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.

Bloqueos Nerviosos. Bases Anatómicas del Dolor Somático Abdomino-Pélvico / Nerve Blocks. Anatomy of the Somatic Innervation of the Abdomino-Pelvic Cavity

El dolor abdominal es una de las sintomatologías que afectan con frecuencia la cavidad abdomino-pélvica. Dicha cavidad posee una inervación somática en la que intervienen del séptimo a doceavo nervios intercostales, ramos colaterales y terminales del plexo lumbar y el nervio pudendo; siendo objetivo de este trabajo la descripción anatómica del dolor abdominopélvico a través del plexo lumbar, nervios intercostales y nervio pudendo, sus diferentes patrones y variaciones de conformación, y las implicancias de éstas últimas en las distintas maniobras clínico-quirúrgicas. Se realizó un estudio descriptivo, observacional y morfométrico de la inervación somática de la cavidad abdomino-pélvica, en 50 preparaciones cadavéricas, fijadas en solución de formaldehído, de la Tercera Cátedra de Anatomía, Facultad de Medicina, Universidad de Buenos Aires, entre Agosto/2017-Diciembre/2019. La descripción clásica del plexo lumbar se encontró en 35 casos; la presencia del nervio femoral accesorio en ningún caso; así como también la ausencia del nervio iliohipogástrico en ningún caso; el nervio obturador accesorio se halló en 2 casos; el nervio genitofemoral dividiéndose dentro de la masa muscular del psoas mayor en 6 casos; el nervio cutáneo femoral lateral emergiendo únicamente de la segunda raíz lumbar en 6 casos y por último se encontró la presencia de un ramo del nervio obturador uniéndose al tronco lumbosacro en un caso. Los nervios intercostales y el nervio pudendo presentaron una disposición clásica en todos los casos analizados. Es esencial un adecuado conocimiento y descripción del plexo lumbar, nervios intercostales y nervio pudendo para un adecuado abordaje de la cavidad abdomino-pélvica en los bloqueos nerviosos.

SUMMARY: Abdominal pain is one of the symptoms that affect the abdominal-pelvic cavity. The abdominal-pelvic cavity has a somatic innervation involving the seventh to twelfth intercostal nerves, collateral and terminal branches of the lumbar plexus and the pudendal nerve. The objective of this work is the description of the lumbar plexus, intercostal nerves and pudendal nerve, its different patterns and structure variations, as well as its implications during pain management in patients. A descriptive, observational, and morphometric study of patterns and structure variations of the lumbar plexus, intercostal nerves and pudendal nerve was conducted in 50 formalin-fixed cadaveric dissections of the Third Chair of Anatomy at the School of Medicine in the Universidad de Buenos Aires from August 2017 to December/2019. The standard description of the lumbar plexus was found in 35 cases; accessory femoral nerve was not present in any of the cases; absence of the iliohipogastric nerve was also not found in any case, while the accessory obturating nerve was found in 2 cases; genitofemoral nerve dividing within the muscle mass of psoas in 6 cases; lateral femoral cutaneous nerve emerging only from the second lumbar root in 6 cases and finally, presence of a branch of the obturating nerve was found joining the lumbosacral trunk in one case. The pudendal and intercostal nerve patterns presented a typical pathway in all cases. Adequate knowledge and description of the lumbar plexus, intercostal nerves and pudendal nerve is essential for an adequate approach of the abdominal-pelvic cavity in nerve blocks.

Nerve relationships to the sacrospinous ligament: application to suspension procedures and transgluteal approaches for nerve repair and tumor removal with three case illustrations.

BACKGROUND: Transvaginal suspension procedures often use the sacrospinous ligament (SSL), which attaches onto the ischial spine (IS). However, nerve-related sequelae (e.g., sciatic nerve injury) following such procedures have been reported. Therefore, the current anatomical study was performed to better understand these relationships. Additionally, three case illustrations of patients with injury to the sciatic nerve following sacrospinous ligament suspension procedures are included to exemplify the significance of a thorough knowledge of this anatomy. METHODS: In 20 human adult cadavers (40 sides), a gluteal dissection was performed to expose the IS and SSL and regional nerves near the greater sciatic foramen. Measurements between the IS and SSL were made between these structures and surrounding nerves. RESULTS: The average distance between the IS and sciatic nerve was 1.4 cm. From this bony part, the average distance to the S1 and S2 ventral rami was 3.1 cm and 1.9 cm, respectively. From the IS to the lumbosacral trunk, pudendal nerve, nerve to obturator internus, and superior gluteal nerve, the mean distance was 4 cm, 0.5 cm, 0.7 cm, and 4.5 cm, respectively. From the SSL to the lumbosacral trunk, S1 ventral ramus, and S2 ventral ramus, there was an average distance of 4.2 cm, 1.6 cm, and 0.8 cm, respectively. Statistically, in females, the distances from the IS and SSL to the sciatic nerve, lumbosacral trunk, superior gluteal nerve, and S1 and S2 ventral rami were shorter when compared to males. CONCLUSION: An improved understanding of the relationship between the SSL and IS and nerves near the greater sciatic foramen can lead to fewer intraoperative complications during approaches to various peripheral nerves in this region. Lastly, these relationships might help better understand the nerve injuries following pelvic suspension procedures that use the SSL.

Morphometry of spinal nerve composition and thicknesses of lumbar plexus nerves for use in clinical applications / Morfometría de la composición del nervio espinal y espesores de nervios del plexo lumbar para su uso en aplicaciones clínicas

SUMMARY: The aim of this study was to clarify the diverse spinal compositions of the branches of the lumbar plexus in terms of their prevalence rates and thicknesses. Thirty lumbar plexuses extracted from Korean adults were used in this study. The nerve fascicles were separated and traced with the aid of a surgical microscope. The thickness of each spinal nerve component was calculated based on the mean of the largest and smallest diameters using digital calipers under the surgical microscope. The most common patterns of the spinal composition of the branches of the lumbar plexus were as follows: The iliohypogastric nerve (IHN) and the ilioinguinal nerve (IIN) arose from the ventral ramus of the first lumbar nerve (L1), the genitofemoral nerve (GFN) arose from the anterior division of the ventral ramus of the second lumbar nerve (L2), and the lateral femoral cutaneous nerve (LFCN) arose from the posterior division of the ventral ramus of theL2, the femoral nerve (FN) arose from the posterior division of the ventral ramus of L2-the fourth lumbar nerve (L4), with the thickest spinal component derived from the third lumbar nerve (L3), and the obturator nerve (OBN) arose from the anterior division of the ventral ramus of L2-L4, with the thickest spinal component derived from L3. However, when L5 constituted the FN and OBN, the thickest spinal components of the FN and OBN was L4. This morphometric study has measured the thicknesses of diverse spinal components that constitute the branches of the lumbar plexus after separating the nerve fascicles. The thicknesses of the various spinal components of these branches can be compared in order to understand which make the main and minor contributions to the lower limb.

RESUMEN: El objetivo de este estudio fue evaluar las diversas composiciones espinales de los ramos del plexo lumbar en cuanto a sus tasas de prevalencia y grosor. Se utilizaron treinta plexos lumbares extraídos de individuos adultos coreanos. Se separaron y trazaron los fascículos nerviosos por medio de un microscopio quirúrgico. El grosor de cada componente del nervio espinal se calculó con base en la media de los diámetros mayor y menor utilizando calibradores digitales bajo el microscopio. Los patrones más comunes de la composición espinal de los ramos del plexo lumbar fueron los siguientes: el nervio iliohipogástrico (NIH) y el nervio ilioinguinal (NII) surgieron del ramo ventral del primer nervio lumbar (L1). El nervio genitofemoral (NGF) surgió de la división anterior del ramo ventral del segundo nervio lumbar (L2). El nervio cutáneo femoral lateral (NCFM) surgió de la división posterior del ramo ventral L2. El nervio femoral (NF) surgió de la división posterior del ramo ventral de L2. El cuarto nervio lumbar (L4), con el componente espinal más grueso derivado del tercer nervio lumbar (L3) y el nervio obturador (NOB) surgieron de la división anterior del ramo ventral de L2-L4, con el componente espinal más grueso derivado de L3. Sin embargo, cuando L5 constituía el NF y NOB, los componentes espinales más gruesos del NF y NOB eran de L4. Este estudio morfométrico analizó los espesores de diversos componentes espinales que constituyen las ramas del plexo lumbar después de separar los fascículos nerviosos. Es posible comparar los espesores de los diversos componentes espinales de estos ramos para comprender las contribuciones principales y menores al miembro inferior.

Origin and distribution of the lumbosacral plexus anatomy in van cats / Origen y distribución de la anatomía del plexo lumbosacro en gatos van

SUMMARY: The innervation of the pelvic limbs of the Van cat is investigated in this research. The origins of the nerves, the innervated muscles and nerve diameters were shown in a table. Five cat cadavers were used in the study. The pudendal nerve originated from the S1-S2 spinal nerves. The femoral nerve consisted of the ventral branches of the 5th and 6th lumbar nerves in 4 cats The ischiatic nerve was composed of the 6th and 7th lumbar (L6-L7) and S1 spinal nerves in all cadavers. The ischiatic nerve was the thickest branch of sacral plexus (the average diameter on the right side was 3.31 ± 0.27 mm and the average diameter on the left side was 3.28 ± 0.29 mm). The lumbosacral plexus was formed by the ventral branches of the L4-S3 spinal nerves. N.genitofemoralis consisted of only the ventral branches of L4 in all cadavers. N. femoralis did not give rise to a branch to the m. iliopsoas. N.plantaris lateralis was found to give a branch to the 3th finger. The quadriceps femoris muscles did not take any branches from either the ischiadicus nerve or the pudendal nerve. The obturator nerve did not receive any branches from the L4 spinal nerves. There was no branch to the skin from the caudal gluteal nerve. The thinnest nerve was the pudendal nerve. Due to the scarcity of studies on the lumbosacral plexus of cats, it is thought that this study will complete a gap in the field of veterinary anatomy.

RESUMEN: En esta investigación se estudió la inervación de los miembros pélvicos del gato Van. Los orígenes de los nervios, los músculos inervados y los diámetros de los nervios son mostrados en una tabla. En el estudio se utilizaron cinco cadáveres de gatos. En cuatro gatosel nervio pudendo se originaba a partir de los nervios espinales S1-S2. El nervio femoral consistió en los ramos ventrales de los nervios lumbares quinto y sexto. El nervio isquiático estaba compuesto por los nervios espinales sexto y séptimo lumbar (L6-L7) y S1 en todos los cadáveres. El nervio isquiático era el ramo más grueso del plexo sacro (el diámetro medio del lado derecho medía de 3,31 ± 0,27 mm y el diámetro medio izquierdo 3,28 ± 0,29 mm). El plexo lumbosacro estaba formado por los ramos ventrales de los nervios espinales L4-S3. N. genitofemoralis constaba solo de las ramas ventrales de L4 en todos los cadáveres. N. femoralis no dio lugar a un ramo a la m. iliopsoas. Los músculos del cuádriceps femoral no tomaron ningún ramo ni del nervio isquiático ni del nervio pudendo. El nervio obturador no recibió ramos de los nervios espinales L4. No existían ramos a la piel desde el nervio glúteo caudal. El nervio más delgado fue el nervio pudendo. Debido a la escasez de estudios sobre el plexo lumbosacro de los gatos, este estudio completará un vacío en el campo de la anatomía veterinaria.

Useful Pelvic Retroperitoneal Neuroanatomy for Benign Gynecologic Surgery: A Cadaveric Dissection.

OBJECTIVE: Knowledge of the retroperitoneal anatomy is particularly important to facilitate surgical procedure and reduce the number of complications. The objective of this video is to demonstrate pelvic neuroanatomic structures and their relationships in the pelvic sidewall and the presacral space in a laparoscopic cadaveric dissection. DESIGN: Case report (anatomic study). SETTING: Medical training center (AdventHealth Nicholson Center, Orlando, FL). INTERVENTIONS: The dissection started with the mobilization of the iliac vessels from the pelvic sidewall to identify the obturator nerve. The peritoneum of the ovarian fossa was opened, and the ureter was dissected up to the level of the uterine artery. The hypogastric nerve was identified. The close relationship between the ovarian fossa and the obturator nerve could be demonstrated. The deep dissection of the obturator fossa allowed for the identification of the lumbosacral trunk, S1, the sciatic nerve, S2, S3, S4, and the splanchnic nerves. Then, the ischial spine and the sacrospinous ligament were identified. The pudendal nerve and vessels could be observed passing below the sacrospinous ligament, entering the pudendal canal (Alcock's canal). The presacral space was dissected, and the hypogastric fascia was opened. S1 to S4 were identified coming from the sacral foramens. The laparoscopic dissection, using the cadaveric model, allowed for the development of the entire retroperitoneal anatomy, focusing on the dissection of the pelvic innervation. Anatomic relationships among the ureter, the hypogastric nerve, the uterosacral ligament, the splanchnic nerves, the inferior hypogastric plexus, and the organs (bowel, vagina, uterus, and bladder) could be demonstrated. CONCLUSION: A laparoscopic cadaveric dissection can be used as a resource to demonstrate and educate surgeons about the neurologic retroperitoneal structures and their relationships.

Pelvic Neuroanatomy: An Overview of Commonly Encountered Pelvic Nerves in Gynecologic Surgery.

OBJECTIVE: This video tutorial identifies key anatomic landmarks useful in identifying the path of the most commonly encountered pelvic nerves in benign gynecologic surgery. DESIGN: This is a narrated overview of commonly encountered pelvic nerves during benign gynecology, their origin, sensory, and motor function, as well as sequelae related to injury. SETTING: The unintended injury of pelvic neural connections can be a complication of any pelvic surgery, however, surgery for malignancy or endometriosis may increase the likelihood of encountering these nerves. The majority of focus surrounding surgical nerve injury, however, relates to patient positioning [1]. Injury to the pelvic nerves can lead to lifelong sexual, bladder, and defecatory dysfunction [2]. INTERVENTIONS: We review the Genitofemoral, Lateral Femoral Cutaneous, Ilioinguinal, Obturator, Superior and Inferior Hypogastric nerves, Pelvic Splanchnic nerves, and the Sacral nerves. Surgical illustrations are used (Fig. 1) alongside real-time narrated video to help viewers recognize the normal course of commonly encountered pelvic nerves at the time of gynecologic surgery (Figs2-3). CONCLUSION: The surgical management of complex pelvic disease can unfortunately carry significant patient morbidity [3]. The neural pathways traveling through the pelvis via the hypogastric nerves are responsible for proprioception, vaginal lubrication, and proper functioning or the urethral and anal sphincters [4]. Sparing these nerves during pelvic surgery, and especially when anatomic planes are distorted by pelvic disease, requires surgical expertise and an immense understanding of pelvic neuroanatomy [4,5]. Preservation of the pelvic neural pathways is necessary to deliver the best patient outcomes while minimizing unwanted surgical complications. This video tutorial also highlights the origin of these nerves, their anatomic location, procedures in which these nerves may be encountered, and what sequelae occur from their unintended injury.

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.

Posterior Sacrococcygeal Plexus: Application to Spine Surgery and Better Understanding Low-Back Pain.

OBJECTIVE: The sacral dorsal rami form the posterior sacrococcygeal plexus (PSCP), which has been scantly studied. This study's goal was to clarify the PSCP s detailed anatomy and discuss its clinical relevance. METHODS: Ten sides of 5 fresh-frozen cadavers were dissected for this research. After the muscles covering the sacrum were removed, the PSCP was identified and traced under the operating microscope until the entire plexus was exposed. The contributions to this plexus and its relations to surrounding anatomic structures were recorded. RESULTS: The PSCP was found on all sides and was composed of a medial trunk (MT), communicating branches, and a lateral trunk. Each sacral dorsal ramus's MT formed a series of loops created by adjacent sacral dorsal rami placed between the transverse tubercles and the posterior sacral foramina. The MT, communicating branches, and lateral trunk demonstrated potential entrapment sites. CONCLUSIONS: To our knowledge, this is the first anatomic study that provides detailed images that indicate 3 potential sites where surrounding structures could entrap the PSCP. Knowledge of its detailed anatomy might help in better understanding low-back pain, targeting pain sources and guide spine surgeons for avoiding injury to these nerves.

Bloqueos de extremidad inferior / Lower extremity blocks

Lower limb blocks are described with emphasis on distribution according to sensitive distribution and its sonoanatomy.

Se describen los bloqueos de la extremidad inferior haciendo énfasis en la distribución de acuerdo a distribución sensitiva y a su sonoanatomia.

Is it possible to identify the inguinal nerves during hernioplasty? A systematic review of the literature and meta-analysis of cadaveric and surgical studies.

PURPOSE: Patients who undergo inguinal hernioplasty may suffer from persistent postoperative pain due to inguinal nerve injuries. The aim of this systematic review and meta-analysis was to provide comprehensive data on the prevalence (identification rates), anatomical characteristics, and ethnic variations of the ilioinguinal (IIN), the iliohypogastric (IHN) and the genital branch of the genitofemoral (GNF) nerves. METHODS: The systematic literature search was conducted using the PubMed, Scopus and Web of Science databases. RESULTS: A total of 26 articles (5265 half-body examinations) were included in this study. The identification rate of the IIN was 94.4% (95% CI 89.5-97.9) using a random-effects model. Unweighted multiple regression analysis showed that study sample size (ß = - 0.74, p = .036) was the only statistically significant predictor of lower prevalence. The identification rates of the IHN and GNF was 86.7% (95% CI 78.3%-93.3%) and 69.1% (95% CI 53.1%-83.0%) using a random-effects model, respectively. For those outcomes, a visual analysis of funnel and Doi plots indicated irregularity and provided evidence that larger studies tended to have lower identification rates. In terms of the synthesis of anatomical reference points, there was a large and statistically significant amount of heterogeneity for most outcomes. CONCLUSIONS: The identification rates of the inguinal nerves in our study were lower than reported in literature. The lowest was found for GNF, suggesting that this nerve was the most difficult to identify. Knowledge regarding the anatomy of the inguinal nerves can facilitate their proper identification and reduce the risk of iatrogenic injury and postoperative pain.

The inferior gluteal nerve often has a cutaneous branch: A discovery with application to hip surgery and targeting gluteal pain syndromes.

The inferior gluteal nerve has been traditionally described as a solely motor branch innervating the gluteus maximus. However, during routine dissection of the gluteal region, a cutaneous branch of the inferior gluteal nerve was identified. As the gluteal region is vulnerable to the development of pressure ulcers and iatrogenic injury with for example, surgical approaches and injection therapies, a comprehensive understanding of its cutaneous innervation is important. Therefore, the aim of this study was to elucidate the anatomy of this cutaneous branch of the inferior gluteal nerve in a series of cadavers. Twelve sides from six fresh-frozen cadaveric specimens were dissected. When a cutaneous branch was identified piercing the gluteus maximus, its origin from the inferior gluteal nerve was verified and the diameter and length of it measured. Additionally, for localization, the distance from the midline to the exit point of the cutaneous branch from the gluteus maximus was measured. One to two cutaneous branches were identified as arising from the inferior gluteal nerve on nine sides (75%). The branch(es) were usually located in the lower outer quadrant of the gluteus maximus. These branches had a mean distance of 12.5 cm from the midline. Their mean diameter and length was 0.7 mm and 28.6 cm, respectively. On all sides with a cutaneous branch of the inferior gluteal nerve, the skin over the posterior aspect of the greater trochanter was innervated by superior and inferior cluneal nerves and supplemented by cutaneous branch(es) of the inferior gluteal nerve. Side or sex was not a predictor of the presence of a cutaneous branch of the inferior gluteal nerve. To our knowledge, a cutaneous branch derived from the inferior gluteal nerve has not been previously described. Based on our cadaveric findings, the majority of individuals will have the area of skin over the greater trochanter innervated by this nerve. Therefore, surgeons and pain specialists should be aware of its presence and might develop surgical procedures that help avoid it or develop technical advances that target it for various pain syndromes in this area. We propose naming these cutaneous branches the lateral cluneal nerves, which would necessitate renaming the middle cluneal nerves to medial cluneal nerves. Clin. Anat. 31:937-941, 2018. © 2018 Wiley Periodicals, Inc.

Anatomic Variations of the Lateral Femoral Cutaneous Nerve: Remnants of Atypical Nerve Growth Pathways Revisited by Intraneural Fascicular Dissection and a Proposed Classification.

OBJECTIVE: To trace anatomic variations of the lateral femoral cutaneous nerve (LFCN) in its intrapelvic course. METHODS: Forty cadavers (80 sides) fixed in 10% formalin solution were dissected. The following parameters were recorded: LFCN diameter and variations in its origin and number. The dissection comprised exposure and excision of the lumbar plexus, together with the roots of LFCN, followed by retrograde intraneural fascicular dissection using microsurgical instruments. RESULTS: Several types of LFCN origin from the lumbar plexus were observed. Typically, the LFCN appears as a single trunk arising from dorsal divisions of the ventral rami of the lumbar plexus. The most prevalent origin of the nerve was from the L2 and L3 roots (47 cases; 58.75%). The LFCN took an origin from the L1-L2 level in 12 cases (15%) and from the L2 nerve in 9 cases (11.25%). The main observed variations were the presence of the accessory LFCN (2 cases; 2.5%) and branching of the LFCN from the femoral nerve (6 cases; 7.5%). Communications between the LFCN and the femoral or genitofemoral nerves also were observed occasionally. An atypical course of the LFCN with respect to the anterior psoas was observed in our material in 3 of the 80 sides (3.75% of the examined LFCN specimens). CONCLUSIONS: Considerable variability in the origin and the course of the LFCN was observed, which should be taken into account during clinical assessment of nerve lesions and during surgery via transpsoas approaches to the lumbar spine.

Neurovascular Relationships of S2AI Screw Placement: Anatomic Study.

INTRODUCTION: The S2 alar-iliac (S2AI) screw is a modification of the traditional iliac fixation technique and has surgical and biomechanical benefits. However, there are significant regional neurovascular structures along the path of such screws. Therefore the current anatomic study was performed to better elucidate these relationships. METHODS: Using fluoroscopy, S2AI screws were placed in 2 adult cadavers through a standard posterior midline exposure. The screw insertion point was placed 10 mm lateral to a line bisecting the S1 and S2 foramina, adjacent to the sacroiliac joint. Using 30- to 40-degree lateral angulation from the midline and 20- to 30-degree caudal angulation, a pedicle probe was directed toward the anterior inferior iliac spine. The final trajectory was positioned to sit 1-2 cm superior to the greater sciatic foramen. Lastly, the screws and surrounding bone were drilled in order to visualize both lateral and medial neurovascular relationships. RESULTS: Removing the bone around the S2AI-screw illustrated the close relationship to the medial (internal) neurovascular structures including the obturator nerve, lumbosacral trunk, sacral plexus and, specifically, the S1 ventral ramus and iliac vein and artery. By removing the outer cortex of the ilium, the close relationship to the superior gluteal artery, vein, and nerve was observed. In addition, we were able to identify the proximity to the iliopsoas muscle and internal iliac vessels. CONCLUSIONS: A comprehensive knowledge of the surrounding neurovascular anatomy relevant to S2AI screw placement can decrease patient morbidity and allow spine surgeons to better diagnose potential postoperative complications.

Proposed Optimal Fluoroscopic Targets for Cooled Radiofrequency Neurotomy of the Sacral Lateral Branches to Improve Clinical Outcomes: An Anatomical Study.

Background: Current sacroiliac joint (SIJ) cooled radiofrequency (RF) is based on fluoroscopic anatomy of lateral branches (LBs) in three specimens. Recent studies confirm significant variation in LB positions. Objectives: To determine if common fluoroscopic needle placements for cooled SIJ RF are adequate to lesion all S1-3 LBs. If not, would different targets improve lesion accuracy? Methods: The LBs of 20 cadavers were dissected bilaterally (40 SIJs), and 26 G radiopaque wires were sutured to the LBs. With a 10-mm radius ruler centered at each foramen, standard targets were assessed, as judged by a clockface on the right, for S1 and S2 at 2:30, 4:00, and 5:30 positions and at S3 at 2:30 and 4:00. Mirror image targets were assessed on the left. Assuming an 8-mm lesion diameter, the percentage of LBs that would not be ablated for each level was determined. Imaging through the superior end plate of S1 was compared against segment specific (SS) imaging. Results: Nine point four percent of LBs would not be ablated at S1 vs 0.99% at S2 vs 35% at S3, and 60% of the 40 SIJs would be completely denervated using current targets. SS imaging did not improve results. Alternate target locations could improve the miss rate to 2.8% at S1 and 0% at S3 and would ablate all LBs in 95% of SIJs. Conclusions: Using a conservative 8-mm lesion measurement, contemporary cooled RF needle targets are inadequate to lesion all target LBs. Modifications to current targets are recommended to increase the effectiveness of the procedure.

A new endoscopic minimal invasive approach for pudendal nerve and inferior cluneal nerve neurolysis: An anatomical study.

AIM: To describe a new minimal invasive approach of the gluteal region which will permit to perform neurolysis of the pudendal and cluneal nerves in case of perineal neuralgia due to an entrapment of these nerve trunks. METHOD: Ten transgluteal approaches were performed on five cadavers. Relevant anatomic structures were dissected and further described. Neurolysis of the pudendal nerve or cluneal nerves were performed. Landmarks for secure intraoperative navigation were indicated. RESULTS: The first operative trocar for the camera was inserted with regards to the iliac crest in the deep gluteal space. With the aid of pneumodissection, the infragluteal plane was dissected. The piriformis muscle was identified as well as the sciatic and the posterior femoral cutaneous nerve. Consequently, the sciatic tuberosity was visualized together with the cluneal nerves. Hereafter, the second trocar was introduced caudal to the first one and placed on an horizontal line passing at the level of the coccyx, allowing access to the ischial spine and the visualization of the pudendal nerve and vessels. A third 5 mm trocar was then inserted medial from the first one, permitting to dissect and transsect the sacrospinous ligament. The pudendal nerve was subsequently transposed and followed on its course in the pudendal channel. CONCLUSIONS: A reliable exploration of the gluteal region including identification of the sciatic, pudendal, and posterior femoral cutaneous nerves is feasible using a minimal invasive transgluteal procedure. Consequently, the transposition of the pudendal nerve and the liberation of the cluneal nerves can be performed.

The distance of the gluteal nerve in relation to anatomical landmarks: an anatomic study.

INTRODUCTION: Gluteal insufficiency is of concern with lateral approaches to total hip arthroplasty. Damage to the branches of the superior gluteal nerve may cause degeneration of the innervated muscles. The direct anterior approach exploits the intermuscular and internerval interval between tensor fasciae latae laterally and sartorius and rectus femoris muscle medially. In this study, the distance of the superior gluteal nerve in relation to anatomical landmarks was determined. MATERIALS AND METHODS: Two experienced surgeons implanted trial components in 15 alcohol glycerol fixed cadavers with 30 hips. The trials were removed, and the main branch of the superior gluteal nerve and muscular branches of the nerve were exposed from lateral. RESULTS: No visual damage to the main nerve branches and the location of the nerve in relation to the greater trochanter were noted by an experienced surgeon. The superior gluteal nerve and its muscular branches crossed the muscular interval between the gluteus medius and tensor fasciae latae muscles at a mean distance of 39 mm from the tip of the greater trochanter. CONCLUSIONS: The direct anterior approach for total hip arthroplasty minimizes the risk of injuring the superior gluteal nerve, which may result in a gluteal insufficiency. Special care should be paid on avoiding overstretching the tensor fasciae latea muscle using minimum force on retractors during surgery and by taking care of the entrance point of the superior gluteal nerve to the tensor fasciae latae.

[Applied anatomy study of posterior approach via sacrectomy for reaching the deep intrapelvic sacral plexus].

Objective: To observe the possibility of posterior approach via sacrectomy for reaching intrapelvic sacral plexus and expose the deep intrapelvic origin of sciatic nerve from sacral plexus in order to perform nerve graft. Methods: Five adult cadaver specimens were used in the study with prone position in May 2012. Cut off the gluteus maximus along the origins and lift to the lateral side, the piriformis was lay beneath. The sciatic nerve and the inferior gluteal nerve pierced from the infrapiriformis foramen in the operative field. Excise the origin of the piriformis via sacrectomy with osteotome and the length and width of the insertion on sacrum were measured. The piriformis was resected and then the sacral nerve roots beneath were exposed. The S2-S4 sacral nerve roots and the deep intrapelvic origin of sciatic nerve from sacral plexus were revealed after carefully dissecting. From July 2012 to June 2016, nine patients with lumbosacral plexus injury were performed surgery through the posterior approach in Department of Hand Surgery, Beijing Jishuitan Hospital.There were 6 male and 3 female patients, with a mean age of 29 years. All patients were diagnosed as upper and lower sacral plexus injury, in one of them combing with contralateral lower sacral plexus injury. The average time from injury to operation was 8.3 months. Results: The length and width of the piriformis insertion on sacrum were (3.44±0.15) cm and (2.42±0.11) cm, respectively. The deep intrapelvic origin of sciatic nerve from sacral plexus in all nine patients can be revealed clearly and there was enough operative space that nerve transfer or graft can be performed through the posterior approach via sacrectomy. The total blood loss during operation was (1 822±1 523) ml. Conclusion: The piriformis and part of sacrum it attached can be resected safely through the posterior approach and the deep intrapelvic sacral plexus and the origin of sciatic nerve can be well exposed.