Allometry and Sexual Dimorphism in the Human Pelvis

Development of a universal cutting guide for raising deep circumflex iliac artery flaps

PURPOSE

The deep circumflex iliac crest flap (DCIA) is used for the reconstruction of the jaw. For fitting of the transplant by computer-aided planning (CAD), a computerized tomography (CT) of the jaw and the pelvis is necessary. Ready-made cutting guides save a pelvic CT and healthcare resources while maintaining the advantages of the CAD planning.

METHODS

A total of 2000 CTs of the pelvis were divided into groups of 500 by sex and age (≤ 45 and > 45 years). Three-dimensional (3D) pelvis models were aligned and averaged. Cutting guides were designed on the averaged pelvis for each group and an overall averaged pelvis. The cutting guides and 50 randomly selected iliac crests (10 from each group and 10 from the whole collective) were 3D printed. The appropriate cutting guide was mounted to the iliac crest and a cone beam CT was performed. The thickness of the space between the iliac crest and the cutting guide was evaluated.

RESULTS

Overall the mean thickness of the space was 2.137 mm and the mean volume of the space was 4513 mm3. The measured values were significantly different between the different groups. The overall averaged group had not the greatest volume, maximum thickness and mean thickness of the space.

CONCLUSION

Ready-made cutting guides for the DCIA flap fit to the iliac crest and make quick and accurate flap raising possible while radiation dose and resources can be saved. The cutting guides fit sufficient to the iliac crest and should keep the advantages of a standard CAD planning.

Danger Zones of the Gluteal Anatomy: Improving the Safety Profile of the Gluteal Fat Grafting

INTRODUCTION

Knowledge of the vascular anatomy is critical to performing safe gluteal surgery. To date, only the course of the main blood vessels within the muscles has been outlined. These findings are based on MRI and CTA images that do not conform to a topographically standardized and normalized probability distribution.

OBJECTIVES

The aim of this study was to develop a three-dimensional mapping of the gluteal zones of high vascular density in relation to anatomical landmarks.

MATERIALS AND METHODS

This single-center retrospective cohort analysis comprised all consecutive patients who underwent cone-beam computed tomography (CBCT) scans between January 2016 and October 2021. The location of blood vessels in the gluteal region was allometrically normalized in relation to anatomical landmarks. Moreover, the caliber and area of the blood vessels were assessed.

RESULTS

CBCT scans of 32 patients with an average age of 64 ± 12 years (range 34-87 years) were included. Fifty-three percent were female. The median [IQR] caliber of the intramuscular gluteal vessels was 1.47 [1.15-1.88] mm, significantly greater than that of the subcutaneous vessels 1.09 [0.72-1.44] mm (p < 0.001). Vascular density was higher intramuscularly, as 4.5% of the area of the muscle was occupied by blood vessels, as opposed to 0.3% in the adipose tissue.

CONCLUSION

The analysis of the CBCT scans showed a higher vascular density and larger vessels intramuscularly. We, therefore, recommend the injection of autologous fat merely to the subcutaneous plane.

LEVEL OF EVIDENCE II

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

The International Olympic Committee framework on fairness, inclusion and nondiscrimination on the basis of gender identity and sex variations does not protect fairness for female athletes

The International Olympic Committee (IOC) recently published a framework on fairness, inclusion, and nondiscrimination on the basis of gender identity and sex variations. Although we appreciate the IOC's recognition of the role of sports science and medicine in policy development, we disagree with the assertion that the IOC framework is consistent with existing scientific and medical evidence and question its recommendations for implementation. Testosterone exposure during male development results in physical differences between male and female bodies; this process underpins male athletic advantage in muscle mass, strength and power, and endurance and aerobic capacity. The IOC's "no presumption of advantage" principle disregards this reality. Studies show that transgender women (male-born individuals who identify as women) with suppressed testosterone retain muscle mass, strength, and other physical advantages compared to females; male performance advantage cannot be eliminated with testosterone suppression. The IOC's concept of "meaningful competition" is flawed because fairness of category does not hinge on closely matched performances. The female category ensures fair competition for female athletes by excluding male advantages. Case-by-case testing for transgender women may lead to stigmatization and cannot be robustly managed in practice. We argue that eligibility criteria for female competition must consider male development rather than relying on current testosterone levels. Female athletes should be recognized as the key stakeholders in the consultation and decision-making processes. We urge the IOC to reevaluate the recommendations of their Framework to include a comprehensive understanding of the biological advantages of male development to ensure fairness and safety in female sports.

Evolution of the human birth canal

It seems puzzling why humans have evolved such a small and rigid birth canal that entails a relatively complex process of labor compared with the birth canal of our closest relatives, the great apes. This study reviewed insights into the evolution of the human birth canal from recent theoretical and empirical studies and discussed connections to obstetrics, gynecology, and orthopedics. Originating from the evolution of bipedality and the large human brain million years ago, the evolution of the human birth canal has been characterized by complex trade-off dynamics among multiple biological, environmental, and sociocultural factors. The long-held notion that a wider pelvis has not evolved because it would be disadvantageous for bipedal locomotion has not yet been empirically verified. However, recent clinical and biomechanical studies suggest that a larger birth canal would compromise pelvic floor stability and increase the risk of incontinence and pelvic organ prolapse. Several mammals have neonates that are equally large or even larger than human neonates compared to the size of the maternal birth canal. In these species, the pubic symphysis opens widely to allow successful delivery. Biomechanical and developmental constraints imposed by bipedality have hindered this evolutionary solution in humans and led to the comparatively rigid pelvic girdle in pregnant women. Mathematical models have shown why the evolutionary compromise to these antagonistic selective factors inevitably involves a certain rate of fetopelvic disproportion. In addition, these models predict that cesarean deliveries have disrupted the evolutionary equilibrium and led to new and ongoing evolutionary changes. Different forms of assisted birth have existed since the stone age and have become an integral part of human reproduction. Paradoxically, by buffering selection, they may also have hindered the evolution of a larger birth canal. Many of the biological, environmental, and sociocultural factors that have influenced the evolution of the human birth canal vary globally and are subject to ongoing transitions. These differences may have contributed to the global variation in the form of the birth canal and the difficulty of labor, and they likely continue to change human reproductive anatomy.

Analysis of cam location characteristics in FAI syndrome patients from 3D MR images demonstrates sex-specific differences

Cam femoroacetabular impingement (FAI) syndrome is associated with hip osteoarthritis (OA) development. Hip shape features, derived from statistical shape modeling (SSM), are predictive for OA incidence, progression, and arthroplasty. Currently, no three-dimensional (3D) SSM studies have investigated whether there are cam shape differences between male and female patients, which may be of potential clinical relevance for FAI syndrome assessments. This study analyzed sex-specific cam location and shape in FAI syndrome patients from clinical magnetic resonance examinations (M:F 56:41, age: 16-63 years) using 3D focused shape modeling-based segmentation (CamMorph) and partial least squares regression to obtain shape features (latent variables [LVs]) of cam morphology. Two-way analysis of variance tests were used to assess cam LV data for sex and cam volume severity differences. There was no significant interaction between sex and cam volume severity for the LV data. A sex main effect was significant for LV 1 (cam size) and LV 2 (cam location) with medium to large effect sizes (p < 0.001, d > 0.75). Mean results revealed males presented with a superior-focused cam, whereas females presented with an anterior-focused cam. When stratified by cam volume, cam morphologies were located superiorly in male and anteriorly in female FAI syndrome patients with negligible, mild, or moderate cam volumes. Both male and female FAI syndrome patients with major cam volumes had a global cam distribution. In conclusion, sex-specific cam location differences are present in FAI syndrome patients with negligible, mild, and moderate cam volumes, whereas major cam volumes were globally distributed in both male and female patients.

Exploring 3D Pelvis Orientation: A Cross-Sectional Study in Athletes Engaged in Activities with and without Impact Loading and Non-Athletes

Female athletes subjected to various types of impact loading, especially over a long period of time, may experience changes in their pelvic orientation, which may affect their sport performance and increase the likelihood of injury. The aim of the present study was to determine whether female athletes involved in high-impact loading sports (HILS), odd-impact loading sports (OILS), and repetitive non-impact loading sports (NILS) demonstrate changes in pelvis orientation compared to non-athletes (NATH). Pelvic orientation was determined using Euler/Cardan angles, calculated from the coordinates of the right, and left anterior superior iliac spines and pubic symphysis via a novel method. Two-way ANOVA tests showed significant differences between groups for pelvis position in the frontal plane (p < 0.05), with HILS and OILS demonstrating greater pelvic obliquity compared to NILS athletes and NATH. Significant main effects were also obtained for directions within the sagittal plane (p < 0.001). Significant within-group differences were observed in sagittal pelvic position among female athletes engaged in NILS (p < 0.01) and non-athletes (NATH) (p < 0.05), with a greater anterior pelvic tilt compared to posterior. Our findings suggest that pelvis orientation in female athletes across sports is influenced by sport-specific impact loads, potentially affecting performance and injury occurrence.

Effects of Artificially Induced Leg Length Discrepancy on Treadmill-Based Walking and Running Symmetry in Healthy College Students: A Lab-Based Experimental Study

Leg length discrepancy (LLD) is a common postural deviation of musculoskeletal origin, which causes compensatory reactions and often leads to injury. The aim of the study was to investigate the effect of artificially induced LLD on gait symmetry by means of the spatiotemporal gait parameters and ground reaction forces (GRFs) using a treadmill equipped with capacitive sensors (instrumented) as well as the EMG activity of trunk and hip muscles during walking and running. Twenty-six healthy male and female college students were required to perform two sets of four 2.5-min walking and running trials on an instrumented treadmill at 5.6 and 8.1 km·h-1, respectively, without (0) and with 1, 2, and 3 cm LLD implemented by wearing a special rubber shoe. Statistical analysis was performed using one-way repeated measures or a mixed-design ANOVA. Most spatiotemporal gait parameters and GRFs demonstrated an increase or decrease as LLD increased either on the short-limb or the long-limb side, with changes becoming more apparent at ≥1 cm LLD during walking and ≥2 cm LLD during running. The EMG activity of trunk and hip muscles was not affected by LLD. Our findings showed that gait symmetry in terms of treadmill-based spatiotemporal parameters of gait and GRFs is affected by LLD, the magnitude of which depends on the speed of locomotion.

A hierarchical clustering approach for examining the relationship between pelvis-proximal femur geometry and bone stress injury in runners

Bone stress injury (BSI) risk in runners is multifactorial and not well understood. Unsupervised machine learning approaches can potentially elucidate risk factors for BSI by identifying groups of similar runners within a population which differ in BSI incidence. Here, a hierarchical clustering approach is used to identify groups of collegiate cross country runners based on 2-dimensional frontal plane pelvis and proximal femur geometry, which was extracted from dual-energy X-ray absorptiometry scans and dimensionally reduced by principal component analysis. Seven distinct groups were identified using the cluster tree, with the initial split being highly related to female-male differences. Visual inspection revealed clear differences between groups in pelvis and proximal femur geometry, and groups were found to differ in lower body BSI incidence during the subsequent academic year (Rand index = 0.53; adjusted Rand index = 0.07). Linear models showed between-cluster differences in visually identified geometric measures. Geometric measures were aggregated into a pelvis shape factor based on trends with BSI incidence, and the resulting shape factor was significantly different between clusters (p < 0.001). Lower shape factor values, corresponding with lower pelvis height and ischial span, and greater iliac span and trochanteric span, appeared to be related to increased BSI incidence. This trend was dominated by the effect observed across clusters of male runners, indicating that geometric effects may be more relevant to BSI risk in males, or that other factors masked the relationship in females. More broadly, this work outlines a methodological approach for distilling complex geometric differences into simple metrics that relate to injury risk.

Preoperative Virtual Reduction Planning Algorithm of Fractured Pelvis Based on Adaptive Templates

OBJECTIVE

The minimally invasive treatment of pelvic fractures is one of the most challenging trauma orthopedics surgeries, where preoperative planning is crucial for the performance and outcome of the surgery. However, planning the ideal position of fragments currently relies heavily on the experience of the surgeon.

METHODS

A pelvic fracture virtual reduction algorithm for target position is provided based on statistical shape models (SSM). First, according to sexual dimorphism, pelvic SSM based on point cloud curvature down-sampling are constructed as adaptive templates. Then, an optimization algorithm is designed to iteratively adjust the target pose of the fragments and the adaptive matching of the templates. Finally, the feasibility of the method is verified by simulating fractures and clinical data.

RESULTS

The pelvis has complex shape characteristics, which can be analyzed by SSM to clearly understand the pattern of change. Experiments showed that the SSM-based pelvic fracture reduction method had translation and rotation errors of 2.20±1.09 mm and 3.16±1.26° in simulated cases, and 2.78±0.95 mm and 3.10±0.53° in clinical cases, which has higher accuracy than methods based on mean shape models, and wider applicability than methods based on pelvic symmetry.

CONCLUSION

The pelvic digital model created by SSM has good generalization properties, and the SSM-based virtual reduction algorithm can effectively reconstruct the target position of the fractured pelvis in preoperative planning.

SIGNIFICANCE

The proposed reduction method has the characteristics of high precision and wide application range, which provides a powerful tool for the surgeon's virtual preoperative planning.

There is an obstetrical dilemma: Misconceptions about the evolution of human childbirth and pelvic form

Compared to other primates, modern humans face high rates of maternal and neonatal morbidity and mortality during childbirth. Since the early 20th century, this "difficulty" of human parturition has prompted numerous evolutionary explanations, typically assuming antagonistic selective forces acting on maternal and fetal traits, which has been termed the "obstetrical dilemma." Recently, there has been a growing tendency among some anthropologists to question the difficulty of human childbirth and its evolutionary origin in an antagonistic selective regime. Partly, this stems from the motivation to combat increasing pathologization and overmedicalization of childbirth in industrialized countries. Some authors have argued that there is no obstetrical dilemma at all, and that the difficulty of childbirth mainly results from modern lifestyles and inappropriate and patriarchal obstetric practices. The failure of some studies to identify biomechanical and metabolic constraints on pelvic dimensions is sometimes interpreted as empirical support for discarding an obstetrical dilemma. Here we explain why these points are important but do not invalidate evolutionary explanations of human childbirth. We present robust empirical evidence and solid evolutionary theory supporting an obstetrical dilemma, yet one that is much more complex than originally conceived in the 20th century. We argue that evolutionary research does not hinder appropriate midwifery and obstetric care, nor does it promote negative views of female bodies. Understanding the evolutionary entanglement of biological and sociocultural factors underlying human childbirth can help us to understand individual variation in the risk factors of obstructed labor, and thus can contribute to more individualized maternal care.

Sex differences in linear bone measurements occur following puberty but do not influence femoral or tibial torsion

Torsional, angular, and linear measurements in a paediatric population are clinically important but not well defined and understood. Different methods of measurement and discrepancies between assessors leads to a lack of understanding of what should be defined as typical or atypical for the growing skeleton. From a large dataset of 333 paediatric CT scans, we extracted three-dimensional torsional, angular, and linear measurements from the pelvis, femur, and tibia/fibula. Sex differences in linear measurements were observed in bones of children aged 13+ (around puberty), but femoral and tibial torsion were similar between males and females. The rotational profile (femoral anteversion minus tibial torsion) tended to increase with growth. Epicondylar, condylar, and malleolar widths were smaller in females than males for the same bone length after the age of 13 years, which could explain why females may be more at risk for sport injuries during adolescence. This rich dataset can be used as an atlas for researchers and clinicians to understand typical development of critical rotational profiles and linear bone measurements in children.

Pelvic morphologies of developmental dysplasia and primary osteoarthritis on range of motion after total hip arthroplasty

Bony impingement, especially in the anterior inferior iliac spine (AIIS) after total hip arthroplasty (THA), may cause dislocation. However, the influence of AIIS characteristics on bony impingement after THA is not fully understood. Thus, we aimed to determine the morphological characteristics of AIIS with developmental dysplasia of the hip (DDH) and primary osteoarthritis (pOA) and to evaluate its effect on range of motion (ROM) after THA. Hips from 130 patients who underwent THA, including pOA were analyzed. In total, we had 27 male and 27 female participants with pOA, and 38 male and 38 female participants with DDH. The horizontal distances of AIIS from teardrop (TD) were compared. In the computed tomography simulation, flexion ROM was measured, and its relationship to the distance between TD and AIIS was investigated. DDH had a more medial (male: DDH, 36.9 ± 5.8; pOA, 45.5 ± 6.1; p < 0.001) (female: DDH, 31.5 ± 10.0; pOA, 36.2 ± 4.7; p < 0.001) position of AIIS than pOA. In the male with pOA group, flexion ROM was significantly smaller than that in the other groups, and there was a correlation between flexion ROM and horizontal distances (r = -0.543; 95% confidence interval = -0.765 to -0.206; p = 0.003). AIIS position is a factor that limits ROM during flexion after THA, particularly in males. Further studies are required to develop surgical strategies for cases of impingement at the AIIS site after THA. Level of evidence: Ш, retrospective comparative study.

Anthropometric study using three-dimensional pelvic CT scan in sex determination among adult Indonesian population

This study aims to determine pelvic anthropometry characteristics and logistic regression formula for adult sex identification obtained from adult three-dimensional pelvic computed tomography images. This study was an observational analytical study with retrospective regression and cross-sectional approach. The population was all patients at Radiology Installation of Dr. Soetomo General Academic Hospital as referral hospital in East Indonesian region, from September to December 2019 who underwent 3D pelvic CT examination. Then, age distribution and pelvic measurements data were obtained. In this case, statistical analysis was conducted for all the data obtained. A number of 204 samples were included in this study. All radiologic components were also significantly different between sexes (p < 0.05) except for transverse diameter of sacral segment (p = 0.180). Moreover, the conjugate pelvic inlet diameter (CPID), the left innominate height (LIH), and sub pubic angle (SPA) showed significant values for regression formula to determine an adult's sex using 3D pelvic CT. The calculation result > 0 is a prediction for female while < 0 is a prediction for male. From logistic regression model calculation, a high validity value (91.05%) was found with 100% sensitivity to identify male sex and 81.1% specificity to identify female sex. There were differences on radiometric variable characteristics in pelvic anthropometric study among adult Indonesians at Dr. Soetomo General Academic Hospital, Surabaya. The estimated values of pelvic measurements using 3D CT images could develop a pelvic model with a regression formula with high accuracy value using CPID, LIH, and SPA values.

Magnetic resonance imaging study of the sciatic nerve variation in the pediatric gluteal region: Implications for the posterior approach of the sciatic nerve blockade

INTRODUCTION

In pediatric patients, the sciatic nerve is one of the most commonly blocked peripheral nerves during orthopedic procedures of the lower limb. Ultrasound guidance is the current standard for a successful localization of the sciatic nerve in the gluteal region. Relevant anatomical landmarks are also used to determine the nerve location when ultrasound is not available or inadequate. However, reports have demonstrated paucity of information regarding the sciatic nerve location and variation in the hip throughout pediatric development. This imaging study aimed to document and analyze the relative morphometric relationship of the sciatic nerve in the pediatric gluteal region throughout development.

METHODS

The location of the sciatic nerve in relation to bony landmarks was measured in 84 pediatric magnetic resonance imaging of patients aged 0.7-15.8 years.

RESULTS

The sciatic nerve was identified medial to the most lateral point of greater trochanter at the level of ischial spine and the tip of coccyx. The strong positive correlation between sciatic nerve to landmark distances and age and stature demonstrated linear variation between sciatic nerve location with age and growth of children. To predict the nerve location in the gluteal region, regression equations using patient age were created, having implications for the posterior approach of the sciatic nerve blockade in children. Clinically significant differences were found between sexes, specifically in the older age group.

CONCLUSION

Despite the small sample size of younger age group, this study is the first to document the morphometric changes of the sciatic nerve in the gluteal region across pediatric development and may be useful for providing confirmatory guidelines for nerve location when ultrasound is not accessible or cannot be utilized for practice.

Scoliosis Research Society-22r score is affected by standing whole body sagittal alignment, age, and sex, but not by standing balance or skeletal muscle mass in healthy volunteers

PURPOSE

Aging and spinal disease impair standing whole body sagittal alignment (WBS alignment), which leads to stooping. When WBS alignment deteriorates, compensatory mechanisms are activated to maintain standing posture. Increase of the compensation impairs health-related quality of life (HRQOL). The purpose of this research was to determine whether postural factors, age, and sex affect HRQOL.

METHODS

This cross-sectional study evaluated the influence of WBS alignment, standing body sway (balance), skeletal muscle mass (SMM), aging, and sex on HRQOL in healthy volunteers (n = 150; mean age 40.9 years [20-76], 96 women). Age, sex, weight, height, and body mass index (BMI) were obtained. HRQOL was assessed with Scoliosis Research Society-22 (SRS-22r). WBS alignment and balance were measured by EOS imaging with simultaneous force plate measurement. SMM was measured using a medical body composition analyzer. Based on the bivariate analysis between the SRS-22r subtotal and all parameters, selected ten parameters were used for multivariate logistic regression analysis to identify affecting factors to SRS-22r.

RESULTS

Men had significantly higher weight, height, BMI, and SRS-22r score in all domains. The L4-S1 lumbar lordosis angle was greater in men, and pelvic tilt and knee hyperextension were greater in women. Women had a more stable standing posture, whereas men had significantly higher SMM values. Multivariate logistic regression analysis revealed that age, sex, and TPA were identified as significant factors affecting SRS-22r.

CONCLUSIONS

In healthy volunteers, SRS-22r is affected by aging, sex (woman had a lower score), and sagittal malalignment. Neither Standing balance nor SMM, however, affect SRS-22r.4.

Intraoperative Techniques for Gaining Ileoanal Pouch Reach

Ileal pouch-anal anastomosis allows for reestablishing gastrointestinal continuity in patients after proctocolectomy. The technical elements of pouch creation and gaining reach into the pelvis are demanding and require a variety of surgical maneuvers to achieve a tension-free anastomosis. We present a brief review of the literature discussing various approaches aimed at improving ileal pouch reach into the low pelvis. Although these techniques are used with different frequencies, they serve as important adjuncts to the gastrointestinal surgeons' armamentarium.

Effect of hip and knee joint angles on resting hamstring muscles rigidity in men and women

PURPOSE

Hamstring muscle strains are one of the most common injuries in sports practice, for both men and women. However, sex disparities in the rate of muscle injuries have been observed. As these muscular injuries usually occur at long muscle length, this study aimed to determine the effect of sex on hamstring muscles' resting rigidity under different stretching conditions.

METHODS

The shear wave speed (SWS) of resting hamstring muscles was measured in 12 men and 12 women in different hip and knee positions (hip extended with knee flexed, hip flexed with knee extended, both joints extended and both joints flexed).

RESULTS

Combining all the positions, the SWS of the semitendinosus was higher in men than in women (2.96 vs. 2.71 m.s^-1). Regardless of sex, a significant rise in SWS was systematically observed when the semimembranosus was stretched (1.86, 2.37, 2.76 and 4.39 m.s^-1) but it was neither the case for the semitendinosus (p = 0.82) nor for the biceps femoris (p = 0.50). Finally, differences in SWS among the hamstring muscles were only observed at the longest muscle length, with greater SWS values for the semimembranosus and semitendinosus in comparison with the biceps femoris (4.39 and 4.12 vs. 3.38 m.s^-1 respectively).

CONCLUSION

In conclusion, a sex difference was only observed in the resting semitendinosus rigidity. Independently of sex, the increase in resting hamstring muscles SWS with stretch was muscle specific.

Diagnostic accuracy of paranasal sinus measurements on multislice computed tomography for sex estimation: A systematic review, meta-analysis, and meta-regression

This systematic review aimed to answer the question, "Are paranasal measurements obtained with multislice computed tomography able to accurately estimate sex?" This PROSPERO-registered systematic review included six databases and gray literature. Meta-analysis of linear and volumetric data was performed using a random-effects model, mean differences (MDs), and inverse variance. The QUADAS-2 tool-related risk of bias (RoB) and certainty evidence (GRADE approach) were assessed. A total of 1651 articles were initially selected from the main electronic databases for title and abstract screening. After removing duplicates and studies that did not meet the inclusion criteria, 18 studies were eligible for the meta-analysis. The screened studies included 2507 computed tomography of non-pathologic paranasal sinuses of adults aged between 18 and 40 years. Frontal sinus (FS) width (-4.89 mm; p < 0.00001) and maxillary sinus (MS) height (-3.73 mm; p < 0.00001) showed the greatest MD between females and males. Regarding volume, the MD was significant (p < 0.00001) in both paranasal sinuses (-3.01 and -1.04 cm³ , respectively). The best sensitivity (ability to identify males) and specificity (ability to identify females) were found for the anteroposterior (72.3%) and intermaxillary (69%) MS distances, respectively. In general, all studies exhibited low RoB and applicability concerns. The certainty of the evidence was categorized as very low to moderate. Both paranasal sinuses were shown to be dimorphic structures, which could be valuable tools for forensic identification using the FS width and MS anteroposterior distance measurements. However, heterogeneity among studies must be considered.

Anthropometric Equations to Determine Maximum Height in Adults ≥ 60 Years: A Systematic Review

Although it is common to measure bone lengths for study, methodological errors in data measurement and processing often invalidate their clinical and scientific usefulness. This manuscript reviews the validity of several published equations used to determine the maximum height in older adults, since height is an anthropometric parameter widely employed in health sciences. A systematic review of original articles published in the English, Spanish, or Portuguese languages was performed in PubMed, ScienceDirect, EBSCO, Springer Link, and two institutional publisher integrators (UACJ and CONRICYT). The search terms were included in the metasearch engines in a combined way and text form using the Boolean connectors AND and OR {(Determination OR Estimation OR Equation) AND Height AND (Elderly OR "Older adults")}. Eleven manuscripts were selected from 1935 records identified through database searching after applying the following criteria: (1) original articles that designed and validated equations for the determination of height by anthropometric methods in adults 60 years of age and older and (2) manuscripts that presented robust evidence of validation of the proposed regression models. The validity of the reported linear regression models was assessed throughout a manuscript review process called multi-objective optimization that considered the collection of the models, the prediction errors, and the adjustment values (i.e., R², standard error of estimation, and pure error). A total of 64 equations were designed and validated in 45,449 participants (57.1% women) from four continents: America (85.3%, with 46 equations), Asia (8.1%, with 10), Europe (4.6%, with 7), and Africa (2.0%, with 1); the Hispanic American ethnic group was the most numerous in participants and equations (69.0%, with 28). Due to various omissions and methodological errors, this study did not find any valid and reliable equations to assess the maximum height in older adults by anthropometric methods. It is proposed to adjust allometric mathematical models that can be interpreted in the light of ontogenetic processes.

Re-examining our roots: Queer history and anatomy

Since its establishment as one of the major authorities on the human body, Anatomy has played a crucial role in social and political spheres. In this article, I review how the history of Anatomy has intersected with queer history and how the effects of these interactions have affected queer lives today. In these historical cases, I aim to demonstrate how Anatomy has affected the social organization of human culture and society and also how society has affected anatomical knowledge in return. As this reciprocal connection between Anatomy and societal organization is elucidated, I argue that anatomists, clinicians, and educators have an ethical duty to address the connections of this history, both in our research and our classrooms. This historical tour begins in the ancient world, which established a connection between sexuality and physiology and reproduction. This is followed by an exploration of the Renaissance and Enlightenment, which highlight the connections between anatomical knowledge, the law, and social organization. The progressive and modern eras are explored next via modern research into the anatomical and biological origins of same-sex attraction and the use of modern technology in these investigations. Finally, the article ends with a call for reform along with suggestions for future steps.

Assessing the role of the pelvic canal in supporting the gut in humans

The human pelvic canal (true pelvis) functions to support the abdominopelvic organs and serves as a passageway for reproduction (females). Previous research suggests that these two functions work against each other with the expectation that the supportive role results in a narrower pelvic midplane, while fetal passage necessitates a larger opening. In this research, we examine how gut size relates to the size and shape of the true pelvis, which may have implications on how gut size can influence pelvic floor integrity. Pelves and in vivo gut volumes were measured from CT scans of 92 adults (48 female, 44 male). The true pelvis was measured at three obstetrical planes (inlet, midplane, outlet) using 11 3D landmarks. CT volumetry was used to obtain an individual’s gut size. Gut volume was compared to the pelvic planes using multiple regression to evaluate the relationship between gut size and the true pelvis. We find that, in males, larger gut sizes are associated with increased mediolateral canal dimensions at the inlet and midplane. In females, we find that larger gut sizes are associated with more medially-projecting ischial spines and an anteroposteriorly longer outlet. We hypothesize that the association of larger guts with increased canal width in males and increased outlet length in females are adaptations to create adequate space for the gut, while more medially projecting ischial spines reduce the risk of pelvic floor disorders in females, despite its possible spatial consequences for fetal passage.

The evolution of pelvic canal shape and rotational birth in humans

BACKGROUND

The human foetus typically needs to rotate when passing through the tight birth canal because of the complex shape of the pelvis. In most women, the upper part, or inlet, of the birth canal has a round or mediolaterally oval shape, which is considered ideal for parturition, but it is unknown why the lower part of the birth canal has a pronounced anteroposteriorly oval shape.

RESULTS

Here, we show that the shape of the lower birth canal affects the ability of the pelvic floor to resist the pressure exerted by the abdominal organs and the foetus. Based on a series of finite element analyses, we found that the highest deformation, stress, and strain occur in pelvic floors with a circular or mediolaterally oval shape, whereas an anteroposterior elongation increases pelvic floor stability.

CONCLUSIONS

This suggests that the anteroposterior oval outlet shape is an evolutionary adaptation for pelvic floor support. For the pelvic inlet, by contrast, it has long been assumed that the mediolateral dimension is constrained by the efficiency of upright locomotion. But we argue that the mediolateral elongation has evolved because of the limits on the anteroposterior diameter imposed by upright posture. We show that an anteroposteriorly deeper inlet would require greater pelvic tilt and lumbar lordosis, which compromises spine health and the stability of upright posture. These different requirements of the pelvic inlet and outlet likely have led to the complex shape of the pelvic canal and to the evolution of rotational birth characteristic of humans.

The obstetrical dilemma hypothesis: there's life in the old dog yet

The term 'obstetrical dilemma' was coined by Washburn in 1960 to describe the trade-off between selection for a larger birth canal, permitting successful passage of a big-brained human neonate, and the smaller pelvic dimensions required for bipedal locomotion. His suggested solution to these antagonistic pressures was to give birth prematurely, explaining the unusual degree of neurological and physical immaturity, or secondary altriciality, observed in human infants. This proposed trade-off has traditionally been offered as the predominant evolutionary explanation for why human childbirth is so challenging, and inherently risky, compared to that of other primates. This perceived difficulty is likely due to the tight fit of fetal to maternal pelvic dimensions along with the convoluted shape of the birth canal and a comparatively low degree of ligamentous flexibility. Although the ideas combined under the obstetrical dilemma hypothesis originated almost a century ago, they have received renewed attention and empirical scrutiny in the last decade, with some researchers advocating complete rejection of the hypothesis and its assumptions. However, the hypothesis is complex because it presently captures several, mutually non-exclusive ideas: (i) there is an evolutionary trade-off resulting from opposing selection pressures on the pelvis; (ii) selection favouring a narrow pelvis specifically derives from bipedalism; (iii) human neonates are secondarily altricial because they are born relatively immature to ensure that they fit through the maternal bony pelvis; (iv) as a corollary to the asymmetric selection pressure for a spacious birth canal in females, humans evolved pronounced sexual dimorphism of pelvic shape. Recently, the hypothesis has been challenged on both empirical and theoretical grounds. Here, we appraise the original ideas captured under the 'obstetrical dilemma' and their subsequent evolution. We also evaluate complementary and alternative explanations for a tight fetopelvic fit and obstructed labour, including ecological factors related to nutrition and thermoregulation, constraints imposed by the stability of the pelvic floor or by maternal and fetal metabolism, the energetics of bipedalism, and variability in pelvic shape. This reveals that human childbirth is affected by a complex combination of evolutionary, ecological, and biocultural factors, which variably constrain maternal pelvic form and fetal growth. Our review demonstrates that it is unwarranted to reject the obstetrical dilemma hypothesis entirely because several of its fundamental assumptions have not been successfully discounted despite claims to the contrary. As such, the obstetrical dilemma remains a tenable hypothesis that can be used productively to guide evolutionary research.

A geometric morphometric assessment of shape variation in adult pelvic morphology

OBJECTIVES

In humans, the pelvis is the most sexually dimorphic skeletal element and is often utilized in aging and sexing remains. The pelvis has become greatly relied upon in anthropological research (e.g., forensics, demographics, obstetrics, evolutionary history); however, pelvis morphology is highly variable, and very little is known about the nature, sources, patterning, and interpretation of this variation. This study aims to quantify pelvis shape variation, document sexual shape variation, and estimate the plasticity of morphology. This will ultimately give greater ability to interpret modern, archaeological, and evolutionary patterns to gain deeper insight into processes which shape human anatomy.

MATERIALS AND METHODS

Using a sample of 129 Medieval Danish skeletons, shape variation is documented in the greater sciatic notch (GSN), iliac crest (IC), arcuate line (AL), and sub-pubic angle (SPA) using 3D geometric morphometrics. The landmarking method applied here has the advantage of being applicable to fragmentary remains, rather than requiring whole bones. This allows it to be easily applied to archaeological samples and for the interpretation of separate bone features. Differences in shape were statistically analyzed by principle component analysis, linear discriminate analysis, and morphological disparity. Relationships between maximum femur length, body mass, and shape centroid size were also test by allometric regression.

RESULTS

Results quantify the sexual dimorphism and shape variation present in these features. The GSN shape is the most variable, while the AL is the least. Similarly, the IC is the only feature which shows almost no dimorphism in shape, and instead best reflects lifestyle/activity patterns. Evidence of dimorphism in the IC is likely a result of cultural labor patterns rather than genetic and hormonal influence. Finally, the shapes of the GSN, AL, and SPA are more related to body mass than to femur length, such that individuals with increased mass exhibit more classically "male" shapes and those with less mass have more "female" shapes.

DISCUSSION

The results have important implications for the evolution of pelvic anatomy, and sexual dimorphism, but also highlight the plasticity inherent in pelvic morphology. Analyzing pelvis features separately in a clearly defined, relatively genetically homogenous population gives insight into the determinants of bone morphology, which are not readily observable by other means. The relationship between body mass and shape suggests dimorphism in body size and composition may affect bone shape.

Sex-Biased Gene Expression of Mesobuthus martensii Collected from Gansu Province, China, Reveals Their Different Therapeutic Potentials

The scorpions, named Mesobuthus martensii, commonly called Quanxie (全蝎) in Chinese, have been widely used as one of the animal medicines for more than 1,000 years because of the strong toxicity of their venoms. Meanwhile, scorpions are sexually dimorphic in appearance, and many exhibit traits associated with sex-biased gene expression, including maternal care, mating competition, female mating choices, ecology, and even venom composition and lethality. This study aims to explore the differences in composition of the venom of scorpions of different sex using the method of transcriptomics. Whole de novo transcriptomes were performed on the samples of M. martensii captured from Gansu Province to identify their sex-biased gene expression. The conserved CO-1 sequences of the captured samples matched that of M. martensii. A total of 8,444 (35.15%), 7,636 (31.78%), 8,510 (35.42%), 7,840 (32.63%), 9,980 (41.54%), and 11,829 (49.23%) unigenes were annotated with GO, KEGG, Pfam, Swissprot, eggNOG, and NR databases. Moreover, a total of 43 metalloproteases, 40 potassium channel toxins, 24 phospholipases, 12 defensins, 10 peroxiredoxins, 9 cysteine proteinase inhibitors, 7 serine protease inhibitors, 6 sodium channel toxins, 2 NDBPs, 1 calcium channel toxin, 1 waprin-like peptide, 1 antibacterial peptide, 1 antimicrobial peptide, and 1 anticoagulant peptide were screened out. With the fold change of 2 and 0.5, p value < 0.01, and q value < 0.05 as thresholds, a total of 41 out of 157 (26.11%) toxin-related unigenes had significant differential expression, and this ratio was much higher than the ratio of differentially expressed unigenes out of all annotated ones (8.84%). Of these differentially expressed toxins, 28 were upregulated and occupied the majority, up to 68.30%. The female scorpions showed more upregulated unigenes that annotated with toxins and had the potential to be used as more effective therapeutic drugs. In addition, this method of omics can be further used as a useful way to identify the difference between female and male toxic animals.

Sex differences in the pelvis did not evolve de novo in modern humans

It is commonly assumed that the strong sexual dimorphism of the human pelvis evolved for delivering the relatively large human foetuses. Here we compare pelvic sex differences across modern humans and chimpanzees using a comprehensive geometric morphometric approach. Even though the magnitude of sex differences in pelvis shape was two times larger in humans than in chimpanzees, we found that the pattern is almost identical in the two species. We conclude that this pattern of pelvic sex differences did not evolve de novo in modern humans and must have been present in the common ancestor of humans and chimpanzees, and thus also in the extinct Homo species. We further suggest that this shared pattern was already present in early mammals and propose a hypothesis of facilitated variation as an explanation: the conserved mammalian endocrine system strongly constrains the evolution of the pattern of pelvic differences but enables rapid evolutionary change of the magnitude of sexual dimorphism, which in turn facilitated the rapid increase in hominin brain size.

The association of parturition scars and pelvic shape: A geometric morphometric study

OBJECTIVES

Pelvic features, mostly known as parturition scars, have been extensively studied in the last decades and are frequently investigated in archaeological and forensic contexts. It is still unclear, however, whether they really relate to pregnancy and birth, or whether these features are caused by other biomechanical factors. Because the length and difficulty of labor correlates with the form of the birth canal, we studied the association between the expression of pelvic features and pelvic shape using geometric morphometrics.

MATERIALS AND METHODS

We scored the expression of the preauricular sulcus, margo auricularis groove, sacral preauricular extension, dorsal and ventral pubic pitting for 54 individuals from a 19th century collection and 19 individuals from the Bronze Age cemetery of Hainburg-Teichtal, Austria. Based on photogrammetric surface models, pelvic shape was captured by 331 landmarks and semilandmarks. The multivariate association between pelvic features and pelvic shape was explored by partial least squares analysis.

RESULTS

Within the female subsample, we detected a significant association of a constrained birth canal with a strong expression of the preauricular sulcus, the margo auricularis groove, and a retroverted position of the acetabulum. No significant association was found among males.

DISCUSSION

This suggests that difficult or prolonged labor may indeed cause more strongly expressed pelvic features, presumably because of increased strain of the pelvic ligaments during birth. Furthermore, the retroversion of the acetabulum, which is known to cause sacroiliac joint dysfunction, changes the strain on pelvic ligaments and can thus also result in the development of pronounced pelvic features.

Development and application of the average pelvic shape in virtual pelvic fracture reconstruction

BACKGROUND

With unilateral pelvic fractures, the contralateral hemipelvis can be used as a template in virtual reconstruction; however, this cannot be applied for bilateral fractures. Therefore, statistical shape modelling was used to build average pelvic shapes that can serve as templates when reconstructing bilaterally fractured pelvises.

METHODS

Four average shape models were created for male and female, left and right hemipelves from 20 male and 20 female subjects. They were used as templates to reconstruct eight unilaterally fractured pelvises.

RESULTS

The average root-mean-square of deviations between the reconstructed and intact hemipelves was 1.46 ± 0.32 mm, which is less than the 2 mm threshold for causing hip joint complications.

CONCLUSION

This indicates that the reconstructions are reliable and the average shape models can be used to reconstruct bilaterally fractured pelvises. The proposed technique can potentially provide quick and accurate treatment plans for pelvic fracture patients, which is necessary for recovery.

Machine-learning strategies for testing patterns of morphological variation in small samples: sexual dimorphism in gray wolf (Canis lupus) crania

BACKGROUND

Studies of mammalian sexual dimorphism have traditionally involved the measurement of selected dimensions of particular skeletal elements and use of single data-analysis procedures. Consequently, such studies have been limited by a variety of both practical and conceptual constraints. To compare and contrast what might be gained from a more exploratory, multifactorial approach to the quantitative assessment of form-variation, images of a small sample of modern Israeli gray wolf (Canis lupus) crania were analyzed via elliptical Fourier analysis of cranial outlines, a Naïve Bayes machine-learning approach to the analysis of these same outline data, and a deep-learning analysis of whole images in which all aspects of these cranial morphologies were represented. The statistical significance and stability of each discriminant result were tested using bootstrap and jackknife procedures.

RESULTS

Our results reveal no evidence for statistically significant sexual size dimorphism, but significant sex-mediated shape dimorphism. These are consistent with the findings of prior wolf sexual dimorphism studies and extend these studies by identifying new aspects of dimorphic variation. Additionally, our results suggest that shape-based sexual dimorphism in the C. lupus cranial complex may be more widespread morphologically than had been appreciated by previous researchers.

CONCLUSION

Our results suggest that size and shape dimorphism can be detected in small samples and may be dissociated in mammalian morphologies. This result is particularly noteworthy in that it implies there may be a need to refine allometric hypothesis tests that seek to account for phenotypic sexual dimorphism. The methods we employed in this investigation are fully generalizable and can be applied to a wide range of biological materials and could facilitate the rapid evaluation of a diverse array of morphological/phenomic hypotheses.

Assessing thoraco-pelvic covariation in Homo sapiens and Pan troglodytes: A 3D geometric morphometric approach

OBJECTIVES

Understanding thoraco-pelvic integration in Homo sapiens and their closest living relatives (genus Pan) is of great importance within the context of human body shape evolution. However, studies assessing thoraco-pelvic covariation across Hominoidea species are scarce, although recent research would suggest shared covariation patterns in humans and chimpanzees but also species-specific features, with sexual dimorphism and allometry influencing thoraco-pelvic covariation in these taxa differently.

MATERIAL AND METHODS

N = 30 adult H. sapiens and N = 10 adult Pan troglodytes torso 3D models were analyzed using 3D geometric morphometrics and linear measurements. Effects of sexual dimorphism and allometry on thoraco-pelvic covariation were assessed via regression analyses, and patterns of thoraco-pelvic covariation in humans and chimpanzees were computed via Two-Block Partial Least Squares analyses.

RESULTS

Results confirm the existence of common aspects of thoraco-pelvic covariation in humans and chimpanzees, and also species-specific covariation in H. sapiens that is strongly influenced by sexual dimorphism and allometry. Species-specific covariation patterns in chimpanzees could not be confirmed because of the small sample size, but metrics point to a correspondence between the most caudal ribs and iliac crest morphology that would be irrespective of sex.

CONCLUSIONS

This study suggests that humans and chimpanzees share common aspects of thoraco-pelvic covariation but might differ in others. In humans, torso integration is strongly influenced by sexual dimorphism and allometry, whilst in chimpanzees it may not be. This study also highlights the importance not only of torso widths but also of torso depths when describing patterns of thoraco-pelvic covariation in primates. Larger samples are necessary to support these interpretations.

Women's socioeconomic position in ontogeny is associated with improved immune function and lower stress, but not with height

Immune function, height and resource accumulation comprise important life history traits in humans. Resource availability models arising from life history theory suggest that socioeconomic conditions influence immune function, growth and health status. In this study, we tested whether there are associations between family income during ontogeny, adult height, cortisol level and immune response in women. A hepatitis B vaccine was administered to 66 young Latvian women from different socioeconomic backgrounds, and blood samples were then collected to measure the level of antibodies that the women produced in response to the vaccination. Cortisol levels were measured from plasma samples pre- and post-vaccination. Women from wealthier families had lower cortisol levels, and women from the highest family income group had the highest levels of antibody titers against hepatitis B vaccine. No significant relationships were observed between cortisol level and immune function, nor between family income and height. The results show that income level during ontogeny is associated with the strength of immune response and with psychoneuroendocrine pathways underlying stress perception in early adulthood. The findings indicate that the quality of the developmental niche is associated with the condition-dependent expression of immune function and stress response.

Obstetric dimensions of the female pelvis are less integrated than locomotor dimensions and show protective scaling patterns: Implications for the obstetrical dilemma

OBJECTIVES

The "obstetrical dilemma" hypothesis assumes that the modern human female pelvis serves two discrete functions: obstetrics and locomotion. We investigate whether these differing functions create observable patterns of morphological covariation and whether those patterns differ by height, weight, and age. This allows evaluation of evidence for canalization and phenotypic plasticity relevant to obstetric and locomotor function among a living female population.

METHODS

Landmarks (N = 86) were collected and inter-landmark distances were calculated (N = 36) on the pelvis and proximal femur of CT scans of living women aged 20 to 90 years (M = 93) receiving a routine CT scan. Partial least squares and relative SD of eigenvalues analyses were used to evaluate integration overall and within locomotor and obstetric modules, respectively. Ordinary Least Squared regression was used to evaluate scaling relationships between inter-landmark distances and height, weight, and age.

RESULTS

The obstetric pelvis was significantly less internally integrated than the locomotor pelvis. Many obstetric measurements were constrained in absolute terms relative to height; shorter women had relatively larger birth canal dimensions, and several key obstetric dimensions showed relative freedom from height. Lower weight women had some relatively larger obstetric and locomotor dimensions. Regarding age, younger women showed a few relatively larger outlet dimensions.

CONCLUSIONS

This study suggests that the obstetric pelvis and the locomotor pelvis function are morphologically distinct, with the obstetric pelvis showing relatively greater flexibility. These relationships between relative constraints support the hypothesis that the modern female pelvis shows evidence of both canalization and phenotypic plasticity in obstetric and locomotor structures.

Current situation and outcomes of pregnancy in women with Turner syndrome in Japan

AIM

Reports on pregnancy and delivery in women with Turner syndrome (TS) in Japan are limited to case reports, and the current situation remains unclear. Therefore, this study aimed to clarify the current situation of pregnancy and delivery in women with TS in Japan.

METHODS

Our study comprised primary and secondary surveys and we included perinatal centers approved by the Ministry of Health, Labor and Welfare.

RESULTS

A total of 24 cases from 19 facilities were reported, and we obtained individual information for 20 cases from 16 facilities. Of these 20 patients, 13 (65%) had become pregnant via oocyte donation. Three of these patients had received oocyte donation in Japan, while the other 10 had received donations in foreign countries. The other seven patients became pregnant with their own oocyte, with spontaneous menarche. Live babies were delivered by 18 patients, while an induced abortion was required at 18 weeks of gestation in one patient and an intrauterine fetal death from an unknown cause was detected at 38 weeks of gestation in another patient. Cesarean section was performed in 14 patients, with the most frequent indication being cephalopelvic disproportion. The rate of implementation of screening for complications related to TS was low, suggesting insufficient cooperation between facilities responsible for TS treatment, infertility and pregnancy and delivery management.

CONCLUSION

To improve pregnancy outcomes in women with TS, improved cooperation between facilities and laws regarding oocyte donation in Japan are needed.

Sexual dimorphism of the relationship between the gut and pelvis in humans

OBJECTIVES

Obstetric demands have long been considered in the evolution of the pelvis, yet consideration of the interaction of pregnancy, the pelvis, and the gastrointestinal tract (gut) is lacking. Here, we explore sex differences in the relationship of gut volume with body size and pelvic dimensions.

MATERIALS AND METHODS

Computed tomography (CT) scans of living adult Homo sapiens (46 females and 42 males) were obtained to measure in vivo gut volume (GV) and to extract 3D models of the pelvis. We collected 19 3D landmarks from each pelvis model to acquire pelvic measurements. We used ordinary least squares regression to explore relationships between GV and body weight, stature, and linear pelvic dimensions.

RESULTS

The gut-pelvis relationship differs between males and females. Females do not exhibit significant statistical correlations between GV and any variable tested. GV correlates with body size and pelvic outlet size in males. GV scales with negative allometry relative to body weight, stature, maximum bi-iliac breadth, inferior transverse outlet breadth, and bispinous distance in males.

DISCUSSION

The lack of association between GV and body size in females may be due to limits imposed by the anticipation of accommodating a gravid uterus and/or the increased plasticity of the pelvis. The pattern of relationship between GV and the pelvic outlet suggests the role of the bony pelvis in supporting the adominal viscera in females may be small relative to its role in childbirth. We conclude that gut size inference in fossil hominins from skeletal proxies is limited and confounded by sexual dimorphism.

Developmental origins of variability in pelvic dimensions: Evidence from nulliparous South Asian women in the United Kingdom

OBJECTIVES

Pelvic growth may be sensitive to early-life nutrition, with implications for maternal risk of obstructed labor. However, the "developmental origins" of adult pelvic variability require further investigation. We tested whether adult pelvic dimensions are associated with two components of height, indexing different periods of linear growth: tibia length, a proxy for early postnatal growth, and height-residual (height regressed on tibia length), a proxy for later growth. We also tested whether adult pelvic dimensions are associated with birth weight, a marker of nutritional investment in utero.

METHODS

In this cross-sectional study, data were obtained on 68 nulliparous young women of South Asian ancestry. Pelvic dimensions (bi-iliac and bi-acetabular breadth, anteroposterior pelvic inlet and outlet, interspinous and intertuberous diameter) were measured using magnetic resonance imaging. Height and tibia length were measured manually. Birth weight and gestational age were obtained by recall. Multivariable regression models were fitted with a given pelvic dimension regressed on height-residual, tibia, and birth weight, with the latter adjusted for gestational age.

RESULTS

Controlling for birth weight, height-residual was predictive of bi-acetabular breadth, bi-iliac breadth, and the pelvic inlet, while tibia length significantly predicted all dimensions except interspinous diameter. Controlling for the linear growth variables, birth weight was predictive of bi-iliac breadth only.

CONCLUSIONS

Markers of linear growth during both early and later development were associated with adult pelvic dimensions, whereas size at birth was poorly predictive. Efforts to reduce stunting in early life may facilitate the attainment of maximum potential growth for both height and the pelvis.

Evolution of the human pelvis and obstructed labor: new explanations of an old obstetrical dilemma

Without cesarean delivery, obstructed labor can result in maternal and fetal injuries or even death given a disproportion in size between the fetus and the maternal birth canal. The precise frequency of obstructed labor is difficult to estimate because of the widespread use of cesarean delivery for indications other than proven cephalopelvic disproportion, but it has been estimated that at least 1 million mothers per year are affected by this disorder worldwide. Why is the fit between the fetus and the maternal pelvis so tight? Why did evolution not lead to a greater safety margin, as in other primates? Here we review current research and suggest new hypotheses on the evolution of human childbirth and pelvic morphology. In 1960, Washburn suggested that this obstetrical dilemma arose because the human pelvis is an evolutionary compromise between two functions, bipedal gait and childbirth. However, recent biomechanical and kinematic studies indicate that pelvic width does not considerably affect the efficiency of bipedal gait and thus is unlikely to have constrained the evolution of a wider birth canal. Instead, bipedalism may have primarily constrained the flexibility of the pubic symphysis during pregnancy, which opens much wider in most mammals with large fetuses than in humans. We argue that the birth canal is mainly constrained by the trade-off between 2 pregnancy-related functions: while a narrow pelvis is disadvantageous for childbirth, it offers better support for the weight exerted by the viscera and the large human fetus during the long gestation period. We discuss the implications of this hypothesis for understanding pelvic floor dysfunction. Furthermore, we propose that selection for a narrow pelvis has also acted in males because of the role of pelvic floor musculature in erectile function. Finally, we review the cliff-edge model of obstetric selection to explain why evolution cannot completely eliminate cephalopelvic disproportion. This model also predicts that the regular application of life-saving cesarean delivery has evolutionarily increased rates of cephalopelvic disproportion already. We address how evolutionary models contribute to understanding and decision making in obstetrics and gynecology as well as in devising health care policies.

Sex-based differences in human sacroiliac joint shape: a three-dimensional morphological analysis of the iliac auricular surface of modern Japanese macerated bones

The human pelvis is one of the skeletons where sex differences are expressed, but few detailed studies have been conducted on sex-related differences in the sacroiliac joint morphology. Therefore, we conducted a three-dimensional morphological analysis evaluation of the sacroiliac joints to clarify the sex-related difference of the joint's morphology. Right-side macerated innominate bones of Japanese males (n = 100) and females (n = 70) whose ages at death were recorded were included in the study. Three-dimensional images were created from the subjects' iliac auricular surface images, and 16 measurement parameters were acquired on the basis of 11 defined measurement points. All measurement parameters were compared between the male and female groups. The values of the measurement parameters indicating the size of the iliac auricular surface were significantly larger in the male group than in the female group. In addition, the angle between the short and long arms of the auricular surface was larger in the male group. Furthermore, on the basis of the corrected values of the physical disparity, the long arm dimension of the iliac auricular surface was larger in the male group, while the short arm dimension was larger in the female group. The sex-based differences in the iliac auricular surface morphology that were confirmed in this study may reflect the sex-based differences in the sacroiliac joint function. The findings of this study may contribute to the elucidation of the pathophysiology of the sacroiliac joint dysfunction that frequently occurs in women.

Penile Inversion Vaginoplasty Technique

Penile inversion vaginoplasty is a technique of gender-affirming genital surgery that uses primarily genital skin to construct the vulva and neovagina for patients assigned male sex at birth. This article presents present the authors' techniques and other contemporary techniques for this surgery, with particular attention to neovaginal canal construction, neoclitoral construction, and urethroplasty.

TOMOGRAPHIC STUDY OF THE S2-ALAR-ILIAC SCREW TECHNIQUE IN BRAZILIAN MEN

ABSTRACT Objective The use of pedicle screws was a milestone for modern spinal surgery. This type of fixation, due to its superior biomechanics, gave greater fixation power, greater capacity to withstand the pulling forces and, therefore, greater stability and lower rates of pseudoarthrosis. Fixation of the lumbosacral junction, even with the development of these new implants, remains a challenge mainly because the considerable rates of pseudoarthrosis. The use of iliac screws solves the biomechanical difficulties. However, its use shows high rates of surgical wound problems. The S2-Alar-Iliac screw (S2AI) came as a solution to these complications. The lack of studies about anatomical and anthropometric parameters in the Brazilian population justifies the study. Methods Eleven hip tomographies of Brazilian adult males were analyzed by four evaluators. The right and left sides were considered. In each patient, measurements were made of greater and shorter bone length, greater and smaller bone diameter, distance from the entry point to the skin, sagittal and axial angles related to the hypothetical insertion of an S2AI screw and compared to the same measurements obtained with the iliac screw. Results The mean bone length was 136.7 mm, the greatest bone diameter was 24.8 mm, the smallest bone diameter was 19.7 mm and the distance from the screw to the skin was 42.1 mm for the S2AI screw. Conclusions The obtained data present an average of the sample that can be useful in the decision of the surgical technique in the studied group. Level of evidence I; Diagnostic Studies (Anatomical Investigation).

Different predictive and accuracy models for sex and stature estimation from second- and fourth-digit lengths in the Kinnaur population of Himachal Pradesh, North India: Medico-legal and forensic implications

Forensic anthropologists are not only active in courtroom testimonies but also contribute to disaster victim identification. The timely recovery and identification of victims in any disaster is crucial, and anthropologists play a vital role in this process. In mass disasters such as airplane crashes, tsunamis, earthquakes or terrorist attacks, fragments of dead bodies are usually brought for identification. Each fragment demands special tactics to fulfil any of the basic attributes of forensic identification such as age, sex, stature or ancestry. If sex and stature can be estimated from a single fragment, then it can potentially reduce the identification time and possible victim matches. In this study, an attempt has been made to estimate sex and stature from the second- and fourth-digit lengths. Different predictive and accuracy models have been devised using statistical techniques. No bilateral difference was observed in the digit lengths in either sex. Consequently, an average of the digit lengths was employed for model approximations. The fourth-digit length provided the best sex estimates (M=82.1%, F=79.2%) when binary logistic regression (BLR) statistics were applied. It was also observed that overall sex estimations improved from 78.8% (from BLR) to 79.8% when discriminant function analysis was used for sex estimation. Second- and fourth-digit lengths were used independently and together for stature estimation models for males and females individually and for the pooled sample. In stature estimation models, three major interpretations were perceived: (1) the second-digit length provided the best stature estimates; (2) the estimation models compute better stature estimates for females than their counterparts, that is, standard errors are less in females than males; and (3) second and fourth digits predict more reliable stature estimation when the sex of the digits is known than that of the pooled sample.

Testing landmark redundancy for sex-based shape analysis of the adult human os coxa

OBJECTIVES

To test the individual effectiveness of common landmarks used in sex estimation of whole adult coxal bones in sex-based shape analysis and propose a method to determine how many principal components of sex-based shape to include for discriminant function analysis.

METHODS

Three-dimensional models (NextEngine desktop laser scanner) of left and right os coxae from 396 individuals (William Bass Skeletal Collection, Forensic Anthropology Centre, University of Tennessee, Knoxville, TN) were subjected to shape analysis using 32 landmarks (Landmark 3.6, Institute for Data Analysis and Visualization). Each landmark was individually removed and subjected to a new principal component analysis to identify the effect omitting a landmark has on PC1/PC2 ordination. Landmarks that poorly discriminated sex-based shape were considered redundant for analysis on sex estimation.

RESULTS

This study identified 17 landmarks that represent sex-based shape of right and left coxal bones most effectively, these are: the anterior superior iliac spine; posterior superior iliac spine; posterior inferior iliac spine; iliac crest; apex of the auricular surface; greater sciatic notch; ischial spine; superior, inferior and distal points on ischial tuberosity; superior, inferior and midpoint on the symphyseal face; arcuate eminence; ischiopubic ramus; posterosuperior and anterosuperior points on the acetabular rim. The first and second PCs of the 17-landmark configuration correctly predicted sex in 98.5% of cases; better than a 32-landmark configuration (96%) and better than previous landmark studies on whole coxal bone sex-based shape.

CONCLUSIONS

These 17 landmarks represent more meaningful data for sex-based shape analysis in PC1 and 2 and concentrate meaningful sex-based shape data to the first five PCs that make up over 50% of the total shape variance.

Three-dimensional analysis of sexual dimorphism in ribcage kinematics of modern humans

OBJECTIVES

Sexual dimorphism is an important biological factor underlying morphological variation in the human skeleton. Previous research found sex-related differences in the static ribcage, with males having more horizontally oriented ribs and a wider lower ribcage than females. Furthermore, a recent study found sex-related differences in the kinematics of the human lungs, with cranio-caudal movements of the caudal part of the lungs accounting for most of the differences between sexes. However, these movements cannot be quantified in the skeletal ribcage, so we do not know if the differences observed in the lungs are also reflected in sex differences in the motion of the skeletal thorax.

MATERIALS AND METHODS

To address this issue, we quantified the morphological variation of 42 contemporary human ribcages (sex-balanced) in both maximal inspiration and expiration using 526 landmarks and semilandmarks. Thoracic centroid size differences between sexes were assessed using a t test, and shape differences were assessed using Procrustes shape coordinates, through mean comparisons and dummy regressions of shape on kinematic status. A principal components analysis was used to explore the full range of morphological variation.

RESULTS

Our results show significant size differences between males and females both in inspiration and expiration (p < .01) as well as significant shape differences, with males deforming more than females during inspiration, especially in the mediolateral dimension of the lower ribcage. Finally, dummy regressions of shape on kinematic status showed a small but statistically significant difference in vectors of breathing kinematics between males and females (14.78°; p < .01).

DISCUSSION

We support that sex-related differences in skeletal ribcage kinematics are discernible, even when soft tissues are not analyzed. We hypothesize that this differential breathing pattern is primarily a result of more pronounced diaphragmatic breathing in males, which might relate to differences in body composition, metabolism, and ultimately greater oxygen demand in males compared to females. Future research should further explore the links between ribcage morphological variation and basal metabolic rate.

Humans as inverted bats: A comparative approach to the obstetric conundrum

OBJECTIVES

The narrow human birth canal evolved in response to multiple opposing selective forces on the pelvis. These factors cannot be sufficiently disentangled in humans because of the limited range of relevant variation. Here, we outline a comparative strategy to study the evolution of human childbirth and to test existing hypotheses in primates and other mammals.

METHODS

We combined a literature review with comparative analyses of neonatal and female body and brain mass, using three existing datasets. We also present images of bony pelves of a diverse sample of taxa.

RESULTS

Bats, certain non-human primates, seals, and most ungulates, including whales, have much larger relative neonatal masses than humans, and they all differ in their anatomical adaptations for childbirth. Bats, as a group, are particularly interesting in this context as they give birth to the relatively largest neonates, and their pelvis is highly dimorphic: Whereas males have a fused symphysis, a ligament bridges a large pubic gap in females. The resulting strong demands on the widened and vulnerable pelvic floor likely are relaxed by roosting head-down.

CONCLUSIONS

Parturition has constituted a strong selective force in many non-human placentals. We illustrated how the demands on pelvic morphology resulting from locomotion, pelvic floor stability, childbirth, and perhaps also erectile function in males have been traded off differently in mammals, depending on their locomotion and environment. Exploiting the power of a comparative approach, we present new hypotheses and research directions for resolving the obstetric conundrum in humans.

Variation in pelvic shape and size in Eastern European males: a computed tomography comparative study

Background

The significantly accelerated development of human society in the last millennium has brought about changes in human behavior and body mass that may have influenced human bone morphology. Our objective was to analyze the variation in pelvic shape and size in males from modern and medieval populations.

Methods

We obtained 22 pelvic girdles of adult males from a medieval cemetery located in Cedynia, Poland. The control group comprised 31 contemporary male pelves from individuals inhabiting the same region. The analyzed parameters were: interspinous distance (ISD), intercristal distance (ICD), intertuberous distance (ITD), anatomic conjugate of the pelvis, height of the pelvis (HP), iliac opening angle (IOA), iliac tilt angle (ITA), and ISD/ITD/HP ratio. Geometric morphometrics was used to analyze differences in shape in the pelves. All analyses were carried out on three-dimensional CT reconstructions of pelves.

Results

ISD, ICD, and IOA were significantly greater in modern pelves than in those from Cedynia, but no significant differences were seen between the two groups in ITD, anatomical conjugate, HP, or ITA. ISD/ITD/HP ratios were significantly lower in the Cedynia group. Geometric morphometrics revealed significant differences in pelvic shape between the analyzed groups.

Discussion

The pelves of modern males are larger, wider, and flatter than those of medieval males. Changes in the set of daily activities that produce mechanical loading and estimated body mass may constitute the main factors explaining pelvic variability. However, differences in ontogenesis should also be taken into consideration, especially since growth in past populations is often found to be reduced relative to modern populations.

TOMOGRAPHIC STUDY OF THE S2-ALAR-ILIAC SCREW TECHNIQUE IN BRAZILIAN WOMEN

ABSTRACT Objective: Lumbosacral fixation presents problems in its arthrodesis, mainly due to pseudoarthrosis. Iliac screws minimize this problem, however, they show problems in the operative wound. The S2-Alar-iliac (S2AI) screw presents a lower rate of these complications. The anatomical differences between the populations and the sexes analyzed in the literature justify the study of the S2AI screw technique in Brazilian women. Methods: A total of 14 adult female CT scans were analyzed by 4 evaluators. Results: The mean bone length was 131.8 mm, the largest bone diameter was 22.6 mm, and the smallest bone diameter was 22.6 mm. Conclusions: The data presented are compatible with the literature and may assist spine surgeons in choosing the best implant and surgical technique. Level of Evidence I; Diagnostic Studies — Investigating a Diagnostic Test (anatomical investigation).

Circulating Testosterone as the Hormonal Basis of Sex Differences in Athletic Performance

Elite athletic competitions have separate male and female events due to men's physical advantages in strength, speed, and endurance so that a protected female category with objective entry criteria is required. Prior to puberty, there is no sex difference in circulating testosterone concentrations or athletic performance, but from puberty onward a clear sex difference in athletic performance emerges as circulating testosterone concentrations rise in men because testes produce 30 times more testosterone than before puberty with circulating testosterone exceeding 15-fold that of women at any age. There is a wide sex difference in circulating testosterone concentrations and a reproducible dose-response relationship between circulating testosterone and muscle mass and strength as well as circulating hemoglobin in both men and women. These dichotomies largely account for the sex differences in muscle mass and strength and circulating hemoglobin levels that result in at least an 8% to 12% ergogenic advantage in men. Suppression of elevated circulating testosterone of hyperandrogenic athletes results in negative effects on performance, which are reversed when suppression ceases. Based on the nonoverlapping, bimodal distribution of circulating testosterone concentration (measured by liquid chromatography-mass spectrometry)-and making an allowance for women with mild hyperandrogenism, notably women with polycystic ovary syndrome (who are overrepresented in elite athletics)-the appropriate eligibility criterion for female athletic events should be a circulating testosterone of <5.0 nmol/L. This would include all women other than those with untreated hyperandrogenic disorders of sexual development and noncompliant male-to-female transgender as well as testosterone-treated female-to-male transgender or androgen dopers.

The torso integration hypothesis revisited in Homo sapiens: Contributions to the understanding of hominin body shape evolution

OBJECTIVES

Lower thoracic widths and curvatures track upper pelvic widths and iliac blades curvatures in hominins and other primates (torso integration hypothesis). However, recent studies suggest that sexual dimorphism could challenge this assumption in Homo sapiens. We test the torso integration hypothesis in two modern human populations, both considering and excluding the effect of sexual dimorphism. We further assess covariation patterns between different thoracic and pelvic levels, and we explore the allometric effects on torso shape variation.

MATERIAL AND METHODS

A sex-balanced sample of 50 anatomically connected torsos (25 Mediterraneans, 25 Sub-Saharan Africans) was segmented from computed tomography scans. We compared the maximum medio-lateral width at seventh-ninth rib levels with pelvic bi-iliac breadth in males and females within both populations. We measured 1,030 (semi)landmarks on 3D torso models, and torso shape variation, mean size and shape comparisons, thoraco-pelvic covariation and allometric effects were quantified through 3D geometric morphometrics.

RESULTS

Females show narrow thoraces and wide pelves and males show wide thoraces and narrow pelves, although this trend is more evident in Mediterraneans than in Sub-Saharans. Equal thoracic and pelvic widths, depths and curvatures were found in absence of sexual dimorphism. The highest strength of covariation was found between the lowest rib levels and the ilia, and allometric analyses showed that smaller torsos were wider than larger torsos.

CONCLUSIONS

This is the first study testing statistically the torso integration hypothesis in anatomically connected torsos. We propose a new and more complex torso integration model in H. sapiens with sexual dimorphism leading to different thoracic and pelvic widths and curvatures. These findings have important implications in hominin body shape reconstructions.

Is the Pelvis Sexually Dimorphic in Turtles?

Variation in the pelvis is intrinsically linked to life history evolution. This is perhaps best exemplified by sexually dimorphic pelvic variation in bipedal primates. Yet, whether this trend is applicable to other taxa is unclear. Using turtle anatomy as a model, I tested the hypothesis that the pelvis is also sexually dimorphic in egg-laying tetrapods. I sampled a natural turtle population with female-biased sexual size dimorphism (i.e., larger females). I show that the area of the egg canal (pelvic aperture) is greater in females. Morphological differences between sexes were predicted by body size, such that skeletal shape deformation of the female ilium increased proportionally with pelvic aperture area. These results suggest that sexual pelvic dimorphism might be indirectly maintained by selection for large female size, consistent with the pelvic constraint hypothesis in reptiles. However, subsampling of similarly sized individuals revealed that pelvic aperture area and shape may vary in disproportion to body size. Comparisons of pelvic ontogenetic trajectories across multiple lineages are needed to clarify the occurrence of sexual pelvic dimorphism in turtles and other egg-laying tetrapods. My findings provide impetus to further explore how sex-specific functional demands influence the architecture of the pelvic girdle. Anat Rec, 2018. © 2018 Wiley Periodicals, Inc.