Article

Who’s Afraid of the Big Bad Wolff?: ‘‘Wolff’s Law’’ and Bone Functional Adaptation

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Abstract

ABSTRACT ‘‘Wolff ’s law’’ is a concept that has sometimes been misrepresented, and frequently misunderstood, in the anthropological literature. Although it was originally formulated in a strict mathematical sense that has since been discredited, the more general concept of ‘‘bone functional adaptation’’ to mechanical loading (a designation that should probably replace ‘‘Wolff ’s law’’) is supported by much experimental and observational data. Objections raised to earlier studies of bone functional adaptation have largely been addressed by more recent and better-controlled studies. While the bone morphological response to mechanical strains is reduced in adults relative to juveniles, claims that adult morphology re.ects only juvenile loadings are greatly exaggerated. Similarly, while there are important genetic in.uences on bone development and on the nature of bone’s response to mechanical loading, variations in loadings themselves are equally if not more important in determining variations in morphology, especially in comparisons between closely related individuals or species. The correspondence between bone strain patterns and bone structure is variable, depending on skeletal location and the general mechanical environment (e.g., distal vs. proximal limb elements, cursorial vs. noncursorial animals), so that mechanical/behavioral inferences based on structure alone should be limited to corresponding skeletal regions and animals with similar basic mechanical designs. Within such comparisons, traditional geometric parameters (such as second moments of area and section moduli) still give the best available estimates of in vivo mechanical competence. Thus, when employed with appropriate caution, these features may be used to reconstruct mechanical loadings and behavioral differences within and between past populations. Am J Phys Anthropol 129:484–498, 2006. VVC 2006 Wiley-Liss, Inc.

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... During life, the skeleton is exposed to many continuously recurring loads that lead to changes in morphology (modelling) (Prescher, 1998). The plasticity of bone allows it to adapt to external forces from the mechanical environment acting upon it by modelling and remodelling its internal and external structure in the direction of functional stress as a response to mechanical stimulus (Pearson and Lieberman, 2004;Ruff et al., 2006. There are various theories used to explain the process of bone functional adaptation which are discussed after a brief description of the concepts of bone modelling and remodelling which are described below. ...
... Nilsson et al. (2014) suggest that the morphological mechanisms that occur due to mechanical stress-induced changes in bone size are an increase in cortical bone thickness (prevalent during the growth period) and a decrease in endosteal bone loss (prevalent Chapter 4 Bioarchaeology and Activity 55 in the aging population). Ruff et al. (2006) agree with this and report that increased mechanical loading mainly affects internal bone remodelling, with growth towards the medullary cavity. Ruff (2005) reports that estimation of adult activity from the external dimensions of a long bone is fraught with difficulty unless the internal dimensions of the bone are also considered. ...
... This manifests as changes in robusticity of long bones (defined as the thickness of the shaft to its length (Martin and Saller, 1957) and quantified by cross-sectional cortical geometry (Ruff, 2000). The process of bone adaptation is complicated and not fully understood (Pearson and Lieberman, 2004), however, there is still a considerable body of evidence for a direct link between mechanical loading and the geometric properties of long bone diaphyses (Robling et al., 2000;Daly et al., 2004;Warden et al., 2005;Ruff, et al., 2006) and vertebral size (Gilsanz et al., 1994;Mosekilde and Mosekilde, 1990;Mosekilde, 2000). ...
Thesis
This research aims to demonstrate how “form related to function” can be used to explain differences in the degree of zygapophyseal (facet) joint sexual dimorphism seen in populations with differing lifestyles. Whilst sex can be estimated with a reasonable degree of accuracy from the facet joints of the spine in populations with a high degree of sexual dimorphism, it can be problematic in samples that do not. Bone adapts to reflect the physiological strain placed upon it during life. Analysis of the relationship between bony adaptation to occupational stress and facet morphology identifies extrinsic factors that correlate to changes in facet size and to a lesser degree sagittal angle. Extrinsic factors are external biocultural influences on bone morphology (e.g. nutrition and physical activity). The number of discriminant functions that can be derived from a population with a low degree of sexual dimorphism is increased when these factors are included, increasing the potential to estimate sex. The strength of correlation and prevalence of extrinsic factors can also be used to measure the degree of physical activity undertaken by individuals and is indicative of gendered division of labour in the population under study. Analysis of facet size and sagittal angle and the relationship and prevalence of extrinsic factors related to physical activity from skeletal material were examined from three contrasting samples. Two were from 18th century London with differing socio-economic status and the third a composite sample from three 5th -7th century Anglo-Saxon cemeteries located in southeast England. A comparative study of facet size and angle identified inter-sample differences in the degree of sexual dimorphism. Further comparison of differences in lifestyle as evidenced by activity patterns was carried out to assess the impact of extrinsic factors on facet remodelling. In particular, this thesis focuses on evidence of the gendered division of labour as manifest by femoral robusticity, humeral directional asymmetry, vertebral osteophytosis, and osteoarthritis with analysis of the individual diagnostic criteria of eburnation, pitting and osteophytes. A distinct difference in prevalence of these factors was observed in the Anglo-Saxon sample and most obviously in females when compared with the 18th century samples, indicating that there was a difference in intensity of activity undertaken by this group in comparison with the other samples in this study. This suggests that the lack of facet joint sexual dimorphism observed in Anglo-Saxons is attributable to the degree of physical activity undertaken by these females and the subsequent remodelling of the facets as a functional adaptation to the mechanical loading they were subjected to. This research demonstrates that for some populations, sex can be estimated with reasonable accuracy from vertebral facet dimensions but for less dimorphic samples, inclusion of extrinsic factors related to physical activity when deriving discriminant functions increases the opportunity to estimate sex. Furthermore, analysis of inter-sample prevalence rates for extrinsic factors provides supporting evidence of different levels of physical activity between the samples.
... mobility) biomechanical properties as inferred from cross-sectional geometry (Holt 1999(Holt , 2003Holt et al. 2000;Marchi et al. 2006Marchi et al. , 2011Holt and Formicola 2008;Sparacello et al. 2018b;Varalli et al. 2020). The cross-sectional geometric properties (CSG) of long bones were analyzed applying beam theory, under the widely accepted notion that bone tissue optimizes to its mechanical environment so as to maintain physiological strains within the normal limits ("Wolff 's Law", better referred to as "bone functional adaptation"; Pearson and Lieberman 2004;Ruff et al. 2006b). Although bone robusticity is influenced by multiple factors (Pearson and Lieberman 2004), it is generally presumed that variation in CSG properties correlate with activity levels and types, once the effect of body size is factored out (Ruff et al. 2006b). ...
... The cross-sectional geometric properties (CSG) of long bones were analyzed applying beam theory, under the widely accepted notion that bone tissue optimizes to its mechanical environment so as to maintain physiological strains within the normal limits ("Wolff 's Law", better referred to as "bone functional adaptation"; Pearson and Lieberman 2004;Ruff et al. 2006b). Although bone robusticity is influenced by multiple factors (Pearson and Lieberman 2004), it is generally presumed that variation in CSG properties correlate with activity levels and types, once the effect of body size is factored out (Ruff et al. 2006b). This residual level of mechanical strength after standardization by body size is called "robusticity" in CSG research (Ruff et al. 2006b), and can be assessed by dividing the polar second moment of area (J; torsional and (twice) average bending rigidity of the beam) raised to the power of 0.73 (which approximates Zp, or section modulus) by bone mechanical length (as defined in Ruff 2002) and body mass (Ruff 2000). ...
... Although bone robusticity is influenced by multiple factors (Pearson and Lieberman 2004), it is generally presumed that variation in CSG properties correlate with activity levels and types, once the effect of body size is factored out (Ruff et al. 2006b). This residual level of mechanical strength after standardization by body size is called "robusticity" in CSG research (Ruff et al. 2006b), and can be assessed by dividing the polar second moment of area (J; torsional and (twice) average bending rigidity of the beam) raised to the power of 0.73 (which approximates Zp, or section modulus) by bone mechanical length (as defined in Ruff 2002) and body mass (Ruff 2000). Body mass is estimated from the supero-inferior diameter of the femoral head following the guidelines in Trinkaus and Ruff (2012). ...
Article
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In two publications from 1967 and 1971, M. Masali described human skeletal remains presumed to have been found in the Balzi Rossi caves (Ventimiglia, Italy), based on a signed note dated to 1908. Since then, the remains - dubbed "Conio's Finds" and preserved at the University of Torino - had not been further studied. We performed a multidisciplinary investigation aimed at clarifying the geographical and chronological attribution of these specimens. Collagen extraction for AMS dating was unsuccessful, but we obtained two direct dates on the best- preserved crania via 231Pa/235U direct gamma-ray spectrometry (10,500±2,000 years BP and 12,500±2,500 years BP). We analyzed the metrics and morphology of the crania and femora by comparing them with samples belonging to the Upper Paleolithic, Mesolithic, and Neolithic periods, and evidenced that the "Conio's Finds" are morphologically more compatible with a Late Pleistocene rather than Holocene attribution. We analyzed the literature regarding the history of excavations at Balzi Rossi, and we propose that - if any credence should be given to the note accompanying the material - the remains may have been found in front of Grotta dei Fanciulli or Grotta del Caviglione, in the redeposited soil dug up during the installation of lime kilns carried out between the late 18th and the early 19th centuries. These hypotheses may be tested in the future by comparing the speleothem deposited on one of the crania and the remaining deposit at the site.
... Bone structure and density, constituting its strength [1], adapt to prevalent mechanical loading [2,3]. Physical activity and exercise provide natural ways to apply mechanical loading to the bone. ...
... However, not all exercises are equally osteogenic and the effectiveness may vary between anatomical sites [7,8]. Animal experimental studies suggest that the effective loading types are dynamic and include sufficiently high-magnitude strains produced at high strain rate or frequencies [3,9]. For the proximal femur, finding effective exercises is highly important because of increasing social and economic burden caused by hip fractures. ...
... One interesting observation in the present study is that the benefits observed in unadjusted and BW-adjusted higher fracture loads among the specific exercise loading groups disappeared once controlled for LM. According to bone's functional adaptation [2,3], the bone adapts to the prevalent mechanical environment, which does not exclude the contribution from the fat mass. It is the body weight that largely determines the magnitude of mechanical loading. ...
Article
Physical loading makes bones stronger through structural adaptation. Finding effective modes of exercise to improve proximal femur strength has the potential to decrease hip fracture risk. Previous proximal femur finite element (FE) modeling studies have indicated that the loading history comprising impact exercises is associated with substantially higher fracture load. However, those results were limited only to one specified fall direction. It remains thus unclear whether exercise-induced higher fracture load depends on the fall direction. To address this, using magnetic resonance images of proximal femora from 91 female athletes (mean age 24.7 years with >8 years competitive career) and their 20 non-athletic but physically active controls (mean age 23.7 years), proximal femur FE models were created in 12 different sideways fall configurations. The athletes were divided into five groups by typical loading patterns of their sports: high-impact (H-I: 9 triple- and 10 high-jumpers), odd-impact (O-I: 9 soccer and 10 squash players), high-magnitude (H-M: 17 powerlifters), repetitive-impact (R-I: 18 endurance runners), and repetitive non-impact (R-NI: 18 swimmers). Compared to the controls, the FE models showed that the HI and R-I groups had significantly (p < 0.05) higher fracture loads, 11–17% and 22–28% respectively, in all fall directions while the OI group had significantly 10–11% higher fracture loads in four fall directions. The H-M and R-NI groups did not show significant benefit in any direction. Also, the analyses of the minimum fall strength (MFS) among these multiple fall configurations confirmed significantly 15%, 11%, and 14% higher MFSs in these impact groups, respectively, compared to the controls. These results suggest that the lower hip fracture risk indicated by higher fracture loads in athletes engaged in high impact or repetitive impact sports is independent of fall direction whereas the lower fracture risk attributed to odd-impact exercise is more modest and specific to the fall direction. Moreover, in concordance with the literature, the present study also confirmed that the fracture risk increases if the impact is imposed on the more posterolateral aspect of the hip. The present results highlight the importance of engaging in the impact exercises to prevent hip fractures and call for retrospective studies to investigate whether specific impact exercise history in adolescence and young adulthood is also associated with lower incidence of hip fractures in later life.
...  the increase of biomechanical constrains activates mechanotransduction and stimulates osteogenis (Frost, 1994;Ruff, Holt, & Trinkaus, 2006b). ...
... The original law was formulated as follows: "'Thus the law of bone remodeling is the law according to which alterations of the internal architecture clearly observed and following mathematical rules, as well as secondary alterations of the external form of the bone following the same mathematical rules, occur as a consequence of primary changes in the shape and stressing or in the stressing of the bones.'' (cited in Ruff, Holt, & Trinkaus, 2006b). Thus, a theory of bone remodeling where large magnitude signals (> 1000 microstrain) are the main factors for enhancing bone anabolism has been developed: by stimulating osteoclasts to remove damaged bone and osteoblasts to replace it by new material, high magnitude strains enhance bone resorption and formation (e.g. ...
... Thus, a theory of bone remodeling where large magnitude signals (> 1000 microstrain) are the main factors for enhancing bone anabolism has been developed: by stimulating osteoclasts to remove damaged bone and osteoblasts to replace it by new material, high magnitude strains enhance bone resorption and formation (e.g. Frost, 1990;Ruff, Holt, & Trinkaus, 2006b;Turner, 1998). Conceiving remodeling as an adaptation to large magnitude signals has been reinforced by the study of athletes whose long bone diaphyses develop a higher resistance to constrains (e.g. on various bones and various kind of sports: Niinimäki et al., 2017;Shaw & Stock, 2009a;Trinkaus, Churchill, & Ruff, 1994). ...
Thesis
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The understanding of biomechanics is essential to various studies in bioanthropology. Bone is a living tissue that constantly remodels in order to functionally adapt to biomechanical constrains. Long bones diaphyses in particular have been subjected to various analyses notably because the application of beam engineering principles has rendered possible the evaluation of their resistance to various directional constrains based on their shape. Body mass estimation methods lie on this principle. Body mass is partially used since the nineties as a proxy to control the influence of body size on bone’s architecture prior to interpreting variations between populations. More recently, they have been used to estimate physical status (i.e. emaciation, norm, obesity). Using a sample of 64 known body mass individuals, we demonstrated that 11 of the existing body mass estimation methods from the skeleton are reliable and accurate for the estimation of a population’s mean body mass. However, we also showed that they are unreliable and inaccurate to predict an individual’s body mass and derive the physical status. Because multiple clinical studies demonstrated a difference between lean and adipose tissues influence on the skeleton, we endeavored to investigate further the actual impact of those tissues volumes and masses on the lower limb bones. For this purpose, we developed three methods (1) to measure whole-body composition from whole-body CT scans; (2) to estimate whole-body composition from selected CT scans; (3) to measure semi-automatically long bone’s thickness and cross-sectional geometry parameters on the entire length and width of CT scanned diaphyses. We used two CT scans samples originating from the Czech Republic and Denmark. Although based on slightly different analytical procedures, the results are congruent between samples and display a high sexual dimorphism. Female’s femoral diaphyses seem to be more sensitive than male’s to changes in fat mass. This is especially true for femoral cortical thickness. The same sexual dimorphism was found for body mass. Conversely, tibial diaphyseal thickness correlates with the adipose tissue in males only while correlations between lean mass and the tibia are displayed in both sexes. We also show that the prediction of the physical status (exclusively norm and obesity from measure of body fat percentage) based on multiple diaphyseal data can be applied to archeological remains. Cross-sectional geometry parameters measured on the whole length of the tibial and femoral diaphyses also display correlations with body mass and composition, similar to those found with cortical thickness although lower. Our results can be explained by biomechanical (gravitational) and physiological (endocrine, bone remodeling and aging) factors. Those findings are exclusive to adulthood: other studies lead on immatures show opposite results. Our research suggests that body composition and mass possibly have more influence on the architecture of both tibial and femoral diaphyses than it was thought before. The results need to be confirmed on samples representative of the human worldwide variation and extended to other bones and trabecular bone. Nevertheless, body composition, notably fat mass, and body mass should be controlled for as a factor of influence prior to deriving activity, locomotion or mobility from bone’s diaphyseal shape.
... One would expect to observe effects of captivity on the postcranial skeleton owing to confinement to small spaces, resulting in reduced mobility, unnatural substrates including a lack of trees for arboreal taxa, a lack of predatory behaviour and the absence of intraspecies interactions, all of which should reduce mechanical loading. Many experimental and observational studies have shown that bones respond to changes in mechanical loading during life, increasing in mass and strength with increased loading, and decreasing with reduced loading [26][27][28][29][30][31][32][33][34][35][36][37]. Consequently, captivity should result in a decrease in these parameters in comparison to wild counterparts. ...
... We hypothesized that: (i) captive animals would exhibit lower BVF than their wild conspecifics given their reduced mobility owing to the confined spaces in which they live; (ii) there would be a more marked reduction in BVF in species with larger rather than smaller home ranges in the wild; and (iii) forelimbs would show more of an effect of captivity than hindlimbs. Our hypotheses are based on the understanding that decreased activity (mechanical loading) will lead to decreased bone deposition, as demonstrated by experimental and observational research [26][27][28][29]34,40]. Furthermore, because ground reaction forces are higher on the forelimbs during terrestrial locomotion in non-primate mammals [50,51], and because the forelimbs are used in prey capture, they should exhibit a greater effect owing to captivity than the hind limbs. ...
Article
Full-text available
Bone responds to elevated mechanical loading by increasing in mass and density. Therefore, wild animals should exhibit greater skeletal mass and density than captive conspecifics. This expectation is pertinent to testing bone functional adaptation theories and to comparative studies, which commonly use skeletal remains that combine zoo and wild-caught specimens. Conservationists are also interested in the effects of captivity on bone morphology as it may influence rewilding success. We compared trabecular bone volume fraction (BVF) between wild and captive mountain lions, cheetahs, leopards and jaguars. We found significantly greater BVF in wild than in captive felids. Effects of captivity were more marked in the humerus than in the femur. A ratio of humeral/femoral BVF was also lower in captive animals and showed a positive relationship to home range size in wild animals. Results are consistent with greater forelimb than hindlimb loading during terrestrial travel, and possibly reduced loading of the forelimb associated with lack of predatory behaviour in captive animals. Thus, captivity among felids has general effects on BVF in the postcranial skeleton and location-specific effects related to limb use. Caution should be exercised when identifying skeletal specimens for use in comparative studies and when rearing animals for conservation purposes.
... The first assumption behind the MFH is known as Wolff's law, which states that bone is deposited in presence of functional demand and resorbed in its absence in such a way that a decrease in musculoskeletal stress results in size reductions (Wolff 1892(Wolff , 1986. Though the nuances of this relationship have been much questioned, the basic relationship between stress and bone deposition is supported (Ruff, Holt, and Trinkaus 2006). The second, implicit, assumption is that an HG diet results in greater stresses on the masticatory complex than an agricultural one (Carlson and Van Gerven 1977). ...
... Ontogenetic series showing that population-specific morphology is not established at birth are particularly convincing (Holmes and Ruff 2011). The relationship between bone deposition, remodeling, and masticatory strain has been shown by both comparative studies using primates (Hylander 1979), hyraxes (Lieberman et al. 2004), and rodents (Yamada and Kimmel 1991) and in silico simulations of human morphology (Korioth, Romilly, and Hannam 1992;Sella-Tunis et al. 2018); Wolff's law is a persuasive argument for the mechanism behind these functional changes (Wolff 1892(Wolff , 1986Ruff, Holt, and Trinkaus 2006). ...
... According to Frost's (2000) theory of bone functional adaptation, bone is a mechanostat -that is, it has loading thresholds that must be exceeded for deposition or resorption to occur. Because bone remodels in part owing to functional demands, its morphology should be directly reflective of an individual's activity patterns (Frost 2000;Ruff et al. 2006). Regardless of the specific mechanics, and the acknowledgment of the contribution of genetics, many studies have reinforced the idea of "bone functional adaptation" to mechanical loading, particularly in cortical bone (e.g., Pearson 2000;Rogers, 2020;Ruff et al. 2006;Stock 2006;Wescott 2006). ...
... Because bone remodels in part owing to functional demands, its morphology should be directly reflective of an individual's activity patterns (Frost 2000;Ruff et al. 2006). Regardless of the specific mechanics, and the acknowledgment of the contribution of genetics, many studies have reinforced the idea of "bone functional adaptation" to mechanical loading, particularly in cortical bone (e.g., Pearson 2000;Rogers, 2020;Ruff et al. 2006;Stock 2006;Wescott 2006). This includes studies of bone functional adaptation in the modern human foot skeleton (Jashashvili et al. 2015). ...
Article
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The Medieval-Post-Medieval transition in England was an important shift in the human biocultural environment. With urbanization and industrialization came resultant changes in living and working conditions and subsequent effects on the skeleton. In addition, the Post-Medieval period ushered in changes in footwear and activity patterns, with potential consequences on foot bone morphology. The objective of this study is to compare calcaneal and talar lengths between the Medieval and Post-Medieval periods to determine whether there are quantifiable differences that correspond to shifting footwear and activity patterns. T-tests and ANCOVAs (and their non-parametric equivalents) were used to compare calcaneal and talar lengths of 1086 adults from 14 London cemeteries (Medieval n = 8, Post-Medieval n = 6), available in the Oracle Wellcome Osteological Research Database (WORD) curated by the Museum of London. Males and females were also analyzed separately. In the total sample, tali and calcanei are longer in the Medieval period (p < 0.001 for both tarsals). When males and females are analyzed separately, male talar length is greater in the Post-Medieval period (p < 0.001). The difference in talar length between periods is not statistically significant for females (p = 0.093). These differences in talar and calcaneal lengths between periods likely reflect differences in footwear between the Medieval and Post-Medieval periods. The magnitude of these differences varies according to sex, indicating that the change in footwear had differential impacts on men and women. Together, these results suggest that Medieval and Post-Medieval tarsals physically incorporated their respective cultural environments and gendered differences in cultural practice, particularly related to the footwear characteristic of each period.
... In the 19th century, an orthopaedic surgeon and anatomist Julius Wolff described the premise that bone has a continual mutual dynamic relationship with the transmission of forces through it; he referred to this concept as the law of bone remodelling (Ruff 2008;Stein and D´Ambrosia 2008). Today, the term "Wolff's Law" is widely employed, however, the concept is understood in a more general sense -that bones adapt to their mechanical environment, and therefore reflect in some way their mechanical loading history during life (Ruff et al. 2006). ...
... Wolff's law was originally formulated in a strict mathematical sense by the author (Wolff 1892) to explain that the organisation of trabecular bone in the proximal femur and other parts of the skeleton tends to be formed during growth and development in correspondence to principal mechanical stresses affecting the bone (Pearson and Lieberman 2004;Ruff et al. 2006). For this reason, some researchers suggest using the term "bone functional adaptation" when talking about the bone response to loading by altering bone mass ( Figure 2), and advocate that Wolff's law should only refer to the original phenomenon described by Wolff (Ruff et al. 2006). ...
... There are distinct challenges to identifying functional adaptation signals in the carpus, particularly since even elements of the skeleton experiencing high, predictable loads, such as the proximal femur, have often failed to conform to predictions (Carlson et al., 2006;Fajardo et al., 2007;Kivell, 2016b;MacLatchy & Müller, 2002;Ryan & Ketcham, 2002;Tsegai et al., 2018). Firstly, all bones are under a multitude of biological demands and genetic influences that can confound functional signals, affecting not only the structure and architecture of bone, but also its capacity to respond to biomechanical signals (Bertram & Swartz, 1991;Currey, 2003;Lieberman, 1997;Lovejoy et al., 2003;Ruff et al., 2006). Importantly, interspecific analyses have shown that some structural parameters, such as BV/TV or trabecular thickness, have systemic patterning at the genus level, independent of locomotion and predicted stress magnitude. ...
... Secondly, it is still not well understood how trabecular and cortical bone modeling (sensu Barak, 2019) is triggered by variable aspects of biomechanical force such as strain magnitude and loading frequencies (Doube et al., 2011;Lieberman, 1997;Ruff et al., 2006). Many hypotheses have focused on the magnitude of strain, suggesting that functional adaptation reflects the peak strain imposed on a joint (Currey, 2002;Frost, 1987). ...
Article
The morphology of the proximal carpals (scaphoid, lunate, triquetrum) are linked to the range of motion (ROM) at the radiocarpal and midcarpal joints. While the relationship between ROM and habitual locomotor mode is well established, it has yet to be investigated whether relative patterns of internal bone architecture reflect the kinematics and kinetics at the proximal row. As internal bone is known to model its structure to habitually incurred forces, internal architecture has the potential to provide insight into how joints have been loaded during the lifetime of an individual. Using a broad sample of extant great apes and humans (n = 177 total bones), this study investigates whether relative differences in the bone volume to total volume (BV/TV) and degree of anisotropy (DA) across the scaphoid, lunate and triquetrum correlate with the presumed force transfer and biomechanics of the hominoid wrist. Results reveal that broad patterns in BV/TV and DA differentiate hominoids by their predominant locomotor mode. The human pattern suggests the lunate may be the most highly strained bone within the proximal row. Both knuckle-walking taxa (Gorilla, Pan) exhibited similar architectural patterns suggesting they are adapted to resist similar forces in this region of the wrist. The relatively high DA across all Pongo carpals suggests it may have more stereotypical wrist loading than commonly assumed. Finally, the distinctly low DA in the triquetrum across all taxa suggests force transfer via the synapomorphic triangular fibrocartilage complex may leave a distinctive signature in the internal bone architecture that requires further investigation. Objectives Functional adaptation in the trabecular and cortical bone of individual wrist bones has been investigated across hominoid species but functional conclusions remain limited. This study examines whether relative patterns in internal bone architecture across multiple carpal bones can be correlated to the known or assumed kinetics and kinematics of the wrist joint in extant hominoids. Materials and Methods This study applied a whole-bone methodology to quantify the internal architecture (cortical and trabecular bone) of the scaphoid, lunate, and triquetrum of suspensory (Pongo sp.), knuckle-walking (Pan paniscus, Pan troglodytes, Gorilla sp.) and bipedal (Homo sapiens) hominoids (n = 177 total bones). Results H. sapiens showed unique patterns in both measured parameters: a decrease in degree of anisotropy (DA) from the scaphoid to the triquetrum with higher bone volume to total volume (BV/TV) in the lunate relative to the other bones. Knuckle-walking taxa had similar patterns in both parameters: highest mean DA in the lunate and lowest in the triquetrum while significantly higher BV/TV was recorded the triquetrum. Pongo exhibited the same DA pattern as knuckle-walking taxa but a distinct pattern of continual decrease in BV/TV from scaphoid to triquetrum. Discussion Relative differences in the internal bone structure across multiple carpals differentiated locomotor modes in extant hominoids. The triquetrum and lunate are particularly understudied but their importance to differentiating locomotor mode indicates further research is warranted. Establishing patterns across more carpal joints in primates should be a research priority as they will provide critical context to interpreting fossil species represented by single or few carpal elements.
... 71,72 This destructive feedback mechanism is then further fueled by fragments of degraded ECM proteins, such as Col2. 73 75 Bones are considered to reflect to some degree their mechanical loading history including the magnitude and direction of applied loads resulting in, e.g., greater bone strength in directions of higher strain. 75 The bone's morphological response to mechanical strains is also modulated by signaling molecules from surrounding joint tissues which can trigger the formation of bone spurs, also termed osteophytes (see Figure 2). ...
... 73 75 Bones are considered to reflect to some degree their mechanical loading history including the magnitude and direction of applied loads resulting in, e.g., greater bone strength in directions of higher strain. 75 The bone's morphological response to mechanical strains is also modulated by signaling molecules from surrounding joint tissues which can trigger the formation of bone spurs, also termed osteophytes (see Figure 2). 76 Regions of the joint showing OA lesions are exposed to higher loads, which can result in a flattening or depression of the subchondral bone surface termed subchondral bone attrition. ...
Thesis
Osteoarthritis (OA) is among the leading causes for global disability and a growing problem for patients and health care systems. OA onset and progression are characterized by articular cartilage (AC) destruction, but the mechanisms of degeneration remain elusive. So far, only symptomatic treatment is available. The development of disease-modifying drugs and design of clinical trials is not only held up by a lack of mechanistic understanding of early OA pathology, but also by an inability to detect early, potentially reversible disease states. To overcome this shortcoming, this work explored if early OA detection is possible with current clinical technology. A proof-of-concept for an observer-independent and minimally-invasive early OA diagnosis, supported by artificial intelligence, could be developed. This detection is based on a clinically approved probe-based confocal laser-endomicroscope. Here, such an endomicroscope could already be used on AC ex vivo to visualize the superficial chondrocyte spatial organization (SCSO), an image-based biomarker for the earliest structural changes in AC during OA. An early OA pathology, which is not well understood, is the softening of the articular surface (AS). In this work, changes in the elastic modulus of the AS were determined using atomic force microscopy (AFM) nanoindentation on human AC specimens showing varying local severities of OA, as defined by the fluorescence microscopy-determined SCSO. A negative correlation between the elastic modulus of the AS and consecutive OA-related SCSO stages was found. Importantly, an extensive loss of AS stiffness was detected already in those specimens showing an SCSO typical for early OA. Together, this established the SCSO as a visualizable surrogate marker for functionally relevant local tissue architecture changes in early OA. Importantly, this now enables an intra-operative prediction of microscale AS softening. AFM has developed into a powerful tool and it is often the method of choice for the nanoscale surface characterization of biological samples, such as cells. Its applicability to native biological tissues has been limited, because of the large size of tissue samples and their inherently high surface roughness. Here, a combination of AFM and fluorescence microscopy was used to map the microscale mechanical properties and image the nanoscale supramolecular collagen organization on a millimeter-sized AS region and correlate them to the local SCSO. A precise co-localization of early OA SCSO changes with local AS softening, thinning of collagen fibers, and a roughening of the AS was detected. These spatial correlations occurred on the scale of tens of micrometers thus rendering an external cause for the observed damage unlikely. This led to a novel mechanism for AS degeneration in OA, where the proliferative remodeling of the SCSO itself causes local damage to the AS. To gain insights into the pathological processes leading to the loss of tissue function in macroscopically intact AC, high-resolution force-extension curve-based imaging, as well as immunofluorescence and immunogold scanning electron microscopy were used. Changes in the thickness of collagen fibers and their composition at the onset and during progression of OA were uncovered. Interestingly, a gradual and eventually complete loss of thick collagen fibril bundles (>100 nm in diameter) was observed, which led to an overall thinning of fibers. Furthermore, the formation of type I collagen, a marker for mechanically inferior fibrocartilage-like tissue, was demonstrated for the first time distant from focal OA lesions. Based on this collective data, in this thesis a comprehensive mechanism is proposed for the initiation and progression of OA in macroscopically intact regions of OA joints, which might also hold for healthy joints at OA onset. In this model, a proliferative remodeling of the SCSO occurs as part of a generalized response to a distant focal AC damage. This is accompanied by a loss of thick collagen fibril bundles, which results in local softening of the AS and therefore increased mechanical stress on the chondrocytes. Consequently, chondrocyte clusters are formed, followed by further AS softening, collagen fiber thickness decrease and the formation of mechanically inferior fibrocartilage-like tissue (rich in type I collagen). Together, these processes result in a macroscopically intact, but mechanically impaired tissue phenotype, which is prone to further local damage that eventually could lead to the development of larger focal defects. Preservation of the thickest collagen fiber bundles at the AS and modulation of type I collagen synthesis could thus become a major focus of cartilage repair strategies and pharmacological interventions to mitigate the progressive loss of tissue function in OA. Altogether, this work enabled unprecedented topographic, mechanical and biochemical information on cartilage physiology from the nanometer to the millimeter scale under near physiological conditions. The mechanistic insights on the local progression of OA in macroscopically intact tissue uncover starting points for novel therapies and close a gap in our understanding of the order of pathological events in early OA.
... We transferred the ipsilateral fibula and placed it in an intramedullary location. When the graft is located on the mechanical and anatomical axis of the tibia, the risk of fracture is reduced [28]. The vascularised fibula heals through the bone and does not require 'creeping replacement' , which can occur in vascularised grafts, and has all the advantages of a vascularised fibula graft without the requirement of microvascular expertise. ...
... Therefore, the fibula is a good choice for the reconstruction of tibial defects because it has good mechanical properties and the ability to become hypertrophied. The fibula has great potential for remodelling and hypertrophy when subjected to a continuous mechanical load (Wolfe's Law) [28]. ...
Article
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Background Reconstruction of large tibial defects is often a major challenge in limb salvage. This study aimed to evaluate initial follow-up results of ipsilateral fibula transfer for the treatment of large tibial defects in children. Methods A retrospective study was performed between September 2014 and April 2021. Ten children were identified as having large tibial defects. The children underwent ipsilateral fibula transfer. We then evaluated initial healing, tibial length discrepancy, ankle varus/valgus, fibular position, refracture, infection, and function. Results Five boys and five girls, with an average age of 7.2 years, were evaluated. The transferred fibula was united in the patients. The mean follow-up period after fibular transposition was 43 months. The patients achieved primary bone union; the mean time to union was 8.4 months (range, 4–18 months). Complications included refracture (30%), infection (40%), tibia malunion (30%), ankle varus (30%), sensory loss of toes (10%), and ankle valgus (10%). No other major complications were observed. All 10 patients were able to perform activities of daily living and return to their normal activities. Conclusion Ipsilateral fibula transfer is a salvage surgery for the treatment of large tibial defects in children with congenital pseudoarthrosis of the tibia, traumatic nonunion of the tibia, and/or tibial defect after chronic osteomyelitis. However, long-term results still need to be followed up.
... Here, we study convergence in the humerus and the femur, which have a well-known capacity to respond to biomechanical loadings and functionally adapt to locomotion style (Pearson and Lieberman 2004;Ruff et al. 2006;Kivell 2016), resulting in a close relationship with locomotor ecology (e.g., Patel et al. 2013;Botton-Divet et al. 2016;Amson et al. 2017;Mielke et al. 2018b;Fabre et al. 2019;Parsi-Pour and Kilbourne 2020). Both bones can be investigated at different scales of organisation (Francillon-Vieillot et al. 1990). ...
... Several questions should still be answered in detail on the factors affecting prevalently trabecular bone functional adaptation (e.g., contractile forces vs. substrate reaction forces, Judex and Carlson 2009;Robling 2009; high-magnitude loadings vs. high-frequency loadings; Bertram andSwartz 1991, Kivell 2016 and references therein for details and other issues). CSP investigation started earlier than trabecular bone investigation, and several studies have established a straightforward relationship with the biomechanical environment (e.g., Jones et al. 1977;van Der Meulen et al. 1993, 1996Ruff et al. 1994Ruff et al. , 2006van Der Meulen and Carter 1995). However, some in vivo works have revealed that diaphyseal internal bone functional adaptation can be more complex than modeled (e.g., Lanyon and Rubin 1985;Judex et al. 1997;Demes et al. 1998;Wallace et al. 2014). ...
Article
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Identifying ecomorphological convergence examples is a central focus in evolutionary biology. In xenarthrans, slow arboreality independently arose at least three times, in the two genera of ‘tree sloths’, Bradypus and Choloepus, and the silky anteater, Cyclopes. This specialized locomotor ecology is expectedly reflected by distinctive morpho-functional convergences. Cyclopes, although sharing several ecological features with ‘tree sloths’, do not fully mirror the latter in their outstandingly similar suspensory slow arboreal locomotion. We hypothesized that the morphology of Cyclopes is closer to ‘tree sloths’ than to anteaters, but yet distinct, entailing that slow arboreal xenarthrans evolved through ‘incomplete’ convergence. In a multivariate trait space, slow arboreal xenarthrans are hence expected to depart from their sister taxa evolving toward the same area, but not showing extensive phenotypical overlap, due to the distinct position of Cyclopes. Conversely, a pattern of ‘complete’ convergence (i.e., widely overlapping morphologies) is hypothesized for ‘tree sloths’. Through phylogenetic comparative methods, we quantified humeral and femoral convergence in slow arboreal xenarthrans, including a sample of extant and extinct non-slow arboreal xenarthrans. Through 3D geometric morphometrics, cross-sectional properties (CSP) and trabecular architecture, we integratively quantified external shape, diaphyseal anatomy and internal epiphyseal structure. Several traits converged in slow arboreal xenarthrans, especially those pertaining to CSP. Phylomorphospaces and quantitative convergence analyses substantiated the expected patterns of ‘incomplete’ and ‘complete’ convergence for slow arboreal xenarthrans and ‘tree sloths’, respectively. This work, highlighting previously unidentified convergence patterns, emphasizes the value of an integrative multi-pronged quantitative approach to cope with complex mechanisms underlying ecomorphological convergence.
... Fundamentally, human physical adaptation is an inherited ability that facilitates survival in hostile environments [45]. In response to some types of repeated external stimuli, the human body is able to modify over time [46] and, as such, bio-adaptation is an ability related to long-time training, i.e., an ability can only be gradually increased [45,46]. To the best of our knowledge, there is no biomechanical study that exists to date to quantify this training process. ...
... Fundamentally, human physical adaptation is an inherited ability that facilitates survival in hostile environments [45]. In response to some types of repeated external stimuli, the human body is able to modify over time [46] and, as such, bio-adaptation is an ability related to long-time training, i.e., an ability can only be gradually increased [45,46]. To the best of our knowledge, there is no biomechanical study that exists to date to quantify this training process. ...
Article
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Currently, there are pros and cons of research results related to weight cutting in combat sports, resulting in inconclusive results regarding the effects of weight-cut on athletes’ performance, and biomechanical investigations are hardly seen. Therefore, this pilot study tried to fill the gap by initiating an exploration in real-life competitions. It is our hope to add biomechanical insights (advantages/disadvantages) that would discern the impact of weight cutting on competitive performance and help to structure hypotheses in future research. The method consisted of 3D motion capture, EMG measurement and biomechanical modeling. Through the synchronized data, striking power, striking accuracy and reaction time were quantitatively determined. Pre- and post-test design was used to test common strikes before weight cutting and 24 h after weigh-in. Seven male athletes from local clubs were tested during regional competitions. Results were characterized by using descriptive statistics (means and standard deviations) and T-tests were performed to contrast differences between the pre- and post-tests. This pilot study has revealed that there is actually weight-regain instead of weight-loss. The weight-regain would speed up the perceptional and total reaction, slow down the limbs’ movement, worsen the striking accuracy and, possibly, decrease the strike power. The preliminary results are inconclusive regarding the competitive advantages/disadvantages induced by weight cutting. Further biomechanical studies are needed to deal with the controversial subject more objectively and scientifically.
... Here we provide the initial analyses of shaft robusticity, rigidity, and shape for the Maludong partial femur. Cross-sectional geometric (CSG) analyses of femoral diaphyses produce useful insights into body shape and activity patterns, as well as taxonomic relationships (e.g., Puymerail et al., 2012;Ruff, 2009;Ruff, Holt, Sládek, et al. (2006); Ruff, Holt, and Trinkaus (2006) ;Shackelford, 2007;Trinkaus & Ruff, 1999;Wei et al., 2017;Wei, Weng, et al., 2021), although they are not always straightforward reflections of form-function relationships (e.g., see Ruff, Holt, Sládek, et al., 2006;Ruff, Holt, & Trinkaus, 2006). Nonetheless, in order to have a more comprehensive morphological understanding of the Maludong femur and contextualize its comparability to contemporary femora from the broader East Asia region, we produce new estimates of its length with a regressionbased analysis and undertake a systematic internal structural analysis at selected diaphyseal locations. ...
... Here we provide the initial analyses of shaft robusticity, rigidity, and shape for the Maludong partial femur. Cross-sectional geometric (CSG) analyses of femoral diaphyses produce useful insights into body shape and activity patterns, as well as taxonomic relationships (e.g., Puymerail et al., 2012;Ruff, 2009;Ruff, Holt, Sládek, et al. (2006); Ruff, Holt, and Trinkaus (2006) ;Shackelford, 2007;Trinkaus & Ruff, 1999;Wei et al., 2017;Wei, Weng, et al., 2021), although they are not always straightforward reflections of form-function relationships (e.g., see Ruff, Holt, Sládek, et al., 2006;Ruff, Holt, & Trinkaus, 2006). Nonetheless, in order to have a more comprehensive morphological understanding of the Maludong femur and contextualize its comparability to contemporary femora from the broader East Asia region, we produce new estimates of its length with a regressionbased analysis and undertake a systematic internal structural analysis at selected diaphyseal locations. ...
Article
The Late Pleistocene partial right femur from Maludong in southwestern China has been attributed characteristics of early Homo, especially from the Early Pleistocene, putatively representing a late surviving archaic population in the region. Assessment of additional traits is warranted given newly described postcrania from the Late Pleistocene of southwestern China and characterized by relatively modern features. We used micro computed tomography (μCT) to extract and evaluate cross‐sectional diaphyseal structure. New predictions of Maludong femoral length were generated from a regression analysis of Holocene modern humans. Robusticity and shape at multiple, standard diaphyseal regions of interest (ROI) were compared to those of Pleistocene and Holocene humans from East Asia and beyond. Standardized torsional rigidities at mid‐proximal and subtrochanteric Maludong ROIs fell within ranges of variation exhibited by multiple comparative groups, and closest to medians of Early and Middle Upper Paleolithic modern humans (E/MUP). For Ix/Iy diaphyseal ratios, Maludong was higher than comparative groups at both ROIs, falling closest to the upper end of the E/MUP range. For Imax/Imin shape ratios, Maludong fell well above group medians at the mid‐proximal ROI and nearest E/MUP and Middle Pleistocene group medians at the subtrochanteric ROI. In diaphyseal robusticity and rigidity ratios, Maludong fits within variation exhibited by other Late Pleistocene modern humans. While we did not re‐analyze external features described as archaic‐like, internal structure of the Maludong femur contradicts this characterization and instead supports expanding intrapopulation variability expressed by Late Pleistocene modern humans in East Asia.
... While bone microanatomical features are inherited from evolution, bone microanatomy also adapts to functional constraints during the lifetime of organisms (Reina et al., 2017;Sievänen, 2010;Warden et al., 2007). Wolff's law (1986) states that bones adapt, if they have time, to mechanical stresses and gravity (Ruff et al., 2006). Bones thus tend to be stiffer and stronger when subjected to high stresses, with an increase in cortical thickness and trabeculae orientated in the direction of the maximal strain (Barak et al., 2013;Ruimerman et al., 2004;Volpato, 2008;Wolff, 1986). ...
Article
The long bones and associated musculature play a prominent role in the support and movement of the body and are expected to reflect the associated mechanical demands. But in addition to the functional response to adaptive changes, the conjoined effects of phylogenetic, structural and developmental constraints also shape the animal's body. In order to minimise the effect of the aforementioned constraints and to reveal the biomechanical adaptations in the musculoskeletal system to locomotor mode, we here study the forelimb of two closely related martens: the arboreal pine marten (Martes martes) and the more terrestrial stone marten (Martes foina), focusing on their forelimb muscle anatomy and long bone microanatomy; and, especially, on their covariation. To do so, we quantified muscle data and bone microanatomical parameters and created 3D and 2D maps of the cortical thickness distribution for the three long bones of the forelimb. We then analysed the covariation of muscle and bone data, both qualitatively and quantitatively. Our results reveal that species-specific muscular adaptations are not clearly reflected in the microanatomy of the bones. Yet, we observe a global thickening of the bone cortex in the radius and ulna of the more arboreal pine marten, as well a stronger flexor muscle inserting on its elbow. We attribute these differences to variation in their locomotor modes. Analyses of our 2D maps revealed a shift of cortical thickness distribution pattern linked to ontogeny, rather than species-specific patterns. We found that although intraspecific variation is not negligible, species distinction was possible when taking muscular and bone microanatomical data into consideration. Results of our covariation analyses suggest that the muscle-bone correlation is linked to ontogeny rather than to muscular strength at zones of insertion. Indeed, if we find a correlation between cortical thickness distribution and the strength of some muscles in the humerus, that is not the case for the others and in the radius and ulna. Cortical thickness distribution appears rather linked to bone contact zones and ligament insertions in the radius and ulna, and to some extent in the humerus. We conclude that inference on muscle from bone microanatomy is possible only for certain muscles in the humerus.
... Table 5) is very close to the bending resistance of the human cortical bone, which is a very important fact as the materials for implants should have very similar mechanical properties to the bone they are supporting. This relation is best described by Wollf's law, stating that the trabeculae may reflect the loading on the bone performing adaptative changes followed by secondary changes to the external part of the bone [13,[58][59][60]. The bone adapts to the load by increasing its density, this is true for the opposite as well. ...
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Alloys based on magnesium are of considerable scientific interest as they have very attractive mechanical and biological properties that could be used to manufacture biodegradable materials for medical applications. Mechanical alloying is a very suitable process to obtain alloys that are normally hard to produce as it allows for solid-state diffusion via highly energetic milling, producing fine powders. Powders obtained by this method can be sintered into nearly net-shape products, moreover, their phase and chemical composition can be specifically tailored. This work aims to investigate the effect of milling time on the density, microstructure, phase composition, and mechanical properties of Mg-Zn-Ca-Pr powders processed by high energy mechanical alloying (HEMA) and consolidated by spark plasma sintering (SPS). Thus, the results of XRD phase analysis, particle size distribution (granulometry), density, mechanical properties, SEM investigation of mechanically alloyed and sintered Mg-Zn-Ca-Pr alloy are presented in this manuscript. The obtained results illustrate how mechanical alloying can be used to produce amorphous and crystalline materials, which can be sintered and demonstrates how the milling time impacts their microstructure, phase composition, and resulting mechanical properties.
... Self-assembled mineralized fibrils hierarchically arranged in the presence of non-collagenous proteins and water are ultimately responsible for the mechanical properties of bone tissue, delivering at the same time nutrients and especially environmental signals to the implanted osteocytes implanted on it [19,20]. The unique structure of bone tissue is vital to activate mechano-transduction phenomena at the cell level, which is considered a major mechanism providing the bone with the ability to adapt to the loads under which it is placed, as well as to self-repair and self-regenerate upon damage of limited entity [21,22]. To understand the mechanical properties of bone tissue, it is important to underline how bone tissue behaves at various levels of its hierarchical structure [23,24]. ...
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Bone is a complex biologic tissue, which is extremely relevant for various physiological functions, in addition to movement, organ protection, and weight bearing. The repair of critical size bone defects is a still unmet clinical need, and over the past decades, material scientists have been expending efforts to find effective technological solutions, based on the use of scaffolds. In this context, biomimetics which is intended as the ability of a scaffold to reproduce compositional and structural features of the host tissues, is increasingly considered as a guide for this purpose. However, the achievement of implants that mimic the very complex bone composition, multi-scale structure, and mechanics is still an open challenge. Indeed, despite the fact that calcium phosphates are widely recognized as elective biomaterials to fabricate regenerative bone scaffolds, their processing into 3D devices with suitable cell-instructing features is still prevented by insurmountable drawbacks. With respect to biomaterials science, new approaches maybe conceived to gain ground and promise for a substantial leap forward in this field. The present review provides an overview of physicochemical and structural features of bone tissue that are responsible for its biologic behavior. Moreover, relevant and recent technological approaches, also inspired by natural processes and structures, are described, which can be considered as a leverage for future development of next generation bioactive medical devices.
... The phenotypic morphology of bones reflects habitual movement patterns practised during life (Bock, 1965), and this relationship between movement and bone shape, is a fundamental interpretive paradigm in bioarchaeology and palaeoanthropology (Jungers and Minns, 1979;Trinkaus and Ruff, 1999;MacLatchy et al., 2000;Madar et al., 2002;Ruff 2002;Ruff et al., 2006;Boyle et al 2020). Fossil hand and foot bones are rare, but they can be 3 useful for interpreting the evolution of locomotion as they are the primary biomechanical unit to interact with the environment (reviewed e.g., in Klenerman and Wood, ' o t and Aerts, 2008;Stolwijk et al., 2013;Vereecke et al., 2008). ...
Article
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The fossil record is scarce and incomplete by nature. Animals and ecological processes devour soft tissue and important bony details over time and, when the dust settles, we are faced with a patchy record full of variation. Fossil taxa are usually defined by craniodental characteristics, so unless postcranial bones are found associated with a skull, assignment to taxon is unstable. Naming a locomotor category based on fossil bone morphology by analogy to living hominoids is not uncommon, and when no single locomotor label fits, postcrania are often described as exhibiting a “mosaic” of traits. Here, we contend that the unavoidable variation that characterises the fossil record can be described far more rigorously based on extensive work in human neurobiology and neuroanatomy, movement sciences and motor control and biomechanics research. In neurobiology, degeneracy is a natural mechanism of adaptation allowing system elements that are structurally different to perform the same function. This concept differs from redundancy as understood in engineering, where the same function is performed by identical elements. Assuming degeneracy, structurally different elements are able to produce different outputs in a range of environmental contexts, favouring ecological robusticity by enabling adaptations. Furthermore, as degeneracy extends to genome level, genetic variation is sustained, so that genes which might benefit an organism in a different environment remain part of the genome, favouring species’ evolvability.
... Studies of skeletal adaptive plasticity can also contribute to broader discussions of developmental stability (the capacity for a genotype to produce near-similar phenotypes under consistent environmental conditions) as well as the limits to variation imposed by functional constraints, which limit morphological variation in association with the function of the structure in question (Futuyma, 1998) and canalization (the capacity for a genotype to withstand environmental perturbations) (Waddington, 1953). Research consistently demonstrates higher levels of asymmetry and variance in diaphyseal breadths compared to lengths and articular surface dimensions (Auerbach & Ruff, 2006;Buck et al., 2010;Reeves et al., 2016;Ruff et al., 1991) are consistent with the responsiveness of diaphyseal morphology to habitual activity, and greater developmental stability in articular surface and length dimensions (Lieberman et al., 2001;Ruff et al., 2006). Taken as a whole, plasticity in diaphyseal morphology is directly observable in bioarchaeological contexts and provides important information on the habits, dispositions, and practices of past populations. ...
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This article presents outcomes from a Workshop entitled “Bioarchaeology: Taking Stock and Moving Forward,” which was held at Arizona State University (ASU) on March 6–8, 2020. Funded by the National Science Foundation (NSF), the School of Human Evolution and Social Change (ASU), and the Center for Bioarchaeological Research (CBR, ASU), the Workshop's overall goal was to explore reasons why research proposals submitted by bioarchaeologists, both graduate students and established scholars, fared disproportionately poorly within recent NSF Anthropology Program competitions and to offer advice for increasing success. Therefore, this Workshop comprised 43 international scholars and four advanced graduate students with a history of successful grant acquisition, primarily from the United States. Ultimately, we focused on two related aims: (1) best practices for improving research designs and training and (2) evaluating topics of contemporary significance that reverberate through history and beyond as promising trajectories for bioarchaeological research. Among the former were contextual grounding, research question/hypothesis generation, statistical procedures appropriate for small samples and mixed qualitative/quantitative data, the salience of Bayesian methods, and training program content. Topical foci included ethics, social inequality, identity (including intersectionality), climate change, migration, violence, epidemic disease, adaptability/plasticity, the osteological paradox, and the developmental origins of health and disease. Given the profound changes required globally to address decolonization in the 21st century, this concern also entered many formal and informal discussions.
... The strain dependent reaction term is motivated by Wolff's law for bone remodeling, see Wolff (1892). Strain as a driving force for bone regeneration is also supported by more recent work, for example in Ruff et al. (2006). Note that the concentration of bio-active molecules is normalized to unity in healthy tissue. ...
Preprint
We consider the scaffold design optimization problem associated to the three dimensional, time dependent model for scaffold mediated bone regeneration considered in Dondl et al. (2021). We prove existence of optimal scaffold designs and present numerical evidence that optimized scaffolds mitigate stress shielding effects from exterior fixation of the scaffold at the defect site.
... Lower extremity stress seems to be linked to both high hunter-gatherer mobility and high agricultural workload (Eshed 2010;Lieverse 2013;Schlader 2015). Many researchers have identified a trend showing a decrease in DJD and EC in the lower limbs as a consequence of a decline in workload derived from reduced mobility (Hoyme & Bass 1962;Larsen 1995;Formicola 1997;Ruff et al. 2006;Holt & Formicola 2008;Sparacello & Marchi 2008;Larsen & Ruff 2011;Marchi et al. 2011;Stock et al. 2011;Carlson & Marchi 2014;Varalli et al. 2020). In turn, it was considered that changes in subsistence-related activities are better reflected in the upper limbs in a transitional context between hunting-gathering and low-level food production (Eshed et al. 2004;Eshed 2010;Varalli et al. 2020). ...
Article
This study tests the hypothesis that the incorporation of cultigens about ca. 2000 years BP substantially changed hunter-gatherer subsistence and mobility in the Atuel River valley (Central-Western Argentina), where the frontier of pre-Hispanic domesticated resource dispersion was defined. Degenerative joint disease and entheseal change markers were analyzed on skeletal remains from Cañada Seca-1, a burial archaeological site with commingled skeletal remains dated about ca. 1500 years BP (MNI = 24). The results show lower mobility in comparison with hunter-gatherer remains from the neighboring Pampa region and quite different manual activities compared to low-level producers. These trends are explained as a result of a mixed subsistence strategy and mobility in an area where the incorporation of domesticated plants was neither a linear nor a fast process, and a stereotypical view proves to be insufficient to understand it. Although further information is required for future discussions, the present research highlights the potential of commingled skeletal remains for this kind of study.
... The skeletal remains of children and adolescents are relatively rare in archeological contexts, and inferences from the skeleton about their behaviors and activities are challenging due to the structural and material changes that accompany growth and maturation. Ontogenetic trajectories in cortical bone geometry have led to the understanding that the timing of loading is crucial for determining overall bone strength, and that childhood and adolescence are particularly significant periods of mechanically-relevant bone adaptation (Gosman et al., 2013;Ruff et al., 1994Ruff et al., , 2006. This means that mechanical loading related to habitual behaviors plays a key role in shaping limb bone cortical and trabecular structural and material properties; however, it is unclear the extent to which adult skeletal morphology retains any signals of child and adolescent loading patterns and, if so, the nature of these signals. ...
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Objectives Though relationships between limb bone structure and mechanical loading have provided fantastic opportunities for understanding the lives of prehistoric adults, the lives of children remain poorly understood. Our aim was to determine whether or not adult tibial skeletal variables retain information about childhood/adolescent loading, through assessing relationships between cortical and trabecular bone variables and the timing of impact loading relative to menarche in premenopausal adult females. Methods Peripheral quantitative computed tomography was used to quantify geometric and densitometric variables from the proximal tibial diaphysis (66% location) and distal epiphysis (4% location) among 81 nulliparous young adult female controls and athletes aged 19–33 years grouped according to intensity of impact loading both pre- and post-menarche: (1) Low:Low (Controls); (2) High:Low; (3) High:High; (4) Moderate:Moderate; (5) Low:Moderate. ANCOVA was used to compare properties among the groups adjusted for age, stature, and body mass. Results Significant increases in diaphyseal total cross-sectional area and strength-strain index were documented among groups with any pre-menarcheal impact loading relative to groups with none, regardless of post-menarcheal loading history (p < .01). In contrast, significantly elevated distal trabecular volumetric bone mineral density was only documented among groups with recent post-menarcheal loading relative to groups with none, regardless of pre-menarcheal impact loading history (p < .01). Conclusions The consideration of diaphyseal cortical bone geometric and epiphyseal trabecular bone densitometric variables together within the tibia can identify variation in pre-menarcheal and post-menarcheal impact loading histories among premenopausal adult females.
... In general, bone is deposited under both increased peak strain (from hard biting) and cyclical strain (from chewing), and resorbed under opposite conditions (Frost 1987;Hylander and Johnson 1997). Bone has a site-specific optimal strain environment that is maintained via regular loading activities Biewener 1993;Hylander and Johnson 1997;Ruff et al. 2006;Ravosa et al. 2010Ravosa et al. , 2016. Elevated strains in the feeding apparatus and limbs stimulate osteogenesis, resulting in either increased bone volume and/or increased bone mineral content (biomineralization). ...
Article
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The rescue and rehabilitation of young fauna is of substantial importance to conservation. However, it has been suggested that incongruous diets offered in captive environments may alter craniofacial morphology and hinder the success of reintroduced animals. Despite these claims, to what extent dietary variation throughout ontogeny impacts intrapopulation cranial biomechanics has not yet been tested. Here, finite element models were generated from the adult crania of 40 rats (n = 10 per group) that were reared on 4 different diet regimes and stress magnitudes compared during incisor bite simulations. The diets consisted of (1) exclusively hard pellets from weaning, (2) exclusively soft ground pellet meal from weaning, (3) a juvenile switch from pellets to meal, and (4) a juvenile switch from meal to pellets. We hypothesized that a diet of exclusively soft meal would result in the weakest adult skulls, represented by significantly greater stress magnitudes at the muzzle, palate, and zygomatic arch. Our hypothesis was supported at the muzzle and palate, indicating that a diet limited to soft food inhibits bone deposition throughout ontogeny. This finding presents a strong case for a more variable and challenging diet during development. However, rather than the "soft" diet group resulting in the weakest zygomatic arch as predicted, this region instead showed the highest stress among rats that switched as juveniles from hard pellets to soft meal. We attribute this to a potential reduction in number and activity of osteoblasts, as demonstrated in studies of sudden and prolonged disuse of bone. A shift to softer foods in captivity, during rehabilitation after injury in the wild for example, can therefore be detrimental to healthy development of the skull in some growing animals, potentially increasing the risk of injury and impacting the ability to access full ranges of wild foods upon release. We suggest captive diet plans consider not just nutritional requirements but also food mechanical properties when rearing wildlife to adulthood for reintroduction.
... Bone remodelling is dictated by mechanical stimuli (Wolff's Law;Frost, 1994) and works through feedback loops: more bone tissue is developed in response to higher strain rates and, inversely, this bone tissue is reabsorbed following a decrease in strain applied to bone (Ruff et al., 2006). The Mechano-Regulatory-Pathway theory highlights the fact that it is the surrounding environment which influences the type of cells that are generated around a facture site (Prendergast et al., 1997;Lacroix and Prendergast, 2002) with fluid flow and mechanical strain being the most influential factors. ...
Thesis
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Introduction: Supra-malleolar corrective osteotomies (SMOT) are a common surgical procedure for the prevention of early onset of ankle arthritis. The Distal Tibia Nail (DTN; Mizuho®), was previously developed for the reduction of distal tibia fractures. The aim of this project was to identify error sources in biomechanical testing, and to test the feasibility of the DTN for SMOT performed using the medial wedge opening (MWO) technique. Methods: A total of 16 Sawbones® were each implanted with either a DTN or medial distal tibia plate (MDTP; Synthes®), and a MWO simulated. Four testing phases were defined: Phase-0, testing of Sawbones® without implant/osteotomy; Phase-1, samples with MWO and implant; Phase-2, Phase-1 samples with lateral cortex fractured; Phase-3, samples with an A3 type fracture. Stiffness construct and interfragmentary movement (IFM) were analysed. CT scans were taken of the samples at Phases 0 and 1. Results: Up to 80% difference was noticed between Sawbones® samples in Phase-0; in Phases 1 and 2 significant differences were found between stiffness constructs of the implant groups but this amounted to <2 mm IFM. The DTN was significantly more resistant to compression and torsion when supporting an A3 fractures (Phase-3). Elements such as original Sawbones® stiffness construct, implant position, potting material, loading axis, and sample positioning can have a high influence on measured stiffness and bias the results. Conclusion: The DTN is a viable option for the fixation of SMOT performed with a MWO technique. Future studies should pay careful attention to boundary conditions affecting outcomes measures and drawn conclusions
... Others have argued that bone microstructural characters are essentially the outcome of ontogenetic and functional factors, an opinion that does not necessarily exclude the presence of a phylogenetic signal (see Padian 2013). Among these factors, the most often discussed are Amprino's (1947) rule, according to which variation in the growth rate of bone tissue mainly determines variation in its structure (Castanet et al. 1996, 2000, Margerie et al. 2002a, Montes et al. 2010, and Wolff's (1892) law, which postulates that bone microstructure predominantly reflects adaptations to biomechanical constraints (Lanyon 1984, Currey and Alexander 1985, Thomason 1985, Carter et al. 1991, Margerie 2002b, Ruff et al. 2006, Cubo et al. 2015. ...
... Living bone can functionally adapt 1 to loads it experiences and thus reflects, to some extent, the behaviour of individuals over their lifetime. This functional adaptation, caused by modelling and remodelling of bone 2 , has been experimentally demonstrated in external shape change 1,3 , the thickening of cortical bone 1,4 , entheseal shape change on the cortical bone surface 5,6 , and change in the architecture of trabecular bone 7,8 , or a combination of these phenomena. Unlike cortical bone, trabecular architecture is usually completely internal, concentrated in the epiphyses of long bones, and far more porous at the mesoscale 9 . ...
Article
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Bone is a remarkable, living tissue that functionally adapts to external loading. Therefore, bone shape and internal structure carry information relevant to many disciplines, including medicine, forensic science, and anthropology. However, morphometric comparisons of homologous regions across different individuals or groups are still challenging. In this study, two methods were combined to quantify such differences: (1) Holistic morphometric analysis (HMA) was used to quantify morphometric values in each bone, (2) which could then be mapped to a volumetric mesh of a canonical bone created by a statistical free-form deformation model (SDM). Required parameters for this canonical holistic morphometric analysis (cHMA) method were identified and the robustness of the method was evaluated. The robustness studies showed that the SDM converged after one to two iterations, had only a marginal bias towards the chosen starting image, and could handle large shape differences seen in bones of different species. Case studies were performed on metacarpal bones and proximal femora of different primate species to confirm prior study results. The differences between species could be visualised and statistically analysed in both case studies. cHMA provides a framework for performing quantitative comparisons of different morphometric quantities across individuals or groups. These comparisons facilitate investigation of the relationship between spatial morphometric variations and function or pathology, or both.
... Both aspects are crucial for an accurate solution of muscle redundancy issues and to compute muscle forces in humans, and, therefore, by extension, to apply it to the hominin fossil record (Blasi-Toccacceli et al., 2020). As another example, FEA may complement bone functional remodelling laws, since bone morphological adaptation occurs in response to mechanical loading (Ruff et al., 2006). FEA can predict the strain experienced by the bone before computing bone morphological modifications (Hambli, 2014). ...
Article
"Multibody Dynamic Analysis" (MDA) and "Finite Element" Analysis (FEA) are commonly used to investigate biomechanical solicitations relative to a movement. These approaches have been also used in palaeontology to bring extinct animals, such as hominins, "back to life". The purpose of this study is to report on the available literature on the use of MDA and FEA in postcranial palaeoanthropology. We briefly introduce the theoretical aspects of modelling and simulation applied to biomechanics. The theoretical basis and fields of application of MDA and FEA are then presented. A synthesis of the literature highlights palaeoanthropological issues, variables derived, findings obtained and methodological limitations to keep in mind. More generally, this study synthesizes a conceptual framework and recommendations for the use of such approaches in form-function relationships in an evolutionary context.
... Even if the results presented here suggest that the main pattern of evolutionary modularity of the primate pelvis is aligned with developmental partitioning of the pelvic girdle, the tested locomotory-obstetric functional partition (H 5 ) also contained a significant evolutionary modular signal. This could reflect the accumulated effect within primates across time of how at an individual level the developmental programmes interact with these functional regions, even if it remains unclear precisely how these processes interact (Klingenberg 2008, Ruff et al. 2006. The locomotory-obstetric partition has received attention before, particularly in terms of the obstetric dilemma framework. ...
Thesis
This thesis represents, to date, the most comprehensive investigation into the influence of integration (covariation) and modularity (the organisation of integrated units) on the morphological evolution of the primate pelvis. The concepts of integration and modularity are core tenets of evolutionary biology, yet their evolutionary role remains poorly understood. In this thesis, I quantified primate pelvis morphological variation across 4 clades encompassing the main primate locomotory specialisations. Shape was captured in detail, using a surface-based geometric morphometric approach, to test five alternative models of pelvis organisation, calculate integration levels, and reconstruct pelvis evolution. In this thesis, I demonstrate that the primate pelvis is dominantly modulated by developmental pathways, with ilium, ischium, pubis, acetabulum, and sacrum having the capacity to vary and evolve in a relatively independent manner (Chapter 2). This main modular pattern of primates is different to that of carnivores where in the latter group the ischium and pubis covary more closely together. The pubis-ischium parcellation is present in all examined primate phylogenetic groups (Lemuroidea, Ceboidea, Cercopithecoidea, and Hominoidea – humans excluded), suggesting that this parcellation was present in basal primates. Notably, a significant modular signal is also present for the functional hypothesis (locomotion-obstetrics). This suggests that the bony birth canal may vary and evolve relatively independently from the rest of the pelvis shape, alleviating the obstetric dilemma. Overall, this study demonstrates that the modularity pattern of the primate pelvic girdle is not simply limited to its developmental units. Instead, I find modular patterns acting in a complex multi-layered way, with developmental processes synergistically meeting functional needs. Few studies have tried to explicitly clarify the role of integration plays in morphological variability and the evolutionary consequences this entails. In Chapter 3, I calculated the integration levels and tested whether integration may constrain or facilitate evolutionary flexibility and diversity. I found an inverse relationship between integration magnitudes and disparity levels, indicating that the impact of primate pelvis integration is best supported by the hypothesis of constraint across the primate order, its phylogenetic and locomotory groups. My findings highlight the need to consider the impact of integration when modelling shape changes and reconstructing evolutionary pelvic trajectories. In Chapter 4, I examined the role of integration in the morphological divergence of the human pelvis. Human integration levels are marked by a reduction across its developmental and functional pelvic constituents compared to the other sampled primates (Gorilla beringei, Hylobates lar, Pan paniscus and Macaca mulatta). The reduction of inherent human constraint is paired with elevated levels of disparity, indicative of inherent high levels of evolvability present within the human pelvis. Particularly of interest is the low integration signal between the human pubis and ischium, yet the integration levels within these elements are remarkably high. In the case of the pubis, this translates into limited evolutionary possibilities and reduced disparity. Conversely, the high ischium integration acts as a facilitator to morphological disparity, aiding evolutionary responsiveness. The increased evolutionary flexibility of the human ischium played a pivotal role in both bipedal efficiency and increased levels of sexual dimorphism, whereby ischium disparity is also an important aspect in easing parturition. The reduced integration levels between the human developmental and functional pelvis modules provide its pelvic bauplan with increased flexibility to respond to multiple selective pressures, facilitating the complex morphological modifications and divergence of the human pelvis along an evolutionary trajectory that may have otherwise been difficult or even impossible to achieve. This thesis represents a significant advance in the study of pelvic modularity and morphological evolution. Chapters 2 and 3 form a comprehensive baseline for primate pelvis structuration and integration magnitudes, providing an in-depth exploration of hypotheses of modularity and the impact of integration on macroevolutionary patterns. The thesis is also novel in that it investigates developmental and functional integration patterns, and does so across and within species. This provides a multi-layered view of the role of modularity and integration of the primate pelvic girdle.
... Both aspects are crucial for an accurate solution of muscle redundancy issues and to compute muscle forces in humans, and, therefore, by extension, to apply it to the hominin fossil record (Blasi-Toccacceli et al., 2020). As another example, FEA may complement bone functional remodelling laws, since bone morphological adaptation occurs in response to mechanical loading (Ruff et al., 2006). FEA can predict the strain experienced by the bone before computing bone morphological modifications (Hambli, 2014). ...
... Jejich progresivní vývoj může vést k tvorbě entezopatií, tj. k osifikaci svalových úponů ve formě nadměrné tvorby kostní tkáně (Ruff et al. 2006). Některé takové změny vyplývají ze specifičnosti prováděné práce. ...
Book
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The methodology is divided into three basic areas of the cognitive process of sacral architecture, which differ according to the nature of the studied sources. I. Problems of knowledge of sacral architecture on the basis of written, cartographic and pictorial sources. II. Sacral architecture in terms of material sources of archaeological nature (artifacts, ecofacts and their finds). III. Sacral architecture on the basis of material sources of a building nature, examined by a building historical survey. These areas are accompanied by subchapters devoted to other methods, other cognitive and documentation processes. A necessary part are also small excursion chapters, in which specific examples from research practice are described.
... Both cortical and trabecular bone are highly responsive to the loading environments (Barak, 2019;Barak et al., 2011;Carlson & Judex, 2007;Pontzer et al., 2006;Ruff & Hayes, 1982;Ruff et al., 2006;Wolff, 1892), with the rate of bone (re)modeling during the first 2 years of life being higher than in adults, as also suggested by numerous crosssectional studies (Chevalier et al., 2021;Gosman & Ketcham, 2009;Milovanovic et al., 2017;Raichlen et al., 2015;Ryan & Krovitz, 2006;Ryan et al., 2017;Saers et al., 2020). In particular, studies on the tibia (Gosman & Ketcham, 2009;Raichlen et al., 2015), femur (Milovanovic et al., 2017;Ryan & Krovitz, 2006), vertebrae (Acquaah et al., 2015), talus , and calcaneus ) describe a general typical pattern in which, around birth, high bone volume fraction (BV/TV) corresponds to high trabecular number (Tb.N) and low trabecular thickness (Tb.Th) and spacing (Tb.Sp). ...
Article
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The study of the development of human bipedalism can provide a unique perspective on the evolution of morphology and behavior across species. To generate new knowledge of these mechanisms, we analyze changes in both internal and external morphology of the growing human talus in a sample of modern human juveniles using an innovative approach. The sample consists of high‐resolution microCT scans of 70 modern juvenile tali, aged between 8 postnatal weeks and 10 years old, from a broad chronological range from Middle/Late Neolithic, that is, between 4800 and 4500 BCE, to the 20th century. We applied geometric morphometric and whole‐bone trabecular analysis (bone volume fraction, degree of anisotropy, trabecular number, thickness, and spacing) to all specimens to identify changes in the external and internal morphology during growth. Morphometric maps were also generated. During the first year of life, the talus has an immature and globular shape, with a dense, compact, and rather isotropic trabecular architecture, with numerous trabeculae packed closely together. This pattern changes while children acquire a more mature gait, and the talus tends to have a lower bone volume fraction, a higher anisotropy, and a more mature shape. The changes in talar internal and external morphologies reflect the different loading patterns experienced during growth, gradually shifting from an “unspecialized” morphology to a more complex one, following the development of bipedal gait. Our research shows that talar plasticity, even though genetically driven, may show mechanical influences and contribute to tracking the main locomotor milestones.
... Bone function, morphology, and body size can also influence the osteonal parameters of independent bones across a single individual (Parfitt 2002;Gocha and Agnew 2016). Smaller osteons in loadbearing bones of large mammals can be due to biomechanical strain, body size, and mobility as bone maintains mechanical resistance (Ruff et al. 2006;Miszkiewicz and Mahoney 2019). Meanwhile, smaller osteon size in older mammals can be attributed to a decline in osteoclastic activity in senescence (Martin et al. 1980;Dominguez and Agnew 2016). ...
... This also provides greater phenotypic plasticity and may be a response to developing postural and locomotor loads [30]. It is expected that both trabeculae and overall bone shape probably respond in tandem to mechanical loads during ontogeny [140], but that microstructural properties may continue after the adult shape has been attained. Additionally, these results suggest that subchondral bone microstructural properties are remarkably heterogenous. ...
Article
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High-resolution computed tomography images were acquired for 31 proximal human tibiae, age 8 to 37.5 years, from Norris Farms #36 cemetery site (A.D. 1300). Morphometric analysis of subchondral cortical and trabecular bone architecture was performed between and within the tibial condyles. Kruskal-Wallis and Wilcoxon signed-rank tests were used to examine the association between region, age, body mass, and each morphometric parameter. The findings indicate that age-related changes in mechanical loading have varied effects on subchondral bone morphology. With age, trabecular microstructure increased in bone volume fraction (p = 0.033) and degree of anisotropy (p = 0.012), and decreased in connectivity density (p = 0.001). In the subchondral cortical plate, there was an increase in thickness (p < 0.001). When comparing condylar regions, only degree of anisotropy differed (p = 0.004) between the medial and lateral condyles. Trabeculae in the medial condyle were more anisotropic than in the lateral region. This research represents an innovative approach to quantifying both cortical and trabecular subchondral bone microarchitecture in archaeological remains.
... Numerous experimental and observational studies have demonstrated that long bone diaphyses show plasticity when bearing mechanical loadings (Warden et al. 2014(Warden et al. , 2007Ruff et al. 2006;Burr et al. 2002;Heinonen et al. 2002;Robling et al. 2002;Hsieh et al. 2001), and bone tends to model itself locally at the positions where mechanical stimuli are presumably applied (Tiwari and Prasad 2019;Christen et al. 2014;Schulte et al. 2013;Sugiyama et al. 2010;Heinonen et al. 2002). Therefore, there exists the possibility that these local reinforcements displayed on SMAs-MM directly reflect adaptive modeling of humeral diaphyses elicited by specific upper limb utilizations characterizing a subsistence pattern. ...
... resorption. An under-stressed bone can become weaker; an over-stressed bone can also become weakened (Ruff et al., 2006). There is an optimal range of stress for the bone. ...
Thesis
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In 1887, Dr Joseph Cotterill identified a stiffening of the big toe he termed “hallux rigidus”; a manifestation of first metatarsophalangeal joint osteoarthritis. To date, 133 years after its discovery, we are no further in understanding how it occurs except for a higher-odds ratio among the planus foot type. The majority of clinical and basic science research of osteoarthritis has concentrated on the hand, hip, and knee. Although large epidemiological studies are best able to identify at-risk populations, new studies need to focus on the unresolved questions related to biomechanical pathways. While many possible etiological factors of hallux rigidus have been dismissed due to a lack of convincing evidence, the role of first ray hypermobility remains enigmatic. However, there is limited understanding of first ray hypermobility and its relationship to foot structure and function. The purpose of this thesis was to provide insight into the biomechanics of first ray hypermobility as a potential etiological factor in hallux rigidus. Four distinct but related investigations were conducted to address current gaps in knowledge: (1) an epidemiology study of population-based trends in hallux rigidus compared to more frequently studied joints; (2) the design and testing of a novel device to standardise measurements of/and quantify first ray hypermobility; (3) investigation of the differences and relationships between foot structure and function caused by first ray hypermobility, and; (4) development, verification, and validation of a finite element model for predictions of cartilage contact mechanics in the hypermobile first ray. Incidence of hallux rigidus was found to be increasing at a rate comparable to the hip and knee. In contrast to other joints, a bimodal age-distribution was found for hallux rigidus, highlighting a subset of younger patients in whom hallux rigidus may be initiated by biomechanical factors other than wear and tear in old age. The novel device for measurements of first ray mobility was found to be substantially more reliable than the standard, clinical exam. Measurements may be performed in partial- and full-weightbearing conditions to facilitate investigation of aberrant foot mechanics resulting from first ray hypermobility. A study of healthy, asymptomatic subjects with planus and rectus foot types established that individuals with first ray hypermobility were predominantly planus in foot type. Subjects who were characterised as hypermobile exhibited increased maximum force beneath the hallux and greater first metatarsophalangeal joint rotational laxity, demonstrating an interaction with translational first ray mobility. Finite element simulations predicted increased first MTP joint stress in the planus foot with first ray hypermobility which, at a magnitude of 6.5 MPa, was within the upper bound of a proposed 5-7 MPa failure limit of cartilage. Taken together, these interlinked studies may elucidate the role of first ray hypermobility in abnormal structure and function of the foot. In the presence of pes planus and hypermobility, an interaction between translational first ray mobility and rotational first metatarsophalangeal joint flexibility may reduce the mechanical advantage from the Windlass mechanism. Concomitant increased force beneath the hallux likely promotes a higher flexion moment arm between the hallucial load and first metatarsophalangeal joint, subjecting the cartilage to potentially harmful tensile and shear stress. Microtrauma to the first metatarsophalangeal joint’s articular soft tissues, after repetitive excessive loading on a daily basis from first ray hypermobility, may initiate degenerative changes. The significance of this research rests on its potential to reveal the interaction between pes planus and first ray hypermobility as an etiological factor in hallux rigidus onset and progression.
... Bioarchaeologists contribute to our understanding of subsistence activities in past populations by studying human skeletal remains for variation in size and shape that reflect a relationship between bone form and function (Meyer et al., 2011;Ruff et al., 2006;Stock & Shaw, 2007;Trinkaus & Ruff, 1999). For example, studies have demonstrated lower limb robusticity changes in response to the adoption of agriculture (e.g., Macintosh et al., 2014;Marchi et al., 2011); and within- ...
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Late Bronze Age multiple human burials from Deh Dumen, Iran, were uncovered in the Zagros Mountains. Using cross‐sectional geometry and histology, a sample (n = 23) of fragmented femora from these burials was examined to test for possible adaptation to transhumant pastoralism. Midshaft femur remodeling and modeling characteristics examined across males, females, and age‐at‐death groups partly indicated sex‐specific pastoralist behaviors and possible experiences of walking on rugged terrain in this small sample. We discuss the value of combining histology and cross‐sectional geometry techniques when attempting to reconstruct past human behaviors in multiple burial contexts.
Article
Analyses of human skeletal shape and geometry are used to investigate questions related to habitual activities and physical lifeways, as well as biological distance and relatedness. Recently, these methods have been applied to research concerning human evolutionary predisposition for disease, as well as functional experiences of pathological conditions. The use of these methods to address palaeopathological questions are relatively new, but related questions and approaches are gaining momentum. This manuscript provides an in‐depth review of the current state of this palaeopathological research by undertaking a meta‐analysis of anthropological literature. From the results of the meta‐analysis, we observe an increase in the use of quantitative shape analyses in palaeopathology, and identify four key themes in this literature: (1) description and diagnosis, (2) shapes that increase pathological risk, (3) shape change that arises from pathology, and (4) shape used for social insight. As this area of study develops, we recommend adaptations to measurement and data collection; comparative examinations of remains at the individual, population, and species levels; and, when possible, representation of all human variation through the inclusion of pathological individuals in geometric analyses. Palaeopathologists are ideally suited to investigate the relationship between bone shape and health, which may prove essential to the continued understanding of disease in both past and contemporary contexts.
Article
The examination of cross‐sectional properties (CSP) of long bones can inform about differential activity patterns and levels of mobility. Typically, these analyses have focused on the femur and tibia, but metatarsals might also be informative. This study examines femora, tibiae, and first metatarsals to evaluate the relationships between long bone CSP within the lower limb and how this might improve our interpretations of metatarsal variability. The study includes protohistoric Andaman Islanders (n = 26) and Later Stone Age (LSA) Southern Africans (n = 25) from approximately 10,000–500 BP. Skeletal data were acquired from past studies of these groups. Correlations were used to evaluate the relationships between CSP of lower limb bones within individuals. Principal component analyses were used to evaluate how each lower limb bone contributed to variation in CSP among individuals. The correlations between the CSP in the femur and tibia were always strong, but the correlations with the first metatarsal are variable. Variation in femoral loading largely drove PCAs, with less influence by the first metatarsal, or loading in the opposite direction. The femur and tibia experience similar patterns of mechanical loading, specifically in compression and tension, but the first metatarsal does not reflect the same biomechanical patterns as the femur and tibia. Similarly, the first metatarsal often drove variation in the opposite direction as the femur, indicating differences in the mechanical loading pattern between the two bones.
Article
Region-specific differences in age-related bone remodeling are known to exist. We therefore hypothesized that the decline in tissue-level strength and post-yield strain (PYS) with age is not uniform within the femur, but is driven by region-specific differences in porosity and composition. Four-point bending was conducted on anterior, posterior, medial, and lateral beams from male cadaveric femora (n=33, 18-89 yrs of age). Mid-cortical porosity, composition, and mineralization were assessed using nano-computed tomography (nanoCT), Raman spectroscopy, and ashing assays. Traits between bones from young and elderly groups were compared, while multivariate analyses were used to identify traits that predicted strength and PYS at the regional level. We show that age-related decline in porosity and mechanical properties varied regionally, with highest positive slope of age vs. Log(porosity) found in posterior and anterior bone, and steepest negative slopes of age vs. strength and age vs. PYS found in anterior bone. Multivariate analyses show that Log(porosity) and/or Raman 1246/1269 ratio explained 46-51% of the variance in strength in anterior and posterior bone. Three out of five traits related to Log(porosity), mineral crystallinity, 1246/1269, mineral/matrix ratio, and/or hydroxyproline/proline (Hyp/Pro) ratio, explained 35-50% of the variance in PYS in anterior, posterior and lateral bones. Log(porosity) and Hyp/Pro ratio alone explained 13% and 19% of the variance in strength and PYS in medial bone, respectively. The predictive performance of multivariate analyses was negatively impacted by pooling data across all bone regions, underscoring the complexity of the femur and that the use of pooled analyses may obscure underlying region-specific differences.
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Over the centuries, iconographic representations of St Anthony of Padua, one of the most revered saints in the Catholic world, have been inspired by literary sources, which described the Saint as either naturally corpulent or with a swollen abdomen due to dropsy (i.e. fluid accumulation in the body cavities). Even recent attempts to reconstruct the face of the Saint have yielded discordant results regarding his outward appearance. To address questions about the real appearance of St Anthony, we applied body mass estimation equations to the osteometric measurements taken in 1981, during the public recognition of the Saint’s skeletal remains. Both the biomechanical and the morphometric approach were employed to solve some intrinsic limitations in the equations for body mass estimation from skeletal remains. The estimated body mass was used to assess the physique of the Saint with the body mass index. The outcomes of this investigation reveal interesting information about the body type of the Saint throughout his lifetime.
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The regionalization of the mammalian spinal column is an important evolutionary, developmental, and functional hallmark of the clade. Vertebral column regions are usually defined using transitions in external bone morphology, such as the presence of transverse foraminae or rib facets, or measurements of vertebral shape. Yet the internal structure of vertebrae, specifically the trabecular (spongy) bone, plays an important role in vertebral function, and is subject to the same variety of selective, functional, and developmental influences as external bone morphology. Here we investigated regionalization of external and trabecular bone morphology in the vertebral column of a group of shrews (family Soricidae). The primary goals of this study were to: 1) determine if vertebral trabecular bone morphology is regionalized in large shrews, and if so, in what configuration relative to external morphology; 2) assess correlations between trabecular bone regionalization and functional or developmental influences; and 3) determine if external and trabecular bone regionalization patterns provide clues about the function of the highly modified spinal column of the hero shrew Scutisorex. Trabecular bone is regionalized along the soricid vertebral column, but the configuration of trabecular bone regions does not match that of the external vertebral morphology, and is less consistent across individuals and species. The cervical region has the most distinct and consistent trabecular bone morphology, with dense trabeculae indicative of the ability to withstand forces in a variety of directions. Scutisorex exhibits an additional external morphology region compared to unmodified shrews, but this region does not correspond to a change in trabecular architecture. Although trabecular bone architecture is regionalized along the soricid vertebral column, and this regionalization is potentially related to bone functional adaptation, there are likely aspects of vertebral functional regionalization that are not detectable using trabecular bone morphology. For example, the external morphology of the Scutisorex lumbar spine shows signs of an extra functional region that is not apparent in trabecular bone analyses. It is possible that body size and locomotor mode affect the degree to which function is manifest in trabecular bone, and broader study across mammalian size and ecology is warranted to understand the relationship between trabecular bone morphology and other measures of vertebral function such as intervertebral range of motion.
Article
Previous research has suggested that reduced humeral asymmetry in robusticity in European Late Pleistocene and Early Holocene populations may be a result of increased left humeral robusticity due to muscle loading from increased use of bow hunting. This paper provides a basis for considering the causes of such changes by assessing the overall intensity and level of asymmetry in the distribution of muscle activation and muscle force among living male archers. In this experiment, 20 right-handed archers drew a replica of the self bows characteristic for the Upper Paleolithic and Neolithic. We measured activation of eight muscles (biceps, triceps [long head], triceps [lateral head], deltoid [anterior part], deltoid [middle part], deltoid [posterior part], infraspinatus, and latissimus) using surface electromyography. We observed about a 15%–28% left bias in total maximum muscle force. The main muscles employed were triceps (lateral head), deltoid (middle part), and deltoid (posterior part) on both sides and triceps (long head) on the left arm. The most asymmetrical toward the right arm was the activation of biceps (123% right bias in mean muscle activation) and toward the left was triceps (long head) and triceps (lateral head) (70%–110% left bias in mean muscle activation). We conclude that left biased asymmetry in maximum muscle force produced during bow shooting may be responsible for the increase in robusticity of the left humerus and that the pattern of activation of specific individual muscles suggests that archery may be identifiable in the prehistoric record using skeletal features associated with muscle activity. Download link (good for 50 days from 7/1/2022): https://authors.elsevier.com/c/1fLRc15SlTv9X6
Article
Mass reduction is a main issue in mechanical design. Over millions of years, Nature had to face this issue. Nature came up with an efficient solution using a stress-driven structure to reduce the mass of bones while saving their mechanical performances. This optimized structure is used in several species and persists throughout Evolution. Thus, it may be considered as optimal for this issue. In this article, a method bio-inspired from both bone medullar cavity and trabecular structure is proposed to reduce the mass of parts subjected to mechanical stresses. The objective of this method is to provide high mass reduction, just like bone does. First, the method removes iteratively unloaded areas of material from the mechanical part to mimic the medullar cavity structure. Second, a final mass reduction is done integrating small holes bio-inspired from trabecular structure in the remaining material. An experimental validation was carried out on a torsion disc and provided a 60% mass reduction. Using this mass reduction rate, the topology optimization method was used to define a standard geometry to evaluate the mechanical performances of the proposed method. Experimental results highlight that regarding torsional stiffness, the bio-inspired part is 27% stiffer than the standard one.
Article
In the hip stem prostheses domain, stress shielding represents a major issue due to its potential implant loosening effect. This phenomenon occurs when the implant is much stiffer than the bone itself. A way to reduce this stiffness difference is to remove material from the implant. In addition, this solution leads to mass reduction of the implant, improving the patient quality of life. To insure the implant will withstand the loading, material must be distributed in a specific way. Bones use the same objectives of lightness and mechanical efficiency while using a minimal amount of material. In addition, these biological structures are well spread and reliable in living beings, especially in mammals and avian species. In this paper, a method bio-inspired by trabecular bone structure is proposed to remove material from parts considering their mechanical stress field. In Nature, trabecular bone is defined as a graded porous material with bone material locally oriented along the local stresses’ direction. To mimic this natural behavior, the proposed method generates local porosities bio-inspired in position, shape, size and orientation. To evaluate the proposed method performance, experimental tests were carried out on a hip prosthesis stem. Test results demonstrated that the method can be used to reduce the stiffness of the prosthesis while withstanding the applied constrains.
Article
Objectives: This study aims to explore the structural properties along entire humeral diaphyses of Late Pleistocene and Early Holocene East Asian modern humans relative to the contemporaneous Neandertal specimen Regourdou 1 to provide insight into adaptive behaviors within temporal and regional hominin contexts. Materials and methods: The humeri of three individuals from East Asia securely dated from the Late Pleistocene to Early Holocene were selected: Tianyuan 1, Zhaoguo M1, and Qihe M2. These specimens were scanned using microcomputed tomography to evaluate structural properties: cortical bone thickness (CBT), second moment of area (SMA), external radius (ER), and polar moment of area (J). Results: The distribution patterns of CBT, ER, and J were similar across all specimens. However, the magnitude of these variables was notably large in Regourdou 1 right humerus. The SMA, ER, and J of left humerus of Tianyuan 1 were less than that of other East Asian specimens, whereas those from the right humerus of the Qihe M2 individual were slightly larger than two other East Asian individuals. Additionally, the humeral asymmetry of Tianyuan 1 was greater than that of Zhaoguo M1 and Qihe M2. Discussion: Compared to Regourdou 1, East Asian specimens had reduced humeral robusticity. Within East Asia, the Late Pleistocene modern humans exhibit greater humeral asymmetry than the Early Holocene humans, indicating a universal reduction of humeral asymmetry related to technological changes across Eurasia during this time. The current study contributes to developing a more thorough understanding of
Article
This study aims to explore the structural properties along entire humeral diaphyses of Late Pleistocene and Early Holocene East Asian modern humans relative to the contemporaneous Neandertal specimen Regourdou 1 to provide insight into adaptive behaviors within temporal and regional hominin contexts. The humeri of three individuals from East Asia securely dated from the Late Pleistocene to Early Holocene were selected: Tianyuan 1, Zhaoguo M1, and Qihe M2. These specimens were scanned using microcomputed tomography to evaluate structural properties: cortical bone thickness (CBT), second moment of area (SMA), external radius (ER), and polar moment of area (J). The distribution patterns of CBT, ER, and J were similar across all specimens. However, the magnitude of these variables was notably large in Regourdou 1 right humerus. The SMA, ER, and J of left humerus of Tianyuan 1 were less than that of other East Asian specimens, whereas those from the right humerus of the Qihe M2 individual were slightly larger than two other East Asian individuals. Additionally, the humeral asymmetry of Tianyuan 1 was greater than that of Zhaoguo M1 and Qihe M2. Compared to Regourdou 1, East Asian specimens had reduced humeral robusticity. Within East Asia, the Late Pleistocene modern humans exhibit greater humeral asymmetry than the Early Holocene humans, indicating a universal reduction of humeral asymmetry related to technological changes across Eurasia during this time. The current study contributes to developing a more thorough understanding of intergroup humeral structural variation across Eurasia during the Late Pleistocene and Early Holocene.
Article
As growth at the periosteal and endosteal surfaces varies with age, cross‐sectional geometric (CSG) properties derived from periosteal (“solid”) contours may not produce comparable results to those from endosteal and periosteal contours (“true”), contrary to findings from adults. Error in CSG properties derived from the “solid” sections is compared with “true” sections in a sample of archeologically derived skeletons with estimated dental ages ranging from 1.5 months to 23.5 years. Cross sections were extracted from 3D surface models, and endosteal contours were located from biplanar radiographs for 56 femora and 59 humeri. Polar second moment of area (J), cross‐sectional shape (Imax/Imin), and polar section modulus (Zp) were calculated from solid and true sections. Relationships between solid and true properties were examined with least squares regression. Multiple regression examined the effect of age and % cortical area on solid section CSG error. While correlations were high (R2 = 0.72–0.99, all p < 0.001), the results indicate that solid CSG properties are not within an acceptable error range (%SEE of ≤8.0, and %PE of ≤5.0) of true CSG. Error was most affected by %CA, while estimated age was not correlated with %CA, %PE, or percent difference of true‐solid CSG. Periosteal contours alone should not be used to calculate CSG properties from individuals during the period of growth and development. Variation in bone growth and/or adaptive responses independent of age may account for the inconsistent age effects.
Article
A detailed analysis of differences in skeletal shape among many individuals is expected to reveal the mechanical significance behind various morphological features. To confirm the distribution of the cortical bone region in cross sections, the relative position of the central mass distribution (CMD) of the cortical bone region to the CMD of the entire cross section was examined. A total of 90 right human femoral skeletons were examined using clinical multi-slice computed tomography. For nine cross sections of each femur, we determined the CMD of the whole area, including both cortical bone and medullary areas, as CMD-W, and that of the cortical bone region in the same cross section as CMD-C, and they were compared. The medial and anterior portion of the cortex was relatively thick just below the lesser trochanter. The posterior cortical bone tended to be relatively thick in the region from the center to the distal part of the diaphysis. Females had a significantly more medially deviated CMD than males throughout the entire diaphysis. These results suggest that femurs with advanced cortical bone thinning tend to have a concentration of cortical bone in their medial portion. CMD-C was located farther from the diaphysis axis as the degree of medial bending increased. Conversely, the greater the lateral bending of the diaphysis, the closer CMD-C was to the diaphysis axis. As the amount of bone decreases with age, self-adjustment could occur so that the cortical bone's critical area remains to prevent a decrease in mechanical strength.
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The bones of the lower leg were examined from the viewpoint of strength of materials. The area, the moment of inertia of area and the polar moment of inertia of area of the cross-section at the middle of the lower leg bones were calculated. The resistance of the bone against the normal force, against the bending moment and against the torsion can be shown by these properties of the cross-section. The properties of the shape of the bones do not correlate with the age of the specimen. The sexual dimorphism is clear. The fibula is very much weaker than the tibia. The index of cross-section has no direct correlation with the strength of bones nor with the curvature of tibia shaft.
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Our understanding of developmental biology burgeoned during the last decade. This review summarizes recent advances, provides definitions and explanations of some basic principles, and does so in a way that will aid anthropologists in understanding their profound implications. Crucial concepts, such as developmental fields, selector and realizator genes, cell signaling mechanisms, and gene regulatory elements are briefly described and then integrated with the emergence of skeletal morphology. For the posteranium, a summary of events from limb bud formation, the appearance of anlagen, the expression of Hox genes, and the fundamentals of growth plate dynamics are briefly summarized. Of particular importance are revelations that bony morphology is largely determined by pattern formation, that growth foci such as physes and synovial joints appear to be regulated principally by positional information, and that variation in these fields is most likely determined by cis-regulatory elements acting on restricted numbers of anabolic genes downstream of selectors (such as Hox). The implications of these discoveries for the interpretation of both contemporary and ancient human skeletal morphology are profound. One of the most salient is that strain transduction now appears to play a much reduced role in shaping the human skeleton. Indeed, the entirety of "Wolff's Law" must now be reassessed in light of new knowledge about pattern formation. The review concludes with a brief discussion of some implications of these findings, including their impact on cladistics and homology, as well as on biomechanical and morphometric analyses of both ancient and modern human skeletal material.
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MAK-VP-1/1, a proximal femur recovered from the Maka Sands (ca. 3.4 mya) of the Middle Awash, Ethiopia, and attributed to Australopithecus afarensis, is described in detail. It represents the oldest skeletal evidence of locomotion in this species, and is analyzed from a morphogenetic perspective. X-ray, CT, and metric data are evaluated, using a variety of methods including discriminant function. The specimen indicates that the hip joint of A. afarensis was remarkably like that of modern humans, and that the dramatic muscle allocation shifts which distinguish living humans and African apes were already present in a highly derived form in this species. Its anatomy provides no indication of any form of locomotion save habitual terrestrial bipedality, which very probably differed only trivially from that of modern humans.
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A conceptual framework is presented for understanding and investigating structural adaptation of cortical bone. The magnitudes, orientations, and sense (tension or compression) of the physiologically incurred cyclic principal strains vary markedly throughout the skeleton. It is probable, therefore, that the strain/remodeling response of bone is site specific. Furthermore, there is some indication that immature bone is more responsive to alterations of cyclic strains than mature bone. Animal experimental studies and complementary stress and strain analyses suggest that the structural adaptation due to changes in cyclic strain fields may be a very nonlinear response. Bone loss in mature animals due to immobilization is sensitive to even small changes in the cyclic bone strains. Under normal conditions, however, there appears to be a broad range of physical activity in which bone is relatively unresponsive to changes in loading history. With severe repeated loading, bone hypertrophy can be pronounced. These observations open the possibility that bone atrophy and hypertrophy are controlled by different mechanisms. Therefore, two (or more) complementary control systems may be involved in the regulation of bone mass by bone cyclic strain histories. It is probable that bone mechanical microdamage is one control stimulus for affecting an increase in bone mass.
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Recent advances in integrative studies of Locomotion have revealed several general principles. Energy storage and exchange mechanisms discovered in walking and running bipeds apply to multilegged Locomotion and even to flying and swimming. Nonpropulsive lateral forces can be sizable, but they may benefit stability, maneuverability, or other criteria that become apparent in natural environments. Locomotor control systems combine rapid mechanical preflexes with multimodal sensory feedback and feedforward commands. Muscles have a surprising variety of functions in locomotion, serving as motors, brakes, springs, and struts. Integrative approaches reveal not only how each component within a Locomotor system operates but how they function as a collective whole.
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Wolff’s law is generally considered to be a philosophical statement to the effect that, over time, the mechanical load applied to living bone influences the structure of bone tissue. But Wolff’s claim was beyond the philosophical statement; his claim was that it was rigorous or mathematical law. From the 19th to the 20th century many argued that the rigid or “mathematical” form of Wolff’s law of trabecular architecture, that promulgated by Wolff, is not valid. That view is endorsed here. The law compares things that appear to be similar but are not, namely, stress trajectories in a homogeneous isotropic elastic material and the trabecular architecture of cancellous bone-this comparison is referred to here as the false premise.
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- Forces in Joints, - Skeletal Biology, - Analysis of Bone Remodeling, - Mechanical Properties of Bone, - Fatigue and Fracture Resistance of Bone, - Mechanical Adaptation of the Skeleton, - Synovial Joint Mechanics, - Mechanical Properties of Ligament and Tendon
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Proximal femoral dimensions were measured from radiographs of 80 living subjects whose current body weight and body weight at initial skeletal maturity (18 years) could be ascertained. Results generally support the hypothesis that articular size does not change in response to changes in mechanical loading (body weight) in adults, while diaphyseal cross-sectional size does. This can be explained by considering the different bone remodeling constraints characteristic of largely trabecular bone regions (articulations) and largely compact cortical bone regions (diaphyses). The femoral neck shows a pattern apparently intermediate between the two, consistent with its structure. When the additional statistical "noise" created by an essentially static femoral head size is accounted for, the present study supports other studies that have demonstrated rather marked positive allometry in femoral articular and shaft cross-sectional dimensions to body mass among adult humans. Body weight prediction equations developed from these data give reasonable results for modern U.S. samples, with average percent prediction errors of about 10%-16% for individual weights and about 2% for sample mean weights using the shaft dimension equations. When predicting body weight from femoral head size in earlier human samples, a downward correction factor of about 10% is suggested to account for the increased adiposity of very recent U.S. adults.
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Cross-sectional geometric properties of the human femur and tibia are compared in males and females in a number of recent and archaeological population samples extending back to the Middle Paleolithic. There is a consistent decline in sexual dimorphism from hunting-gathering to agricultural to industrial subsistence strategy levels in properties which measure relative anteroposterior bending strength of the femur and tibia in the region about the knee. This trend parallels and is indicative of reductions in the sexual division of labor, in particular differences in the relative mobility of males and females. Sexual dimorphism in mediolateral bending strength near the hip shows no consistent temporal trend, probably reflecting relatively constant sex differences in pelvic structure related to the requirements of childbirth. Upper and Middle Paleolithic samples are indistinguishable in terms of sexual dimorphism from modern huntergatherers, suggesting a similar sexual division of labor. The results illustrate the utility of cross-sectional geometric parameters of long bone diaphyses in reconstructing behavioral differences within and between past populations. Some variations in the accuracy of sexing techniques based on diaphyseal measurements of the lower limb long bones may also be explained by these behavioral and structural factors.
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By Clark Spencer Larsen. New York: Cambridge University Press. 1997. 461 pp. ISBN 0-521-49641-1. $85.00 (cloth).
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The microstructure of the compact bone of the tibia was studied after long-term intermittent loading in rabbits aged 74–200 days. For loading the tibia we used an electromagnetic apparatus attached to the ends of wires inserted in the frontal plane into the proximal and distal metaphysis. The tibia was loaded by bending with a force of 1–3 kg at 1–2 second intervals, 2–3 h daily for up to 30 days. Discernible thickening of the substantia compacta of the loaded sides occurred in all the rabbits. Activation of Haversian remodeling was found in the loaded sides of the tibia (medial and lateral) compared with the unloaded sides (anterior and posterior) and compared with the control (contralateral) tibia. A statistically significant increase occurred in the number of new vascular buds, of newly formed osteones and in the degree of osteonization of the bone. Intermittent loading did not affect the structure of the primary bone, however, and no changes were found in the size of the osteocytes, the diameter of the vascular canals and the appearance of the extracellular matter.
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The Loridae are an arboreal family of small primates that are specialized for slow and quiet climbing. This paper examines the relationship between lorid locomotory behaviour and postcranial skeletal morphology. Lorid humeral and femoral diaphyseal geometric cross-sectional properties, articular surface areas, and lengths are compared to those properties in other small primates with less specialized locomotory behaviour. The comparative sample includes both closely related prosimians and more distantly related platyrrhines. Results indicate that lorids have greater humeral and femoral diaphyseal rigidity than other quadrupedal primates of similar body size, suggesting that lorid limbs are subjected to greater forces. Lorids also have relatively larger humeral and femoral articulations, corresponding to field and laboratory observations which indicate that lorid joints are highly mobilc. In addition, lorids have long humeri relative to femoral length, and compared to humeral length in less specialized prosimians of similar body mass. Long humeral length relative to femoral length is interpreted as a climbing adaptation because similar limb proportions are also seen in many non-primate climbers. Altogether, humeral and femoral diaphyseal cross-sectional properties, articular surface areas, and lengths comprise a suite of characters which have potential for identifying climbing specialists in the fossil record.
Article
Three Neandertal tibias are naturally broken at or near midshaft allowing calculation of geometrical and mechanical parameters. Comparisons are made with a sample of 15 modern human tibias using identical methods. Relative torsional and bending strengths of the Neandertal specimens were twice those of the comparative sample. Basic morphometrics of the Neandertal tibia are also included.
Article
The order Primates is composed of many closely related lineages, each having a relatively well established phylogeny supported by both the fossil record and molecular data.1 Primate evolution is characterized by a series of adaptive radiations beginning early in the Cenozoic era. Studies of these radiations have uncovered two major trends. One is that substantial amounts of morphological diversity have been produced over short periods of evolutionary time.2 The other is that consistent and repeated patterns (variational tendencies3) are detected. Taxa within clades, such as the strepsirrhines of Madagascar and the platyrrhines of the Neotropics, have diversified in body size, substrate preference, and diet.2, 4–6 The diversification of adaptive strategies within such clades is accompanied by repeated patterns of change in cheiridial proportions7, 8 (Fig. 1) and tooth-cusp morphology.9 There are obvious adaptive, natural-selection based explanations for these patterns. The hands and feet are in direct contact with a substrate, so their form would be expected to reflect substrate preference, whereas tooth shape is related directly to the functional demands of masticating foods having different mechanical properties. What remains unclear, however, is the role of developmental and genetic processes that underlie the evolutionary diversity of the primate body plan. Are variational tendencies a signature of constraints in developmental pathways? What is the genetic basis for similar morphological transformations among closely related species? These are a sampling of the types of questions we believe can be addressed by future research integrating evidence from paleontology, comparative morphology, and developmental genetics.
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Non-invasive characterization of limb bone cross-sectional geometry would be useful for biomechanical analyses of skeletal collections. Computed tomography (CT) is potentially the method of choice. Additionally, CT images are suitable for automated analysis. CT is here shown to be both accurate and precise in the analysis of cross-sectional geometry of prehistoric femora. Beam hardening artifacts can be reduced by using a water bath. As the availability of CT for research increases, both bone density and geometry could be determined simultaneously with this method.
Article
The strain environment of the tibial midshaft of two female macaques was evaluated through in vivo bone strain experiments using three rosette gauges around the circumference of the bones. Strains were collected for a total of 123 walking and galloping steps as well as several climbing cycles. Principal strains and the angle of the maximum (tensile) principal strain with the long axis of the bone were calculated for each gauge site. In addition, the normal strain distribution throughout the cross section was determined from the longitudinal normal strains (strains in the direction of the long axis of the bone) at each of the three gauge sites, and at the corresponding cross-sectional geometry of the bone. This strain distribution was compared with the cross-sectional properties (area moments) of the midshaft. For both animals, the predominant loading regime was found to be bending about an oblique axis running from anterolateral to posteromedial. The anterior and part of the medial cortex are in tension; the posterior and part of the lateral cortex are in compression. The axis of bending does not coincide with the maximum principal axis of the cross section, which runs mediolaterally. The bones are not especially buttressed in the plane of bending, but offer the greatest strength anteroposteriorly. The cross-sectional geometry therefore does not minimize strain or bone tissue. Peak tibial strains are slightly higher than the peak ulnar strains reported earlier for the same animals (Demes et al. [1998] Am J Phys Anthropol 106:87–100). Peak strains for both the tibia and the ulna are moderate in comparison to strains recorded during walking and galloping activities in nonprimate mammals. Am J Phys Anthropol 116:257–265, 2001. © 2001 Wiley-Liss, Inc.
Article
In vivo bone strain experiments were performed on the ulnae of three female rhesus macaques to test how the bone deforms during locomotion. The null hypothesis was that, in an animal moving its limbs predominantly in sagittal planes, the ulna experiences anteroposterior bending. Three rosette strain gauges were attached around the circumference of the bone slightly distal to midshaft. They permit a complete characterization of the ulna's loading environment. Strains were recorded during walking and galloping activities. Principal strains and strain directions relative to the long axis of the bone were calculated for each gauge site. In all three animals, the lateral cortex experienced higher tensile than compressive principal strains during the stance phase of walking. Compressive strains predominated at the medial cortex of two animals (the gauge on this cortex of the third animal did not function). The posterior cortex was subject to lower strains; the nature of the strain was highly dependent on precise gauge position. The greater principal strains were aligned closely with the long axis of the bone in two animals, whereas they deviated up to 45° from the long axis in the third animal.
Article
Variation in long bone cross-sectional geometry can be given a more precise functional interpretation using engineering beam theory. However, difficulties in measurement technique have generally prevented studies of large samples of cross sections in this way. In the present study, an automated system utilizing an electronic digitizer and computer software was used to analyze cross-sectional geometric properties of 11 femoral and tibial locations in 119 individuals from the Pecos Pueblo, New Mexico site. The data generated allow identification of clear differences in geometric properties between different regions of the femur and tibia. These differences appear to be related to specific in-vivo mechanical loadings of the lower limb bones, serving to reduce stress and strain under these loadings. The data are also used to investigate possible differences in loading of the femur and tibia in the Pecos and modern samples, and between humans and a nonhuman primate sample.
Article
We study the influence of a small tilt angle (0 < q < 3 10-20 < \theta < 3 \times 10^{-2}rd) on the Nusselt number in a 1/2 aspect ratio Rayleigh-Bénard cell, at high Rayleigh number (5 x 1011 < Ra < 4 x 1012). The small decrease observed is interpreted as revealing a two rolls structure of the flow. Transitions between different global flows are also observed, on very long times, comparable to the diffusion time on the whole cell. The consequence is that the Nusselt number observed in most high Ra experiments should significantly depend on initial conditions.