Non‐traumatic bone infection in stegosaurs from Como Bluff,Wyoming

Palaeopathologies are relatively common in the fossil record; however, bone histological analyses of these are rare as they are more commonly discovered and described using radiological scans. Here, we describe the bone microstructure of infectious abscesses (osteomyelitis) in the long bones of two Stegosaurus individuals from the Como Bluff area of the Late Jurassic Morrison Formation. Multiple lytic, geographical lesions filled with reactive lamellar bone occur in a femur of a juvenile specimen. A single lesion was found in an adult tibia. This lesion is characterized by the presence of spiculated periosteal reactive growth perpendicular to the bone surface and the formation of new trabeculae within the lesion.     

Osteohistological insight into the early stages of growth in Mussaurus patagonicus (Dinosauria,Sauropodomorpha)

Here, we describe the bone histology of juvenile specimens of the basal sauropodomorph Mussaurus patagonicus and interpret its significance in terms of the early growth dynamics of this taxon. Thin sections from three juvenile specimens (femur length, 111–120 mm) of Mussaurus were analysed. The sampled bones consist of multiple postcranial elements collected from the Late Triassic Laguna Colorada Formation (El Tranquilo Group, Patagonia). The cortical bone is composed of fibrolamellar bone tissue. Vascularisation is commonly laminar or plexiform in the long bones. Growth marks are absent in all the examined samples. The ‘epiphyses’ of long bones are all formed by well-developed hypertrophied calcified cartilage. The predominance of woven-fibred bone matrix in cortical bones indicates a fast growth rate in the individuals examined. Moreover, given the existence of growth marks in adult specimens of Mussaurus, as in other sauropodomorphs, and assuming that the first lines of arrested growth was formed during the first year of life, the absence of growth marks in all the bones suggest that the specimens died before reaching their first year of life. Compared with the African taxon Massospondylus carinatus (another basal sauropodomorph for which the bone histology has been previously studied), it appears that Mussaurus had a higher early growth rate than Massospondylus.     

Wing and leg bone microstructure reflects migratory demands in resident and migrant populations of the Dark-eyed Junco (Junco hyemalis)

Migration is the primary strategy that temperate birds use to avoid overwintering under harsh conditions. As a consequence, migratory birds have evolved specific morphological features in their wings and skeleton. However, in addition to varying in overall shape and size, bone can also change at the microstructural level by, for example, increasing its thickness. Such changes are critical to preventing fracture and damage under repeated loading (fatigue), yet it is not known whether migratory behaviour influences bone microstructure. To address this gap in the literature, we performed micro-computed tomography on skeletons of resident and migrant subspecies of the Dark-eyed Junco Junco hyemalis. We investigated the differences in the major wing bone, the humerus, and the major leg bone, the femur. In each bone, we studied the microarchitecture of the two types of bone tissue: cortical bone, the thick outer layer of bone; and trabecular bone, which is the porous network of bone tissue at the ends of long bones. We used linear models to quantify morphological features with respect to body mass and migratory behaviour. Humeri from migratory birds were thinner, wider and had higher overall geometric stiffness, i.e. a higher polar moment of inertia, relative to humeri from resident birds. These features may help keep their bones stiff to maintain their increased body mass during migration. In contrast, migrant femora were shorter, thinner and had lower geometric stiffness than femora of residents, potentially to reduce total body mass. Tissue mineral density was lower in both the humerus and the femur of migratory birds. In addition, migratory subspecies had less trabecular bone (lower bone volume fraction) due primarily to a loss of trabecular thickness. Migratory behaviour may thus select for improved stiffness and fatigue resistance in the wing bones and reduced mass of leg bones. Our work demonstrates how important insights into morphological adaptation can be obtained by investigating bone microstructure.     

Mathematical modeling of appendicular bone growth in glaucous‐winged gulls

Development of locomotor activity is crucial in tetrapods. In birds, this development leads to different functions for hindlimbs and forelimbs. The emergence of walking and flying as very different complex behavior patterns only weeks after hatching provides an interesting case study in animal development. We measured the diaphyseal lengths and midshaft diameters of three wing bones (humerus, ulna, and carpometacarpus) and three leg bones (femur, tibiotarsus, and tarsometatarsus) of 79 juvenile (ages 0–42 days) and 13 adult glaucous‐winged gulls (Larus glaucescens), a semiprecocial species. From a suite of nine alternative mathematical models, we used information‐theoretic criteria to determine the best model(s) for length and diameter of each bone as a function of age; that is, we determined the model(s) that obtained the best tradeoff between the minimized sum of squared residuals and the number of parameters used to fit the model. The Janoschek and Holling III models best described bone growth, with at least one of these models yielding an R² ≥ 0.94 for every dimension except tarsometatarsus diameter (R² = 0.87). We used the best growth models to construct accurate allometric comparisons of the bones. Early maximal absolute growth rates characterize the humerus, femur, and tarsometatarsus, bones that assume adult‐type support functions relatively early during juvenile development. Leg bone lengths exhibit more rapid but less sustained relative growth than wing bone lengths. Wing bone diameters are initially smaller than leg bone diameters, although this relationship is reversed by fledging. Wing bones and the femur approach adult length by fledging but continue to increase in diameter past fledging; the tibiotarsus and tarsometatarsus approach both adult length and diameter by fledging. In short, the pattern of bone growth in this semiprecocial species reflects the changing behavioral needs of the developing organism. J. Morphol., 2009. © 2008 Wiley‐Liss, Inc.     

Bone tissue changes in rats during prolonged restriction of motor activity

The objective of this investigation was to measure the effect of prolonged restriction of motor activity (hypokinesia) of rats on the mass, density, mineral composition, reconstruction parameters and elemental composition of their bone tissue. The studies were done during 90 days of hypokinesia (HK) on 90 male Wistar rats equally divided into two groups: (1) vivarium control rats (VCR) and (2) hypokinetic rats (HKR). For the simulation of the hypokinetic effect the HKR group was kept for 90 days in small individual cages made of wood that restricted the movements of rats in all directions without hindering food and water intakes. During the prehypokinetic period of 15 days and during the hypokinetic period of 90 days bone mass, bone density, bone calcium and phosphorus concentrations, bone reconstruction parameters and elemental composition of bones were determined. During the same periods food intake and body weight losses were also measured. In the HKR group signs of osteoporosis in the spongy structures of the tubular bones were observed; they also showed significant decrease in rat femur weight, and in cross section of the rat femur, and in mineral concentrations of the femoral head when compared with the VCR group. The HKR group also show a significant decrease in food intake and body weight when compared with the VCR group. The corresponding parameters did not change significantly in the VCR group when compared with the baseline control values. It was concluded that prolonged exposure to HK induced osteoporosis and structural changes in bones. This apparently occurred due to inhibition of bone tissue formation in the HKR group.     

The Exploitation of Ungulate Bones in Homo neanderthalensis and Homo sapiens

Analysis of ungulate bones recovered from a number of Upper and Middle Palaeolithic sites in southern Italy revealed differences in the presence of anatomical elements. There is a lack of clear evidence of carnivore activities, and differences can be attributed to human activity. Indeed, these differences were probably due to different patterns of skeletal exploitation between Homo neanderthalensis and H. sapiens. Small limb bones (carpals, tarsals, sesamoids, long bone epiphyses and especially phalanges) are rarely found in Middle Palaeolithic deposits, but are abundant in the Upper Palaeolithic. The observation of unidentified bone fragments at these sites indicates that during the middle Palaeolithic, marrow extraction regarded essentially the treatment of long bones. First and second phalanges were not frequently used for this practice, but they were often fragmented by H. sapiens. Lack of these bones among the remains of meals of Neanderthal suggests that these bones were probably destroyed by their utilisation as fuel.     

Study of lead accumulation in bones of Wistar rats by X-ray fluorescence analysis: aging effect

The accumulation of lead in several bones of Wistar rats with time was determined and compared for the different types of bones. Two groups were studied: a control group (n = 20), not exposed to lead and a contaminated group (n = 30), exposed to lead from birth, first indirectly through mother's milk, and then directly through a diet containing lead acetate in drinking water (0.2%). Rats age ranged from 1 to 11 months, with approximately 1 month intervals and each of the collections had 3 contaminated rats and 2 control rats. Iliac, femur, tibia-fibula and skull have been analysed by Energy Dispersive X-ray Fluorescence Technique (EDXRF). Samples of formaldehyde used to preserve the bone tissues were also analysed by Electrothermal Atomic Absorption (ETAAS), showing that there was no significant loss of lead from the tissue to the preservative. The bones mean lead concentration of exposed rats range from 100 to 300 μg g(-1) while control rats never exceeded 10 μg g(-1). Mean bone lead concentrations were compared and the concentrations were higher in iliac, femur and tibia-fibula and after that skull. However, of all the concentrations in the different collections, only those in the skull were statistically significantly different (p < 0.05) from the other types of bones. Analysis of a radar chart also allowed us to say that these differences tend to diminish with age. The Spearman correlation test applied to mean lead concentrations showed strong and very strong positive correlations between all different types of bones. This test also showed that mean lead concentrations in bones are negatively correlated with the age of the animals. This correlation is strong in iliac and femur and very strong in tibia-fibula and skull. It was also shown that the decrease of lead accumulation with age is made by three plateaus of accumulation, which coincide, in all analysed bones, between 2nd-3rd and 9th-10th months.     

Charles de Gerville et les premiers restes de Plesiosauria signalés dans le Jurassique inférieur de France (Hettangien,région de Valognes,Manche)

The historian, archaeologist, and naturalist Charles de Gerville (1769–1853) reported as early as January 1816 the presence of fossil bones in the quarries of the region of Valognes, in the department of Manche. These quarries exploited the “Calcaire de Valognes” and the underlying “Argiles et Calcaires d’Huberville”, both formations dated as Lower Hettangian (Lower Jurassic). De Gerville communicated to Jacques-Louis-Marin Defrance a watercolour drawing of one of these fossil bones, discovered in July 1820, in which it is possible to recognize a plesiosaur femur. This femur, as well as a fragment of rib and three vertebrae of Plesiosauria from de Gerville's collection, was then figured in a publication by Arcisse de Caumont, in 1825. The plesiosaur femur was later acquired by Pierre Tesson of Caen, who owned one of the most important collections of fossils in Normandy. The Tesson collection was later purchased in 1857 by the British Museum (now The Natural History Museum, London), where the femur has been rediscovered. This specimen is the first known plesiosaur specimen ever discovered in the Lower Jurassic of France, before the genus Plesiosaurus was established upon material from the Lias of southwestern England. One of the vertebrae figured by de Caumont has been rediscovered in the “Muséum Emmanuel-Liais” (Cherbourg-en-Cotentin), which had acquired part of de Gerville's collection. The interpretation of the “fossil bones of Valognes” by Georges Cuvier, Henri Marie Ducrotay de Blainville, Arcisse de Caumont, Jacques-Amand Eudes-Deslongchamps and Constant Duméril is revealed through unpublished documents.     

Ontogenetic change of bone microstructures and its ethological implication in Champsosaurus (Diapsida,Choristodera)

Compact cortex in a Champsosaurus (Diapsida, Choristodera) femur is ontogenetically replaced with extensively developed cancellous bone. This histological shift, together with retention of calcified cartilage to late ontogenetic stage, was previously considered to show that adult champsosaurs were more adapted to aquatic environments than juveniles. However, the new histological examination reveals the nearly amedullar condition of a juvenile femur consisting of thick periosteal cortex and less cancellous bone tissue and the amedullar but more porous condition of adult femora. This likely demonstrates that the femoral inner structure of the juvenile is denser than those of the adults, and therefore, juveniles were more aquatic. It is suggested that morphological variations between two sympatric species of Champsosaurus reflect sexual dimorphism in a single species and limb bones with more robust morphology, showing better terrestrial adaptation for nesting on land, belong to females. The similarity of gross limb bone morphology between juveniles and inferred adult males indicates aquatic habitats for juveniles, coincident with the new interpretation of bone microstructures. No differences are, however, recognised in femoral microstructure between inferred sexes in adults. The possibly lowered density of femur in adults is considered as an adaptation to increase the mobility in water.     

Wall thickness of gas- and marrow-filled avian long bones: measurements on humeri, femora and tibiotarsi in crows (Corvus corone cornix) and magpies (Pica pica)

We studied how the ratio K of the internal to external diameter of gas- and marrow-filled avian long bones follows the biomechanical optima derived for tubular bones with minimum mass designed to fulfil various mechanical requirements. We evaluated radiographs of numerous humeri, femora and tibiotarsi in Corvus corone cornix and Pica pica. The K-values of the gas-filled humerus (K=0.78+/-0.03) and the marrow-filled femur (K=0.79+/-0.02) in Corvus are practically the same, while K of the marrow-filled tibiotarsus (K=0.71+/-0.04) is significantly smaller. The same is true for the gas-filled humerus (K=0.78+/-0.02) and the marrow-filled femur (K=0.77+/-0.02) and tibiotarsus (K=0.67+/-0.05) in Pica. K in Corvus is slightly larger than K in Pica, but the differences are statistically not significant. The standard deviation DeltaK of the tibiotarsi (DeltaK=0.04-0.05) is approximately two times as large as that of the humeri (DeltaK=0.02-0.03) and femora (DeltaK=0.02) in both species. Accepting the assumption of earlier authors that the ratio Q of the marrow to bone density is 0.5, our data show that the marrow-filled tibiotarsi of Corvus and Pica are optimized for stiffness, while the marrow-filled femora are far from any optimum. The relative wall thickness W=1-K of the gas-filled avian humeri studied is much larger than the theoretical optimum W*=1-K*=0.07, and thus these bones are thicker-walled than the optimal gas-filled tubular bone with minimum mass.     

Surgical bone marrow aspiration in Aotus lemurinus griseimembra

Aotus lemurinus griseimembra are highly susceptible to infection by human malaria parasites and reproduce some of its clinical manifestations, including anemia. We developed a new surgical technique to obtain bone marrow samples from Aotus by surgical aspiration of the femur. First, we determined that the femur offered advantages over other bones, primarily due to lower fracture vulnerability. We tested a surgical technique using 20 G IV catheters in formaldehyde-preserved animals, then conducted the procedure on 27 live animals. This technique provided easy, quick surgical access to adequate volumes of bone marrow and was safe for almost all animals: only one died; another developed nervous impairment of the lower limb. Adequate cell samples were obtained in all animals and allowed cytological studies. This procedure offers a useful tool for bone marrow research in Aotus and helps overcome current limitations of such research in human where these studies are limited by ethical and technical issues.     

Mammalian tooth marks on the bones of dinosaurs and other Late Cretaceous vertebrates

Abstract: We describe bones from the Late Cretaceous of Alberta – including bones of large dinosaurs, a femur from the aquatic reptile Champsosaurus, and a dentary from the marsupial Eodelphis– that bear tooth marks made by animals with opposing pairs of teeth. Of the animals known from the Late Cretaceous of North America, only mammals are capable of making such tooth marks. In particular, multituberculates, which have paired upper and lower incisors, are the most likely candidates for the makers of these traces. The traces described here represent the oldest known mammalian tooth marks. Although it is possible that some of these tooth marks represent feeding traces, the tooth marks often penetrate deep into the dense cortices of the bone. This raises the possibility that, much as extant mammals gnaw bone and antler, some Cretaceous mammals may have consumed the bones of dinosaurs and other vertebrates as a source of minerals. However, none of the tooth marks described here resemble the extensive gnaw traces produced by Cenozoic multituberculates or rodents. This suggests that specialized gnawing forms may have been rare or absent in the Late Cretaceous of North America.     

In vivo strains in the femur of the nine‐banded armadillo (Dasypus novemcinctus)

The capacity of limb bones to resist the locomotor loads they encounter depends on both the pattern of those loads and the material properties of the skeletal elements. Among mammals, understanding of the interplay between these two factors has been based primarily on evidence from locomotor behaviors in upright placentals, which show limb bones that are loaded predominantly in anteroposterior bending with minimal amounts of torsion. However, loading patterns from the femora of opossums, marsupials using crouched limb posture, show appreciable torsion while the bone experiences mediolateral (ML) bending. These data indicated greater loading diversity in mammals than was previously recognized, and suggested the possibility that ancestral loading patterns found in sprawling lineages (e.g., reptilian sauropsids) might have been retained among basal mammals. To further test this hypothesis, we recorded in vivo locomotor strains from the femur of the nine‐banded armadillo (Dasypus novemcinctus), a member of the basal xenarthran clade of placental mammals that also uses crouched limb posture. Orientations of principal strains and magnitudes of shear strains indicate that armadillo femora are exposed to only limited torsion; however, bending is essentially ML, placing the medial aspect of the femur in compression and the lateral aspect in tension. This orientation of bending is similar to that found in opossums, but planar strain analyses indicate much more of the armadillo femur experiences tension during bending, potentially due to muscles pulling on the large, laterally positioned third trochanter. Limb bone safety factors were estimated between 3.3 and 4.3 in bending, similar to other placental mammals, but lower than opossums and most sprawling taxa. Thus, femoral loading patterns in armadillos show a mixture of similarities to both opossums (ML bending) and other placentals (limited torsion and low safety factors), along with unique features (high axial tension) that likely relate to their distinctive hindlimb anatomy. J. Morphol. 26:889–899, 2015. © 2015 Wiley Periodicals, Inc.     

The biomechanics of human femurs in axial and torsional loading: comparison of finite element analysis, human cadaveric femurs, and synthetic femurs

To assess the performance of femoral orthopedic implants, they are often attached to cadaveric femurs, and biomechanical testing is performed. To identify areas of high stress, stress shielding, and to facilitate implant redesign, these tests are often accompanied by finite element (FE) models of the bone/implant system. However, cadaveric bone suffers from wide specimen to specimen variability both in terms of bone geometry and mechanical properties, making it virtually impossible for experimental results to be reproduced. An alternative approach is to utilize synthetic femurs of standardized geometry, having material behavior approximating that of human bone, but with very small specimen to specimen variability. This approach allows for repeatable experimental results and a standard geometry for use in accompanying FE models. While the synthetic bones appear to be of appropriate geometry to simulate bone mechanical behavior, it has not, however, been established what bone quality they most resemble, i.e., osteoporotic or osteopenic versus healthy bone. Furthermore, it is also of interest to determine whether FE models of synthetic bones, with appropriate adjustments in input material properties or geometric size, could be used to simulate the mechanical behavior of a wider range of bone quality and size. To shed light on these questions, the axial and torsional stiffness of cadaveric femurs were compared to those measured on synthetic femurs. A FE model, previously validated by the authors to represent the geometry of a synthetic femur, was then used with a range of input material properties and change in geometric size, to establish whether cadaveric results could be simulated. Axial and torsional stiffnesses and rigidities were measured for 25 human cadaveric femurs (simulating poor bone stock) and three synthetic "third generation composite" femurs (3GCF) (simulating normal healthy bone stock) in the midstance orientation. The measured results were compared, under identical loading conditions, to those predicted by a previously validated three-dimensional finite element model of the 3GCF at a variety of Young's modulus values. A smaller FE model of the 3GCF was also created to examine the effects of a simple change in bone size. The 3GCF was found to be significantly stiffer (2.3 times in torsional loading, 1.7 times in axial loading) than the presently utilized cadaveric samples. Nevertheless, the FE model was able to successfully simulate both the behavior of the 3GCF, and a wide range of cadaveric bone data scatter by an appropriate adjustment of Young's modulus or geometric size. The synthetic femur had a significantly higher stiffness than the cadaveric bone samples. The finite element model provided a good estimate of upper and lower bounds for the axial and torsional stiffness of human femurs because it was effective at reproducing the geometric properties of a femur. Cadaveric bone experiments can be used to calibrate FE models' input material properties so that bones of varying quality can be simulated.     

A comparison of mechanical properties derived from multiple skeletal sites in mice

Laboratory mice provide a versatile experimental model for studies of skeletal biomechanics. In order to determine the strength of the mouse skeleton, mechanical testing has been performed on a variety of bones using several procedures. Because of differences in testing methods, the data from previous studies are not comparable. The purpose of this study was to determine which long bone provides the values closest to the published material properties of bone, while also providing reliable and reproducible results. To do this, the femur, humerus, third metatarsal, radius, and tibia of both the low bone mass C57BL/6H (B6) and high bone mass C3H/HeJ (C3H) mice were mechanically tested under three-point bending. The biomechanical tests showed significant differences between the bones and between mouse strains for the five bones tested (p < 0.05). Computational models of the femur, metatarsal, and radius were developed to visualize the types of measurement error inherent in the three-point bending tests. The models demonstrated that measurement error arose from local deformation at the loading point, shear deformation and ring-type deformation of the cylindrical cross-section. Increasing the aspect ratio (bone length/width) improved the measurement of Young's modulus of the bone for both mouse strains (p < 0.01). Bones with the highest aspect ratio and largest cortical thickness to radius ratio were better for bending tests since less measurement error was observed in the computational models. Of the bones tested, the radius was preferred for mechanical testing because of its high aspect ratio, minimal measurement error, and low variability.     

Evolution of hindlimb bone dimensions and muscle masses in house mice selectively bred for high voluntary wheel‐running behavior

We have used selective breeding with house mice to study coadaptation of morphology and physiology with the evolution of high daily levels of voluntary exercise. Here, we compared hindlimb bones and muscle masses from the 11th generation of four replicate High Runner (HR) lines of house mice bred for high levels of voluntary wheel running with four non‐selected control (C) lines. Mass, length, diameter, and depth of the femur, tibia‐fibula, and metatarsal bones, as well as masses of gastrocnemius and quadriceps muscles, were compared by analysis of covariance with body mass or body length as the covariate. Mice from HR lines had relatively wider distal femora and deeper proximal tibiae, suggesting larger knee surface areas, and larger femoral heads. Sex differences in bone dimensions were also evident, with males having thicker and shorter hindlimb bones when compared with females. Several interactions between sex, linetype, and/or body mass were observed, and analyses split by sex revealed several cases of sex‐specific responses to selection. A subset of the HR mice in two of the four HR lines expressed the mini‐muscle phenotype, characterized mainly by an ～50% reduction in hindlimb muscle mass, caused by a Mendelian recessive mutation, and known to have been under positive selection in the HR lines. Mini‐muscle individuals had elongated distal elements, lighter and thinner hindlimb bones, altered 3rd trochanter muscle insertion positions, and thicker tibia‐fibula distal widths. Finally, several differences in levels of directional or fluctuating asymmetry in bone dimensions were observed between HR and C, mini‐ and normal‐muscled mice, and the sexes. This study demonstrates that skeletal dimensions and muscle masses can evolve rapidly in response to directional selection on locomotor behavior.     

Comparison of radiologic and gross examination for detection of cancer in defleshed skeletons

The reliability of visual examination of defleshed bones was assessed for detection of postcranial metastatic disease in individuals known to have had cancer. This was compared with standard clinical radiologic techniques. The skeletons of 128 diagnosed cancer patients from an early 20th century autopsied skeletal collection (Hamann-Todd Collection) were examined. Radiologic examination detected evidence of metastatic disease in 33 individuals, compared to 11 by visual examination of the postcranial skeletons. Four of these cases were detected by both techniques. Blastic lesions were most commonly overlooked on visual examination, because they were localized to trabecular (internal bone) structures. The ilium was the most commonly affected bone, with lytic or blastic lesions detected in 30 of 33 individuals. While the proximal femur was affected in only nine individuals, x-ray of the proximal femur and ilium detected all individuals with postcranial evidence of metastatic disease. Skeletal distribution of metastases provides no clue to the location of origin or histologic subtype of the cancer. Survey of archeological human remains for metastatic cancer requires radiologic examination. Such skeletal surveys should x-ray at least the ilia and femora. © 1995 Wiley-Liss, Inc.     

X-ray diagnosis of hemophiliac pseudotumors]

Of 259 hemophiliacs bone pseudotumors were diagnosed in 11 (4.3%); they were localised in the femur (6 cases), calcaneus (4) and in the iliac bone (3). Two cases of combined femoral and calcaneal lesions and 4 cases of bone fracture were observed. As a rule, pseudotumors developed in hemophiliacs with severe disease. An x-ray picture of a pseudotumor depended on its site and was characterized by a large soft tissue tumor shadow, often with calcinosis, and serious destructive changes in bones in the form of round foci of 7 cm in diameter with clear-cut contours. An edge defect of the cortical layer was defined in the diaphysis of the femoral bone (15 cm long). Destructive changes were often accompanied by osteosclerosis and periostitis.     

Bone size and mechanics at the femoral diaphysis across age and sex

The reasons for the increase in fracture rates with age are not fully understood. It is known that there is a decrease in bone mass with a presumed loss of strength. This decrease may possibly be compensated for by changes in cross-sectional geometry. Previous studies, which have been limited by lack of information on subjects’ heights and weights, were not able to resolve this issue. In this study, measurements of cross-sectional geometry (area and second moments of area) from 107 specimens of human femoral diaphysis from subjects aged 21–92 years were analysed. Mathematical models of the variation in bone geometry with age were developed. These models included the effects of sex, height and weight. Values of parameters from these models were then used in a biomechanical analysis of the static stresses at the mid-shaft of the femur. Results indicate that although there was a reduction in cortical area in old age, bone tissue was redistributed so that neither bending stresses in the coronal plane nor torsional stresses were higher in old age than in young adulthood. An additional finding was that at any age women had smaller bones, less cortical bone area and higher bone stresses than men. This finding may have some bearing on the higher fracture incidence seen in older women.     

Structural properties of a new design of composite replicate femurs and tibias

The purpose of this study was to compare the structural properties of a new vs. established design of composite replicate femurs and tibias. The new design has a cortical bone analog consisting of short-glass-fiber-reinforced (SGFR) epoxy, rather than the fiberglass-fabric-reinforced (FFR) epoxy in the currently available design. The hypothesis was that this new cortical bone analog would improve the uniformity of structural properties between specimens, while having mean stiffness values in the range of natural human bones. The composite replicate bones were tested under bending, axial, and torsional loads. In general, the new SGFR bones were significantly less stiff than the FFR bones, although both bone designs reasonably approximated the structural stiffnesses of natural human bones. With the exceptions of the FFR bone axial tests, the highest variability between specimens was 6.1%. The new SGFR bones had similar variability in structural properties when compared to the FFR bones under bending and torsional loading, but had significantly less variability under axial loading. Differences in epiphyseal geometry between the FFR and SGFR bones, and subsequent seating in the testing fixtures, may account for some of the differences in structural properties; axial stiffness was especially dependent on bone alignment. Stiffness variabilities for the composite replicate bones were much smaller than those seen with natural human bones. Axial strain distribution along the proximal-medial SGFR femur had a similar shape to what was observed on natural human femurs by other investigators, but was considerably less stiff in the more proximal locations.