation is not very clear.1 In the infraumbilical area there is a wide variety of thickness of adipose tissue depending on the patient’s weight. It is important to know this anatomy when there is a difference in subcutaneous thickness between the flap and the area inferiorly to the abdominal incision. In such cases, the removal of the lamellar layer deep to Scarpa’s fascia can be a good option. This removal can be performed up to the umbilicus2 or in all the extension of the abdominal flap.

Blood Supply of the Abdominal Wall

The abdominal skin is supplied by a subdermal arterial plexus originated from a complex network of superficial vessels. Most of these vessels are supplied by the superficial epigastric artery, the superficial circumflex iliac artery, and also from perforators of the superior and inferior epigastric artery. Superficial branches of the intercostal arteries and lumbar branches are also part of this arterial supply.3 When describing the arterial anatomy of the abdominal wall, it is important to define the zones of blood supply which will have an important role in necrosis prevention. There are three areas of blood supply4 that have been described from the perspective of the surgeon. Knowledge of these areas guides the surgeon during abdominal flap undermining (Fig. 19.1). Zone I is the most important area and should be preserved as much as possible during flap undermining. It is located at the supraumbilical region, in which the main arterial flow comes from the perforators of the deep superior epigastric artery. By performing a more localized undermining, surgeons can preserve some of these arteries.

Sensitive Innervation of the Abdominal Wall

The intercostal, subcostal, iliohypogastric and ilioinguinal nerves are responsible for the sensitivity innervation of the anterior abdominal wall.5 The intercostal nerves are branches originating from T7 to T11. The subcostal nerves originate from T12 whereas the iliohypogastric and ilioinguinal nerves originate from L1. Branches from T7 to T9 innervate the supraumbilical area, T10 innervates the periumbilical area and the branches originating from T12 and L1 provide innervation to the infraumbilical area.

Lymphatic System

The lymphatic system of the subcutaneous tissue of the supraumbilical area drains to the axillary lymph nodes, whereas the infraumbilical system drains to the superficial inguinal lymph nodes.6 The periumbilical area may also drain to deep abdominal periaortal lymph nodes. Inefficient lymphatic drainage can be one of the causes of seroma.

Myoaponeurotic Anatomy

The rectus abdominis muscle is enfolded by two aponeurosis: the anterior and the posterior rectus sheath.

The anterior rectus sheath covers all the anterior surface of the rectus abdominis muscle. Its composition is different depending on its position. Above the arcuate line the anterior sheath is formed by aponeurotic fibers that originate from the external and internal oblique muscles. Below the arcuate line, the external, internal oblique and transverse aponeurosis blend to form the anterior rectus sheath. The arcuate line is in a variable position between the umbilicus and the pubis.

The posterior rectus sheath does not cover the entire posterior surface of the rectus muscle. It is interrupted below the arcuate line. Above this level, this sheath is formed by aponeurotic fibers of the internal oblique and transverse muscles. Below the arcuate line there is no aponeurosis and the muscle is separated from the peritoneum by the transversalis fascia.

After describing the rectus sheath anatomy, it is easy to understand why the plication of the anterior rectus sheath is a reliable procedure. As there is a dense attachment between the anterior sheath and the muscle, the plication will effectively bring these muscles together.711 However, if these muscles present a lateral origin in the rib cage, recurrence of the plication may occur, as repeated muscle contraction may lead to suture disruption in the upper abdomen.12

The muscles of the flank of the abdomen are the external oblique, internal oblique, and the transverse muscle. The fibers of the oblique muscles are perpendicular to the internal oblique fibers and there is a loose connective tissue between them. This is taken into account if a plication of the external oblique aponeurosis is performed; there is a real decrease of the distance between the origin and insertion of the muscle, thus promoting a more efficient contraction of the muscle and a positive cosmetic effect. It is also important to stress that the arterial supply to the external oblique muscle and its innervation penetrates the muscle laterally to the anterior axillary line.13 Therefore, when the advancement of the external oblique muscle is performed, the undermining on the loose connective tissue above the internal oblique muscle can be performed safely laterally to the anterior axillary line.

The Umbilicus

The attractive umbilicus should have a central depression, a superior skin hood and should also be more vertically shaped. The most accepted position of the umbilicus is at the level above the iliac crests.14 It is not an easy task to achieve all these goals when performing an abdominoplasty. To obtain an attractive umbilicus will depend on the design of the incisions used in the skin and in the umbilicus, on the skin closure tension, and on the abdominal level chosen to place the umbilicus.

Preoperative Preparation

Candidates for abdominoplasty should have a stable weight by the time of the operation to obtain the best possible result. If the patient is overweight and there is some difficulty advancing the flap on the pinch test, weight loss will benefit the patient’s result. Women should be past all their pregnancies before abdominoplasty; however, if a patient gets pregnant after this operation, there is a chance that the musculoaponeurotic deformity will not recur.9 A compressive abdominal garment is used for 1 week before the surgery to adapt the abdominal wall to the myoaponeurotic correction. Smoking and birth control medication should be discontinued for at least 15 days preoperatively.

Blood cell count, coagulation test, serum glucoses, sodium, potassium, urea and creatinine are basic blood exams that should be done for these patients. Ultrasound of the abdominal wall may be performed in cases where the plastic surgeon suspects abdominal wall hernias.

Diagnosis of the Abdominal Wall Deformities and Surgical Technique