Origin, course and distribution of the superior gluteal nerve

Superior Gluteal Nerve Anatomy and Its Injuries: Aiming for a More Secure Surgical Approach of the Pelvic Region

Because most of the recognized causes of superior gluteal nerve (SGN) injury are iatrogenic, detailed knowledge of the anatomy of the SGN is crucial to prevent its injury associated with surgical procedures. This study aims to describe the precise location of SGN or its branches at the greater sciatic foramen, measure the distances of these neural structures to palpable bony landmarks, and evaluate the possible correlation between these parameters and pelvis size. Twenty human cadaveric hemipelvises were studied. After dissection to expose the SGN or its branches at the greater sciatic foramen, the distances from these neural structures to the greater trochanter (GT), to the anterior superior iliac spine (ASIS), to the posterior superior iliac spine (PSIS), to the ischial tuberosity (IT), and to the greater sciatic notch apex were measured. We found that at the greater sciatic foramen, the SGN emerges as a common trunk in 75% of hemipelvises, and already divided in its superior and inferior branches in 25% of hemipelvises. When the SGN exits the pelvis as a common trunk, it does so, in most cases, in contact with the bone at the apex of the greater sciatic notch or superior to the level of the apex. The median distance from the SGN at the greater sciatic notch to the PSIS, ASIS, GT and IT is 7.6 cm, 10.9 cm, 7.5 cm and 10.8 cm, respectively. We found a positive correlation between some of the analyzed parameters and the size of the pelvis. The anatomical data of this study may serve as pivotal guides during orthopedic pelvic surgery, contributing to minimize SNG iatrogenic lesions with significant implications in the patient's quality of life.

Pelvic floor and perineal muscles: a dynamic coordination between skeletal and smooth muscles on pelvic floor stabilization

The purpose of this review is to present our researches on the pelvic outlet muscles, including the pelvic floor and perineal muscles, which are responsible for urinary function, defecation, sexual function, and core stability, and to discuss the insights into the mechanism of pelvic floor stabilization based on the findings. Our studies are conducted using a combination of macroscopic examination, immunohistological analysis, 3D reconstruction, and imaging. Unlike most previous reports, this article describes not only on skeletal muscle but also on smooth muscle structures in the pelvic floor and perineum to encourage new understanding. The skeletal muscles of the pelvic outlet are continuous, which means that they share muscle bundles. They form three muscle slings that pass anterior and posterior to the anal canal, thus serving as the foundation of pelvic floor support. The smooth muscle of the pelvic outlet, in addition to forming the walls of the viscera, also extends in three dimensions. This continuous smooth muscle occupies the central region of the pelvic floor and perineum, thus revising the conventional understanding of the perineal body. At the interface between the levator ani and pelvic viscera, smooth muscle forms characteristic structures that transfer the lifting power of the levator ani to the pelvic viscera. The findings suggest new concepts of pelvic floor stabilization mechanisms, such as dynamic coordination between skeletal and smooth muscles. These two types of muscles possibly coordinate the direction and force of muscle contraction with each other.

The morphometrical and topographical evaluation of the superior gluteal nerve in the prenatal period

Introduction

Advances in medical science are helping to break down the barriers to surgery. In the near future, neonatal or in utero operations will become the standard for the treatment of defects in the human motor system. In order to carry out such procedures properly, detailed knowledge of fetal anatomy is necessary. It must be presented in an attractive way not only for anatomists but also for potential clinicians who will use this knowledge in contact with young patients. This work responds to this demand and presents the anatomy of the superior gluteal nerve in human fetuses in an innovative way. The aim of this work is to determine the topography and morphometry of the superior gluteal nerve in the prenatal period. We chose the superior gluteal nerve as the object of our study because of its clinical significance—for the practice of planning and carrying out hip surgery and when performing intramuscular injections.

Material and methods

The study was carried out on 40 human fetuses (20 females and 20 males) aged from 15 to 29 weeks (total body length v-pl from 130 to 345 mm). Following methods were used: anthropological, preparatory, image acquisition with a digital camera, computer measurement system Scion for Windows 4.0.3.2 Alpha and Image J (accuracy up to 0.01 mm without damaging the unique fetal material) and statistical methods.

Results

The superior gluteal nerve innervates three physiologically significant muscles of the lower limb’s girdle: gluteus medius muscle, gluteus minimus muscle and tensor fasciae latae muscle. In this study the width of the main trunk of the nerve supplying each of these three muscles was measured and the position of the nerve after leaving the suprapiriform foramen was observed. A unique typology of the distribution of branches of the examined nerve has been created. The bushy and tree forms were distinguished. There was no correlation between the occurrence of tree and bushy forms with the body side (p > 0.05), but it was shown that the frequency of the occurrence of the bushy form in male fetuses is significantly higher than in female fetuses (p < 0.01). Proportional and symmetrical nerve growth dynamics were confirmed and no statistically significant sexual dimorphism was demonstrated (p > 0.05).

Conclusions

The anatomy of the superior gluteal nerve during prenatal period has been determined. We have identified two morphological forms of it. We have observed no differences between right and left superior gluteal nerve and no sexual dimorphism. The demonstrated high variability of terminal branches of the examined nerve indicates the risk of neurological complications in the case of too deep intramuscular injections and limits the range of potential surgical interventions in the gluteal region. The above research may be of practical importance, for example for hip surgery.

A Retrospective Comparative Study of Modified Percutaneous Endoscopic Transforaminal Discectomy and Open Lumbar Discectomy for Gluteal Pain Caused by Lumbar Disc Herniation

Introduction

This study aimed to demonstrate the safety and effectiveness of modified percutaneous endoscopic transforaminal discectomy (PETD) in the surgical management of single-segment lumbar disc herniation (LDH) gluteal pain and to determine whether it provides a better clinical outcome than open lumbar discectomy (OD).

Methods

A retrospective analysis of patients treated with modified PETD and OD for gluteal pain in LDH from January 2015 to December 2020 was conducted. Sample size was determined using a priori power analysis. Demographic information, surgical outcomes including procedure time (minutes), intraoperative blood loss (mL), hospital days, costs (RMB), fluoroscopy shots, recurrence and complications, etc., were recorded and analyzed. Prognostic outcomes were assessed using the visual analog scale (VAS), the Oswestry Disability Index (ODI), the Japanese Orthopedic Association Score (JOA) and modified MacNab criteria. The preoperative and postoperative VAS, ODI and JOA scores were recorded by two assistants. When the results were inconsistent, the scores were recorded again by the lead professor until all scores were consistently recorded in the data. MRI was used to assess radiological improvement and all patients received follow-ups for at least one year.

Results

The sample size required for the study was calculated by a priori analysis, and a total of 72 participants were required for the study to achieve 95% statistical test power. A total of 93 patients were included, 47 of whom underwent modified PETD, and 46 of whom underwent OD. In the modified PETD intragroup comparison, VAS scores ranged from 7.14 ± 0.89 preoperatively to 2.00 ± 0.58, 2.68 ± 0.70, 2.55 ± 0.69, 2.23 ± 0.81, and 1.85 ± 0.72 at 7 days, 1 month, 3 months, 6 months, and 12 months postoperatively. Patients showed significant pain relief postoperatively (P &lt; 0.01). According to the modified MacNab score, the excellent rate in the PETD group was 89.36%. There was no significant difference compared to the OD group (89.13%, P &gt; 0.05). Complication rates were lower (P &gt; 0.05) but recurrence rates were higher (P &gt; 0.05) in the modified PETD group than in the OD group. The modified PETD group had a faster operative time (P &lt; 0.01), shorter hospital stay (P &lt; 0.01), less intraoperative bleeding (P &lt; 0.01), and less financial burden to the patient (P &lt; 0.01) than the OD group. At 7 days postoperatively, the VAS score for low back pain was higher in the OD group than in the modified PETD group (P &lt; 0.01). The VAS and JOA scores at 1, 3, 6, and 12 months postoperatively were not significantly different between the modified PETD and OD groups (P &gt; 0.05), and the ODI was significantly different at 3 months postoperatively (P &lt; 0.05).

Conclusion

Modified PETD treatment is safe and effective for gluteal pain due to L4/5 disc herniation and has the advantages of a lower complication rate, faster postoperative recovery, shorter length of stay, fewer anesthesia risks and lower cost of the procedure compared with OD. However, modified PETD has a higher recurrence rate.

A novel method for predicting superior gluteal nerve safe zones in the lateral approach to the hip

INTRODUCTION

The superior gluteal nerve (SGN) is at risk for laceration during lateral approach total hip arthroplasty (THA). The purpose of this study is to assess the accuracy of the trochanter-to-iliac crest distance (TCD) and the nerve-to-trochanter distance (NTD) ratio in determining a reproducible safe zone around the SGN independent of height.

MATERIALS AND METHODS

Eighteen hemipelvises were dissected and the SGNs were exposed. The distance (NTD) from greater trochanter (GT) to the most inferior branch of the SGN encountered in each of the three approaches (Bauer et al., 1979) was measured. A reference distance (TCD) was measured from the GT to the highest point on the iliac crest. The NTD was divided by the TCD to generate standardized ratios. Coefficient of variation CV = (SD/mean) × 100 was calculated for each distance and ratio to measure relative variability.

RESULTS

The standardized ratios (and CV) were determined for the nerve branches in three different surgical approaches: Hardinge 0.464 (0.9%), Bauer 0.406 (1.7%), and Frndak 0.338 (4.1%). There was a strong correlation of the individual NTDs with the TCD: NTD for Hardinge (r = 0.996, p < .001), NTD for Bauer (r = 0.984, p < .001), and NTD for Frndak (r = 0.932, p < .001).

CONCLUSION

By measuring the TCD preoperatively and using the respective standardized ratios, surgeons can accurately predict the NTD and how proximal to the GT each SGN branch can be expected to be encountered during lateral approach to the hip. This will allow surgeons to work with a more precise safe zone around the SGN and minimize the possibility for a nerve injury.

Possible pathogenic mechanism of gluteal pain in lumbar disc hernia

Recent reported results by Fang et al. published in BMC Musculoskeletal Disorders have added to the weight of evidence supporting association between gluteal pain and lumbar disc hernia. Their clinical finding shows the L4/5 level is the main level responsible for gluteal pain in lumbar disc hernia. Indeed, many possible mechanisms may explain why patients experience pain in the gluteal area. In this Correspondence, we would like to highlight several possible mechanisms of LDH-related gluteal pain based on detailed analysis of the sensory innervation of the gluteal region. We hope this can better explain the phenomenon found by Fang et al. We believe the principle mechanism is compression/irritation of L5 or S1 dorsal rami (intraspinal portion), which produce gluteal pain by irritating superior/medial cluneal nerve and referred pain from facet joints and sacroiliac joints. In addition, the presence of proximal sciatica could also induce gluteal pain. Lastly, fibers in the superior or inferior gluteal nerve could be compressed/irritated in LDH, inducing LDH-related gluteal pain. However, additional studies are needed in the future to delineate the exact mechanism(s).

Relationship Between the Superior Gluteal Vessels and Nerve at the Greater Sciatic Notch

Bleeding from the superior gluteal (SG) blood vessels at the greater sciatic notch is frequently encountered during acetabular fracture surgery. The purpose of this study is to define the positional anatomy of the superior gluteal vessels and nerve (SGVAN) at the greater sciatic notch. Twenty-three hemipelvi were dissected in whole human cadavers. The greater sciatic notch and SGVAN were visualized via a posterior surgical approach, identified deep in the greater sciatic notch, and traced superficially. Branches of the SGVAN and their anatomical relationship to each other were recorded. In the notch, SG arteries comprised a single vessel in 18 (78%) of 23 specimens, with all of these dividing at varying distances (1-3.5 cm) along the lateral ilium after dividing into superior and inferior branches. The SG artery branches were contiguous with periosteum of the bony notch in all specimens. More than 1 SG nerve branch was seen in the greater sciatic notch of all specimens, including an inferior branch that exited caudal or caudal-superficial to the SG vessels. The caudal-most SG nerve branch was directly adjacent to the bony notch's periosteum in 15 (65%) of 23 specimens. The SGVAN are at risk in patients undergoing acetabular fracture surgery. Individuals performing surgery along the acetabulum's posterior column would expect to encounter a major SG nerve branch (deep inferior) before encountering the SG vessels in all cases. Iatrogenic injuries to the SGVAN might be prevented by avoiding use of cautery in this area if hemorrhage is encountered.

How to avoid injuries of the superior gluteal nerve

BACKGROUND

Injuries to the superior gluteal nerve are a common complication in hip replacement surgery. They can be avoided with a good anatomical knowledge of the course of the superior gluteal nerve.

METHODS

We dissected 29 half pelvises of adult cadavers. The distance and the angle from the entry points of branches of the superior gluteal nerve into the deep surface of the gluteus medium and minimus muscles to the midpoint of the superior border of the greater trochanter were measured.

RESULTS

The dissections revealed that the nerve divided into 2 branches (86.20%) or 3 branches (13.8%). The more caudal branch was responsible for innervation of the tensor fascia latae.

CONCLUSIONS

A 2-3-cm safe area above the greater trochanter is appropriate to prevent nerve damage.

Technical application and the level of discomfort associated with an intramuscular electromyographic investigation into gluteus minimus and gluteus medius

Our current theoretical understanding of gluteus minimus (GMin) and gluteus medius (GMed) function is primarily based on cadaveric studies and biomechanical modelling. There is an absence of electromyographic (EMG) research that aims to verify this understanding, particularly in relation to the potentially unique functional roles of structurally distinct segments within GMin (anterior and posterior) and GMed (anterior, middle and posterior). The aim of this paper is to provide a comprehensive technical description for inserting intramuscular EMG electrodes into uniquely oriented segments of GMin and GMed; and to report the levels of discomfort associated with gluteal intramuscular electrode insertions. Fifteen healthy volunteers took part in a series of walking trials after intramuscular EMG electrodes were inserted into segments of GMin (×2) and GMed (×3) according to previously verified guidelines. Visual analogue scores following walking trials at comfortable and fast speed indicate that discomfort levels associated with these insertions were low (2.4±1.4 and 1.6±0.7 respectively). The technical descriptions and illustrations provided in this paper will allow trained intramuscular electromyographers to insert electrodes into these muscle segments with confidence.

The safe distance for the superior gluteal nerve in direct lateral approach to the hip and its relation with the femoral length: a cadaver study

INTRODUCTION

The most inferior branch (MIB) of the superior gluteal nerve (SGN) is vulnerable during direct lateral approach to the hip. A safe distance proximal to the tip of the greater trochanter varying from 3 to 5 cm has been reported in different studies. Anatomical studies defining safe zones and clinical studies reporting the results use various reference points, and the oblique course of the MIB contributes to the confusion. Numerous efforts have been made to standardize the safe zone using patient characteristics such as body height; however, contradictory results have been reported. The purpose of this study was to measure the safe distance in line to the gluteal split and also to determine the relationship of the safe distance with femoral length, as a stable component of body height.

MATERIALS AND METHODS

Fifteen lower extremities of 12 formalin-fixed cadavers (M/F: 7/5) were dissected. The most prominent lateral palpable part of the trochanter major (TM) was determined and the dissection in the gluteus medius muscle (GMM) was performed starting from this point upwards in line of the muscle fibers. The distances between the MIB in the plane of dissection in the GMM to the TM and also to the trochanteric apex (TA) were measured. Femoral lengths were measured between the TM point and the lateral epicondyle. Spearman's correlation and Mann-Whitney U tests were used for statistical analysis.

RESULTS

The SGN in 13 hips had spray pattern and neural trunk pattern in two. The plane of dissection was within the anterior third of the GMM in all hips. The average femoral length was 37.5 cm. Average distance between TM and MIB was 44 mm; in three hips, the distance was <30 mm. The average distance between TA and TM was 21 mm. There was no statistically significant correlation between femoral length and TM-MIB distance.

CONCLUSION

The distance from the TM to the MIB is highly variable and independent from body height or femoral length. The so called "safe zone" in which damage of significant nerve damage is excluded can have a rather small dimension in some patients. Short patients are not at increased risk and tall patients are not risk free. Modern techniques in total hip replacement which try to minimize proximal interruption of the GMM are therefore justified.

Intramuscular nerve distribution pattern of the oblique and transverse heads of the adductor hallucis muscles in the human foot

To understand which layer of the intrinsic muscles of the foot the adductor hallucis muscle belongs to, it is essential to investigate the innervation patterns of this muscle. In the present study, we examined the innervation patterns of the adductor hallucis muscles in 17 feet of 15 Japanese cadavers. We investigated the intramuscular nerve supplies of the adductor hallucis muscles in six feet and performed nerve fiber analysis in three feet. The results indicate that: (i) the oblique head of the adductor hallucis muscle is divided into three compartments (i.e. lateral, dorsal and medial parts) or two compartments (i.e. dorsal and medial parts) based on its intramuscular nerve supplies, but we could not classify the transverse head into any parts; (ii) the communicating twig between the lateral and medial plantar nerves penetrated the oblique head of the adductor hallucis muscle in 13 of 17 feet (76.5%); (iii) the penetrating twig entered between the lateral and dorsal parts of the oblique head, passed between the lateral and medial parts of this muscle and then connected with the medial plantar nerve; and (iv) the majority of the nerve fibers of the penetrating twig derived from the lateral plantar nerve. The present study demonstrated that only the lateral part of the oblique head of the adductor hallucis muscle had a unique innervating pattern different from other parts of this muscle, suggesting that the lateral part of the oblique head has a different origin from other parts of this muscle.

Ramification pattern of the deep branch of the lateral plantar nerve in the human foot

To understand how the oblique and transverse heads of the adductor hallucis muscle of the human foot are phylogenitically and ontogenetically developed, it is essential to know nerve supplies of these two heads of the muscle. In the present study, we dissected seven feet of five Japanese cadavers in detail to clarify the ramification patterns of the deep branch of the lateral plantar nerve by peeling off its epineurium (the nerve fascicle analysis method). We found that the muscular branch to the oblique head of the adductor hallucis muscle directly separated from nerve fascicles constituting the deep branch of the lateral plantar nerve, whereas the muscular branch to the transverse head arose in common with branches which innervated other intrinsic muscles of the foot, i.e., the 2nd and 3rd lumbrical muscles and the 1st and 2nd dorsal interossei muscles. The present study revealed that two heads of the adductor hallucis muscle, the oblique and transverse, had different innervating patterns, suggesting that two heads of the human adductor hallucis muscle develop from different primordia, and not from common ancestors.

Anatomic considerations for the choice of surgical approach for hip resurfacing arthroplasty

A number of surgical exposures have been advocated over the past 20 years by the pioneers of resurfacing hip arthroplasty and include the anterior, anterolateral, lateral, and posterolateral approaches. Not all of these approaches, however, appear to provide adequate exposure while respecting the local biology that seems to be imperative for the procedure. Based on an anatomic study, the most "bio-logical" surgical approach for hip resurfacing arthroplasty appears to be through a lateral or posterolateral approach using a digastric trochanteric osteotomy combined with an anterior hip dislocation. These exposures avoid injury to the medial femoral circumflex artery supplying the femoral head and allow access and treatment to the commonly observed hip pathologies that are frequently located anteriorly.

Risks to the superior gluteal neurovascular bundle during percutaneous iliosacral screw insertion: an anatomical cadaver study

BACKGROUND

Iliosacral screws are a popular technique used to treat complicated injuries of the pelvis. It is well recognized that this technique entails some potentially disabling complications, including damage to vessels and lumbosacral nerves. The recommended insertion site for iliosacral screws into the S1 body lies along the posterior ilium between the greater sciatic notch and the iliac crest. The anatomy and course of the superior gluteal nerve and vessels have been described along the outer aspect of the posterior ilium. Injury to the superior gluteal nerve and vessels has been reported during pelvic surgery, including the insertion of iliosacral screws. The purpose of this study is to assess the risks of injury and proximity of percutaneously inserted iliosacral screws to the superior gluteal nerve and vessels using a cadaver model.

MATERIALS AND METHODS

Twenty-nine cadaver pelvises for a total of 58 sides (58 screws) were studied. Percutaneous iliosacral screws were placed into the first sacral bodies using multiplanar fluoroscopic guidance. The superior gluteal neurovascular bundle was then studied via a posterior dissection. Injury to the neurovascular bundle was noted if it occurred, and the distance between the screw head and the neurovascular bundle was measured. Distances from the screw head to the crista glutea, greater sciatic notch, and iliac crest were also measured.

RESULTS

The branching pattern of the superior gluteal nerve and vessels after they exit the greater sciatic notch demonstrated considerable variation, but was generally consistent with prior descriptions in most cases. Ten of 58 (18%) iliosacral screws caused injury to the superior branch of the superior gluteal nerve and vessels; 8 neurovascular bundles were impaled and 2 others were partly entrapped between the screw head and the ilium. The mean distance from the head of the iliosacral screws to the deep superior branches of the superior gluteal nerve and vessels was 9.1 mm (+/- 6.8 mm). The mean distances from the screw head to the crista glutea, sciatic notch, and iliac crest were 19.5 mm (+/- 4.9 mm), 33.0 mm (+/- 6.4 mm) and 50.3 mm (+/- 4.6 mm). Of the screws that caused superior gluteal nerve and vessels injury, all were within the "desired" area of insertion.

CONCLUSIONS

The deep superior branch of the superior gluteal nerve and vessels, which provides major blood and nerve supply to the G. medius and G. minimus, is at significant risk during the percutaneous placement of iliosacral screws even when "well placed" and soft tissue protecting cannulas are used. The clinical effects of these injuries remain poorly understood.

Reliability of the safe area for the superior gluteal nerve

The authors investigated the reliability of the safe area, which previously was defined to prevent injury to the superior gluteal nerve during the lateral approach to the hip, and its relation to body height. The distance between the point of entry of the superior gluteal nerve into the gluteus medius muscle and the greater trochanter, in the regions which were defined as the anterior and posterior halves of the muscle, were measured in 23 cadaveric hips. There was a significant correlation between the height of the cadavers and the distance in the anterior and posterior regions. In all of the anterior regions and 78% of the posterior regions of the hips, the superior gluteal nerve as found to be in the safe area. The current study showed that the average distance between the innervation point of the gluteus medius muscle and the greater trochanter might change as a function of body height. The risk of damage to the superior gluteal nerve may be higher if the direct lateral approach to the hip is used. These data show that it is possible that the safe area is not always safe.

Transverse subgluteal-ilioinguinal approach to the acetabulum

An approach to the acetabulum is described. This approach consists of an anterior and a posterior part. The anterior part is nearly identical with the ilioinguinal approach. The posterior part resembles Kocher's (Gibson, J Bone Joint Surg 1950;32B:183-186) original description in that the plane of dissection passes between the motor territories of the superior gluteal nerve anterolaterally and the inferior gluteal nerve posteromedially. Two modifications have been introduced, however. First, the incision is a transverse one; superior and inferior fasciocutaneous flaps are elevated. Second, the gluteus maximus is not only disinserted from the fascia lata and the gluteal tuberosity at the upper end of the femur but from the iliac crest as well. After ligating the superficial branch of the superior gluteal artery to the gluteus maximus, the muscle itself is reflected posteromedially. We have used this approach to explore the lumbosacral plexus and its branches, particularly the sciatic nerve at the greater sciatic notch. Due to the excellent exposure of both columns of the acetabulm, this approach may be equally used in fractures of the acetabulum.

Tensor fasciae latae flap: alternative donor as a functioning muscle transplantation

The functioning tensor fasciae late muscle was used for a patient with both a complete defect of the deltoid muscle and a defect of overlying skin. The configuration of the tensor fasciae latae including the length of the muscle belly as well as the muscle fiber arrangement was similar to that of the deltoid. In addition, the spatial relationship between the muscle, donor vessels, and motor nerve fulfilled the requirements for the recipient site of deltoid reconstruction. The transferred muscle successfully replaced the function of the deltoid and provided sufficient strength for elevation of the arm. Simultaneous skin coverage was also satisfactory. The case report here clearly indicates that the tensor fasciae latae muscle is a promising candidate for functioning muscle transplantation, and can also be applied for other disorders. However, several points such as limited motor nerve length should be considered when tensor fasciae latae is used as a functioning muscle.