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Concept: Ischium


A major challenge in understanding the origin of terrestrial vertebrates has been knowledge of the pelvis and hind appendage of their closest fish relatives. The pelvic girdle and appendage of tetrapods is dramatically larger and more robust than that of fish and contains a number of structures that provide greater musculoskeletal support for posture and locomotion. The discovery of pelvic material of the finned elpistostegalian, Tiktaalik roseae, bridges some of these differences. Multiple isolated pelves have been recovered, each of which has been prepared in three dimensions. Likewise, a complete pelvis and partial pelvic fin have been recovered in association with the type specimen. The pelves of Tiktaalik are paired and have broad iliac processes, flat and elongate pubes, and acetabulae that form a deep socket rimmed by a robust lip of bone. The pelvis is greatly enlarged relative to other finned tetrapodomorphs. Despite the enlargement and robusticity of the pelvis of Tiktaalik, it retains primitive features such as the lack of both an attachment for the sacral rib and an ischium. The pelvic fin of Tiktaalik (NUFV 108) is represented by fin rays and three endochondral elements: other elements are not preserved. The mosaic of primitive and derived features in Tiktaalik reveals that the enhancement of the pelvic appendage of tetrapods and, indeed, a trend toward hind limb-based propulsion have antecedents in the fins of their closest relatives.

Concepts: Coelacanth, Fin, Sacrum, Fish, Ischium, Sarcopterygii, Tetrapod, Pelvis


The skeletal anatomy of the hip provides two main locations for impingement: abnormal contact between the acetabulum and femur (femoroacetabular impingement) or between the ischium and femur (ischiofemoral impingement). We report a case of bilateral ischiofemoral impingement in a patient with hereditary multiple exostoses. The association of exostoses and femoral metaphyseal widening resulted in the narrowing of the ischiofemoral spaces. Pain was improved on the left side by resection of the ischial exostosis.

Concepts: Iliopsoas, Ischium, Hip, Ilium, Skeletal system, Exostosis, Hereditary multiple exostoses, Pelvis


Should the trocar suddenly lose contact with bone during bone marrow aspiration, it may result in visceral injury. The anatomy of the ilium and the structures adjacent to the iliac bone were studied to determine the danger of breach by a trocar introduced into the iliac crest.

Concepts: Bone, Ischium, Acetabulum, Greater pelvis, Ilium, Pelvis, Bone marrow, Iliac crest


Australian Oligo-Miocene mekosuchines (Crocodylia; Crocodyloidea) display wide diversity in cranial shape and inferred hunting strategies. Terrestrial habitus has been inferred for these distinctive predators. A direct morphological signal for locomotion can be expected in the postcrania, particularly the pelvic and pectoral girdles. Here we describe fossil materials of the girdles, which chart their morphological variation in the subfamily from Eocene through to Middle Miocene. Over this period, both girdles undergo significant morphological changes. Notably, an enclosed, ventrally orientated acetabulum in the ilium is developed in one lineage. This recapitulates the erect parasagittal configuration of the pelvic limb seen in many Mesozoic crocodylomorph lineages, suggesting consistent use of erect high-walking in these mekosuchines. Other pelves from the same Oligo-Miocene deposits display morphology closer to modern crocodilians, suggesting a partitioning of locomotory strategy among sympatric mekosuchines. Plesiomorphic and derived pelvic girdles are distinguishable by parsimony analysis, and the earliest examples of the mekosuchine pelvis more closely resemble gavialids and alligatorids while latter forms converge on crown group crocodylids in the morphology of the iliac crest. This suggests that a revaluation of the base relationship of Mekosuchinae within Eusuchia is necessary.

Concepts: Ischium, Mekosuchinae, Greater pelvis, Pubis, Acetabulum, Crocodilia, Ilium, Pelvis


The human pelvis has evolved over time into a remarkable structure, optimised into an intricate architecture that transfers the entire load of the upper body into the lower limbs, while also facilitating bipedal movement. The pelvic girdle is composed of two hip bones, os coxae, themselves each formed from the gradual fusion of the ischium, ilium and pubis bones. Unlike the development of the classical long bones, a complex timeline of events must occur in order for the pelvis to arise from the embryonic limb buds. An initial blastemal structure forms from the mesenchyme, with chondrification of this mass leading to the first recognisable elements of the pelvis. Primary ossification centres initiate in utero, followed post-natally by secondary ossification at a range of locations, with these processes not complete until adulthood. This cascade of events can vary between individuals, with recent evidence suggesting that fetal activity can affect the normal development of the pelvis. This review surveys the current literature on the ontogeny of the human pelvis. Anat Rec, 300:643-652, 2017. © 2017 Wiley Periodicals, Inc.

Concepts: Ilium, Acetabulum, Hip, Human anatomy, Sacrum, Hip bone, Ischium, Pelvis


Iliac bone malformations are rare and result from early disturbance of the genetic and epigenetic processes that come together to form the pelvic girdle. We report the case of a 5-month-old boy found to have a duplication of the ilium and describe the likely causes of this very rare malformation.

Concepts: Perineum, Iliac crest, Acetabulum, Ischium, Ilium, Greater pelvis, Pelvis


Stabilization of pelvic ring injuries and certain acetabular fractures using percutaneous techniques is becoming increasingly more common. Intramedullary superior ramus screw fixation is beneficial in both injury types. While implants can be placed in an antegrade or retrograde direction, parasymphyseal ramus fractures benefit from retrograde implant insertion. In some patients, the parabolic osseous anatomy or obstructing soft tissues of the anterior pelvis or thigh can prevent appropriate hand and instrumentation positioning for appropriate retrograde ramus screw insertion through the entire osseous fixation pathway. Instead of abandoning medullary fixation, we propose a technique utilizing cannulated screws to successfully place retrograde screws in this distinct clinical scenario.

Concepts: Thigh, Tissues, Acetabulum, Ilium, Ischium, Bone, Pelvis, Human anatomy


The pelvic girdle provides physical support and attachment for the hind limb musculature. In birds there is variability in pelvic morphology across different orders and this has been used as evidence for various types of locomotion. However, the morphological variation of pelvic bones has yet to be studied systematically in birds. Therefore, we investigated basic allometric relationships among female body mass (as a size proxy) and various pelvic measurements in a phylogenetic context. We also examined in detail the inter-relationships among various pelvic measurements. Also considered were the effects of broader taxonomic relationships at the level of order, with further examination of the influence of style of terrestrial locomotion on the allometric relationships. Positive relationships were initially found among all pelvic linear measurements and female body mass (FBM). The relationships among measures of pelvic width and FBM were isometric, whereas those between pelvic length and FBM showed positive allometry. Also, FBM explained more of the variance in pelvic length than in width. Similarly, the angle of the pelvis had a significant negative relationship, but FBM only explained a very low proportion of the variation in pelvic angles. In general terms, ancova showed that the effect of FBM was smaller than the effect of locomotor style in this species set. Both the synsacrum and pelvic girdle play roles in weight support and therefore scale in proportion to body weight accordingly. All three parts of the pelvis (ilium, ischium and pubis) are attached around the acetabulum and also provide muscle attachment points, so it might be expected for them to scale in a similar manner. Increased angulation of the pelvis is linked to orders which employ their hind limbs in feeding, perching and running, although FBM also explains a very low proportion of the variation in pelvic angle. Muscle attachment and the confines on morphology presented by locomotion explain much of the variation exhibited by the relationships among pelvic measurements.

Concepts: Pubic symphysis, Human anatomy, Ischium, Mass, Ilium, Pubis, Acetabulum, Pelvis


The bony pelvis of primates is a composite structure serving a variety of functions, and exhibiting a complex pattern of modularity and integration. Still little is known, however, about how patterns of modularity and integration arise, and how they change throughout ontogeny. Here we study the ontogeny of modularity and integration in developmental and functional units of the pelvis of our closest living relatives, the chimpanzees. We use methods of biomedical imaging and geometric morphometrics to quantify pelvic shape change from late fetal stages to adulthood, and to track changes in patterns of covariation within and among pelvic regions. Our results show that both developmental and functional units of the pelvis exhibit significant levels of modularity throughout ontogeny. Modularity of developmental units (ilium, ischium, and pubis) decreases with increasing age, whereas modularity of functional units tends to increase. We suggest that the decreasing modularity and increasing integration of developmental units reflects their gradual fusion. In contrast, increasing modularity of functional pelvic units likely reflects changing functional demands during an individual’s lifetime. Overall, ontogenetic changes in patterns of modularity and integration imply that natural selection could act differently on each module, either developmental or functional, at different stages of ontogeny. This further implies that adult patterns of covariation in the pelvis provide only limited information about its evolvability. Anat Rec, 300:675-686, 2017. © 2017 Wiley Periodicals, Inc.

Concepts: Pubic symphysis, Pubis, Ilium, Change, Developmental biology, Acetabulum, Ischium, Pelvis


The pelvic skeleton is formed via endochondral ossification. However, it is not known how the normal cartilage is formed before ossification occurs. Furthermore, the overall timeline of cartilage formation and the morphology of the cartilage in the pelvis are unclear. In this study, cartilage formation in the pelvic skeletons of 25 human fetuses (crown-rump length [CRL] = 11.9-75.0 mm) was observed using phase-contrast computed tomography and 7T magnetic resonance imaging. The chondrification center of the ilium, ischium, and pubis first appeared simultaneously at Carnegie stage (CS) 18, was located around the acetabulum, and grew radially in the later stage. The iliac crest formed at CS20 while the iliac body’s central part remained chondrified. The iliac body formed a discoid at CS22. The growth rate was greater in the ilium than in the sacrum-coccyx, pubis, and ischium. Connection and articulation formed in a limited period, while the sacroiliac joint formed at CS21. The articulation of the pubic symphysis, connection of the articular column in the sacrum, and Y-shape connection of the three parts of the hip bones to the acetabulum were observed at CS23; the connection of the ischium and pubic ramus was observed at the early-fetal stage. Furthermore, the degree of connection at the center of the sacrum varied among samples. Most of the pelvimetry data showed a high correlation with CRL. The transverse and antero-posterior lengths of the pelvic inlet of the lesser pelvis varied among samples (R2 = 0.11). The subpubic angle also varied (65-90°) and was not correlated with CRL (R2 = 0.22). Moreover, cartilaginous structure formation appeared to influence bone structure. This study provides valuable information regarding the morphogenesis of the pelvic structure.

Concepts: Ilium, Ischium, Sacroiliac joint, Acetabulum, Pubic symphysis, Pubis, Bone, Pelvis