Page 77 - Clinical Anatomy

ECA2 7/18/06 6:42 PM Page 62

62 The abdomen and pelvis

The transrectus incision
Occasionally, the rectus muscle is split in the line of the paramedian inci-
sion. The rectus receives its nerve supply laterally and the muscle medial to
the incision must, in consequence, be deprived of its innervation and
undergo atrophy; it is an incision therefore best avoided.

Subcostal incision

The subcostal (Kocher) incision is used on the right side in biliary surgery
and, on the left, in exposure of the spleen. The skin incision commences at
the midline and extends parallel to, and 1in (2.5cm) below, the costal
margin.
The anterior rectus sheath is opened, the rectus cut and the posterior
sheath with underlying adherent peritoneum incised. The small 8th inter-
costal nerve branch to the rectus is sacrificed but the larger and more impor-
tant 9th nerve, in the lateral part of the wound, is preserved. The divided
rectus muscle is held by the intersections above and below and retracts very
little. It subsequently heals by fibrous tissue. This incision is valuable in the
patient with the wide subcostal angle. Where this angle is narrow, the para-
median incision is usually preferred.

The muscle split or gridiron approach to
the appendix

The oblique skin incision centred at McBurney’s point (two-thirds of the way
laterally along the line from the umbilicus to the anterior superior iliac
spine) is now less popular than an almost transverse incision in the line of
the skin crease forwards from, and 1in (2.5cm) above, the anterior spine.
The aponeurosis of the external oblique is incised in the line of its fibres
(obliquely downwards and medially); the internal oblique and transversus
muscles are then split in the line of their fibres, and retracted without their
having to be divided. On closing the incision, these muscles snap together
again, leaving a virtually undamaged abdominal wall.

Transverse and oblique incisions

Incisions cutting through the lateral abdominal muscles do not damage
their richly anastomosing nerve supply and heal without weakness. They
are useful, for example, in exposing the sigmoid colon or the caecum or, by
displacing the peritoneum medially, extraperitoneal structures such as the
ureter, sympathetic chain and the external iliac vessels.

Thoraco-abdominal incisions

An upper paramedian or upper oblique abdominal incision can be
extended through the 8th or 9th intercostal space, the diaphragm incised
and an extensive exposure achieved of both upper abdomen and thorax.