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

Sex estimation of the adult Neandertal Regourdou 1 (Montignac, France): Implications for sexing human fossil remains

Sex is a biological trait fundamental to the study of hominin fossils. Among the many questions that can be addressed are those related to taxonomy, biological variability, sexual dimorphism, paleoobstetrics, funerary selection, and paleodemography. While new methodologies such as paleogenomics or paleoproteomics can be used to determine sex, they have not been systematically applied to Pleistocene human remains due to their destructive nature. Therefore, we estimated sex from the coxal bone of the newly discovered pelvic remains of the Regourdou 1 Neandertal (Southwest France, MIS 5) based on morphological and metric data employing two methods that have been recently revised and shown to be reliable in multiple studies. Both methods calculate posterior probabilities of the estimate. The right coxal bone of Regourdou 1 was partially reconstructed providing additional traits for sex estimation. These methods were cross validated on 14 sufficiently preserved coxal bones of specimens from the Neandertal lineage. Our results show that the Regourdou 1 individual, whose postcranial skeleton is not robust, is a male, and that previous sex attributions of comparative Neandertal specimens are largely in agreement with those obtained here. Our results encourage additional morphological research of fossil hominins in order to develop a set of methods that are applicable, reliable, and reproducible.

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.

Anatomical framework for pre-operative planning of laparoscopic left-sided colorectal surgery: Potential relevance of the distance between the inferior mesenteric artery and inferior mesenteric vein

BACKGROUND

The medial-to-lateral approach is favored by most colorectal surgeons for laparoscopic retroperitoneal dissection and mobilisation of the left colon. The peritoneal access window, i.e. the distance between the inferior mesenteric vein (IMV) and inferior mesenteric artery (IMA) must be large enough to perform the procedure safely and successfully. However, studies investigating the IMA-IMV distance and factors affecting this variable, are scarce. Therefore, we examined the IMA-IMV and D3-IMA distances to determine an anatomical framework on planning and adapting surgical therapy.

BASIC PROCEDURES

The IMA-IMV and D3-IMA distances were retrospectively measured in 230 patients (127 Male/103 Female, Median Age=54.5) who had undergone pre-operative CT-scanning before laparoscopic left-sided colorectal surgery. Two observers rated the images and interrater reliability was calculated. Subgroup, simple and multiple linear regression analyses were performed in order to detect potential interaction between morphometric variables and IMA-IMV distance.

MAIN FINDINGS

We demonstrated a significant correlation between the inferior margin of the duodenum and the origin of IMA. Determination of the IMA-IMV distance was simple and reproducible. Approximately 45% of patients undergoing laparoscopic colorectal procedures had a narrow distance (≤50mm). There was a sexual dimorphism in IMA-IMV distance, being consistently large in males. There were no other pre-operative factors which predicted whether the peritoneal dissection window for a medial-to-lateral approach was sufficient.

CONCLUSIONS

Our results provide new data for a better understanding of metric variations in abdominal vascular structures and complement previous observations. In view of our results, we recommend pre-operative measurement of the IMA-IMV before colorectal surgery where the medial-to-lateral approach is planned. Given that a narrow distance may predict a difficult dissection, this factor should be taken into account to determine the optimal surgical approach in each patient.