Retroperitoneal course of iliohypogastric, ilioinguinal, and genitofemoral nerves: A study to improve identification and excision during triple neurectomy

Variations of the extrapsoas course of the lumbar plexus with implications for the lateral transpsoas approach to the lumbar spine: a cadaveric study

BACKGROUND

Together with an increased interest in minimally invasive lateral transpsoas approach to the lumbar spine goes a demand for detailed anatomical descriptions of the lumbar plexus. Although definitions of safe zones and essential descriptions of topographical anatomy have been presented in several studies, the existing literature expects standard appearance of the neural structures. Therefore, the aim of this study was to investigate the variability of the extrapsoas portion of the lumbar plexus in regard to the lateral transpsoas approach.

METHODS

A total of 260 lumbar regions from embalmed cadavers were utilized in this study. The specimens were dissected as per protocol and all nerves from the lumbar plexus were morphologically evaluated.

RESULTS

The most common variation of the iliohypogastric and ilioinguinal nerves was fusion of these two nerves (9.6%). Nearly in the half of the cases (48.1%) the genitofemoral nerve left the psoas major muscle already divided into the femoral and genital branches. The lateral femoral cutaneous nerve was the least variable one as it resembled its normal morphology in 95.0% of cases. Regarding the variant origins of the femoral nerve, there was a low formation outside the psoas major muscle in 3.8% of cases. The obturator nerve was not variable at its emergence point but frequently branched (40.4%) before entering the obturator canal. In addition to the proper femoral and obturator nerves, accessory nerves were present in 12.3% and 9.2% of cases, respectively.

CONCLUSION

Nerves of the lumbar plexus frequently show atypical anatomy outside the psoas major muscle. The presented study provides a compendious information source of the possibly encountered neural variations during retroperitoneal access to different segments of the lumbar spine.

Neuroproliferative dyspareunia in endometriosis and vestibulodynia

INTRODUCTION

Endometriosis is a common cause of deep dyspareunia, while provoked vestibulodynia is a common cause of superficial dyspareunia. The etiology of dyspareunia in both conditions is multifactorial and may include the role of local nerve growth (neurogenesis or neuroproliferation) that sensitizes pelvic structures and leads to pain with contact.

OBJECTIVES

To review the evidence for neuroproliferative dyspareunia in endometriosis and provoked vestibulodynia.

METHODS

Narrative review.

RESULTS

The pelvic peritoneum and vulvar vestibule receive somatic and autonomic innervation. Various markers have been utilized for nerve subtypes, including pan-neuronal markers and those specific for sensory and autonomic nerve fibers. The nerve growth factor family includes neurotrophic factors, such as nerve growth factor and brain-derived neurotrophic factor, and their receptors. Studies of endometriosis and provoked vestibulodynia have demonstrated the presence of nerve fibers around endometriosis epithelium/stroma in the pelvic peritoneum and within the vulvar vestibule. The number of nerve fibers is higher in these pain conditions as compared with control tissue. Nerve growth factor expression by endometriosis stroma and by immune cells in the vulvar vestibule may be involved in local neuroproliferation. Local inflammation is implicated in this neuroproliferation, with potential roles of interleukin 1β and mast cells in both conditions. Several studies have shown a correlation between nerve fibers around endometriosis and dyspareunia severity, but studies are lacking in provoked vestibulodynia. There are several possible clinical ramifications of neuroproliferative dyspareunia in endometriosis and provoked vestibulodynia, in terms of history, examination, biopsy, and surgical and medical treatment.

CONCLUSIONS

A neuroproliferative subtype of dyspareunia may be implicated in endometriosis and provoked vestibulodynia. Additional research is needed to validate this concept and to integrate it into clinical studies. Neuroproliferative pathways could serve as novel therapeutic targets for the treatment of dyspareunia in endometriosis and provoked vestibulodynia.

Anatomical Variations of the Iliohypogastric Nerve: A Systematic Review of the Literature

Several anatomical variations of the iliohypogastric nerve branches have been observed in earlier studies. Knowledge of these variations is useful for the improvement of peripheral nerve blocks and avoidance of iatrogenic nerve injuries during surgeries. The purpose of this study was to perform a systematic review of the literature about the anatomical topography and variations of the iliohypogastric nerve. An extensive search on PubMed, Scopus, and Web of Science electronic databases was conducted by the first author in November 2021, based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Anatomical or cadaveric studies about the origin, the course, and the distribution of the iliohypogastric nerve were included in this review. Thirty cadaveric studies were included for qualitative analysis. Several anatomical variations of the iliohypogastric nerve were depicted including its general properties, its origin, its branching patterns, its course, its relation to anatomical landmarks, and its termination. Among them, the absence of the iliohypogastric nerve ranged from 0 to 34%, its origin from L1 ranged from 62.5 to 96.5%, and its isolated emergence from psoas major ranged from 47 to 94.5%. Numerous anatomical variations of the iliohypogastric nerve exist but are not commonly cited in classic anatomical textbooks. The branches of the iliohypogastric nerve may be damaged during spinal anesthesia and surgical procedures in the lower abdominal region. Therefore, a better understanding of the regional anatomy and its variations is of vital importance for the prevention of iliohypogastric nerve injuries.

A Crucial But Neglected Anatomical Factor Underneath Psoas Muscle and Its Clinical Value in Lateral Lumbar Interbody Fusion-The Cleft of Psoas Major (CPM)

Objective

To describe the anatomical feature positioned beneath the psoas muscle at the lateral aspect of the lower lumbar, and to create a new location system to identify the risk factors of lateral lumbar interbody fusion.

Methods

Six cadavers were dissected and analyzed. The anatomy and neurovascular distribution beneath the psoas major from L₃ to S₁ was observed and recorded, with particular focus on the L_4/5 disc and below. The psoas major surface was divided homogeneously into four parts, from the anterior border of psoas major to the transverse process. The cranial‐to‐caudal division was from the lower edge of the psoas muscle attachment on the L₄ vertebrae to the upper part of the S₁ vertebrae, and was divided into five segments. Then a grid system was used to create 20 grids on the psoas major surface, from the anterior border of the muscle to the transverse process and from L₄ to superior S₁, which was used to determine the anatomical structures' distribution and relationship beneath the psoas major.

Results

A cleft was identified beneath the psoas major, from the level of L_4/5 downwards. It was filled with loose connective tissue and neurovascular structures. We termed it the cleft of psoas major (CPM). The sympathetic trunk, ascending lumbar vein, iliolumbar vessels, obturator nerve, femoral nerve and occasionally the great vessels are contained within the CPM, although there is significant interpersonal variation. The grid system on the psoas major surface helped to identify the anatomical structures in CPM. There was a considerably lower frequency of occurrence of neurovascular structures in the grids of I/II at the L_4/5 level where can be considered the “safe zones” for the lateral lumbar interbody fusion. In contrast, the distribution of neurovascular structures at the L₅S₁ level is dense, where the operation risk is high.

Conclusion

The CPM exists lateral to the vertebral surface from L₄ and below. Although the occurrence and distribution of neurovascular structures within the CPM is complex and varies greatly, it can provide a potential cavity for visualization during lateral lumbar interbody fusion. Using psoas major as a reference, this novel grid system can be used to identify the risk factors in CPM and thus identify a safe entry point for surgery.

A study to improve identification of the retroperitoneal course of iliohypogastric, ilioinguinal, femorocutaneous and genitofemoral nerves during laparoscopic triple neurectomy

BACKGROUND

Laparoscopic triple neurectomy is an available treatment option for chronic groin pain, but a poor working knowledge of the retroperitoneal neuroanatomy makes it an unsafe technique.

OBJECT

Describe the retroperitoneal course of iliohypogastric, ilioinguinal, lateral femoral cutaneous and genitofemoral nerves, to guide the surgeon who operates in this region.

METHODS

Fifty adult cadavers were dissected resulting in 100 anatomic specimens. Additionally, 30 patients were operated for refractory chronic inguinal pain, using laparoscopic triple neurectomy. All operations and dissections were photographed. Measurements were made between the nerves of the lumbar plexus and various landmarks: interneural distances in a vertical midline plane, posterior or anterior iliac spine and branch presentation model.

RESULTS

The ilioinguinal and iliohypogastric nerves were independent in 78% (Type II) and separated by an average of 2.5 ± 0.8 cm. In surgery study, only 38% were recognized as Type II and at a significantly greater distance (3.5 ± 1.2 cm, p < 0.001). The distance between ilioinguinal and lateral femoral cutaneous nerves was also greater during surgery, with statistical significance (5.1 ± 1.5 versus 4.2 ± 1.5, p < 0.005). The distance of the nerves to their bone references were not statistically different. The genitofemoral nerve emerged from the psoas major muscle in 20% as two separate branches (Type II), regardless of the study. The lateral femoral cutaneous nerve had a mean distance of 0.98 ± 1.6 cm medial to the anterior superior iliac spine.

CONCLUSION

The identification of the IH, II, FC and GF nerves is essential to reduce the rate of failures in the treatment of CGP. The frequent anatomical variations of the lumbar plexus nerves make knowledge of their courses in the retroperitoneal space essential to ensure safe surgery. The location of the nerves in the LTN is distorted by up to 1 cm. regarding references in the cadavers.