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Siegal et al. Plast Aesthet Res 2019;6:25 I http://dx.doi.org/10.20517/2347-9264.2019.35 Page 9 of 20

to the ribs, and not to inadvertently divide diaphragm fibers that interdigitate with the TA in the cranial-
medial aspect. Doing so may create an iatrogenic diaphragm hernia. At the superior/medial extent of the
dissection, the TA release will join a subxiphoid pre-peritoneal dissection plane (discussed in next section).

Working caudally, it is important to remember that the TA muscle fibers do not reach as far medial as they
do in the upper abdomen. By the level of the umbilicus, there is only a bilayered aponeurotic insertion of
the TA to divide as part of the TAR. The plane between the TA aponeurosis (tendon) and the underlying
peritoneum can be dissected bluntly in a relatively straightforward fashion. Further caudally, there will be
substantial fat within the pre-peritoneal plane that further facilitates this dissection [Figure 6]. The ease of
separation of the layers is the basis for a “bottom-up” TAR. By bluntly dissecting from the retrorectus space
towards the myopectineal orifice, a pre-peritoneal/pretransversalis plane can be created. Further blunt
dissection cranially separates the TA aponeurosis from the underlying layers, and the aponeurosis can then
be divided. Some surgeons prefer the “bottom-up” approach to TAR because of the ease of starting the
plane at this level.

Midline crossover/transition
When the sublay plane is fully dissected to the superior and inferior extent, the right and left retromuscular
planes need to be connected. This is sometimes referred to as “plane hopping” or “crossing over”. Inferiorly,
the space of Retzius should be exposed down to the pubis. Connecting the right and left sides at this
level requires no more than ensuring the dissection planes (either pre-peritoneal or pre-transversalis)
meet in the midline. If one side is performed pre-peritoneal and one side pre-transversalis, they will not
meet properly in the midline without additional division of transversalis fibers off of the linea alba in the
midline. For low (European Hernia Society Classification: M4 or M5 zone) hernias, Cooper’s ligaments
[23]
should be exposed and may be used as fixation points for mesh . Any hernias of the myopectineal
orifice should be identified and reduced (including lipomas of the cord). The round ligament in women
can routinely be divided, while the spermatic cord in men must be carefully dissected around. With this
exposure, the sublay planes will connect at the caudal aspect.

For the cranial dissection, if the hernia defect approaches xiphoid process in the M1 zone, the insertion of
the posterior rectus sheath into the linea alba is divided to the level of the xiphoid. First, a plane superficial
to the falciform ligament and deep to linea alba must be developed. Next, retroxiphoid space should be
accessed. This is a fatty subxiphoid plane that extends to the sternum. This can be finger-swept posteriorly
off the xiphoid. Additionally, this preperitoneal space can be worked along the diaphragm to the central
tendon. The process of connecting the right and left retrorectus spaces with the pre-peritoneal plane of
the falciform ligament in the midline is referred to by some as the “pant leg maneuver” because of the
appearance of the undivided planes [Figure 7]. The insertion should be cut 0.5 cm lateral to the linea alba
on each side, which will drop the edge of the posterior sheath to allow reapproximation. Dividing the
posterior sheath insertion into the lineal alba, moving cranially along the xiphoid process, connects these
spaces [Figure 8].

Closure of the posterior sheath
Once the entirety of the retromuscular plane is developed, the posterior sheath is closed. Small defects
in the posterior sheath should be closed with an absorbable suture, generally in a transverse direction
(perpendicular to the midline) to prevent herniation of bowel into the retromuscular pocket. Larger defects
or areas that are extremely thin may not be closable primarily. In such circumstances, a piece of autologous
tissue (hernia sac and omentum) can be used to patch the graft. At times, difficulty with reconstruction of
the posterior layer can be predicted before any myofascial release is performed. In such cases, we generally
take the hernia sac off the subcutaneous tissues in the midline and leave it attached to the posterior
rectus sheath to serve as a continuous layer for reconstruction later. Larger defects can also be closed