Anatomic Landmarks

The abdomen spans the area between the costal margin, midaxillary line, iliac crest, and symphysis pubis. The anterior and lateral contours of the abdominal wall, as well as the position of the umbilicus, are important landmarks that must be respected. The umbilicus is midline and is generally located at the level of the superior iliac crest. The umbilicus is normally located 14 cm above the pubic symphysis and 10 cm above the pubic hair. Checking these landmarks is helpful to ensure that the umbilicus is positioned appropriately postoperatively. The surgeon should also consider that the female abdomen has a more hourglass shape and is wider at the hips compared with the male abdomen that continues to narrow at the hips.

Muscle and Fascia Anatomy

The abdominal wall is composed of 4 paired muscle groups: the rectus abdominis, external oblique, internal oblique, and transversalis ( Fig. 2 ). In addition to flexion and rotation of the trunk, the abdominal muscles support the abdominal contents and assist in breathing. The midline of the abdomen is marked by a dense confluence of fascia known as the linea alba. Patients with a history of pregnancy or previous morbid obesity will frequently have a wider diastasis. The term abdominal diastasis refers to weakening and spreading of the midline fascia at the linea alba without the formation of a true hernia. In these cases aggressive plication may be used to improve and further flatten the abdomen and correct the diastasis.

Muscles of the abdominal wall. ( Reprinted with permission from Netter Anatomy Illustration Collection, © Elsevier Inc. All rights reserved.)

The paired rectus muscles are located on either side of the linea alba. The origin of the rectus abdominis muscle is the fifth, sixth, and seventh costal cartilages, costoxiphoid ligaments, and xiphoid process. The insertion of the rectus abdominis muscle is the crest of the pubis, pubic tubercle, and front of symphysis pubis. There are several horizontal inscriptions located on each rectus muscle. These condensations of fascia improve the mechanical advantage of the rectus muscle. The paired semilunar lines mark the lateral border of the rectus abdominis muscles. These vertical landmarks correspond to the aponeurosis of the external oblique, internal oblique, and transversus abdominis muscles. The aponeurotic portions of the oblique and transversus abdominis muscles surround the rectus abdominis muscles and join in the midline to form the linea alba.

The arcuate line is a horizontal transition point where the rectus fascia composition is different. Above the arcuate line the internal oblique fascia splits and part of the internal oblique fascia joins the external oblique to form the anterior rectus fascia. The other portion joins the aponeurosis of the transversus abdominis to form the posterior rectus sheath. Below the arcuate line, all 3 muscle aponeuroses pass anterior to the rectus abdominis muscle, leaving only preperitoneal fat between the rectus muscle and the underlying peritoneum.

The superficial and deep layers of fat in the abdominal wall are divided by Scarpa’s fascia. Scarpa’s fascia is a landmark dividing the better vascularized superficial fat from the less dense and less well vascularized deep fat. In addition, Scarpa’s fascia can be sutured to take tension off of the skin incisions. Suturing of Scarpa’s fascia may help achieve a fine line scar and limit scar migration.

Zones of Adherence

An understanding of the abdominal zones of adherence will facilitate appropriate design of flaps and prevent scar migration. There are zones of adherence located in the lower inguinal regions bilaterally and one centrally just above the mons pubis. The central zone may be less adherent in some individuals. These zones of adherence of the abdomen are important to prevent migration of abdominoplasty scars. Many advocate a deep layer of sutures using Scarpa’s fascia to facilitate anchoring at these zones of adherence. Note that there are also zones of adherence bilaterally between the hip and lateral thigh fat deposits as well as a zone of adherence overlying the spine. These latter zones are important particularly when abdominoplasty is combined with circumferential procedures. The zones of adherence are often most evident in patients with massive weight loss.

Nerve Anatomy

The cutaneous sensation to the abdominal wall is provided by the lateral cutaneous and anterior cutaneous branches of intercostal nerves T7 through T12 ( Fig. 3 ). These nerves typically perforate the intercostal muscles at the midaxillary line to travel within the subcutaneous plane. Therefore, nerves to the remaining skin flap are typically preserved in abdominoplasty. Also, consider the ilioinguinal and iliohypogastric nerves during abdominoplasty. Although they do not innervate the abdomen proper, they can be disrupted particularly with dissection in the lateral abdomen, resulting in sensory deficits in the medial thigh and groin.

Nerves of the abdominal wall. ( Reprinted with permission from Netter Anatomy Illustration Collection, © Elsevier Inc. All rights reserved.)