Some women find that their abdomen continues to protrude after childbirth, despite regular exercise and not being overweight. This protrusion is related to muscle separation in the midline of the abdomen.
The anterior abdominal wall is composed of two rectus abdominis muscles in the central abdomen. The oblique muscles and transversalis muscles on the side are fused to form the anterior and posterior rectus sheath that wrap around the rectus muscle before forming the linea alba in the midline (Figure 1).
In pregnancy, the expanding uterus affects the shape of the abdomen and the lumbar spine position. This results in an increase in the distance between the attachments, which mean that the abdominal muscles become elongated and the angle of the attachments change. Functionally, this is manifested by the reduction in strength, affecting the rectus abdominis muscles. Due to the hormonal elastic connective tissue changes and mechanical strain, this results in the stretching of the linea alba, leading to the widening of the distance between the medial borders of the rectus muscles.
The separation of the two rectus abdominis muscle at the linea alba is more commonly known as diastasis rectus abdominal muscle (DRAM) or divarication rectus abdominis (DRA). In pregnancy, the reported incidence of DRAM or DRA varies between 66-100% in the final trimester of pregnancy and 36% up to 12 months post-natally. This can also happen in older and menopausal population. The definition of DRAM is variable and is based on the palpable separation of the two muscles or a perception of gapping (Figure 2).
The patient may notice some loose skin as well as some abdominal bulging when standing. The divarication can be seen when the patient is asked to lie supine and lift both legs or head off the ground. The increase in intra-abdominal pressure will exaggerate the midline bulging.
The abdominal wall has important functions in posture, trunk and pelvic stability, respiration, trunk movement and support of the abdominal viscera. An increase in the inter-recti distance puts these functions in jeopardy and can weaken abdominal muscles and influence their function. This may result in altered trunk mechanics, impaired pelvic stability and a change in posture, which can leave the lumbar spine and pelvis more vulnerable to injury.
Many publications have looked into the association of DRAM with lower back pain, weaker pelvic floor muscles, lumbo-pelvic pain and incontinence. Publications have suggested that DRAM width may be associated with health-related quality of life, abdominal muscle strength and severity of low back pain.
HOW CAN DRAM OR DRA BE PREVENTED?
Evidence has shown that exercise during the ante-natal period can reduce the presence of DRAM by 35% and the width of the separation may be reduced by exercising during the ante- and post-natal periods. In the post-natal period, physiotherapy can start 6-8 weeks postpartum. Currently, there is no specific programme but exercises such as abdominal sit-ups, crunches and lifting heavy objects are not beneficial. Literature has suggested that physiotherapy did not lead to the resolution of abdominal rectus diastasis in the relaxed state but that physiotherapy could achieve a limited reduction of the inter-recti distance during contraction of the muscles. Post-natal physiotherapy of up to 12 months will certainly be helpful but persistent divarication will require surgical intervention.
WHAT TREATMENT IS AVAILABLE?
In majority of cases, rectus divarication is repaired by suturing the medial edge of the rectus sheath together. This will reduce the widening of the linea alba and re-align the rectus muscles. The rectus divarication can be approached directly through a central midline incision but more commonly, it is corrected in combination with abdominoplasty (Figure 3).
Abdominoplasty is the surgery of choice when there is excess tissue and skin in the abdomen. When there is muscle divarication, the divarication can be repaired after the upper skin flap is mobilised to expose the defect. After repairing the divarication and excising the excess skin and tissue, the skin defect can then be closed, leaving a low transverse abdominal scar that is more aesthetically pleasing than a vertical midline scar.
Post operatively, gentle mobilization is recommended for a period of 6 weeks like with all abdominoplasty surgery. A physiotherapy programme to strengthen oblique muscles and core muscles with Pilates may be helpful.