Anatomical variations of the inguinal nerves and risks of injury in 110 hernia repairs

Abstract

The aim of this study was to identify the anatomical variations in the inguinal course of the ilioinguinal nerve (IIN) and the iliohypogastric nerve (IHN) during operative repair of inguinal hernias. A consecutive series of 110 primary inguinal hernias were repaired by the mesh technique. Particular attention was paid to early identification and recording of the course of both the IIN and IHN and preserving them throughout the operative procedure. The course of both nerves was found to be consistent with that described in anatomical texts in only 46 of 110 explorations (41.8%). The course of one or both nerves was found to be a variant in the other 64 of 110 (58.2%) explorations and often rendered them susceptible to injury. These variations included: (1) acute infero-lateral angulation of the IIN at its exit behind the superficial inguinal ring (SIR) fibers in 20 of 64 cases; (2) similar direction of the IIN but in a plane superficial to the external oblique aponeurosis (EOA) and proximal to the SIR in 18 of 64 cases; (3) a single stem for both nerves over the spermatic cord in 24 of 64 cases, with variation in the subsequent course; (4) absence of one or both nerves in 8 of 64 cases; (5) accessory IIN or IHN in 3 of 64 cases; and (6) aberrant origin of the IIN from the genitofemoral nerve (GFN) in 2 of 64 cases. None of 68 of 105 patients seen at 3 months postoperatively (compliance rate 65%) complained of sensory disturbances or pain in a dermatome distribution of the IIN or IHN. It is concluded that anatomical variations in the inguinal course of the IIN and the IHN are extremely common but readily identifiable. Their early identification and preservation is likely to abolish, or considerably decrease, the incidence of postoperative sensory changes and/or neuralgia pain.

Anatomic variability of groin innervation

“…The inguinal nerves are often found to follow variable patterns of distribution [1,5,6]. In a recent study of patients undergoing hernia repair, Al-Dabbagh [1] found that the course of the ilioinguinal and iliohypogastric nerves was only consistent with anatomic texts in 41.8% of cases.…”

“…In a recent study of patients undergoing hernia repair, Al-Dabbagh [1] found that the course of the ilioinguinal and iliohypogastric nerves was only consistent with anatomic texts in 41.8% of cases. Furthermore one or both of these nerves was found to be absent in 7.3% of cases [5].…”

“…Injury to the innervation of this area can lead to postoperative pain [6,7]. For instance, in 49 out of 110 hernia repairs reported by Al-Dabbagh [1], the atypical superficial placement of the ilioinguinal nerve left it particularly vulnerable to transection in the early stages of the operation. The nerve was found either emerging through the fibres of the external oblique muscle, proximal to the superficial inguinal ring or running parallel and in proximity to the latter [1].…”

“…For instance, in 49 out of 110 hernia repairs reported by Al-Dabbagh [1], the atypical superficial placement of the ilioinguinal nerve left it particularly vulnerable to transection in the early stages of the operation. The nerve was found either emerging through the fibres of the external oblique muscle, proximal to the superficial inguinal ring or running parallel and in proximity to the latter [1]. Such placement increases the risk of it being severed when the external oblique aponeurosis and superficial inguinal ring are split [5].…”

A test for the evaluation of the lateral cutaneous branch of the iliohypogastric nerve using somatosensory evoked potentials

“…The described method however, is not suited for testing the anterior cutaneous branch. In addition there may be bulging of the muscles of the lower quadrant of the abdominal wall [6].…”