The evolution, development and skeletal identity of the crocodylian pelvis: revisiting a forgotten scientific debate.

Unlike most tetrapods, in extant crocodylians the acetabulum is formed by only two of the three skeletal elements that constitute the pelvis, the ilium, and ischium. This peculiar arrangement is further confused by various observations that suggest the crocodylian pelvis initially develops from four skeletal elements: the ilium, ischium, pubis, and a novel element, the prepubis. According to one popular historical hypothesis, in crocodylians (and many extinct archosaurs), the pubis fuses with the ischium during skeletogenesis, leaving the prepubis as a distinct element, albeit one which is excluded from the acetabulum. Whereas the notion of a distinct prepubic element was once a topic of considerable interest, it has never been properly resolved. Here, we combine data gleaned from a developmental series of Alligator mississippiensis embryos, with a revised interpretation of fossil evidence from numerous outgroups to Crocodylia. We demonstrate that the modern crocodylian pelvis is composed of only three elements: the ilium, ischium, and pubis. The reported fourth pelvic element is an unossified portion of the ischium. Interpretations of pelvic skeletal homology have featured prominently in sauropsid systematics, and the unambiguous identification of the crocodylian pubis provides an important contribution to address larger scale evolutionary questions associated with locomotion and respiration.

Does the Latissimus dorsi insert on the iliac crest in man? Anatomic and ontogenic study.

OBJECTIVE: The Latissimus dorsi muscle is usually considered as inserted on the iliac crest, but it is separated from it by the thoracolumbar fascia. In our experience based on the harvesting of pedicled Latissimus dorsi flaps to cover cervicofacial loss of substances, we have found that in some cases, the muscular fibers of the anterior border of the muscle are directly inserted on the iliac crest. In these cases, the harvesting of the flap could be more distal. METHODS: To determine whether this direct muscular insertion is frequent or not, we performed dissections on 30 fresh cadavers of the lower insertion of the Latissimus dorsi muscle, and 6 dissections of human fetuses to study the ontogeny of these insertions. RESULTS: The Latissimus dorsi muscle presented direct muscular insertions on the iliac crest in 13.33% of cases. The fetal dissections showed that before 30 weeks of development, the anterior part of the muscle was directly inserted on the iliac crest, and after it was separated from it by the thoracolumbar fascia. Although the harvesting of the Latissimus dorsi in continuity with the thoracolumbar fascia has been described in pedicled flaps, it is usually considered that it is impossible to harvest Latissimus dorsi musculocutaneous flaps in contact with the iliac crest, because there are no perforating vessels from the thoracolumbar fascia to the skin. According to our results, in some cases, it could be possible to harvest a pedicled musculo-cutaneous LD flap more distal that it is usually described.

Size and location of the kidneys during the fetal period.

PURPOSE: The aim of this study was to determine the morphometric development and location of the kidneys during the fetal period. METHODS: Three hundred and forty-four fetal kidneys, obtained from 172 human fetuses and aged between 9 and 40 weeks, were used in this study. Fetuses were divided into four groups according to the gestational weeks: first trimester, second trimester, third trimester, and full-term gestation. First, the anterior abdominal wall was dissected. Topographic localization of the kidneys in the abdominal cavity was then assessed. The distance between the inferior pole of the kidney and iliac crest was measured. The vertebral levels of the superior and the inferior poles and relations to ribs of the kidneys were determined. The distances between hilum of the kidneys and inferior vena cava, abdominal aorta, and midline of the vertebral column were determined. The dimensions (width, length, and thickness), weight, and volume of kidneys were measured. RESULTS: The results showed that the distance between the inferior poles of the kidneys and the iliac crest increases with gestational age. The vertebral levels of the superior and inferior poles of the kidneys increased during the fetal period. The level of the left kidney was higher than the level of the right kidney in the fetal period. The posterior surface relations to the ribs showed certain ascendance during gestation, corresponding to vertebral levels. However, fetal kidneys do not reach the same level as adults at full term. The kidneys move farther apart from the midline of the body during the fetal period. The dimensions, weight, and volume of the kidneys increased with gestational age during the fetal period. The ratio between kidney weights and fetal body weights were determined, and we observed that the ratio decreased during the fetal period. There were no sex or laterality differences in any parameter. CONCLUSIONS: The morphometric parameters and the location of the fetal kidneys were determined by the present study. This will also contribute to imaging of fetal kidneys and detection of kidney abnormalities in the intrauterine period. We hope that the present results can provide some useful findings for radiological (ultrasound and MR) studies.

Iliac crest angle: a novel sonographic parameter for the prediction of Down syndrome risk during the second trimester of pregnancy.

OBJECTIVES: To validate a new sonographic technique for the display and measurement of fetal iliac crest angle (ICA), and to determine the relative contribution of standardized fetal pelvic measurements for estimating risk of Down syndrome during the second trimester of pregnancy. METHODS: Three-dimensional ultrasonography of the fetal pelvis was performed during a second-trimester scan for genetic amniocentesis. A coronal view of the 'virtual pelvis' was obtained by applying a maximum intensity projection algorithm to visualize both iliac wings. Two different ICAs were measured from a coronal projection of the fetal pelvis (ICA-coronal 1 and ICA-coronal 2); the latter approach relied on using ischial tuberosities as reference landmarks. Next, a coronal projection of the fetal pelvis was rotated to demonstrate a rendered view of the axial fetal pelvis. Axial inner (ICA-inner), middle (ICA-middle) and outer (ICA-outer) ICAs were measured. The maximum anterior iliac distance measurement was defined as the widest separation between the most anterior points of the rendered iliac crests. The reproducibility of each ICA method was analyzed using Bland-Altman statistics. Simple and multiple logistic regression analysis determined the relative contribution of each parameter as a prenatal predictor of Down syndrome. RESULTS: Ninety-four normal fetuses and 19 fetuses with Down syndrome were examined. The ICA-middle and ICA-coronal 2 parameters were the most reproducible angle measurements. The mean +/- SD ICA-middle measurement for fetuses with Down syndrome was significantly greater than that for normal subjects (94.5 +/- 9.8 degrees vs. 83.1 +/- 6.5 degrees ; P < 0.001). The mean +/- SD ICA-coronal 2 angle measurement for fetuses with Down syndrome was slightly greater than that for normal subjects (57.9 +/- 5.5 degrees vs. 51.9 +/- 7.1 degrees ; P = 0.0014). A multiple logistic regression model including ICA-middle and ICA-coronal 2 provided a predictive ability of 88.1% based on the area under the receiver-operating characteristics curve. This combination had a sensitivity of 94.4% for a false-positive rate of 5% in the detection of Down syndrome. CONCLUSIONS: Standardized iliac crest measurements of the fetal pelvis can be used to identify some fetuses at risk for trisomy 21 during the second trimester of pregnancy.

Development of the fetal ilium--challenging concepts of bipedality.

Macroradiographs of 30 human fetal and neonatal ilia were analysed to investigate the early pattern of trabecular bone organization prior to the influences of direct weight-bearing locomotion. Consistent and well-defined patterns of internal organization were identified within the fetal and neonatal ilium, which correspond with previously recognized regions that have been attributed directly to forces associated with bipedal locomotion. This study proposes that patterns previously attributed to weight-bearing locomotive responses are present in the earliest stages of the development of this bone. It is suggested that the rudimentary scaffold seen in the fetal and neonatal ilium could indicate a predetermined template upon which locomotive influences may be superimposed and perhaps reinforced at a later age. Alternatively, this early pattern may mimic the adult form due to the effects of in-utero limb movement activity even though it is not weight bearing. This is a preliminary study that will be supported in a further communication with three-dimensional micro-computed trabecular analysis.

Avian pelvis originates from lateral plate mesoderm and its development requires signals from both ectoderm and paraxial mesoderm.

The pelvic girdle is composed of three skeletal elements: ilium, pubis, and ischium. In comparison with other parts of the postcranial skeleton, its development is not well known to date. To elucidate the embryonic origin of the avian pelvic girdle and the signaling centers that control its development, we have performed extirpation and quail-to-chick grafting experiments. The results reveal that the entire pelvic girdle originates from the somatopleure at somite levels 26 to 35. No somitic cell contribution to skeletal elements of the pelvis has been detected. Removal of the surface ectoderm covering the lateral plate mesoderm has revealed that ectodermal signals control the development of the pelvic girdle, especially the formation of the pubis and ischium. The impaired development of the ischium and pubis correlates with the downregulation of Pax1 and Alx4, two transcription factors that control the normal development of the ischium and pubis. Although of somatopleural origin, the development of the ilium depends on somitic signals. Insertion of a barrier between somites and somatopleure disrupts the expression of Emx2 and prevents normal development of the ilium but does not affect the expression of Pax1 or Alx4 and the development of the pubis and ischium. Thus, the development of the ilium, but not of the pubis and ischium, depends on somitic and ectodermal signals.

Automated method to measure trabecular thickness from microcomputed tomographic scans and its application.

Trabeculae form the internal bony mesh work and provide strength to the bone; interconnectivity, overall density, and trabecular thickness are important measures of the integrity of the internal architecture. Such strength is achieved only gradually during ontogeny, whereby an increase in trabecular thickness precedes an increase in mineralization. Loss of bone mass later in life may be compensated for by thickening of the remaining trabeculae. These facts, and the role of trabeculae in mineral homeostasis, highlight the importance of investigating trabecular thickness within and between species. While nondestructive imaging techniques (i.e., muCT and MRI) are becoming increasingly popular, quantification of trabecular thickness using nondestructive techniques has proved difficult owing to limitations imposed by scanning parameters, uniform thresholding, and partial volume averaging. Here we present a computer application, which aims to overcome these problems. Validation is carried out against a phantom and against trabecular thickness measured in corresponding histological sections. Good agreement was found between these measurements. Furthermore, when trabecular thickness is recorded for modern human fetal ilia, a trend toward trabecular thickness increase is found and is in line with reports of ontogenetic morphometric changes using histological sections. However, there are discrepancies. These may in part be due to partial volume effects of obliquely oriented structures. More crucial, however, are problems inherent in histological sections, e.g., shrinkage and distortion, especially where differences in mineralization are concerned; this may affect biological interpretations.

[Anthropometric and densitometric investigations into the prenatal development of the human pelvic bone]. / Rozwój kosci miednicznej plodów ludzkich w swietle badan antropometrycznych i densytometrycznych.

The aim of this work was to study the prenatal development and mineralization of ossification centres (OC) in the pelvic bone (ilium, ischium, and pubic bone) using radiography and optical density measurements. The material consisted of 90 human fetuses (29 males and 61 females) with a gestational age of 12 to 28 weeks. Both pelvic bones were obtained and radiographs directed at OC were taken. Analysis was done with a computer after digitalization of the radiographs. The area of each OC was determined. With prior standardisation, optical density of the radiographs was measured and mean density was calculated for each OC. OC appear in the ischium between week 12 and 16 and in the pubic bone between week 19 and 24 of gestation. The pelvic bone does not demonstrate sexual differences during prenatal development. Anthropometric findings regarding OC of the pelvic bone correlated positively with fetal age. The dynamics of OC formation varies, being fastest in the case of ilium in the direction from acetabulum to extension of the anterior margin of greater sciatic notch. The mineral density of the pelvic bone increases with age and the mineralization rate changes throughout fetal life.

Fetal bony pelvis in the bladder exstrophy complex: normal potential for growth?

OBJECTIVES: To provide the first look at the bony histologic features of fetuses with the exstrophy complex, specifically evaluating the endochondral ossification, stage of development, and microscopic potential for normal growth. METHODS: Three fetuses between 28 and 30 weeks of gestation, one with classic bladder exstrophy, one with cloacal exstrophy, and one control, were obtained from France. The bony pelves were dissected and preserved in formalin, and multiple representative sections were sliced from all pelvic areas: pubis, ischium, ilium, and sacrum. These slices were sequentially processed as slides, stained with hematoxylin-eosin, and evaluated microscopically for histologic changes, developmental stage, and degree of endochondral ossification. RESULTS: All slides from the three specimens showed cartilage analogue with endochondral ossification. Histologically the exstrophy specimens were identical to the control and appeared completely normal; bone development was occurring at an expected rate with the potential for continued normal growth. CONCLUSIONS: These new findings illustrate that fetal bone in the exstrophy complex displays normal microscopic growth patterns and unhindered endochondral ossification at 28 weeks of gestation, well beyond the embryologic period. With no evident microscopic bony defect, the gross bony anomalies in exstrophy should be surgically correctable, leading us to conclude that early reapproximation of the physiologic shape of the pelvis could lead to more normal gross bone growth, decreased shortage of bone, and a more appropriate distribution of the mechanical and developmental forces on a closed, normally functioning pelvic ring.

Sirenomelia sequence according to the distance between the first sacral vertebra and the ilia.

The development of the iliac bones and lower limbs are parallel processes depending on the normal ontogeny of the caudal blastema [O'Rahilly and Müller, 1989; Opitz, 1993; Opitz et al., 2000]. We hypothesized that the pathogenetic mechanisms leading to fused lower limbs would in parallel displace the ilia caudally and medially and that the degree of this displacement might correlate with the severity of the iliac and lower limb defects. Thus the purpose of the study was to test this hypothesis in a sample of 12 sirenomelic fetuses. The fetuses GA 16-39 weeks, spontaneously or therapeutically aborted, were radiographed in the frontal projection as part of a requested autopsy. From each radiograph, a line was drawn connecting the most cranial part or the two ilia. After that the distance was measured vertically between this line and the most cranial part of the first sacral vertebral body (iliac-sacral distance (ISD)). A second distance was measured horizontally between the most lateral part of the two iliae (bi-iliac distance (BD)). As a result, ISD correlates with the iliac/femur phenotype. Separate ilia and femora occur only in cases with normal ISD. Fused ilia or femora or both are seen only in fetuses with mildly increased ISD, whereas a single iliac bone and femur occur only in cases with greatly increased ISD. The increase of the ISD does not correlate with the severity of more distal limb involvement. There was a correlation between the ISD and the BD values; the higher the ISD, the shorter the BD. Based on these findings, we propose an extended classification of Sirenomelia to be tested by other researchers.

Fetal iliac angle measurements by three-dimensional sonography.

OBJECTIVE: To determine the technical reliability of fetal iliac angle measurements by three-dimensional sonography as a prenatal marker for Down syndrome. METHODS: Three-dimensional multiplanar views of the fetal pelvis were used to standardize iliac angle measurements from 35 normal second-trimester pregnancies. Measurement reliability for a single examiner and between two different examiners were analyzed by intraclass correlation. Normal iliac angle measurements were compared to those obtained from 16 fetuses with trisomy 21. RESULTS: The mean axial angle for normal fetuses was 79 +/- 5.5 degrees, which was significantly less than that observed in fetuses with trisomy 21 (87.7 +/- 4.9 degrees ) (P < 0.001). Iliac angles did not correlate with gestational age. Axial angles were reproducible between two examiners who measured the same multiplanar view of the pelvis. Inter- and intraobserver reliability were also acceptable after a standardized multiplanar view was independently obtained by each examiner (intraclass correlation = 0.91 for both). Coronal angles were unreliable because of difficulties with finding a reproducible measurement plane. For a false-positive rate of 5%, an axial angle threshold of 87 degrees correctly identified 56% of fetuses with trisomy 21. CONCLUSION: Axial iliac angle measurements are reliable by standardized three-dimensional multiplanar views of the pelvis and can be used to identify some fetuses at increased risk for trisomy 21.

The anterior iliac separation: alternative index for pelvic morphometry in fetuses with Down syndrome.

OBJECTIVE: The goal of this study was to assess the diagnostic use of an anterior iliac separation measurement as an alternative index for the iliac angle in the assessment of fetal pelvic morphometry. SUBJECTS AND METHODS: In 358 fetuses, the anterior iliac separation, iliac length, and iliac angle were prospectively measured on antenatal sonography. All measurements were obtained at two axial levels (superior and inferior). The gestational age of the fetus was recorded. The anterior iliac separation was normalized by iliac length, and coefficients of variation were calculated for all measurements. The effects of axial level and gestational age were assessed in a linear regression model. The diagnostic use of the anterior iliac separation relative to that of the iliac angle was assessed in a comparison of 24 fetuses with Down syndrome and 247 non-Down syndrome fetuses. RESULTS: The anterior iliac separation was less variable than the iliac angle at both superior and inferior levels. There were statistically significant effects for gestational age and axial level on both the anterior iliac separation and the iliac angle, but there was no significant effect for either factor when the anterior iliac separation was normalized by the iliac length. Comparing Down and non-Down syndrome fetuses, we found that the normalized anterior iliac separation had discriminating power similar to the iliac angle. CONCLUSION: The linear measurement of the anterior iliac separation has diagnostic properties similar to the iliac angle and is subject to less measurement variability. This simpler measurement may be particularly useful when normalized by the iliac length.

[Expression of sexual dimorphism in the fetal pelvic girdle]. / Expression du dimorphisme sexuel sur le bassin du foetus.

The objective of this study was to analyse the development of the foetal pelvis in order to define normal anatomic reference values as a function of gender and gestational age. The study population included 500 stillborn foetuses between the gestational ages of 18 and 41 weeks. Those foetuses without known demographic histories were strictly excluded. For each case studied, an AP radiograph was performed with the following parameters measured by two independent observers: pelvic width, inter-iliac width, inter-sciatic nodes, inter-pubic width and bi-ischial width. The correlation between these radiographic measurements and the gestational age as well as the gender was analysed. The result indicated that the inter-ischiatic distance is significantly greater in the female foetus after the 26-27th week of gestation (P < 0.0062). Standard growth for the female and the male foetal pelvis is proposed with potential application in the study of normal and pathological development of the foetus.

Echographic signs of trisomy 21 in the second trimester of pregnancy: actual value after analysis of the literature. / Signes échographiques de trisomie 21 au deuxième trimestre de la grossesse: valeur actuelle après analyse de la littérature.

OBJECTIVE: To evaluate the interest and to compare the major echographic signs of Down syndrome in the second trimester of pregnancy. METHODS: A bibliographic research has been performed for most of the echographic signs known and studied until now. For each study and in average for each sign, we have computed its sensitivity, its specificity, its positive and negative predictive values using the results of the different authors. Then, we have compared the benefits/risk ratio for each of these signs: the number of Down syndrome cases detected versus healthy fetus lost due to amniocentesis complications. RESULTS: The different signs can be ranked according to their benefits/risk ratio from top to bottom as follows: nuchal skinfold thickness, wide space between first and second toe, pyelectasis, large iliac angle, short humerus, short femur, hypoplasia of the middle phalanx of the fifth digit. CONCLUSION: These results suggest that second trimester echographic signs of Down syndrome must be evaluated as a function of the Down syndrome risk in the population under study. The presence of these signs does not always justify an amniocentesis; it should lead to a re-evaluation of the individual risk of a Down syndrome (a chart is given to guide this re-evaluation).

Normal fetal pelvis: important factors for morphometric characterization with US.

PURPOSE: To prospectively evaluate iliac angle and iliac length in a large number of normal fetuses and to identify factors that may influence these measurements. MATERIALS AND METHODS: At antenatal ultrasonography (US) in 356 fetuses, the iliac angle and iliac length were measured at two axial levels (superior and inferior). In mixed linear models, the statistical significance and magnitude of effect on the measurement of iliac angle and iliac length were estimated for gestational age, fetal sex, maternal diabetes status, axial level, and spine position relative to the transducer. RESULTS: Statistically significant effects were found for gestational age, axial level, and spine orientation but not for fetal sex or maternal diabetes status. The iliac angle was found to decrease by 15.7 degrees from the superior to inferior portion of the pelvis, decrease by approximately 0.37 degrees /wk, and decrease by as much as 15.6 degrees when the spine is directed to the side. Iliac length was found to increase by 0.8 mm/wk from 13 weeks to term, decrease by 1.2 mm from the superior to the inferior portion of the pelvis, and increase by as much as 1.29 mm when the spine is not directly subjacent to the transducer. CONCLUSION: The axial level of measurement, gestational age, and spine orientation must be accounted for if these morphometric indexes are used to discriminate fetuses with and those without Down syndrome.

Iliac angle as a marker for Down syndrome in second-trimester fetuses: CT measurement.

PURPOSE: To determine if the iliac angle is greater in second-trimester fetuses with trisomy 21 than in euploid fetuses and to establish the best level and plane for measuring this angle by using three-dimensional computed tomography (CT). MATERIALS AND METHODS: CT was performed in 18 formalin-preserved fetuses (eight trisomy 21, 10 euploid control fetuses), and the pelvic bone anatomy was reconstructed three-dimensionally. Iliac angles were measured in axial views at three levels in two planes. Data were analyzed nonparametrically with the Mann-Whitney test. RESULTS: The mean gestational ages for trisomy 21 and control fetuses were 17.0 and 16.7 weeks, respectively. The external plane was the easiest to measure and the most reproducible. The mean iliac angles were significantly greater (P < .05) in the trisomy 21 fetuses than in the control fetuses and were as follows: superior level, 95.6 degrees vs 76.4 degrees; middle level, 84.5 degrees vs 62.5 degrees; and lower level, 78.1 degrees vs 57.5 degrees. With a 90 degrees threshold, the superior iliac angle measurement had a sensitivity of 75%, a specificity of 89%, and an odds ratio of 24 for Down syndrome. CONCLUSION: Second-trimester fetuses with trisomy 21 have a significantly greater iliac angle than euploid fetuses have. The iliac angle varies with the axial level, with the widest angle at the most superior level. Measurement of the iliac angle at the most superior level is supported as a potential marker for Down syndrome at prenatal ultrasonography.

A morphological study of the fetal ilium; focusing on the sexual differences of the greater sciatic notch.

A number of studies on sexual differences in the ilium have been reported. However, most of these studies have focused on the adult ilium. With regard to sexual differences in the fetal ilium, few studies have been carried out. Especially, there have few studies regarding sexual differences in the fetal ilium using dry bones. In the present study, sexual differences in the morphological characteristics of the greater sciatic notch were investigated using dry fetal iliac bones. We examined 212 fetuses (106 males and 106 females) measuring 20.0 cm or more in fetal length with free of gross malformations or deformities which were collected at Saga Medical School. The iliac bones were excised from these fetuses and dried as materials for study. Fetal length was measured in the fully extended position and was classified into six groups each for males and females in 5-cm increments, giving a total of twelve groups. The inner lateral surface of the greater sciatic notch was magnified 25x using projector, traced, and the tracings were inputted to a computer (7600/120: Apple Co. Ltd) using a flatbed scanner. The width and height of the greater sciatic notch were measured, as well as the area of the greater sciatic notch. No sexual differences were noted regarding the increase in the width of the greater sciatic notch in fetuses up to 39.9 cm in fetal length. In fetuses measuring between 40.0 anf 44.9 cm, a significant sexual difference was observed, with the increase in greater sciatic notch width markedly greater in females. With respect to the increase in the height of the greater sciatic notch, no significant differences were noted. No significant differences were observed in the total area of the greater sciatic notch in fetuses up to 39.9 cm in fetal length. On the other hand, a significant sexual difference was observed in fetuses measuring 40.0 cm or more, with the total area markedly increased in females. In addition, no significant differences were found in the area between the two sides of the greater sciatic notch in fetuses up to 39.9 cm in fetal length, although significant differences were observed in fetuses measuring 40.0 cm or more. In female fetuses 40.0 cm or more in fetal length, the greater sciatic notch was found to be wider than in males, and the peak of the greater sciatic notch was displaced in the anteroinferior direction, farther from the auricular surface of the ilium and nearer the pubic bone. Thus these female fetuses show morphological characteristics of the adult female pelvic bone. Based on the results obtained, it is concluded that sexual differences can be identified in fetuses from the 8th month of pregnancy (fetal length 40.0 cm or more).

Ultrasonographic dimensions of the vertical span of the fetal iliac bone and relationship with some fetal parameters.

Using fetal ultrasonography, disorders of developmental delay and congenital malformations are promptly diagnosed. Skeletal abnormalities are relatively easy to notice once standards of growth are established. The iliac bone is frequently affected in skeletal problems, yet it has not been extensively studied. In this study, a total of 296 fetuses were evaluated and the vertical span of the iliac bone was measured in the oblique coronal plane. The size of the fetal iliac bone (in cm) was calculated according to the cubic regression formula y = -4.6891 + 0.5757x (gestational age in weeks) - 0.0159x2 + 0.0001x3. Standards of normal vertical growth of the iliac bone were established and it was noted that the humerus/iliac bone and femur/iliac bone ratios were uniform with minimal variation after the 16th gestational week, with mean values (SD) of 1.82 (0.14) and 2.09 (0.15), respectively. The iliac wing may be unaltered and the vertical span may be changed considerably in some skeletal dysplasias. For complete evaluation of the skeletal system and to distinguish between different conditions with different prognoses and outcomes, measurement of the vertical span of the iliac bone as a complementary measurement is recommended.

Statistical study of sexual dimorphism in the human fetal sciatic notch.

Whether human fetal skeletal remains exhibit sexual dimorphism has been the subject of considerable debate. Most attention in this debate has focused on the greater sciatic notch of the ilium, since it is a gross morphological characteristic with known sex differences in the adult and is easily seen in fetal skeletal remains. Unfortunately, previous traditional morphometric analyses of the fetal sciatic notch have led to ambiguous results. The purpose of this study is to determine whether differences between the sexes can be discerned when modern morphometric techniques are applied to the fetal sciatic notch. Photographs of the ventral side of 133 fetal ilia of known age and sex from the Trotter Collection of Washington University were digitized, and the trace coordinates used for all subsequent analyses. The results of the analysis demonstrate that there is significant sexual dimorphism in the anterior to posterior location of the maximum depth of the sciatic notch, but that the depth of the notch itself is not dimorphic. While there is significant sexual dimorphism in the shape of the sciatic notch, the amount of overlap between males and females is too great for the sciatic notch to be used as a reliable indicator of sex.