Brian P. Jacob, David C. Chen, Bruce Ramshaw, Shirin Towfigh (eds.) - The SAGES Manual of Groin Pain-Springer International Publishing (2016)

14
I.A. Gawlas and W.J. Peacock
Variations in Neuroanatomy and Intraoperative
Considerations
It is estimated that, during open repair, all three inguinal nerves can
be distinctly identified in 70–90 % of patients [ 3 ]. The anatomy of the
iliohypogastric and ilioinguinal nerves is highly variable. The L1 nerve
trunks may divide into its two nerves early or late as it crosses quadratus
lumborum, or even may continue as one nerve as far as the anterior
abdominal wall before dividing. They are generally inversely proportional
in size.
Within the inguinal canal, the ilioinguinal nerve may be found within
the cremasteric sheath (as opposed to its usual position where it lies on
the anterior surface of the cord) [ 4 ]. Occasionally, it may not pass
through the external ring but may pierce the external oblique aponeurosis
more proximally [ 5 ].
During open repair, the genital branch of the genitofemoral nerve is
prone to injury as it enters the canal at the internal ring when the cord is
encircled with a Penrose drain while the floor of the inguinal ligament
is being exposed [ 6 ].
The iliohypogastric nerve may be injured in open repairs while
securing the superior edge of mesh to the aponeurosis of the transversus
and internal oblique muscles. During laparoscopy, it can also be injured
while the superior edge of the mesh is tacked into place, as this nerve
will not be seen where it runs in the neurovascular plane between the
transversus and internal oblique [ 6 ]. As they approach the internal ring,
the genital branch of the genitofemoral nerve will be inferior, and the
ilioinguinal nerve lateral, and both also may be inadvertently tacked during
laparoscopic repair.
Clearly, an awareness of the classic anatomy, as well as its possible
variations, is extremely important to avoid nerve damage.
References
1. Wagner JP, Brunicardi FC, Amid PK, Chen DC. Inguinal hernias. In: Brunicardi FC,
Andersen DK, Billiar TR, Dunn DL, Hunter JG, Matthews JB, Pollock RE, editors.
Schwartz’s principles of surgery. 10th ed. New York: McGraw Hill Medical; 2014.
p. 1495–521. Ch. 37.
2. Mirilas P, Mentessidou A, Skandalakis JE. Secondary internal inguinal ring and associated
surgical planes: surgical anatomy, embryology, applications. J Am Coll Surg.
2008;206(3):561–70.