Applied surgical anatomical approach to pudendal nerve: Step-by-step key neurovascular structures for pelvic nerve surgery

Objective To define and demonstrate a step-by-step surgical anatomical approach to pudendal nerve dissection using female cadavers, focusing on the identification of safe roadmap and key neurovascular structures to optimize pelvic nerve surgery.

A descriptive anatomical study was conducted on 60 hemipelvises from 30 female cadavers. Dissections were performed in three stages comprising nine procedural steps to expose the pudendal nerve and related pelvic nerves. Key neurovascular landmarks were documented using video recordings.

The dissection was organized into three stages: (1) exposure of the genitofemoral nerve and obturator fossa and its contents, (2) identification of the lumbosacral trunk and sciatic nerve, and greater sciatic notch (3) visualization of the pudendal nerve beneath the sacrospinous ligament. Variations in pudendal nerve branching and anatomical relationships with adjacent structures, including the sacrospinous ligament and ischial spine, were documented. This stepwise approach provided clear surgical landmarks to minimize the risk of nerve injury during pelvic surgery.

This cadaveric study provides a detailed, practical roadmap for pudendal nerve dissection, enhancing anatomical understanding of pelvic neurovascular structures. The defined surgical approach in three stages, nine steps, and this comprehensive anatomical understanding can improve surgical precision and supports safer nerve-sparing techniques in complex pelvic surgery including gynecologic pelvic surgical procedures, surgeries for pudendal neuralgia, and deep infiltrating endometriosis. 1 INTRODUCTION The pudendal nerve (PN), arises from the ventral rami of the second to fourth sacral nerve roots.1 Pudendal neuralgia, a neuropathic pain syndrome within the PN distribution, typically results from injury to the PN or lumbosacral plexus branches. Its prevalence is estimated at around 1% in the general population.2 Pudendal nerve injury can result from trauma, stretch, compression, or entrapment. Although injury may occur along its entire course, common entrapment sites include the space between the sacrospinous and sacrotuberous ligaments, Alcock's canal, and the inferior pubic ramus. Neuroma formation from compression or direct PN injury during pelvic surgery is a recognized cause of pudendal neuralgia. However, detailed anatomical descriptions of its surrounding connective tissues are limited. In refractory cases, PN decompression may be performed, but its indications and efficacy remain controversial.3 Laparoscopic, robotic or laparatomic excision of deep endometriosis involving pelvic nerves is technically demanding, and when pudendal neuralgia is caused by nerve infiltration, precise identification of surrounding anatomy, including the genitofemoral (GFN), obturator (ON), lumbosacral trunk (LST), and sciatic (SN) nerves, is critical for safe PN access and injury prevention.4-9 Detailed surgical anatomical descriptions of the PN, its variations, and its relationships with connective tissues are essential to guide treatment and clarify injury mechanisms.10 Detailed anatomical knowledge is required in PN surgeries, including those for deep infiltrating endometriosis (DIE) or neuroma, advanced surgical skills are essential for safe nerve-sparing techniques. This study aims to delineate stepwise surgical anatomical approaches to PN dissection in female cadavers, with a focus on identifying a safe dissection roadmap and key neurovascular structures. 2 MATERIALS AND METHODS 2.1 Specimens This descriptive anatomical study was performed on 60 hemipelvises between October 2024 and July 2025 from 30 female cadavers (20 formalin fixed and 10 fresh frozen). All cadavers were obtained from Ankara University School of Medicine, Department of Anatomy by body donation program, which included consent for educational use, research, and science. Dissections were recorded using a Sony EX1R video camera. Key anatomical structures were highlighted with animations on still images extracted from the video recordings. Dissection and evaluation were not initiated in cadavers with previous abdominopelvic surgery, pelvic pathology, or damage. 2.2 Ethics statement This study was exempt from institutional review board review. All procedures performed in this study involving human cadaveric material were in accordance with the ethical standards of the institutional research committee and with the 1964 Helsinki declimitlaration and its later amendments. 2.3 Cadaveric dissection and analyzing of data After identifying the sigmoid colon on the left, pelvic anatomy was assessed using the sacral promontory as a midline landmark. On the right, the ureters and gonadal vessels were visualized beneath the posterior peritoneum. All neurovascular structures surrounding the PN, along with the adjacent surgical approaches, were carefully exposed in all specimens. The distance between the origin of the PN and the palpated tip of the ischial spine (IS) was determined using a short measuring stick, and the marked segment was subsequently measured on the dissection table using a digital caliper. All data were analyzed using IBM SPSS version 16.0 (SPSS Inc., Chicago, IL, USA). Continuous variables are presented using descriptive statistics as mean ± standard deviation or median (minimum–maximum), and categorical variables as percentages. 2.4 Description of surgical steps from anatomical dissections - Stage I focused on the dissection of the GFN and the obturator fossa contents (see Video 1). - Stage II involved the dissection of the LST, the SN, and the greater sciatic notch (see Video 2). - Stage III demonstrated the dissection of the PN, sacrospinous ligament (SSL), and sacral nerve roots (see Video 3). 3 RESULTS - Lateral approach: between the external iliac vessels laterally and the iliopsoas muscle medially. - Medial approach: between the internal iliac vessels laterally and the external iliac vessels medially. 3.1 Stage I 3.1.1 Step 1 After mobilizing the sigmoid mesentery from the posterior pelvic wall, the iliac vessels were exposed, with the ureter crossing anteriorly, followed by the gonadal vessels. Upon entering the peritoneal cavity, dissection proceeded carefully into the retroperitoneal space over the iliac vessels, within the embryologic avascular plane, separating the visceral fascia. The GFN, located on the psoas major (PM) adjacent to these vessels, was identified, with its femoral branch lateral and genital branch medial. The nerve was then medialized over the major vessels as dissection advanced. Cranially, the GFN lies near the inferior vena cava and external iliac vein, while caudally, the external iliac vein crosses the PM and courses laterally beneath the inguinal canal. Accurate identification of the nerve's course is essential for its preservation during pelvic surgery (Figure 1A). 3.1.2 Step 2 To access the obturator fossa containing the ON and, if present, the accessory ON, the peritoneum was incised after medializing the gonadal vessels and ureter relative to the iliac vessels, exposing the internal iliac vessels. Following the medial border of the PM may reveal sympathetic ganglia. Retraction of the iliac vessels exposed the lumbar sympathetic ganglia and descending sympathetic chain medial to the PM. Dissection proceeded to identify the ON, which emerges below the iliac bifurcation and courses laterally between the external and internal iliac vessels toward the obturator canal. The obturator artery and vein lie beneath the nerve (Figure 1B). 3.1.3 Step 3 The paravesical space was opened anterior to the round ligament to visualize the obturator canal entry and the corona mortis. The obturator fossa can be approached laterally via the iliac vessels or medially via the PM, facilitating lymph node dissection. In this area, the obturator vessels and nerves lie in close proximity to the LST and SN. Additionally, the iliolumbar vessels and multiple smaller branches extend laterally from the iliac vessels and may be encountered during lymphadenectomy, deep endometriosis surgery, or hemostasis (Figure 1C). 3.2 Stage II 3.2.1 Step 1 Following access to the obturator fossa, the SN can be approached medially by retracting the iliac vessels carefully and gently laterally and the ON and obturator vessels medially, allowing direct visualization of the SN (Figure 2A). 3.2.2 Step 2 The most cranial root of the SN is the LST, formed by L4 and L5, which passes medial to the PM and joins the sacral nerves to form the lumbosacral plexus. Both the ON and LST are visible in this region. To clarify their anatomical relationship and the trunk's contribution to the SN, several small lateral branches of iliolumbar vessels may require transection. Retraction of iliolumbar vessel branches allows access to the deeper sciatic foramen for direct approach to the SN (Figure 2B). 3.2.3 Step 3 This exposes the LST descending toward the greater sciatic foramen, where it contributes to the formation of the SN. Dissection directed toward the sciatic notch highlights the convergence of additional sacral nerve roots forming the SN. At this level, the greater sciatic notch as the SN passes beneath it, becomes a key landmark, where the SSL borders it. The LST, derived from L4 and L5, is identifiable at this step. Laterally to iliac vessels this exposure can be obtained (Figure 2C). 3.3 Stage III 3.3.1 Step 1 Medially to iliac vessels wide exposure the SN can be obtained where the course of superior and inferior gluteal branches of the internal iliac artery can be recognized between the sacral nerve roots contributing to its formation. Beneath these structures lies the piriformis muscle, along with the superior and inferior gluteal vessels. In this region, the SN appears fully suspended and clearly visualized, demonstrating its convergence with the LST and sacral roots (Figure 3A,D). 3.3.2 Step 2 This step allows exposure of the PN, which courses beneath the SSL at the level of the IS. In cases of PN branching variations, where the nerve bifurcates, and part of the SSL lies between the branches, one branch may course superomedially and appear superficial to the SSL, while the other, a continuation of the sacral plexus, passes inferolaterally beneath it. With careful preservation of the superficial branch, the ligament can be safely pulled up to access the deeper branch. In the absence of such variation, the PN lies entirely beneath the SSL (here transected for demonstration) (Figure 3B). 3.3.3 Step 3 With minimal retraction, the tip of the IS can be clearly palpated and visualized. Following retraction of the SSL, the underlying PN becomes clearly visible. This exposes the IS, the ligament's attachment site, enabling identification of the PN alongside the pudendal vessels (Figure 3C,D). The anatomical structures encountered during these stages and steps are summarized in Table 1 and additionally, some direct pathways are demonstrated in a flowchart (Figure 4). | Encountered anatomical structures | ||| |---|---|---|---| | Step 1 | Step 2 | Step 3 | | | Stage I | Genitofemoral nerve | Accessory obturator nervea | Corona mortisa | | Sympathetic ganglia | Obturator vessels | || | Obturator nerve | Iliolumbar vessels | || | Stage II | Sciatic nerveb | Lumbar 4–5 nerve roots | Sciatic nervec with lumbar 4–5 nerve roots Lumbosacral trunk | | Lumbosacral trunk | Greater sciatic notch | || | Obturator nerve | ||| | Iliolumbar vessels | ||| | Stage III | Sacral nerve roots (Sacral 1–4) | Sciatic nerveb | Ischial spine | | Sciatic nerveb | Sacrospinous ligament | Sacrospinous ligament | | | Piriformis muscle | Pudendal nerved | Pudendal nerve | | | Superior–inferior gluteal vessels | - a If exist. - b From medial approach. - c From lateral approach. - d In case of variation of some fibers from pudendal nerve passed separated superomedially to the sacrospinous ligament and underneath the cut sacrospinous ligament other fibers are recognized. The mean age of the cadavers was 68.33 ± 14.56 years. Nerve variations encountered were a furcal nerve with a connection with ON (found in two of 60 hemipelvises [3.3%]). Additionally, in three of 60 (5.0%) hemipelvises the PN fibers were divided, coursing both superomedially and inferolaterally to the SSL. The median distance from the origin of the PN to the tip of the IS was 24.84 mm (range 16.71–32.43 mm). In all cadavers the PN was lying medial to IS (entirely on SSL), or on the IS. 4 DISCUSSION Endometriosis involving somatic nerves, particularly the PN, is uncommon but may significantly impair visceral and motor functions. Nerve-sparing pelvic surgery, especially in cases with distorted pelvic anatomy, requires advanced surgical expertise and comprehensive neuroanatomical knowledge.7, 11 Furthermore, laparoscopic excision of parametrial deep endometriosis involving the sacral nerve roots is highly complex, demanding advanced anatomical knowledge and refined surgical skill.12 As pelvic nerve dissection is an essential initial step in pelvic surgery, meticulous technique and thorough anatomical knowledge are critical to prevent GFN injury.13 In Stage I, Step 1, the GFN dissection was delineated, emphasizing that familiarity with its course and bifurcation, commonly encountered during extended pelvic lymphadenectomy, is essential to prevent iatrogenic injury.13 The next objective is access to the obturator fossa, which can be achieved through two approaches. Stage I, Steps 2 and 3 may be performed sequentially; however, Step 3 can be omitted if the LST and sympathetic ganglion are not involved. In such cases, the obturator fossa can be accessed medially to the PM and laterally to the iliac vessels, enabling direct progression to Stage II, which can be defined as a shortcut to SN. This alternative route, defined as Stage II, Step 1, enables direct access to the SN via the medial approach to the obturator fossa. In case of LST involvements, extensive exposure of the LST will be needed, which was defined in Stage II, Step 2. When dissection of the LST and pelvic sympathetic ganglia is required during pelvic surgery, meticulous technique in Stage I, Step 2, and Stage II, Step 2 is essential to minimize the risk of nerve injury. LST injury during pelvic surgery in women is rare, with an estimated incidence of less than 0.1%,14, 15 while ON injury occurs in 0.2%–5.7% of pelvic procedures.16 Variations in the LST and lumbar plexus are clinically significant due to their association with atypical sciatic pain, often related to anomalous nerve roots. The furcal nerve usually arises as a single branch from L4, though dual origins from L4 and the ON have been documented.17 In the current study, dissections identified a connection between the furcal nerve and the ON, which should be anticipated during Stage I, Step 3. After navigation, the iliolumbar vessels and their branches, including the LST and SN, become visible as outlined in Stage II, Step 3. The IS, a key gynecologic landmark and attachment site of the SSL, can be visualized and palpated in Stage III, Step 3. Entrapment of the SN may arise from increased susceptibility to compression at specific sites or secondary to scarring, trauma, or hematoma.14, 18 For adequate exposure, the anatomical structures related to the SN can be approached in Stage II, Step 1 and/or Step 3. Detailed dissections of these anatomical landmarks and related surgical steps were demonstrated in Stage III, Steps 1–3. The close relationship between the SSL and adjacent neurovascular structures underscores its clinical significance, particularly the risk of PN and SN injury.4, 19, 20 Injury to the PN during pelvic surgery in women is uncommon, but clinically significant. The incidence is estimated at less than 0.5% in routine procedures includng hysterectomy but increases to 5%–10% in DIE surgeries involving the SSL or IS.21 Comprehensive anatomical knowledge of the SSL, IS, and adjacent nerves at the greater sciatic foramen may help to reduce intraoperative complications during peripheral nerve surgery in this region. This study further illustrates dissections of these structures in Stage II, Steps 1–3, and Stage III, Steps 1–3. Endometriotic or fibrotic involvement of the sacral plexus, PN, and SN represents a frequent endopelvic cause of pelvic and anogenital pain. Transection of the SSL is seldom required in deep endometriosis surgery, as distal nerve dissection is usually unnecessary.14 Complete excision of the pudendal segment of an endometriotic nodule may require sacrificing the obturator vessels and pudendal lesser venous branches,14 as demonstrated in Stage II, Step 2 of this study. If PN exposure is unnecessary, the procedure may be concluded at Stage III, Step 1. Conversely, when PN dissection is the primary objective and wide SN exposure is not required, Stage III, Step 1 can be omitted. In Stage III, Step 2, a portion of the PN may course superomedially and superficially to the SSL, allowing its direct visualization. The clinical presentation and surgical challenges of endometriosis including PN endometriosis, reflect its rarity,22-24 as it was observed in this study. Few studies have detailed the stepwise surgical neurovascular anatomy of the PN; in contrast, this study provides a structured description of PN dissection. Reported incidence rates of nerve injuries, including GFN, ON, LST, SN, and PN, are consistent with previous data, though exact figures may vary due to underreporting and diagnostic challenges.13-16, 19, 20 Recognizing anatomical variations, such as the furcal nerve's dual origin and its connection to the ON, is crucial, as these variants have been linked to clinical outcomes in anatomical and clinical studies.17 The anatomical relationships of the SN and PN to the IS and SSL observed in this study confirm and expand upon previous findings.4 Reported risks of nerve injury during pelvic organ prolapse repair and deep endometriosis surgery involving the SSL are consistent with earlier estimates of up to 12%.19, 20, 25 A detailed cadaveric dissection is presented, systematically demonstrating a reproducible, step-by-step surgical anatomical approach for identifying the PN and adjacent pelvic neurovascular structures. This work is particularly relevant in the context of nerve-sparing techniques and the management of DIE. By integrating precise anatomical delineation with a structured methodology, the study provides clinically applicable insights that may enhance surgical navigation, facilitate intraoperative nerve identification and preservation, and reduce the risk of iatrogenic nerve injury. It represents a valuable contribution to surgical anatomical education and serves as a practical and high-value resource for pelvic surgeons. The current study provides a reproducible, stepwise approach for pelvic nerve identification and preservation. The described approach warrants further validation in open, laparoscopic, and robotic pelvic surgeries. Clinical studies and further morphometric analyses of related neurovascular landmarks can be performed and will be supportive. The study emphasizes the importance of comprehensive neuroanatomical knowledge and advanced laparoscopic expertise, particularly in complex posterior pelvic compartment and DIE cases. Application of these methods may reduce the risk of iatrogenic nerve injury while enabling complete excision, thereby improving pain control and functional outcomes. Studies evaluating clinical outcomes and incorporating additional morphometric analyses of neurovascular landmarks could further validate and refine these approaches. The structured dissection steps offer a replicable practical guide for intraoperative nerve identification and preservation, especially in complex posterior pelvic compartment surgeries, LST, SN, PN decompression procedures, and DIE surgeries. In conclusion, a comprehensive knowledge of deep pelvic neuroanatomy during lateral and medial surgical approaches, defined in three stages and nine surgical steps to reach the PN is practical for carrying out gynecologic procedures, including deep endometriosis and neuropelvic surgeries. These surgical anatomical dissection steps serve as a valuable tool for demonstrating the anatomical relationships among the GFN, sympathetic chain/ganglia, ON, LST, SN, and PN. This cadaveric study delineates step-by-step surgical approaches for accessing the pudendal nerve, thereby enhancing anatomical understanding and may help to prevent nerve injuries during complex pelvic surgeries. AUTHOR CONTRIBUTIONS MDET and AC contributed to the planning, design, and conduction of the study and drafted the article or revised it critically for important intellectual content. MDET, HIA, AC, ZGK, and HOT contributed to the acquisition of data. MDET interpretated the data. MDET, HIA, and AC annotated the images and videos. MDET wrote the manuscript. All authors gave their final approval. ACKNOWLEDGMENTS The authors sincerely thank those who donated their bodies to science that enabled this anatomical research. Results from such research can potentially increase humanity's overall knowledge, which can then improve patient care. Therefore, these donors and their families deserve our highest gratitude. FUNDING INFORMATION None. CONFLICT OF INTEREST STATEMENT The authors have no conflicts of interest. DATA AVAILABILITY STATEMENT Data sharing is not applicable to this article as no new data were created or analyzed in this study.