Trabecular bone structure correlates with hand posture and use in hominoids

Bone is capable of adapting during life in response to stress. Therefore, variation in locomotor and manipulative behaviours across extant hominoids may be reflected in differences in trabecular bone structure. The hand is a promising region for trabecular analysis, as it is the direct contact between the individual and the environment and joint positions at peak loading vary amongst extant hominoids. Building upon traditional volume of interest-based analyses, we apply a whole-epiphysis analytical approach using high-resolution microtomographic scans of the hominoid third metacarpal to investigate whether trabecular structure reflects differences in hand posture and loading in knuckle-walking (Gorilla, Pan), suspensory (Pongo, Hylobates and Symphalangus) and manipulative (Homo) taxa. Additionally, a comparative phylogenetic method was used to analyse rates of evolutionary changes in trabecular parameters. Results demonstrate that trabecular bone volume distribution and regions of greatest stiffness (i.e., Young's modulus) correspond with predicted loading of the hand in each behavioural category. In suspensory and manipulative taxa, regions of high bone volume and greatest stiffness are concentrated on the palmar or distopalmar regions of the metacarpal head, whereas knuckle-walking taxa show greater bone volume and stiffness throughout the head, and particularly in the dorsal region; patterns that correspond with the highest predicted joint reaction forces. Trabecular structure in knuckle-walking taxa is characterised by high bone volume fraction and a high degree of anisotropy in contrast to the suspensory brachiators. Humans, in which the hand is used primarily for manipulation, have a low bone volume fraction and a variable degree of anisotropy. Finally, when trabecular parameters are mapped onto a molecular-based phylogeny, we show that the rates of change in trabecular structure vary across the hominoid clade. Our results support a link between inferred behaviour and trabecular structure in extant hominoids that can be informative for reconstructing behaviour in fossil primates

Premolar root and canal variation in South African Plio-Pleistocene specimens attributed to Australopithecus africanus and Paranthropus robustus

South African hominin fossils attributed to Australopithecus africanus derive from the cave sites of Makapansgat, Sterkfontein, and Taung, from deposits dated between about 2 and 3 million years ago (Ma), while Paranthropus robustus is known from Drimolen, Kromdraai, and Swartkrans, from deposits dated between about 1 and 2 Ma. Although variation in the premolar root complex has informed taxonomic and phylogenetic hypotheses for these fossil hominin species, traditionally there has been a focus on external root form, number, and position. In this study, we use microtomography to undertake the first comprehensive study of maxillary and mandibular premolar root and canal variation in Australopithecus africanus and Paranthropus robustus (n = 166 teeth) within and between the species. We also test for correlations between premolar size and root morphology as predicted under the ‘size/number continuum’ (SNC) model, which correlates increasing root number with tooth size. Our results demonstrate previously undocumented variation in these two fossil hominin species and highlight taxonomic differences in the presence and frequency of particular root types, qualitative root traits, and tooth size (measured as cervix cross-sectional area). Patterns of tooth size and canal/root number are broadly consistent with the SNC model, however statistically significant support is limited. The implications for hominin taxonomy in light of the increased variation in root morphology documented in this study are discussed

Cortical bone mapping: An application to hand and foot bones in hominoids

Bone form reflects both the genetic profile and behavioural history of an individual. As cortical bone is able to remodel in response to mechanical stimuli, interspecific differences in cortical bone thickness may relate to loading during locomotion or manual behaviours during object manipulation. Here, we test the application of a novel method of cortical bone mapping to the third metacarpal (Mc3) and talus of Pan, Pongo, and Homo. This method of analysis allows measurement of cortical thickness throughout the bone, and as such is applicable to elements with complex morphology. In addition, it allows for registration of each specimen to a canonical surface, and identifies regions where cortical thickness differs significantly between groups. Cortical bone mapping has potential for application to palaeoanthropological studies; however, due to the complexity of correctly registering homologous regions across varied morphology, further methodological development would be advantageous

Characterisation of wear areas on UHMWPE total knee replacement prostheses through study of their areal surface topographical parameters

Total knee replacement is one of the most common elective surgeries in the world, and presents a number of challenges related to the wear of ultra-high molecular weight polyethylene (UHMWPE). This paper presents an analysis of the surface topographical properties of the worn and unworn condylar surfaces on a small cohort of both wear simulated and retrieved prostheses of varying designs. A number of measurement points were taken on each prostheses in a mixture of worn and unworn areas through the use of focus-variation microscopy (FVM), a non-contact method of surface measurement. Surface areal parameters were extracted from this data to analyse and search for patterns within the data. It was found that in general, worn implant surfaces appear to show smoother, less peak dominated surfaces than unworn area. It was also found that wear simulated and retrieved implants display similar characteristics of surface topography. In addition, variation was noted between different designs of TKR device, with posterior stabilised designs found to be peak dominated and cruciate retaining type implants being valley dominated

Development and management of systemic lupus erythematosus in an HIV-infected man with hepatitis C and B co-infection following interferon therapy: a case report

<p>Abstract</p> <p>Introduction</p> <p>The association of human immunodeficiency virus and immune dysfunction leading to development of autoimmune markers is well described, but human immunodeficiency virus infection is relatively protective for the development of systemic lupus erythematosus. In contrast, development of systemic lupus erythematosus with hepatitis C and with interferon therapy is well described in a number of case reports. We here describe the first case of systemic lupus erythematosus developing in a man infected with human immunodeficiency virus, hepatitis C and hepatitis B co-infection where the onset seems to have been temporally related to interferon therapy.</p> <p>Case presentation</p> <p>We report the occurrence of systemic lupus erythematosus complicating interferon-α therapy for hepatitis C in a 47-year-old asplenic male with haemophilia co-infected with human immunodeficiency virus and hepatitis B. He presented with a truncal rash, abdominal pains and headache and later developed grade IV lupus nephritis requiring haemodialysis, mycophenolate mofetil and steroid therapy. We were able to successfully withdraw dialysis and mycophenolate while maintaining stable renal function.</p> <p>Conclusion</p> <p>Interferon-α is critical in antiviral immunity against hepatitis C but also acts as a pathogenic mediator for systemic lupus erythematosus, a condition associated with activation of plasmacytoid dendritic cells that are depleted in human immunodeficiency virus infection. The occurrence of auto-antibodies and lupus-like features in the coinfections with hepatitis C require careful assessment. Immunosuppressant therapy for lupus risks exacerbating underlying infections in patients with concurrent human immunodeficiency virus, hepatitis B and C.</p

Locomotion in Homo floresiensis: reconstructing foot use from the internal bone structure of the metatarsals of LB1

The enigmatic Homo floresiensis displays a unique combination of cranial and post-cranial morphology [1-3], distinguishing it from other species of the genus Homo. Although its skeletal anatomy shows clear adaptations for terrestrial bipedalism, it also retains a suite of features conducive to arboreal behaviours. Thus, exactly how the locomotor behaviours of H. floresiensis compare with those of other hominins remains an important research question. The foot of the holotype (LB1) is long relative to its femoral length, has a longer forefoot than hindfoot, long phalanges relative to the non-hallucial metatarsals (Mts), and a short Mt1 relative to the other Mts [3]. However, it also possesses a human-like Mt head morphology and relative robusticity pattern [2-3]. Here, we assess the internal morphology of the Mts of LB1 to further assess foot functional morphology and locomotor kinematics in H. floresiensis. Using high resolution micro-CT scans of the Mts of LB1 and a comparative sample of Homo sapiens (N=10), Pan troglodytes (N=15), Pan paniscus (N=15), Gorilla spp. (N=10) and Pongo spp. (N=9), we conducted a cross-sectional geometric analysis at mid-shaft and analysis of trabecular bone distribution in the Mt head. As the head was only fully preserved for the right Mt5 of LB1, trabecular analysis was limited to this element.Cross-sectional geometry of the Mts at mid-shaft distinguishes between ape-like and human-like biomechanics, with greater loading of the Mt2 and Mt3 in apes compared with more lateral loading in humans [4]. The Mts of LB1 are internally robust, having a high cross-sectional area relative to bone length. Results show that the relative strength of the Mts, based on the internal structure, differs from the previously reported human-like pattern, which was based on external measurements of midshaft circumference [2-3]. We find that, after scaling by total bone length, the robusticity pattern for the left Mts of LB1 is 1>2>5>3>4 for CSA and Z, and 1>5>2>4>3 for J. Although there is some variation among humans, in general the Mt3 and Mt2 have lower measures of robusticity than the Mt4 and Mt5 [4]. In LB1, the Mt2 is consistently more robust than is expected in humans, with the pattern being 1>2/5>3/4 compared to 1>4/5>2/3 in humans. The distribution of trabecular bone in the Mt5 head distinguishes between locomotor groups. In H. sapiens, where the foot is loaded in dorsiflexion there is a dorsal concentration of bone, which is asymmetric in extending dorsomedially. In African apes, where the toes are positioned dorsally during knuckle-walking and disto-plantarly during climbing (depending on substrate size) the distribution of trabecular bone extends dorsally to plantarly on the metatarsal head. In Pongo, trabecular bone is distributed distally and plantarly reflecting a grasping foot. The distribution of trabecular bone in the Mt5 of LB1 is located dorsally and distally but does not extend plantarly. This distribution pattern differs from humans in being centrally located, rather than medially, and in extending further distally. This suggests that the metatarsophalangeal joint in LB1 was loaded in a more a neutral position than in humans.Together, the results suggest that loading of the foot of H. floresiensis differed from modern humans. First, the distribution of load across the foot was likely higher in the Mt2, a feature that could relate to higher loading of the second ray in a foot with a relatively short first ray. Secondly, the trabecular pattern suggests loading of the Mt5 head more distally than in humans, and with less asymmetric loading. This differing position of the metatarsophalangeal joint could be related to the long, curved phalanges of LB1. Future research exploring whole-bone cortical and trabecular structure of the metatarsals will shed new light on the kinematics of locomotion in H. floresiensis

Trabecular bone structure of the proximal capitate in extant hominids and fossil hominins with implications for midcarpal joint loading and the dart‐thrower's motion

Objectives: This research examines whether the distribution of trabecular bone in the proximal capitates of extant hominids, as well as several fossil hominin taxa, is associated with the oblique path of the midcarpal joint known as the dart‐thrower's motion (DTM). Materials and Methods: We analyzed proximal capitates from extant (Pongo n = 12; Gorilla n = 11; Pan n = 10; fossil and recent Homo sapiens n = 29) and extinct (Australopithecus sediba n = 2; Homo naledi n = 1; Homo floresiensis n = 2; Neandertals n = 3) hominids using a new canonical holistic morphometric analysis, which quantifies and visualizes the distribution of trabecular bone using relative bone volume as a fraction of total volume (rBV/TV). Results: Homo sapiens and Neandertals had a continuous band of high rBV/TV that extended across the scaphoid, lunate, and hamate subarticular regions, but other fossil hominins and extant great apes did not. A. sediba expressed a distinct combination of human‐like and Pan‐like rBV/TV distribution. Both H. floresiensis and H. naledi had high rBV/TV on the ulnar‐side of the capitate but low rBV/TV on the radial‐side. Conclusion: The proximal capitates of H. sapiens and Neandertals share a distinctive distribution of trabecular bone that suggests that these two species of Homo regularly load(ed) their midcarpal joints along the full extent of the oblique path of the DTM. The observed pattern in A. sediba suggests that human‐like stress at the capito‐scaphoid articular surface was combined with Pan‐like wrist postures, whereas the patterns in H. floresiensis and H. naledi suggest their midcarpal joints were loaded differently from that of H. sapiens and Neandertals

Does repeatedly viewing overweight versus underweight images change perception of and satisfaction with own body size?

Body dissatisfaction is associated with subsequent eating disorders and weight gain. One-off exposure to bodies of different sizes changes perception of others' bodies, and perception of and satisfaction with own body size. The effect of repeated exposure to bodies of different sizes has not been assessed. We randomized women into three groups, and they spent 5 min twice a day for a week completing a one-back task using images of women modified to appear either under, over, or neither over- nor underweight. We tested the effects on their perception of their own and others' body size, and satisfaction with own size. Measures at follow-up were compared between groups, adjusted for baseline measurements. In 93 women aged 18–30 years, images of other women were perceived as larger following exposure to underweight women (and vice versa) (p < 0.001). There was no evidence for a difference in our primary outcome measure (visual analogue scale own size) or in satisfaction with own size. Avatar-constructed ideal (p = 0.03) and avatar-constructed perceived own body size (p = 0.007) both decreased following exposure to underweight women, possibly due to adaptation affecting how the avatar was perceived. Repeated exposure to different sized bodies changes perception of the size of others' bodies, but we did not find evidence that it changes perceived own size