Page 73 - International guidelines for groin hernia management

Hernia

followed 1–6 years after the operation. Pain risk factors Key question
included: age below median, female gender, direct hernia,
open technique, postoperative complications noted in KQ19P.c What is the most common inguinal nerve dis-
patient files at 30-day review, recurrent hernia repair, and tribution pattern and how common is it?
chronic pain of other origin in the 3 years prior to opera-
tion. 153 Similar results were found in another register study Evidence in literature
of 2456 patients followed for 2–3 years. 154 Several anatomic studies have been performed to elucidate
Another author, in a more holistic review, confirmed the the course of one or more of the inguinal nerves. 157–170
same risk factors and added the significance of mental Anesthesiology-based studies have been done to improve
151
state, anxiety, and patient expectations. nerve block success. 157–159 Surgical anatomical studies
A prospective cohort study investigated psychological have been done in the hopes of preventing nerve injury
models for prediction of chronic postoperative pain after during different approaches in this area. 157, 160–168 These
hernia surgery. These models are useful for predicting anesthesiology-based and surgical anatomical studies
acute pain and in non-surgical contexts, for predicting report data on retroperitoneal and/or anterior nerve distri-
transition from acute to chronic pain. A finding of higher bution patterns.
pain intensity 1-week postoperatively predicted higher pain This section focuses on the most common course of
intensity at 4 months. Lower preoperative optimism was an the ilioinguinal (IIN), iliohypogastric (IHN), and the
independent risk factor for chronic pain occurrence. 155 genitofemoral (GFN) nerves retroperitoneally over the
A systematic review of predictive experimental pain quadratus lumborum and psoas muscles and anteriorly
studies of quantitative sensory testing investigated after they pierce the transverse abdominal muscle
156
mechanical, thermal, and electrical stimuli. The review (TAM).
found that preoperative pain tests may predict 4–54% of Pooled results of anatomical studies indicate that the
the variance in postoperative pain occurrence. However, IHN was present in 864 of 879 inguinal dissections (98%,
the review concluded that there is no simple reliable range 60–100%). 157, 159–166, 168 The IIN was present in
prognostic assessment method for postoperative pain. 156 1217 of 1443 dissections (84%, range 56–100%). 157–169
The genital branch (GB) of the GFN was present in 256 of
Discussion 258 dissections (99%) 160, 165, 166, 170 .
A consensus on the definition of CPIP does not exist, In 68% (578 of 844) of dissections, the IIN and IHN
although a time threshold has been suggested. Most IH emerged separately lateral to the psoas muscle instead of
literature uses a 3-month duration to define chronic pain. emerging as a single trunk 157–161, 163, 168 . Thereafter, the
As discussed, for mesh-based repairs, a 6-month time IHN runs anteriorly over the quadratus lumborum muscle
frame may be more appropriate. to pierce the TAM usually just cranial to the iliac crest, and
In a similar manner, discomfort severity that seems runs shortly between the TAM and the internal oblique
clinically meaningful has been set at a level of ‘‘bother- muscle (IOM) to pierce the IOM and run dorsally to the
some moderate pain impacting daily activities.’’ Using this external oblique muscle (EOM). The IIN does the same,
cutoff, roughly 10–12% of patients experience this chron- except that in most cases a part of its course is caudal to the
ically after IH surgery. iliac crest, anterior to the iliac muscle. 160
Pain etiology does not enter into the definition of pain The GFN emerges through the psoas muscle as a single
itself. However, etiology, treatment, prognosis, and, above branch in the majority of patients (58%) and divides into
all, prevention, is of utmost importance for the research femoral and genital branches anterior to the psoas
into pain following IH surgery. muscle. 165
In most patients, the IHN innervates the hypogastric
Inguinal nerve anatomy region, after a course just cranial to the spermatic cord.
Cutaneous innervation of the medial thigh, pubic, and
Introduction scrotal/labial area and inguinal crease is provided jointly by
the IIN and GB. The same applies to the motor innervation
CPIP is thought to be primarily of a neuropathic origin. of the cremasteric muscle. When present, the IIN usually
Therefore, knowledge of the most common inguinal nerve runs anteriorly and parallel to the spermatic cord. The
distribution patterns and variants is paramount in its pre- course of the genital branch is usually laterocaudal at the
vention and treatment. level of the internal inguinal ring. 166
The dorsal nerve branch of the pudendal nerve, which
originates from S2 to S4, innervates the posterior scrotum/

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