Anterior Abdominal Muscles

Hyperlordosis

As the anterior abdominal wall muscles are the main flexors of the vertebral column, weakness in or underdevelopment of these muscles can result in hyperlordosis of the lumbar vertebral column and anterior tilt of the pelvis. Anatomically, lordosis is the normal inward (anterior) curvature of cervical and lumbar regions of the vertebral column. The curvatures of the spine allow the weight of the trunk to be carried correctly over the pelvis for a stable gait and posture. Hyperlordosis occurs where there is excessive lordosis of the lumbar spine. It is caused by incorrect action of the extensor muscles of the vertebral column, such as a spasm brought on by lifting heavy objects incorrectly. Insufficient contraction of the anterior abdominal wall muscles to oppose hyperlordosis is a contributing factor. Observation of an exaggerated lumbar lordosis is a visual sign of hyperlordosis. X-ray can be used to measure the angle of lordosis in the lumbar spine. Hyperlordosis is treated mainly by corrective exercises to strengthen the muscle groups contributing to posture, including the gluteal region, the abdominal wall muscles, the hip flexor muscles, the quadriceps and the hamstrings. 

Anterior pelvic tilt

Anterior pelvic tilt is the abnormal tilting of the pelvis so that the pelvic inlet is oriented anteriorly. Weakness of the anterior abdominal wall muscles is a contributing factor in anterior pelvic tilt, along with other groups such as the gluteal muscles and hamstrings. Weakness of these muscle groups results in an inability to oppose the action of the quadriceps and hip flexors. Treatment is by strengthening the rectus abdominis and the pyramidalis muscles to counteract the action of the quadriceps and hip flexor muscles which are causing the anterior tilt. 

Abdominal surgery

In abdominal surgery, a paramedian incision is the typical surgical approach used to decrease the risk of inguinal herniation post surgery. The abdomen is incised over the belly of the rectus abdominis muscle. While the fascia is incised, the muscle, however, remains intact and it can be pushed laterally without its neurovascular supply being interrupted. This is because the nerves and vessels enter the muscle on the lateral aspect. During a cesarean section, a horizontal incision is typically made across the abdomen, and the rectus abdominis muscles are separated and moved laterally to gain access to the pelvic cavity. 

Divarication of the Recti

Divarication of the Recti occurs where increased strain is placed on the anterior abdominal wall, such as in the case of obesity, pregnancy, or chronic straining. This leads to a widening of the space between the rectus abdominis muscles, meaning that the force being transmitted by the anterior abdominal wall muscles is not directed all the way across the midline through the linea alba and is instead directed through the separate rectus abdominis muscles either side of the linea alba. As a result, the abdominal contents bulge against the wall in the midline as the muscles contract on either side, without actually extending out through the wall as occurs in a herniation. 

Divarication of the recti usually presents as a midline ridge beneath the skin anywhere between the xiphoid process and the pubis, becoming more prominent with contraction of rectus abdominis. Diagnosis is usually made by physical examination, but radiological imaging such as ultrasound or CT can be used to confirm the diagnosis. Treatment of the condition itself is not usually necessary. However, treatment of complications, such as umbilical hernias, may be required. 

Umbilical hernias

Umbilical hernias occur when some of the abdominal contents protrude through the anterior abdominal wall, specifically through the linea alba, above or below the umbilicus. They present as a bulge near the umbilicus that may or may not be obvious depending on whether or not the abdomen is relaxed. True congenital umbilical hernias occur where there is usually an abnormality present from birth. In some instances, the developing gut tube (midgut), which protrudes into the umbilical cord during weeks 6-10 of development, does not fully re-enter the abdomen and partially remains present as a sac enclosed by peritoneum outside of the anterior abdominal wall. This is called an omphalocele. Infantile umbilical hernias are present in the newborn and are mostly associated with increased intra-abdominal pressure. Umbilical hernias can also occur in the adult. These are acquired umbilical or paraumbilical hernias, and are usually the result of a weakening at a point along the linea alba.

Diagnosing an umbilical hernia is typically done by physical examination. Ultrasound or CT can also be used to confirm the diagnosis. Umbilical hernias can be dangerous as strangulation of the intestines can occur, leading to a blockage of the gut. The part of the intestines that protrudes through the abdominal wall might also be deprived of adequate blood supply, which can cause necrosis of that section of the gut. Should complications present, surgery may be required to repair the herniation. The surgical procedure is relatively straightforward. It involves a small incision being made near the umbilicus through which the intestines can be safely pushed back into the abdomen followed by closure with stitches. The abdominal wall is usually reinforced by a mesh to prevent further herniation before the incision is closed. 

Pregnancy

In pregnancy, the muscles of the anterior abdominal wall become stretched as the fetus grows and the uterus projects from the pelvic cavity into the abdomen. Pregnant women are susceptible to divarication of the recti because of the increase in intra-abdominal pressure the developing fetus places on the anterior abdominal wall. Postpartum, divarication of the recti can also occur due to residual weakness in the muscles.