Does pregnancy and/or shifting positions create more room in a woman's pelvis?

OBJECTIVE

The purpose of this study was to assess the impact of different positions on pelvic diameters by comparing pregnant and nonpregnant women who assumed a dorsal supine and kneeling squat position.

STUDY DESIGN

In this cohort study from a tertiary referral center in Germany, we enrolled 50 pregnant women and 50 nonpregnant women. Pelvic measurements were obtained with obstetric magnetic resonance imaging pelvimetry with the use of a 1.5-T scanner. We compared measurements of the depth (anteroposterior (AP) and width (transverse diameters) of the pelvis between the 2 positions.

RESULTS

The most striking finding was a significant 0.9-1.9 cm increase (7-15%) in the average transverse diameters in the kneeling squat position in both pregnant and nonpregnant groups. The average bispinous diameter in the pregnant group increased from 12.6 cm ± 0.65 cm in the supine dorsal to 14.5 cm ± 0.64 cm (P < .0001) in the kneeling squat; in the nonpregnant group the increase was from 12 cm ± 0.76 cm to 13.9 cm ± 1.04 cm (P < .0001). The average bituberous diameter in the pregnant group increased from 13.6 cm ± 0.93 cm in the supine dorsal to 14.5 cm ± 0.83 cm (P < .0001) in the kneeling squat position; in the nonpregnant women the increase was from 12.6 cm ± 0.92 cm to 13.5 cm ± 0.88 cm (P < .0001).

CONCLUSION

A kneeling squat position significantly increases the bony transverse and anteroposterior dimension in the mid pelvic plane and the pelvic outlet. Because this indicates that pelvic diameters change when women change positions, the potential for facilitation of delivery of the fetal head suggests further research that will compare maternal delivery positions is warranted.

ANTHROPOMETRIC STUDY OF ISCHIOPUBIC INDEX OF THE ISOKO AND BENIN IN NIGERIA

BACKGROUND

The ischiopubic index is calculated by dividing the pubic length by the ischial length and multiplying by 100. It has been said to be one of the parameters affecting the pelvic inlet and this is of interest to obstetricians and anatomic anthropologists.

OBJECTIVES

To determine and compare the pubic length, ischial length andischiopubic index among the males and females of Isoko and Bini ethnic groups of Nigeria.

DESIGN

A retrospective cross sectional study.

SETTING

University of Benin teaching hospital (UBTH), Irrua Specialist teaching hospital (ISTH) and Eku Baptist Hospital.

SUBJECTS

Four hundred antero-posterior radiographs; two hundred for the Isoko (males 105 and females 95) and two hundred also for the Bini (males 110 and females 90) adult pelvis in the age range of 18 - 65 years were evaluated.

RESULTS

Pubic length, ischial length, and ischiopubic index were measured. The mean pubic length, mean ischial length and mean ischiopubic index of Isoko males are respectively (mm) 78.42 ± 3.40, 69.41 ± 5.10, 75.2-97.5, 87.52 ± 1.30. The range and point of demarcation are (mm): 75.2-97.5, < 86.22. For Isoko females, the mean pubic length, mean ischial length and mean ischiopubic index are (mm): 81.20 ± 5.0, 74.30 ± 6.10, 106.21 ± 9.10. The range and demarcation point are (mm): 87-125.10, < 97.11. The mean pubic length, mean ischial length and mean ischiopubic index of Bini males are respectively (mm): 74.32 ± 5.40, 82.71 ± 7.20, 88.72 ± 2.40. The range and point of demarcation are (mm) 70-98,< 86.32. For Bini females they are (mm); 86.48 ± 4.20, 78.61± 7.41, 112.21 ± 7.71. The range and point of demarcation are (mm): 84.1-132.50, < 104.50 respectively.

CONCLUSION

The study showed sexual dimorphism in the ischipubic index of the study population and a significant difference in actual mean values and demarking points between the two population groups studied. This contributes growing database of anthropologically and obstetrically significant data for ethnic groups in Nigeria and could help in identification of skeletal remains in the hitherto restive Nigerian Niger-Delta region.

Tactile surgical navigation system for complex acetabular fracture surgery

The authors describe a tactile surgical navigation system using custom 3-dimensional (3D) models of the bony pelvis for complex acetabular fracture surgery. The bone area of interest was extracted from the Digital Imaging and Communications in Medicine (DICOM) data of computed tomography scans. A standard triangulated language file was used to create 3D models of the bony pelvis by layered manufacturing using a 3D printer and non-cytotoxic, sterilizable, acrylic-based photopolymers. No infections and no toxic or other adverse events were observed. The models were useful for preoperative assessment, planning, and simulation; intraoperative assessment; obtaining informed consent; and education.

Anatomical study of anterior column screw tunnels through virtual three-dimensional models of the pelvis

We created 66 male and 74 female virtual three-dimensional models of the pelvis based on computed tomography data from 140 patients. Virtual cylindrical bolts (VCBs) were placed in the anterior column (AC), which was then resliced serially along the bolt's long axis. AC screw tunnel mainly comprises two long, narrow triangular prisms [zone III (acetabular fossa) and zone V (obturator foramen)]--forming the III/V angle--linked by a larger, shorter cylinder [zone IV (acetabular notch)]. VCBs' mean length and maximum diameter were 111.13 ± 7.33 and 7.37 ± 1.90 mm, respectively. The models' anatomical zone lengths were similar between the sexes. Zone V's narrowest diameters and the III/V angles were significantly different. VCBs >6.5 mm were accommodated in 65 of 66 male models and 31 of 74 female models. VCBs >5.0 and <6.5 mm were accommodated in one male and 30 female models. Eleven female models accommodated only VCBs >3.5 and <5.0 mm. However, to 13 female pelvic models with maximum VCB accommodation of <5 mm for the anterior column, the maximum diameter of the VCBs was 8.23 ± 1.22 mm in medial passage and 10.3 ± 1.91 mm in lateral passage, respectively. Percutaneous fixation of the AC with screws is a safe technique, even though in Chinese female patients. The narrowest diameters in zone V and the III/V angles are the key factors for application of AC screws. Female patients with a smaller interosseous space at zone V and a large III/V angle can accommodate segmental passage screws.

Fully automated localization of multiple pelvic bone structures on MRI

In this paper, we present a fully automated localization method for multiple pelvic bone structures on magnetic resonance images (MRI). Pelvic bone structures are currently identified manually on MRI to identify reference points for measurement and evaluation of pelvic organ prolapse (POP). Given that this is a time-consuming and subjective procedure, there is a need to localize pelvic bone structures without any user interaction. However, bone structures are not easily differentiable from soft tissue on MRI as their pixel intensities tend to be very similar. In this research, we present a model that automatically identifies the bounding boxes of the bone structures on MRI using support vector machines (SVM) based classification and non-linear regression model that captures global and local information. Based on the relative locations of pelvic bones and organs, and local information such as texture features, the model identifies the location of the pelvic bone structures by establishing the association between their locations. Results show that the proposed method is able to locate the bone structures of interest accurately. The pubic bone, sacral promontory, and coccyx were correctly detected (DSI > 0.75) in 92%, 90%, and 88% of the testing images. This research aims to enable accurate, consistent and fully automated identification of pelvic bone structures on MRI to facilitate and improve the diagnosis of female pelvic organ prolapse.

Three-dimensional morphologic study of the child's hip: which parameters are reproducible?

BACKGROUND

Biplanar x-ray images obtained with patients in a standing weightbearing position allow reconstruction of three-dimensional (3-D) bone geometries, with lower radiation exposure than CT scans and better bone definition than MRI.

QUESTIONS/PURPOSES

We determined the reproducibility of 3-D parameter values of the hips and pelves of healthy children, using biplanar x-ray images.

METHODS

We built 3-D models of the hips of 33 children without musculoskeletal problems: 10 subjects younger than 9 years and 23 who were 9 years or older. Three anatomic landmarks and nine hip and pelvic parameters were computed for each reconstruction. To determine the reliability of these landmarks and parameters, each bone was reconstructed four times by two independent observers, leading to a total of 264 reconstructions, and parameters were studied for the two age groups and compared between dancers and nondancers.

RESULTS

Taking into account all reconstructions, the interobserver reproducibility ranged from 2 to 4 mm for landmark positions or distance parameters, and 2° to 6° for angular parameters. The most reproducible point was the center of the femoral head (range, 0.2-17 mm). The distance between this center and its projection on the plane fitting the edge of the acetabulum, and the pelvic tilt were the most reproducible parameters.

CONCLUSIONS

Reproducible 3-D reconstructions of hips and pelves of children were possible using biplanar x-ray images, regardless of the children's ages. Although we report preliminary values for 3-D parameters in healthy children's hips, further work is needed to obtain direct validation of our parameters using CT reconstructions of cadaveric specimens to avoid high doses of radiation.

Radiographic examination of the greater sciatic notch in determining the sex among Iranian people

The distinctive morphology of the human innominate bone (os coxae) and its clear sexual dimorphism make it of interest from anatomical, anthropological and forensic points of view. The features of the greater sciatic notch of the coxae are characteristic and are commonly used to determine sex in unknown individuals. In this study, several measurements of the greater sciatic notch, e.g. width (AB), depth (OC) and width of the posterior segment (OB) were taken and indices I and II were calculated in 64 adult (32 men and 32 women) and side (right: left) coxae radiography (A-P view). Results indicated that out of all the parameters studied, width of the notch (right and left) (P < 0.001), posterior segment width (right and left) (P < 0.001), right (P = 0.036) and left (P = 0.008) index II of notch were found to be significantly greater in women as compared with men. Discriminant function analysis showed that the accuracy of sex determination varied from 100% in the men and 40% in the women groups to 70% for the total group. These results can be used as an aid to the identification of human skeletal remains in Iranian people.

A new small-bodied azhdarchoid pterosaur from the lower cretaceous of England and its implications for pterosaur anatomy, diversity and phylogeny

BACKGROUND

Pterosaurs have been known from the Cretaceous sediments of the Isle of Wight (southern England, United Kingdom) since 1870. We describe the three-dimensional pelvic girdle and associated vertebrae of a small near-adult pterodactyloid from the Atherfield Clay Formation (lower Aptian, Lower Cretaceous). Despite acknowledged variation in the pterosaur pelvis, previous studies have not adequately sampled or incorporated pelvic characters into phylogenetic analyses.

METHODOLOGY/PRINCIPAL FINDINGS

The new specimen represents the new taxon Vectidraco daisymorrisae gen. et sp. nov., diagnosed by the presence of a concavity posterodorsal to the acetabulum and the form of its postacetabular process on the ilium. Several characters suggest that Vectidraco belongs to Azhdarchoidea. We constructed a pelvis-only phylogenetic analysis to test whether the pterosaur pelvis carries a useful phylogenetic signal. Resolution in recovered trees was poor, but they approximately matched trees recovered from analyses of total evidence. We also added Vectidraco and our pelvic characters to an existing total-evidence matrix for pterosaurs. Both analyses recovered Vectidraco within Azhdarchoidea.

CONCLUSIONS/ SIGNIFICANCE

The Lower Cretaceous strata of western Europe have yielded members of several pterosaur lineages, but Aptian pterosaurs from western Europe are rare. With a pelvis length of 40 mm, the new animal would have had a total length of c. 350 mm, and a wingspan of c. 750 mm. Barremian and Aptian pterodactyloids from western Europe show that small-bodied azhdarchoids lived alongside ornithocheirids and istiodactylids. This assemblage is similar in terms of which lineages are represented to the coeval beds of Liaoning, China; however, the number of species and specimens present at Liaoning is much higher. While the general phylogenetic composition of western European and Chinese communities appear to have been approximately similar, the differences may be due to different palaeoenvironmental and depositional settings. The western Europe pterodactyloid record may therefore be artificially low in diversity due to preservational factors.

Biometric characteristics of the pelvis in female-to-male transsexuals

The objective of the study was to evaluate the metric features of pelvises of 24 female-to-male (FtM) transsexuals as compared to control groups of 24 healthy males and 24 healthy females. The participants had their pelvises X-rayed with the same X-ray apparatus and in the same position. Seventeen measurements were taken on the basis of X-ray pictures of FtM transsexuals' pelvises and both comparison groups. Additionally, their body height was compared. The results showed that FtM transsexuals having female body height represent an intermediate size of three pelvic features and male values of five variables. In order to develop a model based on metric variables of the pelvis that would best discriminate the FtM transsexuals, the control females, and the control males, a discriminant analysis was applied. The model included four variables out of 17 metric features: the height of the pubic symphysis, the greatest pelvic breadth, the interischial distance, and the acetabular diameter. The model was found to be the best in discriminating males from females and FtM transsexuals, but considerably less effective in discriminating transsexuals from the two control groups. The results demonstrate that a number of FtM transsexuals' pelvic measurements reveal "masculinization," which confirms current results demonstrating a shift in the somatometric traits of transsexual females towards male traits. A discriminant analysis based only on pelvic metric features shows some differences between the size of the pelvis and chromosomal sex in FtM transsexuals, which might indicate a biological basis for gender identity disorder.

Three-dimensional terahertz computed tomography of human bones

Three-dimensional terahertz computed tomography has been used to investigate dried human bones such as a lumbar vertebra, a coxal bone, and a skull, with a direct comparison with standard radiography. In spite of lower spatial resolution compared with x-ray, terahertz imaging clearly discerns a compact bone from a spongy one, with strong terahertz absorption as shown by additional terahertz time-domain transmission spectroscopy.

Comparison of methods to determine sex by evaluating the greater sciatic notch: Visual, angular and geometric morphometrics

Sex estimation is the first step for biological profile reconstruction of an unknown skeleton (archaeological or contemporary) and consequently for positive identification of skeletal remains recovered from forensic settings. Several tools have been developed using different osseous structures. With the intention to provide an objective method comparison, we reported the analysis of three different methods (visual, metric and geometric morphometrics) for sex assessment of the greater sciatic notch. One hundred and thirty pelvic bones (45.4% females and 54.6% males) from the National Autonomous University of Mexico Skeletal Collection pertaining to the contemporary Mexican population were analyzed. We used the ROC-analysis to test between desired false positive thresholds (1-specificity) and expected true positive rates (sensitivity) in order to predict the best approach to sex assessment. The comparison of the area under the ROC-curves shows significant differences among visual and metric methods. At the same time, the analysis suggested that higher morphological variation among the sexes is independent of the methodological approach. The results indicate that the metric (angle), with a high percent of indeterminate cases (34.6%), and visual, with 26.2% of the cases allocated as intermediate cases, were poorly accurate; we cannot recommend these techniques for sexing an unknown specimen. On the other hand, the geometric morphometrics approach improves sex estimation in 82.3% of correctly classified individuals with more than 95% of posterior probability. In addition to the method comparison, the major sexual variation of the greater sciatic notch was determined to be located on its posterior border.

Ethnic and sex differences in bone marrow adipose tissue and bone mineral density relationship

The relationship between bone marrow adipose tissue and bone mineral density is different between African Americans and Caucasians as well as between men and women. This suggests that the mechanisms that regulate the differentiation and proliferation of bone marrow stromal cells may differ in these populations.

INTRODUCTION

It has long been established that there are ethnic and sex differences in bone mineral density (BMD) and fracture risk. Recent studies suggest that bone marrow adipose tissue (BMAT) may play a role in the pathogenesis of osteoporosis. It is unknown whether ethnic and sex differences exist in the relationship between BMAT and BMD.

METHODS

Pelvic BMAT was evaluated in 455 healthy African American and Caucasian men and women (age 18-88 years) using whole-body T1-weighted magnetic resonance imaging. BMD was measured using whole-body dual-energy X-ray absorptiometry.

RESULTS

A negative correlation was observed between pelvic BMAT and total body BMD or pelvic BMD (r = -0.533, -0.576, respectively; P < 0.001). In multiple regression analyses with BMD as the dependent variable, ethnicity significantly entered the regression models as either an individual term or an interaction with BMAT. Menopausal status significantly entered the regression model with total body BMD as the dependent variable. African Americans had higher total body BMD than Caucasians for the same amount of BMAT, and the ethnic difference for pelvic BMD was greater in those participants with a higher BMAT. Men and premenopausal women had higher total body BMD levels than postmenopausal women for the same amount of BMAT.

CONCLUSIONS

An inverse relationship exists between BMAT and BMD in African American and Caucasian men and women. The observed ethnic and sex differences between BMAT and BMD in the present study suggest the possibility that the mechanisms regulating the differentiation and proliferation of bone marrow stromal cells may differ in these populations.

A pilot investigation into the effects of different office chairs on spinal angles

PURPOSE

To investigate the effects of four office chairs on the postural angles of the lumbopelvic and cervical regions.

RESEARCH QUESTION

Which chair(s) produce an "ideal" spinal posture?

METHODS

An experimental same subject design was used involving healthy subjects (n = 14) who conducted a typing task whilst sitting on four different office chairs; two "dynamic" chairs (Vari-Kneeler and Swopper), and two static chairs (Saddle and Standard Office with back removed). Data collection was via digital photogrammetry, measuring pelvic and lumbar angles, neck angle and head tilt which were then analysed within MatLab. A repeated measures ANOVA with Bonferroni corrections for multiple comparisons was conducted.

RESULTS

Statistically significant differences were identified for posterior pelvic tilt and lumbar lordosis between the Vari-Kneeler and Swopper chairs (p = 0.006, p = 0.001) and the Vari-Kneeler and Standard Office chairs (p = 0.000, 0.000); and also for neck angle and head tilt between the Vari-Kneeler and Swopper chairs (p = 0.000, p = 0.000), the Vari-Kneeler and Saddle chairs (p = 0.002, p = 0.001), the Standard Office and Swopper chairs (p = 0.000, p = 0.000), and the Standard Office and Saddle chairs (p = 0.005, p = 0.001). This study confirms a within region association between posterior pelvic tilt and lumbar lordosis, and between neck angle and head tilt. It was noted that an ideal lumbopelvic position does not always result in a corresponding ideal cervical position resulting in a spinal alignment mismatch.

CONCLUSION

In this study, the most appropriate posture for the lumbopelvic region was produced by the Saddle chair and for the cervical region by both the Saddle and Swopper chairs. No chair consistently produced an ideal posture across all regions, although the Saddle chair created the best posture of those chairs studied. Chair selection should be based on individual need.

Posterior pelvic ring injuries: when to perform open reduction and internal fixation

Unstable posterior pelvic ring injuries are commonly treated with percutaneous iliosacral screw fixation. Despite the efficiency of the minimally invasive technique, complications and failures occur. To maximize reduction quality and fixation stability, open techniques for pelvic ring fixation exist. Timing, approaches, clamp positioning, and implant options determine the effectiveness of the open techniques.

Evaluation of pelvis slope and flattening on children gymnasts by Biophotogrammetry technique

This work proposes to detect possible affections or abnormalities in pelvic belt region in a group of rhythmic gymnastics due to the need for studies in the field of biomechanics and structural evaluation of human being. The methodology for this study used a tool called Biophotogrammetry. This technique has analyzed, through scanned images, the structural pelvic girdle bone profile of 64 practitioners of rhythmic gymnastics. The results of this study have presented weighted averages of 45.07±9.78° between the right pelvic slope (RPS) and left pelvic slope (LPS) and 91.74±2.50° for flattening of the pelvis (FP). Therefore, it is concluded that the Biophotogrammetry technique provides data related to the gold standard radiography test, used as reference for the pelvic girdle measurements.

[Anthropometric analysis of obstetrical pelvis from Neolithic area: obstetrical consequences. Preliminary study]

OBJECTIVES

To study female pelves from Neolithic area (5000 years AD) in order to better understand the evolution of obstetrical mecanisms.

MATERIALS AND METHODS

The fossil material comprised 73 Homo sapiens pelves: we reconstructed all the 20 adult female bony pelves. We realised the shape and morphometric analysis of the pelvic cavity. Changes in pelvic neolithic morphology were compared with pelvic modern morphology.

RESULTS

The pelves of prehistoric female were similar in shape with modern female. However, they differ in relative dimensions (transversal diameter of the pelvis inlet: respectively 118 mm vs 125 mm, p=0.02).

DISCUSSION AND CONCLUSION

Reconstructions based on Neolithic hominin fossils suggest that obstetrical mechanisms were probably common to Neolithic and modern humans: childbirth would probably require social adaptations and risks of perinatal and obstetric complications were undoubtedly high. However, the differences in morphometric analysis could suggest a change of human pelvis and raise the question of the evolution in obstetrical mechanisms in the future.

The role of the anterior border of the hip bone in sexual dimorphism: a morphometric study in the North Indian population

Understanding sexual dimorphism is very important in studies of human evolution and skeletal biology. The ability to determine sex from unknown skeletal remains is vital and methods to do this on the various bones of the human skeleton have been researched extensively especially in the studies related to forensic anthropology. The distinctive morphology and clear sexual dimorphism of the hip bone makes it an ideal bone for sex determination. Whereas the roles of the parameters of its posterior border (including the greater sciatic notch) are well established, those of the anterior border are not much explored. The present study was designed to establish the morphometric pattern of the anterior border of the hip bone and its role in sexual dimorphism. Material for the current investigation comprised 100 hip bones belonging to 50 cadavers ([M:F = 80:20] and [R:L = 50:50]) obtained from the Department of Anatomy, Government Medical College, Amritsar, Punjab, India. Sixteen parameters of the anterior border were taken and three indices were calculated. Eight parameters were significantly greater in males: (i) straight distance anterior superior iliac spine (ASIS)-symphyseal surface (SS); (ii) straight distance ASIS-pubic tubercle (PT); (iii) straight distance anterior inferior iliac spine (AIIS)-SS; (iv) straight distance AIIS-PT; (v) arch of anterior interspinous notch (ASIS-AIIS); (vi) arch between AIIS and ilio-pubic (IP); (vii) depth of notch between AIIS and IP; (viii) arch of anterior border (ASIS-SS). The results of the present study could be helpful in pronouncing an opinion, for a single specimen, about its origin in general terms or sex.

Role of the greater sciatic notch of the hip bone in sexual dimorphism: a morphometric study of the north Indian population

The distinctive morphology and sexual dimorphism of the human hip bone makes it of interest from the anatomical, anthropological and forensic points of view. The shape of the greater sciatic notch has attracted great attention in the past. In the current investigation, an attempt has been made to find the baseline data of various parameters pertaining to the greater sciatic notch of 100 hip bones of known sex (male:female = 80:20) and side (right:left = 50:50), obtained from the Department of Anatomy, Government Medical College, Amritsar, Punjab, India, during the period 2007-2009. Seven parameters of the notch, viz. width, depth, posterior segment width, total angle, posterior segment angle, index I and index II of the greater sciatic notch were studied. The results thus obtained were compiled, tabulated, statistically analysed and were compared with the accessible literature. Out of all the parameters studied, width of the notch, posterior segment width, total angle, posterior segment angle and index II of notch were found to be significantly greater in women as compared with men. Thus the greater sciatic notch can serve as a reliable sex indicator even when the complete hip bone has not been well preserved.

Development and testing of a more realistic pelvis for the Hybrid III 6-year-old ATD

OBJECTIVE

Design and test a new pelvis for the Hybrid III 6-year-old (6YO) anthropometric test device (ATD) with a more humanlike bone structure, flesh contour, and flesh stiffness intended to provide more realistic interaction with belt restraints.

METHODS

Target geometry for the new pelvis bone was based on a 3D model of the skeletal pelvis derived from statistical analysis of pediatric computed tomography (CT) scans. The current pelvis bone was reshaped to better match the target geometry, with a particular emphasis on the contour in the areas of belt interaction. The prominence representing the anterior-superior iliac spine (ASIS) was lowered by 15 mm. The pelvis flesh was molded using softer vinyl while maintaining a 10-mm flesh margin over the ASIS. A series of 20 sled tests was conducted to compare the performance of the modified pelvis with the current Hybrid III pelvis.

RESULTS

In a series of sled tests using a range of belt anchorage locations, a dummy equipped with the new pelvis did not submarine in conditions where the lap belt was positioned below the ASIS. Tests run with the lap belt initially positioned over the ASIS resulted in submarining, unlike tests performed with the standard dummy pelvis.

CONCLUSIONS

The new pelvis for the 6YO Hybrid III ATD better represents the skeletal and flesh geometry of similar-sized children. The ATD equipped with the new pelvis is more sensitive to lap belt geometry than the standard ATD. The modified ATD may provide an improved assessment of booster seats and belt restraints intended for child occupants.

The impact of racial metric variation in the os coxae on the morphological assessment of sex

This study examines whether sex determination based on morphological traits in the os coxae is impacted by racial quantitative variation. Nineteen traits were evaluated independently by two observers in 876 os coxae. Chi-square test was used on a random sample of 400 individuals to assess whether the distribution of correct sex assessment varied for white and black individuals based on each trait individually and all 19 traits collectively, as well as on inter-observer agreement in correct sex assessment. Results indicate that accuracy of sex assessment varied between white and black individuals in certain individual traits; however, accuracy was not impacted when all traits were considered together. Furthermore, traits that showed significant variation in correct sex assessment between races generally were not related to size, but instead were "discrete." Finally, analyses of inter-observer variation suggest that disparities in sex assessment for some traits may be related to differences in trait interpretation between observers rather than morphological dissimilarities between races.