Architectural differences in the anterior and middle compartments of the pelvic floor of young-adult and postmenopausal females

Contrast-enhanced Micro-CT imaging of a foetal female pelvic floor reveals anatomical details

BACKGROUND

The pelvic floor is a highly important structure for the stability of the pelvis, providing support for the organs that lie within it. Until today, the detailed anatomy of the female perineal centre and the exact course of surrounding muscles remain controversial. We demonstrate a method to non-destructively obtain high-resolution contrast-enhanced x-ray microtomography images from a long-fixed sample and thereby aim to contribute to the detailed anatomical knowledge about the female pelvic floor.

MATERIALS AND METHODS

A human foetal pelvis of 20-21 weeks gestational age, formalin-fixed for 4 years, was immersed in Lugol solution and tomographically scanned periodically to document the staining process. The influence of the former fixation time was addressed by comparison with a short time fixed mouse pelvis. High-resolution imaging was performed using µCT, with detailed anatomical analysis supported by segmentation and 3D reconstruction.

RESULTS

Lugol staining of long-fixed tissue was effective and showed no disadvantages compared to short-fixed tissue. Lugol staining and high-resolution µCT images provided a nicely stained image-stack with clearly identifiable tissue types. The anatomy of the foetal pelvis and its structures were resolved in detail. Interconnections between the external anal sphincter, the bulbospongiosus muscle and the superficial transverse perineal muscle could be shown within the perineal centre. There was no evidence for a skeletal muscle that corresponded to the formerly described deep transverse perineal muscle, instead there was cloudy-looking tissue, most likely smooth muscle fibres dispersed in connective tissue in a 3-D arrangement.

CONCLUSIONS

X-ray microtomography of Lugol-stained tissue is an excellent method to gain anatomical details in high resolution, in a non-invasive and non-destructive way, independently of the fixation time. Using this method, the topographical relationships of the pelvic floor muscles could be illustrated, showing their linkage within the perineal centre.

Three-dimensional measurement and analysis of the compressor urethrae and urethra in postpartum women

Background

The position and lines of the compressor urethrae, as well as the different segments and morphological characteristics of the compressor urethrae and urethra have not been systematically characterized. This study thus aimed to quantify the lines, thickness, volume, surface area, and position of the compressor urethrae, as well as the thickness, volume, and surface area in the upper, middle, and lower urethra, in postpartum females via three-dimensional (3D) measurement and analysis methods.

Methods

This retrospective study included a total of 90 postpartum women. The 3D models of compressor urethrae and urethra were constructed based on the imaging pictures of these women. The indicators that were analyzed in a 3D plane included volume, surface area, thickness, and diameter lines of the compressor urethrae; the ratio of the compressor urethrae length (CUL) to the urethral length (UL); the distance between the compressor urethrae and the pubic symphysis; the volume, surface area, and thickness of urethra and its different segments; the UL; and the urethral inclination angle (UIA). These indicators were compared between a postpartum-stress urinary incontinence (SUI) group and a control group. Differences in indicators between the segments of urethra were compared. The relationship between related indicators of the compressor urethrae and of the urethra with age was determined.

Results

The length, width, and volume of the compressor urethrae in the control group were 23.24±3.29 mm, 24.61±3.79 mm, and 1.47±0.49 cm3, respectively. The upper, middle and lower regions of the urethral volume in the control group were 2.58±0.59, 2.10±0.32, and 0.84±0.37 cm3, respectively. The volume and thickness of the compressor urethrae, the CUL, and volume of the upper and middle regions of the urethra in the control group were significantly larger than those in the SUI group (P=0.002, P=0.02, P=0.01, P=0.003, and P<0.001, respectively). The volume and surface area of middle urethra were significantly larger than those of the lower urethra (P<0.001 and P<0.001, respectively). The compressor urethrae volume (r=-0.506; P=0.004), compressor urethrae surface area (r=-0.523; P=0.003), middle urethral volume (r=-0.403; P=0.03), and middle urethral thickness (r=-0.629; P<0.001) were negatively correlated with age.

Conclusions

This study provides reference criteria for the volume, thickness, and surface area of different portions of the compressor urethrae and urethra. The upper and middle urethra may be particularly significant to female urinary continence. Meanwhile, strengthening of the compressor urethrae might help treat female urinary continence.

The development of the external genitals in female human embryos and foetuses. Part 2: Vaginal vestibule, anal canal, perineal raphe and perineal cutaneous muscles

Concomitant with the rupture of the cloacal membrane, the perineal skin epithelium thickens (see accompanying article). In this study, we establish in female embryos and foetuses that the thick skin area divides into ventral and dorsal areas at ~14 weeks and gradually becomes restricted to the vaginal vestibule and anal canal thereafter. The dense mesenchymal core of the labia minora, which forms at ~8 weeks, extends dorsally to the anal canal as a midline reinforcement. The skin epithelium overlying this reinforcement is much thinner than the flanking 'thick skin', and is supported by an interrupted basement membrane, which implies epithelial-mesenchymal transformation of the thin midline epithelium and the subsequent establishment of the perineal raphe by the merging of the adjacent thick epithelium. Meanwhile, the anogenital distance in the perineum increases rapidly in length. Perhaps as a consequence, the labia minora cover only the ventral third of the vaginal vestibule at 20 weeks. The endodermal ducts of Bartholin's glands are identifiable at 7 weeks, while acini form at ~12 weeks. The vestibular bulbs become identifiable at ~10 weeks and form vascular networks after ~14.5 weeks. After the rupture of the cloacal membrane, the diameter of the junction of the dorsal cloaca with the anal canal is just a pinhole but widens dorsoventrally after the 7th week. The cutaneous muscles of the perineal area form as a ventrally open U-shaped mesenchymal mass, from which the anal sphincter and bulbospongiosus muscle develop. In conclusion, our findings show that thick skin epithelium persists in the vaginal vestibule and anal canal.

Anterior Colporrhaphy and Paravaginal Repair for Anterior Compartment Prolapse: A Review

Pelvic organ prolapse, particularly in the anterior compartment, is a prevalent condition that significantly impacts women's quality of life. Two common surgical approaches for managing anterior vaginal wall prolapse are anterior colporrhaphy and paravaginal repair. Anterior colporrhaphy, a traditional technique, involves the plication of weakened fascial tissues to restore support to the bladder and anterior vaginal wall. Paravaginal repair addresses lateral detachment of the anterior vaginal wall by reattaching it to its supportive structures. This review aimed to compare the indications, techniques, and outcomes between these surgical methods, discussing their efficacy, recurrence rates, and complications. Although anterior colporrhaphy is widely used, paravaginal repair may offer superior results in specific cases, particularly those involving lateral defects. The review also explored the evolution of these techniques, the role of grafts and mesh, and the potential benefits of minimally invasive approaches such as laparoscopy and robotic surgery. The goal is to provide clinicians with comprehensive insights into choosing the appropriate surgical option based on individual patient anatomy and clinical presentation, thus optimizing outcomes and minimizing recurrence.

Towards a Terminologia Anatomica Humana

Unfortunately, the long-awaited revision of the official anatomical nomenclature, the Terminologia Anatomica 2 (TA2), which was issued in 2019 and after a referendum among the Member Societies officially approved by the General Assembly of the International Federation of Associations of Anatomists in 2020, is built on a new version of the Regular Anatomical Terminology (RAT) rules. This breaks with many traditional views of terminology. These changes in the Terminologia Anatomica of 1998 (TA98) met great resistance within many European Anatomical Societies and their members are not willing to use terms following the RAT rules. European anatomy teachers and scientists using traditional Latin in their teaching, textbooks and atlases will keep using the TA98. The German Anatomical Society (Anatomische Gesellschaft) recently announced the usage of the TA2023AG in curricular anatomical media such as textbooks and atlases, based on the TA98 and the Terminologia Neuroanatomica (TNA). We are preparing a more extensive improvement of the TA98, called Terminologia Anatomica Humana (TAH). This project is fully based on the noncontroversial terms of TA98, incorporating the recent digital version (2022) of the TNA from 2017. Further, it is completed with many new terms, including those in TA2, along with their definitions and relevant references, clinical terms, and correcting inconsistencies in the TA98. The TAH is still in process, but many chapters are already freely available at the IFAA Website in Fribourg ( https://ifaa.unifr.ch ) as is the digital version of the TNA.

Twisted orientation of the muscle bundles in the levator ani functional parts in women: Implications for pelvic floor support mechanism

This study presents a comprehensive investigation of the anatomical features of the levator ani muscle. The levator ani is a critical component of the pelvic floor; however, its intricate anatomy and functionality are poorly understood. Understanding the precise anatomy of the levator ani is crucial for the accurate diagnosis and effective treatment of pelvic floor disorders. Previous studies have been limited by the lack of comprehensive three-dimensional analyses; to overcome this limitation, we analysed the levator ani muscle using a novel 3D digitised muscle-mapping approach based on layer-by-layer dissection. From this examination, we determined that the levator ani consists of overlapping muscle bundles with varying orientations, particularly in the anteroinferior portion. Our findings revealed distinct muscle bundles directly attached to the rectum (LA-re) and twisted muscle slings surrounding the anterior (LA-a) and posterior (LA-p) aspects of the rectum, which are considered functional parts of the levator ani. These results suggest that these specific muscle bundles of the levator ani are primarily responsible for functional performance. The levator ani plays a crucial role in rectal elevation, lifting the centre of the perineum and narrowing the levator hiatus. The comprehensive anatomical information provided by our study will enhance diagnosis accuracy and facilitate the development of targeted treatment strategies for pelvic floor disorders in clinical practice.

Comparative study of female pelvic floor among undeformed high-resolution thin-sectional anatomical (visible human) images and MRI and ultrasound images

PURPOSE

Using visible human, MRI and ultrasound images, we aim to provide an anatomical basis for the identification and diagnosis of pelvic floor structure and disease by ultrasound imaging.

METHODS

One Chinese visible human (CVH) image, one American visible human image, 9 MRI images of normal volunteers, and 40 ultrasound images of normal volunteers or pelvic organ prolapse patients were used. Pelvic organs, pelvic floor muscles, and the connective tissue in CVH, VHP, MRI, and ultrasound images were selected for comparative study.

RESULTS

We successfully identified the boundary of the anal sphincter complex, including the subcutaneous, superficial, and deep parts of the external anal sphincter, conjoined longitudinal muscles and internal anal sphincter; the levator ani muscle (LAM), including the internal and external parts of the pubovisceral muscle and the superficial and deep parts of the puborectal muscle; the urethral sphincter complex, including the urethral sphincter proper and the urethral compressor; and the perineal body, the rectoperineal muscle and superficial transverse perineal muscle.

CONCLUSIONS

We successfully recognized and studied the location, subdivisions, 2D morphology and spatial relationships of the LAM, anal sphincter complex, urethral sphincter complex and perineal body in ultrasound images, thereby helping sonologists or clinicians accurately identify pelvic floor muscles and supporting structures in ultrasound images.

Analysis of multisite surface electromyography characteristics of pelvic floor muscles in postpartum patients with diastasis recti abdominis

AIM

To explore the electrophysiological characteristics of the independent muscles in the pelvic floor muscle (PFM) group of postpartum women with diastasis recti abdominis (DRA) and analyze the correlation between the rectus abdominis interval and PFM function.

METHODS

A total of 133 women who underwent postpartum re-examination from August 2021 to July 2022 were collected. The participants were divided into DRA and control groups based on the occurrence of DRA on ultrasonography. General data of the participants were collected, and the multisite surface electromyography (sEMG) assessment of the PFMs was performed using a intravaginal novel airbag-type stretchable electrode array device developed by the team. The sEMG characteristics of the different PFMs in the two groups were compared, and the correlation between the maximum rectus abdominis interval and the sEMG parameters of different PFMs was analyzed.

RESULTS

There were no differences in the baseline demographics and incidence of pelvic floor dysfunction between the two groups (p > 0.05). The mean amplitude of vaginal sphincter endurance contraction in the DRA group was significantly lower than that in the control group (28.44 ± 15.59 vs. 22.03 [12.22, 28.00], p < 0.05). Spearman's rank correlation analysis showed a weak negative correlation between the maximum rectus abdominis interval and the endurance contraction mean amplitude of the urethral and external anal sphincters (r = -0.173, -0.217, p < 0.05).

CONCLUSIONS

Patients with DRA had weakened PFM endurance, and there was a weak negative correlation between the maximum rectus abdominis interval and the endurance contraction mean amplitude of the PFM.

Three-dimensional endovaginal ultrasound assessment using the levator ani deficiency score in primiparas: A replication study

INTRODUCTION

It is essential to assess the levator ani properly as part of clinical care in patients presenting with pelvic floor dysfunction. The levator ani deficiency scoring system is a previously published method to assess levator ani defects with three-dimensional endovaginal ultrasound. The primary aim of this study was to determine the intra- and interrater reliability of the levator ani deficiency score in a cohort of non-instrumentally delivered primiparas.

MATERIAL AND METHODS

Primiparas (n = 141) were examined at least 1 year after vaginal birth. Three-dimensional endovaginal ultrasound volumes were acquired by a single examiner using two different automated ultrasound probes. The volumes were analyzed by two separate raters who were blinded to each other's assessments. Descriptive statistics were calculated for levator ani deficiency score and categorized into three levels (mild, moderate, severe). Kendall's tau-b was calculated for intra- and interrater comparisons.

RESULTS

Intrarater comparisons of levator ani deficiency score and levator ani deficiency category were high (Kendall's tau-b ≥0.80 for Rater 1; >0.79 for Rater 2). Interrater comparisons of levator ani deficiency score and levator ani deficiency category were also high (Kendall's tau-b >0.9 for assessment 1 and >0.78 for assessment 2). Varying by rater, probe and assessment, 75.9%-80.1% of the study population had no/mild deficiency, 6.4%-9.2% had moderate deficiency, and 4.3%-6.4% had severe levator ani deficiency.

CONCLUSIONS

The levator ani deficiency scoring system is a feasible method to assess defects of the levator ani muscle and can be reproduced with high intra- and interrater correlations. Using the scoring system in clinical practice may facilitate concordant assessment between different examiners. However, the system should be used to support clinical findings and symptomatology and not as a screening tool, as the score is lacking the category of no levator ani deficiency.

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.

Creation of the biomechanical finite element model of female pelvic floor supporting structure based on thin-sectional high-resolution anatomical images

PURPOSE

The main purpose of this study is to obtain a finite element biomechanical model that accurately mimics pelvic organ prolapse in women, to study pelvic floor supporting structures' biomechanical properties and function. We used thin-sectional high-resolution anatomical images (Chinese Visible Human, CVH) to reconstruct a detailed three-dimensional (3D) biomechanical finite element model of the female pelvic floor supporting structure including cardinal ligament, uterosacral ligament, levator ani muscle (LAM) and perianal body. The Valsalva maneuver was simulated by loading the uterus and bladder with a pressure increasing from 0 to 10 kPa. The stress, strain and displacement of supporting structures were calculated. The cardinal ligament, the uterosacral ligament and the LAM were stressed greatly when the uterus moved downward, and the maximum stress could reach 0.267 MPa, 1.51 MPa and 0.065 MPa respectively, and the maximum strain could reach 0.154, 0.16, 0.265, and the maximum displacement could reach 1.786 cm, 1.946 cm and 0.567 cm. Displacement of the perineal body also occurred, and its stress, strain and displacement were 0.092 MPa, 0.381, 0.73 cm. The stress, strain and displacement of the supporting structure around the urethra were 0.339 MPa, 0.169, 1.491 cm. Our model based on CVH has more detailed anatomical structures, which is superior to that based on MRI. Our simulation results were consistent with previous findings, which verified the unbalance of abdominal pressure and pelvic floor supporting structures will lead to POP, which provide a theoretical basis for pelvic floor anatomy and function as well as obstetrical surgery.

The variation in shape and thickness of the pelvic floor musculature in males and females: a geometric-morphometric analysis

INTRODUCTION AND HYPOTHESIS

In women, the risk of pelvic floor prolapse is known to be associated with age and parity. Different studies suggested that it is also related to pelvic dimensions, e.g. biomechanical modelling showed that a larger pelvic canal results in higher values of displacement, stress and strain in the pelvic floor muscles, which can increase the risk of pelvic floor disorders. To better understand the multiple factors contributing to pelvic floor disorders, we assessed how age, body weight, body height, parity (in women), pelvic canal size and overall muscle development affected pelvic floor geometry.

METHODS

A comprehensive geometric morphometric analysis of variation in pelvic floor muscle shape was conducted based on a dense set of 3D landmarks measured on CT scans in a cohort of 49 deceased men and 52 deceased women. The multivariate association between biological variables (parity, dimensions of the true pelvis, age, body weight, height) and pelvic floor muscle morphology was explored by reduced rank regression in both sexes.

RESULTS

In women, advanced age, high body weight relative to body height and a large pelvic canal were associated with a deeper pelvic floor. Surprisingly, parity did not have any strong association with overall pelvic floor shape. In men, high body weight was associated with a deep pelvic floor. Age had little effect on male pelvic floor shape, except for the thickness of the ischiocavernosus muscle, which reduced with age.

CONCLUSION

These results suggest that age, relative body weight and the size of the pelvic canal contribute to the risk of female pelvic floor disorders via their effect on pelvic floor shape, independently of birth-related factors such as injury and avulsion of pelvic floor muscles.

Study of female pelvic floor muscle in overactive bladder based on MRI 3D reconstruction

Background

This study examined the three-dimensional (3D) morphological changes of the urination and urinary continence anatomical structures in overactive bladder (OAB) patients, to offer a morphological data for OAB diagnosis and treatment.

Methods

Eleven OAB patients, 9 healthy females and 22 pelvic organ prolapse (POP) patients were enrolled and underwent MRI scans. The anatomical components of urination (bladder detrusor) and the urinary continence (main part of the urethral sphincter, compressor urethrae, and levator ani muscle (LAM) were 3D reconstructed and measured with Amira software. We also analyze the relativity between pelvic floor muscle’s morphological parameters among the volunteers, OAB and POP group.

Results

Through 3D reconstruction, increased thickness and volume of the bladder detrusor were found in the OAB patients compared with volunteers (3.1 ± 0.7 mm vs. 1.9 ± 0.3 mm; P = 0.000 and 50,632.0 ± 19,724.7 mm³ vs. 23,386.6 ± 7826.3 mm³; P = 0.001). The volume of LAM showed no significant difference between the OAB patients and volunteers (27,089.4 ± 5015.0 mm³ vs. 27,294.4 ± 4461.4 mm³; P = 0.924); whereas, LAM’s volume of the POP patients was significantly larger than that of the volunteers (34,130.6 ± 7968.3 mm³ vs. 27,294.4 ± 4461.4 mm³; P = 0.023). The thickness and volume of the main part of urethral sphincter were significantly lower in the OAB patients compared with volunteers (2.2 ± 0.5 mm vs. 2.7 ± 0.3 mm; P = 0.018 and 2558.6 ± 703.2 mm³ vs. 23,267.3 ± 681.9 mm³; P = 0.035). The volume of the compressor urethrae was significantly lower in the OAB patients than that in the volunteers (630.3 ± 301.2 mm³ vs. 866.1 ± 514.2 mm³; P = 0.247).

Conclusions

In OAB patients, the bladder detrusor has long-term tension and contraction, which thickened muscle and increased volume, and aggravate urination. The compressor urethral and main part of urethral sphincter are weaker and the anterior part of LAM hiatus is relaxed, easily resulting in leakage of urine and ultimately incontinence. The MRI 3D reconstruction and measurement can help to evaluate pelvic floor urination and continence function, and accurately diagnose.

Creation and application of war trauma treatment simulation software for first aid on the battlefield based on undeformed high-resolution sectional anatomical image (Chinese Visible Human dataset)

BACKGROUND

Effective first aid on the battlefield is vital to minimize deaths caused by war trauma and improve combat effectiveness. However, it is difficult for junior medical students, which have relatively poor human anatomy knowledge and first aid experience. Therefore, we aim to create a treatment simulation software for war trauma, and to explore its application for first aid training. METHODS : This study is a quantitative post-positivist study using a survey for data collection. First, high-resolution, thin-sectional anatomical images (Chinese Visible Human (CVH) dataset) were used to reconstruct three-dimensional (3D) wound models. Then, the simulation system and the corresponding interactive 3D-PDF, including 3D models, graphic explanation, and teaching videos, were built, and used for first aid training in army medical college. Finally, the interface, war trauma modules, and training effects were evaluated using a five-point Likert scale questionnaire. All measurements are represented as mean and standard deviations. Moreover, free text comments from questionnaires were collected and aggregated.

RESULTS

The simulation software and interactive 3D-PDF were established. This included pressure hemostasis of the vertex, face, head-shoulder, shoulder-arm, upper forearm, lower limb, foot, and punctures of the cricothyroid membrane, pneumothorax, and marrow cavity. Seventy-eight medical students participated in the training and completed the questionnaire, including 66 junior college students and 12 graduate students. The results indicated that they were highly satisfied with the software (score: 4.64 ± 0.56). The systems were user-friendly (score: 4.40 ± 0.61) and easy to operate (score: 4.49 ± 0.68). The 3D models, knowledge of hemostasis, and puncture were accurate (scores: 4.41 ± 0.67, and 4.53 ± 0.69) and easily adopted (scores: 4.54 ± 0.635, and 4.40 ± 0.648). They provided information about hemostasis and puncture (all scores > 4.40), except for cricothyroid membrane puncture (scores: 4.39 ± 0.61), improved the learning enthusiasm of medical students (score: 4.55 ± 0.549), and increased learning interest (score: 4.54 ± 0.57).

CONCLUSION

Our software can effectively help medical students master first aid skills including hemostasis, cricothyroid membrane and bone marrow puncture, and its anatomy. This may also be used for soldiers and national first aid training.

The Female Pelvic Floor Fascia Anatomy: A Systematic Search and Review

The female pelvis is a complex anatomical region comprising the pelvic organs, muscles, neurovascular supplies, and fasciae. The anatomy of the pelvic floor and its fascial components are currently poorly described and misunderstood. This systematic search and review aimed to explore and summarize the current state of knowledge on the fascial anatomy of the pelvic floor in women. Methods: A systematic search was performed using Medline and Scopus databases. A synthesis of the findings with a critical appraisal was subsequently carried out. The risk of bias was assessed with the Anatomical Quality Assurance Tool. Results: A total of 39 articles, involving 1192 women, were included in the review. Although the perineal membrane, tendinous arch of pelvic fascia, pubourethral ligaments, rectovaginal fascia, and perineal body were the most frequently described structures, uncertainties were identified in micro- and macro-anatomy. The risk of bias was scored as low in 16 studies (41%), unclear in 3 studies (8%), and high in 20 studies (51%). Conclusions: This review provides the best available evidence on the female anatomy of the pelvic floor fasciae. Future studies should be conducted to clarify the discrepancies highlighted and accurately describe the pelvic floor fasciae.

Anatomy of Cowper's gland in humans suggesting a secretion and emission mechanism facilitated by cooperation of striated and smooth muscles

This study presents the detailed anatomy of the Cowper’s gland in humans. Elucidating the mechanism of secretion and emission of the Cowper’s gland requires analysis of the muscles around the Cowper’s gland. We hypothesized that the Cowper’s gland involves not only smooth muscle but also the striated muscles of the pelvic floor. Here, we provide comprehensive and three-dimensional anatomy of the Cowper’s gland and its surrounding structures, which overcomes the current local and planar understanding. In this study, seven male corpses of body donors were used to conduct macroscopic anatomy, histology, and three-dimensional reconstruction. The Cowper’s gland was surrounded laterally and posterosuperiorly by striated and smooth muscles, respectively. The striated muscle bundle was connected from the superficial transverse perineal muscle, levator ani, and external anal sphincter to the external urethral sphincter (rhabdosphincter). The smooth muscle was part of the deep transverse perineal muscle and entered between the bilateral Cowper’s glands and lobules. Our findings indicate that the secretion and emission of the Cowper’s gland in humans are carried out through the cooperation of striated and smooth muscles.

Embedding interactive, three-dimensional content in portable document format to deliver gross anatomy information and knowledge

The Portable Document Format (PDF) is likely the most widely used digital file format for scholarly and scientific electronic publishing. Since format specification version 1.6, three-dimensional (3D) models in Universal 3D (U3D) format can be embedded into PDF files. The present study demonstrates a repertoire of graphic strategies and modes of presentation that exploit the potentials of 3D models embedded in PDF to deliver anatomical information and knowledge. Three-dimensional models and scenes representing anatomical structures generated by 3D surface scanning or by segmentation from either clinical imaging data or cadaver sectional images were converted into U3D format and then embedded into PDF files using both freely and commercially available software. The relevant steps and required software tools are described. Built-in tools in Adobe Acrobat and JavaScript scripting both were used to pre-configure user interaction with 3D contents. Eight successive proof-of-concept examples of increasing complexity are presented and provided as supplementary material, including both unannotated and annotated 3D specimens, use of bitmap-textures, guided navigation through predetermined 3D scenes, 3D animation, and interactive navigation through tri-planar sectional human cadaver images. Three-dimensional contents embedded in PDF files are generally comparable to multimedia and dedicated 3D software in terms of quality, flexibility, and convenience, and offer new unprecedented opportunities to deliver anatomical information and knowledge.

An ultrasound observation study on the levator hiatus with or without diastasis recti abdominis in postpartum women

INTRODUCTION AND HYPOTHESIS

We hypothesized that differences in post-partum levator hiatus (LH) measurements, as well as the area of urethra and bladder (AUB), viewed under ultrasound, correlate with diastasis rectus abdominis (DRA) occurrence. The primary objective of this study is to determine ultrasound parameters available for diagnosing DRA in post-partum women. We compared LH and AUB measurements under ultrasound in primiparous women, with and without DRA, at 24-26 weeks postpartum.

METHODS

One hundred ninety-four women underwent routine examination, including a self-made clinical symptoms questionnaire, DRA evaluation, and LH and AUB measurements. Independent samples t- and chi-squared tests were used to compare the differences between women with and without DRA.

RESULTS

DRA incidence was significantly higher among those who underwent cesarean section (CS) than for vaginal delivery (VD) (P = 0.038). DRA patients could potentially have urinary urgency, frequency, pain, dysuria, and perineal tears. Additionally, statistically significant differences were found between VD patients, with or without DRA, in the resting LH transverse diameter (TrD) (P = 0.032) and the area of the levator hiatus (ALH) (P = 0.048) as well as AUB at Valsalva (P = 0.049). No differences, however, were found between the DRA and no DRA groups for all those measurements among women who had cesarean deliveries.

CONCLUSIONS

DRA was more likely in post-CS women. Furthermore, the results showed a plausible association between DRA occurrence and LH expansion, especially in women with VD under rest and Valsalva. This could be useful for developing therapeutic plans based on these parameters for post-partum rehabilitation of women with DRA to avoid long-term complications.

The series of smooth muscle structures in the pelvic floors of men: Dynamic coordination of smooth and skeletal muscles

Introduction

Recent studies have revealed the extended nature of smooth muscle structures in the pelvic floor, revising the conventional understanding of the “perineal body.” Our aim was to clarify the three‐dimensional configuration and detailed histological properties of the smooth muscle structures in the region anterior to the rectum and anal canal in men.

Materials and methods

Four male cadavers were subjected to macroscopic and immunohistological examinations. The pelvis was dissected from the perineal side, as in the viewing angle during transperineal surgeries. Serial transverse sections of the region anterior to the rectum and anal canal were stained with Masson's trichrome and immunohistological stains to identify connective tissue, smooth muscle, and skeletal muscle.

Results

There was a series of smooth muscle structures continuous with the longitudinal muscle of the rectum in the central region of the pelvic floor, and three representative elements were identified: the anterior bundle of the longitudinal muscle located between the external anal sphincter and bulbospongiosus; bilateral plate‐like structures with transversely‐oriented and dense smooth muscle fibers; and the rectourethral muscle located between the rectum and urethra. In addition, hypertrophic tissue with smooth muscle fibers extended from the longitudinal muscle in the anterolateral portion of the rectum and contacted the levator ani.

Conclusions

The series of smooth muscle structures had fiber orientations and densities that differed among locations. The widespread arrangement of the smooth muscle in the pelvic floor suggests a mechanism of dynamic coordination between the smooth and skeletal muscles.

Interactive three-dimensional teaching models of the female and male pelvic floor

Controversies regarding structure and function of the pelvic floor persist because of its poor accessibility and complex anatomical architecture. Most data are based on dissection. This "surgical" approach requires profound prior knowledge, because applying the scalpel precludes a "second look." The "sectional" approach does not entail these limitations, but requires segmentation of structures and three-dimensional reconstruction. This approach has produced several "Visible Human Projects." We dealt with limited spatial resolution and difficult-to-segment structures by proceeding from clear-cut to more fuzzy boundaries and comparing segmentation between investigators. We observed that the bicipital levator ani muscle consisted of pubovisceral and puborectal portions; that the pubovisceral muscle formed, together with rectococcygeal and rectoperineal muscles, a rectal diaphragm; that the external anal sphincter consisted of its subcutaneous portion and the puborectal muscle only; that the striated urethral sphincter had three parts, of which the middle (urethral compressor) was best developed in females and the circular lower ("membranous") best in males; that the rectourethral muscle, an anterior extension of the rectal longitudinal smooth muscle, developed a fibrous node in its center (perineal body); that the perineal body was much better developed in females than males, so that the rectourethral subdivision into posterior rectoperineal and anterior deep perineal muscles was more obvious in females; that the superficial transverse perineal muscle attached to the fibrous septa of the ischioanal fat; and that the uterosacral ligaments and mesorectal fascia colocalized. To facilitate comprehension of the modified topography we provide interactive 3D-PDFs that are freely available for teaching purposes. Clin. Anat. 33:275-285, 2020. © 2019 Wiley Periodicals, Inc.

Three-Dimensional Portable Document Format (3D PDF) in Clinical Communication and Biomedical Sciences: Systematic Review of Applications, Tools, and Protocols

Background

The Portable Document Format (PDF) is the standard file format for the communication of biomedical information via the internet and for electronic scholarly publishing. Although PDF allows for the embedding of three-dimensional (3D) objects and although this technology has great potential for the communication of such data, it is not broadly used by the scientific community or by clinicians.

Objective

The objective of this review was to provide an overview of existing publications that apply 3D PDF technology and the protocols and tools for the creation of model files and 3D PDFs for scholarly purposes to demonstrate the possibilities and the ways to use this technology.

Methods

A systematic literature review was performed using PubMed and Google Scholar. Articles searched for were in English, peer-reviewed with biomedical reference, published since 2005 in a journal or presented at a conference or scientific meeting. Ineligible articles were removed after screening. The found literature was categorized into articles that (1) applied 3D PDF for visualization, (2) showed ways to use 3D PDF, and (3) provided tools or protocols for the creation of 3D PDFs or necessary models. Finally, the latter category was analyzed in detail to provide an overview of the state of the art.

Results

The search retrieved a total of 902 items. Screening identified 200 in-scope publications, 13 covering the use of 3D PDF for medical purposes. Only one article described a clinical routine use case; all others were pure research articles. The disciplines that were covered beside medicine were many. In most cases, either animal or human anatomies were visualized. A method, protocol, software, library, or other tool for the creation of 3D PDFs or model files was described in 19 articles. Most of these tools required advanced programming skills and/or the installation of further software packages. Only one software application presented an all-in-one solution with a graphical user interface.

Conclusions

The use of 3D PDF for visualization purposes in clinical communication and in biomedical publications is still not in common use, although both the necessary technique and suitable tools are available, and there are many arguments in favor of this technique. The potential of 3D PDF usage should be disseminated in the clinical and biomedical community. Furthermore, easy-to-use, standalone, and free-of-charge software tools for the creation of 3D PDFs should be developed.

Architecture of structures in the urogenital triangle of young adult males; comparison with females

The fibro‐muscular architecture of the urogenital triangle remains contentious. Reasons are small size of the constituting structures and poor visibility with most imaging methods. We reinvestigated the area in serial sections of three males (21–38 years old) of the American and Chinese Visible Human Projects and two 26‐week‐old male fetuses, and compared the findings with earlier observations in females. The mass of the levator ani muscle was approximately twofold smaller and its funnel shape steeper in males than females. In the levator hiatus, a strand of the smooth longitudinal muscle layer of the rectum, the ‘rectourethral (RU) muscle’, extended anteriorly from the anorectal bend to the penile bulb. Fibrous tissue that formed in the inferior reach of the fetal RU muscle identified the location of the developing perineal body (PB) and divided the muscle into posterior ‘rectoperineal’ and anterior ‘deep perineal’ portions. In males, the PB remained small and bipartite, so that the RU muscle presented as an undivided midline structure. The well‐developed female PB, instead, intertwined with the deep perineal muscle and both structures passed the vagina bilaterally to form the perineal membrane in the posterior portion of the urogenital triangle. The urethral rhabdosphincter extended in the anterior portion of the urogenital triangle between the penile bulb inferiorly and the bladder neck superiorly, and consisted of a well‐developed circular ‘membranous’ portion with bilateral posteroinferior ‘wings’ and a thinner ‘prostatic’ portion on the prostate anterior side. In men, muscles occupy the urogenital triangle, but additional tightening of the locally fibrous adipose tissue by the superficial transverse perineal muscle appears necessary to generate functional support in women. An interactive 3D pdf file with these anatomical details (available online) should allow more accurate interpretation of ultrasound, computed tomography and magnetic resonance images.