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The humerus is central for locomotion in turtles as quadrupedal animals. Osteological variation across testudine clades remains poorly documented. Here, we systematically describe the humerus anatomy for all major extant turtle clades based on 38 species representing the phylogenetic and ecological diversity of crown turtles. Three Late Triassic species of shelled stem turtles (Testudindata) are included to establish the plesiomorphic humerus morphology. Our work is based on 3D models, establishing a publicly available digital database. Previously defined terms for anatomical sides of the humerus (e.g., dorsal, ventral) are often not aligned with the respective body sides in turtles and other quadrupedal animals with sprawling gait. We propose alternative anatomical directional terms to simplify communication: radial and ulnar (the sides articulating with the radius/ulna), capitular (the side bearing the humeral head), and intertubercular (opposite to capitular surface). Turtle humeri show low morphological variation with exceptions concentrated in locomotory specialists. We propose 15 discrete characters to summarize osteological variation for future phylogenetic studies. Disparity analyses comparing non-shelled and shelled turtles indicate that the presence of the shell constrains humerus variation. Flippered aquatic turtles are released from this constraint and significantly increase overall disparity. Ontogenetic changes of turtle humeri are related to increased ossification and pronunciation of the proximal processes, the distal articulation areas, and the closure of the ectepicondylar groove to a foramen. Some turtle species retain juvenile features into adulthood and provide evidence for paedomorphic evolution. We review major changes of turtle humerus morphology throughout the evolution of its stem group., (© 2024 The Authors. The Anatomical Record published by Wiley Periodicals LLC on behalf of American Association for Anatomy.)

Background: This study aims to investigate the morphological characteristics of the distal humerus in healthy adults from northern China using computed tomography and three-dimensional reconstruction techniques and compared whether there were diferences in morphology among populations from diferent geographical regions., Methods: The CT data of 80 patients were imported into Mimics software for three-dimensional reconstruction and measurement. The differences in distal humeral morphological parameters between different genders and sides were compared, and the correlation between the parameters was explored. The distal humeral morphological parameters between Western and Chinese populations based on current and previous pooled results were compared., Results: Thirty-one morphological parameters were measured and analyzed in this study. The average (and standard deviation) of capitellum depth, capitellum width, capitellum height, distal humerus width, epitrochlea width, and humeral metaphyseal width was 10.83 ± 1.18 mm, 17.60 ± 2.06 mm, 21.10 ± 2.03 mm, 44.38 ± 4.07 mm, 12.02 ± 1.90 mm and 58.95 ± 4.86 mm, these parameters were significantly higher (P < 0.001*) in males than females. The capitellum width (r = -0.300, P = 0.007*), anterior lateral trochlear depth (r =-0.227, P = 0.043*), medial crest coronal tangential angle (r = 0.307, P = 0.006*), olecranon fossa volume (r = -0.408, P < 0.001*), olecranon fossa surface area (r = -0.345, P = 0.002*) and coronoid fossa surface area (r = -0.279, P = 0.012*) were significantly correlated with the age of the subjects. In the comparison of people from different regions, the capitellum height, lateral trochlear high, trochlear groove high, trochlear depth and medial trochlear high of the Western population were 23.25 ± 2.56 m, 21.6 ± 2.20 mm, 17.8 ± 2.00 mm, 17.80 ± 2.00 mm, 29.9 ± 4.10 mm, are significantly higher than those in the Chinese population. while capitellum width (15.55 ± 2.68 mm) and capitellum depth (9.00 ± 1.00 mm) were slightly lower., Conclusion: The findings provide a basis for the design of distal humeral orthopaedic implants, ensuring greater alignment with the anatomical structure of the distal humerus and improved surgical outcomes. Furthermore, the study provides a reference point for the diagnosis and classification of distal humeral diseases, as well as guidance for patient rehabilitation., (© 2024. The Author(s).)

The angle of inclination of the humerus is the angle between the long axis of the shaft and the central axis of the head of the humerus in the frontal plane. It is about 130° to 150°. Orthopedic surgeons performing reconstruction of the shoulder during prosthetic replacement should consider the size and placement of the head of the humerus. Prosthetic systems with a wide range of modular head sizes, eccentric tapers, and adjustable inclination angles and versions help orthopedic surgeons better to adapt prosthesis to a patient's bone anatomy. The present study aimed to establish the morphometry of the angle of inclination of the humerus in the Bangladeshi population and to correlate with the previous studies. The present prospective study was carried out with 100 (43 right-sided + 57 left-sided) dried humeri of unknown sex and age. In the present study, the mean±SD angle of inclination of the right humeri was 128.89±3.987 degree and the left humeri were 129.19±3.335 degree. In this article, we review the effects of this anatomical parameter on prosthetic design.

Talpid moles (Talpidae, Eulipotyphla) are mammals highly specialised in burrowing using their forelimbs. Fossoriality has allowed moles to expand their ecological niche by enabling access to subterranean resources and spaces. This specialisation in burrowing has led to adaptations in the forelimb bones of moles for humeral rotation digging, a distinctive strategy unparalleled among other diggers. While bone robustness has been examined in moles through external morphology, the adaptation of bone microstructure to digging strategy remains unclear. Based on two assumptions, (1) the humerus of moles is subjected to a torsional load due to humeral rotation digging, and (2) the magnitude of torsional load correlates with the compactness of the substrate in which the individuals can dig, we hypothesised that humeral rotation digging influences bone microstructure. Comparative analyses of transverse sections from the humeri and femora of three mole species (Mogera imaizumii, Mogera wogura and Urotrichus talpoides; Talpidae) and an outgroup eulipotyphlan (Suncus murinus; Soricidae) revealed that (1) vascular canals distributed in the humeri of moles align more predominantly circumferential along the bone walls, indicating an adaptation to the torsion generated by humeral rotation digging, and (2) the laminarity of vascular canals, particularly in Mogera species compared with Urotrichus, potentially reflects differences in the magnitude of load due to substrate compactness during digging. The aligned vascular canals are distinctive traits not observed in mammals employing other digging strategies. This suggests that vascular canal laminarity can be an indicator of not only humeral rotation digging in fossorial animals, but also the variation of eco-spaces in talpid species., (© 2024 Anatomical Society.)

Purpose: This study shows the danger zone and the safety corridor in the lateral approach with bridge plating by measuring the distance between the lateral side of the plate positioned on the lateral aspect of the humerus and the radial nerve after it pierces the lateral intermuscular septum, in the different forearm positions., Methods: Forty arms of 20 human cadavers were used, the radial nerve was identified and marked on the lateral surface the radial nerve at the exit of the lateral intermuscular septum and anteriorisation of the nerve in relation to the humeral shaft and the lateral epicondyle was also marked. The distances were measured with a digital caliper. A submuscular extraperiosteal corridor was created, proximally between the biceps brachialis and deltoid muscle and distally between the triceps and brachioradialis muscle, followed by the positioning of the low contact large fragments contoured plate with 14 combined holes (fixed and cortical angle), inserted from distal to proximal. Measurements were performed in four positions (elbow flexion with forearm pronation, elbow flexion with forearm supination, elbow extension with forearm pronation and elbow extension with forearm supination)., Results: Significant statistical differences occurred with the different positions, and the elbow flexion with forearm supination was shown to be the position that provides the safest submuscular extraperiosteal corridor in a lateral approach of the humerus., Conclusion: The danger zone of radial nerve is an area that extends from 15 cm to 5 cm proximal to the lateral epicondyle and the safest way to create a submuscular and extraperiosteal corridor in the lateral region of the humerus is with the elbow in flexion and the forearm in supination., (© 2024. The Author(s), under exclusive licence to Springer-Verlag France SAS, part of Springer Nature.)

The family Bovidae [Mammalia: Artiodactyla] is speciose and has extant representatives on every continent, forming key components of mammal communities. For these reasons, bovids are ideal candidates for studies of ecomorphology. In particular, the morphology of the bovid humerus has been identified as highly related to functional variables such as body mass and habitat. This study investigates the functional morphology of the bovid distal humerus in isolation due to its increased likelihood of preservation in the fossil record, and the resulting opportunity for a better understanding of the ecomorphology of extinct bovids. A landmark scheme of 30 landmarks was used to capture the 3D distal humerus morphology in 111 extant bovid specimens. We find that the distal humerus has identifiable morphologies associated with body mass, habitat preference and tribe affiliation and that some characteristics are shared between high body mass bovids and those living on hard, flat terrain which is likely due to the high stress on the bone in both cases. We directly apply our findings regarding extant bovids to the extinct alcelaphine bovid, Rusingoryx atopocranion from the mid to late Pleistocene (>33-45 ka) Lake Victoria region of Kenya. This species is known for some peculiar morphologies including a domed cranium with hollow nasal crests, and having small hooves for a bovid of its size. Another interesting aspect of Rusingoryx's skeletal morphology which has not been addressed is an unusual protrusion on the lateral epicondyle of the distal humerus. Despite considerable individual variation in the Rusingoryx specimens, we find evidence to support its historical assignment to the tribe Alcelaphini, and that it likely preferred open grassland habitats, which is consistent with independent reconstructions of the palaeoenvironment. We also provide the most accurate body mass estimate for Rusingoryx to date, based on distal humerus centroid size. Overall, we are able to conclude that the distal humerus in extant bovids is highly informative regarding body mass, habitat preference and tribe, and that this can be applied directly to a fossil taxon with promising results., (© 2024 The Authors. Journal of Anatomy published by John Wiley & Sons Ltd on behalf of Anatomical Society.)

Gestational growth and development of bone is an understudied process compared to soft tissues and has implications for lifelong health. This study investigated growth and development of human fetal limb bone trabecular architecture using 3D digital histomorphometry of microcomputed tomography data from the femora and humeri of 35 skeletons (17 female and 18 male) with gestational ages between 4 and 9 months. Ontogenetic data revealed: (i) fetal trabecular architecture is similar between sexes; (ii) the proximal femoral metaphysis is physically larger, with thicker trabeculae and greater bone volume fraction relative to the humerus, but other aspects of trabecular architecture are similar between the bones; (iii) between 4 and 9 months gestation there is no apparent sexual or limb dimorphism in patterns of growth, but the size of the humerus and femur diverges early in development. Additionally, both bones exhibit significant increases in mean trabecular thickness (and for the femur alone, bone volume fraction) but minimal trabecular reorganisation (i.e., no significant changes in degree of anisotropy, connectivity density, or fractal dimension). Overall, these data suggest that in contrast to data from the axial skeleton, prenatal growth of long bones in the limbs is characterised by size increase, without major reorganizational changes in trabecular architecture., (© 2024. The Author(s).)

Recent discoveries of Homo floresiensis and H. luzonensis raise questions regarding how extreme body size reduction occurred in some extinct Homo species in insular environments. Previous investigations at Mata Menge, Flores Island, Indonesia, suggested that the early Middle Pleistocene ancestors of H. floresiensis had even smaller jaws and teeth. Here, we report additional hominin fossils from the same deposits at Mata Menge. An adult humerus is estimated to be 9 - 16% shorter and thinner than the type specimen of H. floresiensis dated to ~60,000 years ago, and is smaller than any other Plio-Pleistocene adult hominin humeri hitherto reported. The newly recovered teeth are both exceptionally small; one of them bears closer morphological similarities to early Javanese H. erectus. The H. floresiensis lineage most likely evolved from early Asian H. erectus and was a long-lasting lineage on Flores with markedly diminutive body size since at least ~700,000 years ago., (© 2024. The Author(s).)

Objectives: This study tests if femoral and humeral cross-sectional geometry (CSG) and cross-sectional properties (CSPs) in an ontogenetic series of wild-caught chimpanzees (Pan troglodytes ssp.) reflect locomotor behavior during development. The goal is to clarify the relationship between limb bone structure and locomotor behavior during ontogeny in Pan., Materials and Methods: The latex cast method was used to reconstruct cross sections at the midshaft femur and mid-distal humerus. Second moments of area (SMAs) (I x , I y , I max , I min ), which are proportional to bending rigidity about a specified axis, and the polar SMA (J), which is proportional to average bending rigidity, were calculated at section locations. Cross-sectional shape (CSS) was assessed from I x /I y and I max /I min ratios. Juvenile and adult subsamples were compared., Results: Juveniles and adults have significantly greater femoral J compared to humeral J. Mean interlimb proportions of J are not significantly different between the groups. There is an overall decreasing trend in diaphyseal circularity between the juvenile phase of development and adulthood, although significant differences are only found in the humerus., Discussion: Juvenile chimpanzee locomotion includes forelimb- and hindlimb-biased behaviors. Juveniles and adults preferentially load their hindlimbs relative to their forelimbs. This may indicate similar locomotor behavior, although other explanations including a diversity of hindlimb-biased locomotor behaviors in juveniles cannot be ruled out. Different ontogenetic trends in forelimb and hindlimb CSS are consistent with limb bone CSG reflecting functional adaptation, albeit the complex nature of bone functional adaptation requires cautious interpretations of skeletal functional morphology from biomechanical analyses., (© 2024 Wiley Periodicals LLC.)

Stature estimation is a core component to the biological profile in forensic anthropology casework. Here we provide mathematical equations for estimating stature for contemporary American Indians (AI), which currently are lacking in forensic anthropology. Drawing on postmortem computed tomography data from the New Mexico Decedent Image Database we regressed cadaveric length on four long bone length measures of the tibia, femur, and humerus to produce 11 combinations of models. Separate regression models were calculated for the entire pooled sample, by sex, broad AI language groups, and age + sex subsamples and compared. Sex-specific models were statistically better than general models, which were more accurate than language group and age + sex models. Equations were created for general and sex-specific models. Application to an independent test sample demonstrates the equations are accurate for stature estimation with overestimates of less than 1 cm. The equations provide similar levels of precision to stature estimation programs like the FORDISC 3.0 module and other stature equations in the literature. We provide recommendations for equation use in casework based on our results. These equations are the first for estimating stature in contemporary AI. This paper demonstrates the appropriateness of these newly created stature equations for use in New Mexico and the surrounding region., Competing Interests: Declaration of Competing Interest None., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Objectives: Adult upper limb asymmetry is used to reconstruct behavior. However, the developmental trajectory of asymmetry in bone length, cross-sectional geometry (CSG), and joint dimensions is poorly understood. This study examines the development trajectory of humeral asymmetry and if asymmetry in bone length, joint size, and CSG develop in concert., Materials and Methods: Linear measurements of bone length and metaphyseal/epiphyseal breadth, bending rigidity (I max and I min ), and cross-sectional shape (I max /I min ) at 30%, 50%, and 70% of bone length were acquired from 3D models of humeri from four skeletal samples of prehistoric hunter-gatherer populations (n = 82). Dental age cohorts were used to assess ontogenetic trends. Percent absolute (%AA) and directional (%DA) asymmetry were calculated for paired measures. Percentage of matching direction of asymmetry across variables and correlation analysis tested relationships between variables., Results: Within the total pooled sample, I max shows the highest %AA and %DA, followed by shape and linear dimensions. Asymmetry is lowest in neonates and increases with age, particularly %DA of I max in mid-proximal sections. Correlations among variables are low to moderate and strongest between I max measures. Matching direction of asymmetry between variables is low and generally increases with age., Discussion: Higher correlations with age in CSG likely indicate greater responsiveness to mechanical loading. Low correlations in magnitude of asymmetry and side dominance suggest independence in the development of asymmetry between maximum rigidity, shape, and linear measures. Differences in how asymmetric loading affects the ontogeny of linear and CSG variables may account for the heterogeneous development of asymmetry., (© 2024 Wiley Periodicals LLC.)

Aims: This study aimed to investigate age- and menopause-related differences in bone mineral density (BMD), bone structure and estimated bone strength at surgical neck of humerus in Chinese female sample., Methods: We conducted a cross-sectional cohort study of 171 Chinese women. Bone mass, indices of geometric properties and estimated mechanical strength of the surgical neck were evaluated by quantitative computed tomography (QCT). Comparisons were performed across menstrual status categories. Age-related changes in QCT-derived bone parameters were calculated., Results: The age-related difference of BMD and cortical thickness was 40.25 % and 32.86 % between the age of 20 and 86 years. Progressive periosteal and endosteal expansion was associated linearly with age. Estimated mechanical strength indexes showed significant quadratic associations with age, with their peak occurred at the age of 46-55 years. The quartile of women with the greatest medullary diameter also had the lowest valve of BMD and cortical thickness and the greatest in skeletal width. Compared to premenopausal individuals, perimenopausal women were distinguished by lower cortical thickness (18.63 %) and BMD (20.05 %). The continued decrease in cortical thickness and BMD was noted after menopause. The medullary and periosteal diameter increased by 17.98 % and 9.34 % respectively in perimenopausal period, but not after menopause. The accelerated loss of the maximum and polar section modulus was observed in late postmenopausal women., Conclusions: The increase in bone size only occurred during the menopause transition. Obvious loss of resistance to bending was in late postmenopausal period., Competing Interests: Declaration of competing interest Yeming Wang, Jian Li, Yutao Men and Wanfu Wei declare that they have no conflict of interest., (Copyright © 2024. Published by Elsevier Ltd.)

This study aimed to assess the fusion of growth plates and the development of secondary ossification centres in the forelimb bones of maned wolves (Chrysocyon brachyurus), contrasting the findings with established data from domestic dogs. Three maned wolves, comprising one male and two females, initially aged between 3 and 4 months, were subjected to monthly radiographic evaluations until 10-11 months of age, followed by bimonthly assessments until 18-19 months of age, encompassing both forelimbs. The closure times of growth plates were observed as follows: supraglenoid tubercle (7-8 months), proximal humerus (17-19 months), distal humerus (8-9 months), medial epicondyle of the humerus (8-9 months), proximal ulna (9-10 months), proximal radius (13-15 months), distal ulna (13-15 months) and distal radius (17-19 months). Statistical analysis revealed significant differences in the areas of secondary ossification centres in the proximal epiphyses of the humerus and radius, respectively, observed from the initial evaluation at 8-9 months and 6-7 months. Conversely, the epiphyses of the supraglenoid tubercle, distal humerus, proximal ulna, distal ulna, medial epicondyle of the humerus and distal radius did not exhibit significant area differences between 3-4 months and 4-5 months, yet notable distinctions emerged at 5-6 months. In summary, while the radiographic appearance of epiphyseal growth plates and secondary ossification centres in maned wolves resembles that of domestic dogs, closure times vary. These findings contribute to understanding the dynamics of epiphyseal growth plates in this species., (© 2024 Wiley‐VCH GmbH. Published by John Wiley & Sons Ltd.)

The modular organization of tetrapod paired limbs and girdles, influenced by the expression of Hox genes is one of the primary driving forces of the evolution of animal locomotion. The increased morphological diversification of the paired limbs is correlated with reduced between-limb covariation, while correlation within the elements is usually higher than between the elements. The tailed amphibians, such as Lissotriton newts, have a biphasic lifestyle with aquatic and terrestrial environments imposing different constraints on limb skeleton. By employing the methods of computerized microtomography and 3D geometric morphometrics, we explored the pattern of morphological variation, disparity, modularity and morphological integration in the proximal parts of the anterior limbs of six species of Eurasian small bodied newts. Although the species significantly differ in limb shape, there is a great overlap in morphology of scapula and humerus, and there are no differences in morphological disparity. For the scapula, the shape differences related to the duration of the aquatic period are in length, depth and curvature. The shape of the humerus is not affected by the length of aquatic period, and shape differences between the species are related to robustness of the body. The length of aquatic period has statistically supported phylogenetic signal. The scapula and humerus are structures of varying modularity. For the humerus, the strongest support on the phylogenetic level was for the capitulum/shaft hypothesis, which can also be interpreted as functional modularity. For the scapula, the greatest support was for the antero-posterior hypothesis of modularity in case of Lissotriton vulgaris, which can be explained by different functional roles and muscle insertion patterns, while there was no phylogenetic modularity. The modularity patterns seem to correspond with the general tetrapod pattern, with modularity being more pronounced in the distal structure. The future research should include more salamandrid taxa with different habitat preferences and both adult and larval stages, in order to explore how size, phylogeny and ecology affect the morphology and covariation patterns of limbs., (© 2024 Anatomical Society.)

The bicipital groove is a groove on the anterior aspect of the proximal end of the humerus. It lies between the greater and lesser tubercles. The variations of this groove may lead to various pathologies of the biceps brachii tendon, one of the most common causes of shoulder pain. Hence, this study examines the various osteometric parameters of bicipital groove in the Bangladeshi population. This cross-sectional descriptive study was done on 100 dry adult human cadaveric humeri (43 right sides and 57 left sides) in the Department of Anatomy, Mymensingh Medical College, Bangladesh from July 2021 to June 2022. The length, maximum width and depth of the bicipital groove and the length of this groove's medial and lateral walls were measured using a digital Vernier slide caliper. Data were recorded in a predesigned data sheet separately and analyzed statistically using Microsoft Excel and SPSS. According to the present study, the mean±SD length of the bicipital groove of the right humeri was 66.646±11.563mm and the left humeri were 66.002±13.025mm. The mean±SD maximum width of the bicipital groove of the right humeri was 10.870±1.799mm and the left humeri were 11.480±1.402mm. The mean±SD depth of the bicipital groove of the right humeri was 4.242±0.655mm and the left humeri were 4.452±0.854mm. The mean±SD medial wall length of the bicipital groove of the right humeri was 60.671±12.360mm and the left humeri were 59.161±13.660mm. The mean±SD lateral wall length of the bicipital groove of the right-sided humeri was 64.996±11.611mm and the left humeri were 64.074±13.115mm. It is expected that this osteometric study of bicipital groove among the Bangladeshi population will be very helpful for clinical anatomists, orthopaedic surgeons, anthropologists and radiologists.

The long, gracile morphology of the limb bones of the Late Miocene hyaenid Ictitherium ebu has led to the hypothesis that this animal was cursorial. The forelimb and femur of the holotype were compared with specimens of extant Hyaenidae and Canidae. Two morphometric methods were used. The first used measurements to calculate indices of different morphological characters. The second method involved capturing photographs of the anterior distal humerus of each specimen, mapping six landmarks on them, and calculating truss distances. These distances represent a schematic reproduction of the elbow. Multivariate statistical analysis primarily separated the data based on taxonomy, yet locomotor and habitat categories were also considered. Ictitherium ebu has an overall morphology similar to that of the maned wolf and a distal humerus reminiscent of that of the aardwolf. The long, gracile limb bones of I. ebu are suggested to be adaptations for pouncing on prey, for locomotor efficiency, and for looking over the tall grass of the open environments the animal lived in, much like the present-day maned wolf., Competing Interests: The authors declare there are no competing interests., (©2024 van der Hoek and Werdelin.)

There is a need to fully understand intra-skeletal variability within different populations to develop and improve age-at-death estimation methods. This study evaluates age-related histomorphometric changes in three different bones intra-individually in a modern Australian sample. Four female and 13 male elderly Australian adult donors (67-93 years) were examined for osteon population density (OPD), osteon area (On.Ar), and Haversian canal area (H.Ar) of secondary osteons to compare between femora, ribs, and humeri and assess against age. In the pooled sex sample, no statistically significant correlations were observed between age and each histological variable. In the males, OPD of the femur increased significantly with age, as did porosity in the rib. In the male humeri, OPD increased moderately with age, while H.Ar was decreased moderately with age. Intra-bone comparisons showed that males had significantly higher osteon counts in their ribs compared to their femora, while their ribs showed statistically significantly less porosity than their humeri. When bone size was accounted for, by adjusting the femur and humerus histology data by robusticity indices, histology values were found to be similar between bones within the same individual. This is despite the upper and lower limbs receiving different ranges and types of biomechanical load. Our findings demonstrate that bone size influences histomorphometry, and this could confound age-at-death estimations that have not been adjusted for robusticity. Future studies would benefit from examining bone histomorphometry within a larger sample size and incorporating bone robusticity measures into histology analyses., (© 2024 The Authors. Journal of Anatomy published by John Wiley & Sons Ltd on behalf of Anatomical Society.)

Objectives: Estimation of body mass from skeletal metrics can reveal important insights into the paleobiology of archeological or fossil remains. The standard approach constructs predictive equations from postcrania, but studies have questioned the reliability of traditional measures. Here, we examine several skeletal features to assess their accuracy in predicting body mass., Materials and Methods: Antemortem mass measurements were compared with common skeletal dimensions from the same animals postmortem, using 115 rhesus macaques (male: n = 43; female: n = 72). Individuals were divided into training (n = 58) and test samples (n = 57) to build and assess Ordinary Least Squares or multivariate regressions by residual sum of squares (RSS) and AIC weights. A leave-one-out approach was implemented to formulate the best fit multivariate models, which were compared against a univariate and a previously published catarrhine body-mass estimation model., Results: Femur circumference represented the best univariate model. The best model overall was composed of four variables (femur, tibia and fibula circumference and humerus length). By RSS and AICw, models built from rhesus macaque data (RSS = 26.91, AIC = -20.66) better predicted body mass than did the catarrhine model (RSS = 65.47, AIC = 20.24)., Conclusion: Body mass in rhesus macaques is best predicted by a 4-variable equation composed of humerus length and hind limb midshaft circumferences. Comparison of models built from the macaque versus the catarrhine data highlight the importance of taxonomic specificity in predicting body mass. This paper provides a valuable dataset of combined somatic and skeletal data in a primate, which can be used to build body mass equations for fragmentary fossil evidence., (© 2024 Wiley Periodicals LLC.)

Purpose: Several descriptions of the anatomy of the pectoralis major (PM) have been published. However, the precise description of its distal humeral insertion, which is involved in traumatic tears, remains controversial. The distal tendon is classically described as being made of two layers, one anterior (ALPM) and one posterior (PLPM), which regroup at their distal edge. The clavicular head (CH) participates in the ALPM according to most authors. However, others describe a more superficial termination in a close relationship with the deltoid humeral insertion. The objective of this anatomical work is to precisely describe the anatomy of the CH and its relationship with the rest of the distal PM tendon and the distal deltoid tendon., Materials: Twenty-three fresh cadaveric specimens were dissected (41 shoulders). The entire PM as well as the deltoid were exposed. Several measurements were collected to establish the relationships between the distal tendon of the CH and the PM, the deltoid and the bony landmarks., Results: In all cases, the CH muscular portion sits on the ALPM but does not participate in the connective structure of the PM distal tendon. The inferolateral part of its distal end gives a thin tendinous portion that inserts lower on the humerus in conjunction with the distal tendon of the deltoid. In 24.4%, this tendon was more difficult to isolate but was always observed., Conclusions: The distal tendon of the PM only comes from the muscle fibres of its sternal head. The CH fibres do not contribute to this tendon but appear to terminate in a separate tendon fusing with the humeral insertion of the deltoid: the deltopectoral tendon. This could explain the different patterns of tears observed in clinical practice., (© 2024. The Author(s) under exclusive licence to SICOT aisbl.)

Background: Range of motion in the forelimb of the Upper Cretaceous theropod dinosaur Mononykus olecranus , a member of the family Alvarezsauridae, has previously been investigated. However, the method used to investigate range of motion at the shoulder in M. olecranus did not follow the standardized procedure used in subsequent studies. The latter procedure yields more reliable results, and its standardization provides that its results are directly comparable to the results of similar studies in other species. I therefore reinvestigated the range of motion at the shoulder in M. olecranus , using the latter procedure., Methods: Casts of the left scapula and coracoid of M. olecranus were posed on a horizontal surface, supported from beneath with modeling clay, with the medial surface of the scapula facing toward the horizontal surface. A cast of the left humerus was posed at the limits of motion through the transverse and parasagittal planes. Photos of the poses in orthal views were superimposed and used to measure range of motion, which was measured as the angle between lines drawn down the long axis of the humerus in each position., Results: Through the transverse plane, the humerus of M. olecranus could be elevated to a subhorizontal position and depressed to a subvertical position. It could move through the parasagittal plane from a subvertical position at full protraction to a position above the horizontal at full retraction. These results correct the previous mischaracterization of shoulder motion in M. olecranus as restricted to a small arc with the arms held in a permanent sprawl. The range of humeral motion in M. olecranus is much greater than that found by the previous method and allowed the animal to tuck its arms in at the sides, in addition to allowing them to sprawl so as to orient the palm downward. The wide range of humeral motion allowed M. olecranus to forage for insects by employing hook-and-pull digging at surfaces with a wider range of orientations than the previous study showed to be possible., Competing Interests: The author declares that they have no competing interests., (© 2023 Senter.)

Buttonquails (family Turnicidae of the order Charadriiformes) are a morphologically specialized group of small, predominantly tropical birds of open landscapes, which is extremely poorly represented in the fossil record. The article describes a fragmentary humerus of a buttonquail from the Lower Pleistocene of the Taurida Cave in central Crimea. This is the first find of the family Turnicidae in Eurasia in a chronological interval from the Pliocene through the Middle Pleistocene. The find highlights the limited nature of available information on the taxonomic composition of Early Quaternary Eurasian avifaunas, even at the family level, and sheds light on the Late Cenozoic evolutionary history of Turnicidae., (© 2023. Pleiades Publishing, Ltd.)

The middle Pliocene site of Woranso-Mille in the Afar Region of Ethiopia has yielded numerous significant early hominin fossils representing multiple, coexisting taxa. Here we report on another significant discovery, the oldest partial skeleton of the papionin, Theropithecus. The specimen was recovered from the Aralee Issie collection area over multiple field seasons from 2004 through 2019. The specimen was unearthed in situ from the fluvial facies of the Mesgid Dora Tuff dated to 3.66-3.57 Ma. The partial skeleton, ARI-VP-1/26, is that of a subadult male lacking a skull. In the absence of unambiguously associated craniodental remains, the male status of the specimen was established from the dimensions of the long bones in comparison to those of other Theropithecus from Woranso-Mille. ARI-VP-1/26 is noteworthy because it preserves partial hand and foot skeletons, including a complete set of metacarpals from the left side. The theropith status of ARI-VP-1/26 was established based on the detailed anatomy of the postcranial skeleton, especially the proximal and distal humerus, proximal radius, and proximal femur. The morphology of the postcranium of ARI-VP-1/26 is consistent with that of recognized Theropithecus from Woranso-Mille and, specifically, with specimens recognized as Theropithecus oswaldi cf. darti from other sites. The ratio of the lengths of the first metacarpal to metacarpals 2-5 in ARI-VP-1/26 is intermediate between that seen in extant Papio and Theropithecus. In Theropithecus gelada and Theropithecus brumpti, the pairing of pollical and indical metacarpals of near equal length contributes to the species' high opposability index and is associated with a 'manual grazing' feeding habit. Cercopithecids constitute 43% of the identified vertebrates at Aralee Issie, and T. oswaldi cf. darti is the most common mammalian species. The monkeys of Aralee Issie lived in an open shrubland habitat, but the specific reasons for their high prevalence at the site are unclear., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

The fossil colobine genus Mesopithecus is the oldest European monkey, ranging from the Late Miocene to the earliest Pleistocene. It is one of the most successful genera of Old World monkeys since the late Neogene. Its ecology, as an indicator of Late Miocene environments, is of particular interest. Several investigations have clarified the locomotor adaptations of the middle and late Turolian Balkan Mesopithecus pentelicus, but such studies are virtually absent for the earliest known taxon, the early Turolian Mesopithecus delsoni, due to the lack of fossil material. However, a large collection of postcranial material of M. delsoni from the Bulgarian Early Turolian locality of Hadjidimovo provides the first opportunity for such an analysis. The present study examines the functional morphology of the fossil humeri of M. delsoni from Hadjidimovo, Bulgaria, and of M. pentelicus from Bulgarian and Greek fossil localities. We provide detailed comparative qualitative descriptions and use univariate and multivariate quantitative analyses of one angular and 12 linear measurements in comparison with 149 extant Cercopithecidae, representing 14 genera and 34 species. Our analyses demonstrate that the humeral elements from Hadjidimovo show important morphological differences from those of M. pentelicus from Pikermi, Kalimantsi, and Gorna Sushitsa, suggesting strong terrestrial tendencies for M. delsoni. This finding, when considered together with the paleobiologial inference of semiterrestriality for the early cercopithecoid Victoriapithecidae, might indicate that the first colobines (still unknown) were also semiterrestrial. Finally, the morphological features related to terrestriality in M. delsoni, which differ from those of the later M. pentelicus, provide additional data in support of the idea that the older taxon represents a separate species., (Copyright © 2023 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Purpose: We aimed to clarify the morphology of the olecranon aperture (OA) of the humerus with its relationship to the distal end of the humerus (epicondylar width) and the width of the medullary canal., Methods: In total, 156 dry adult humeri were examined for the presence of OA. When present, we reported their shape, measured transverse (TD) and vertical diameter (VD), the distance from its medial border to the tip of medial epicondyle (D1), lateral border to the tip of lateral epicondyle (D2) and lower border to the tip of trochlea (D3). The epicondylar width (EW) and the width of the medullary canal were also measured in all the humeri., Results: OA was reported in 32 humeri (20.6%) with left side predominance, translucent septum in 35.8%, and opaque septum in 43.6%. The most typical shape noted was oval. On right side, mean VD and TD was 4.30±0.54mm and 5.85±0.45mm, respectively, whereas on left, these value were 4.21±0.56mm and 5.64±0.43mm, respectively. The mean of D1, D2 and D3 was 25.86±0.43mm, 26.50±0.28mm and 15.07±0.53mm on right and 24.80±0.41mm, 26.84±0.21mm and 15.81±0.31mm on left with significant difference (P<0.05). The medullary canal was significantly smaller in humeri with OA., Conclusion: Topographic location of OA may have possible role in determining safe zone for retrograde nailing in supracondylar humeral fractures. Since OA has a direct relation to the size of the intramedullary canal, it is crucial during preoperative planning and choosing an adequate surgical approach involving lower segment of humerus., (Copyright © 2022 Elsevier Masson SAS. All rights reserved.)

The greater cane rat (Thryonomys swinderianus) is mainly distributed in the humid and sub-humid regions of the sub-Saharan Africa. It is believed to be the second largest African rodent. The aim of this study was to describe the normal osteology and radiographic anatomy of the thoracic limb of the greater cane rat as a reference for teaching, clinical use, anatomical studies and biomedical research. Five intact dead greater cane rats were used for radiographic examination. Radiographic findings were correlated with bone specimens. The clavicle was seen in all animals. The scapula was wide with well-developed acromion and coracoid process. The major and minor tubercles did not extend higher than the head of the humerus. The deltoid tuberosity was very prominent. The medial epicondyle was larger than its lateral counterpart, and the supratrochlear foramen was present. The radial tuberosity was further distally located. The ulnar head was well-developed, and the olecranon tuber was square-shaped. The distal physes for the radius and ulna appeared transverse. The carpus had eight bones. The manus presented with five widely spread digits. The first digit was reduced in size and placed such that the dorsal and palmar surfaces face almost medial and lateral, respectively. Additionally, two rudimentary digits were seen. Variations exist in the normal osteology and radiographic anatomy of the thoracic limb in different species. Knowledge of the normal osteology and radiographic anatomy of the thoracic limb of individual species is important for species identification and diagnosis of musculoskeletal diseases involving the thoracic limb., (© 2022 Wiley-VCH GmbH.)

During evolution, several vertebrate lineages have shown trends towards an increase in mass. Such a trend is associated with physiological and musculoskeletal changes necessary to carry and move an increasingly heavy body. Due to their prominent role in the support and movement of the body, limb long bones are highly affected by these shifts in body mass. Elephants are the heaviest living terrestrial mammals, displaying unique features allowing them to withstand their massive weight, such as the columnarity of their limbs, and as such are crucial to understand the evolution towards high body mass in land mammals. In this study, we investigate the shape variation of the six limb long bones among the modern elephants, Elephas maximus and Loxodonta africana, to understand the effect of body mass and habitat on the external anatomy of the bones. To do so, we use three-dimensional geometric morphometrics (GMMs) and qualitative comparisons to describe the shape variation, at both the intraspecific and interspecific levels. Our results reveal that the two species share similar negative ontogenetic allometric patterns (i.e. becoming stouter with increased length) in their humerus and femur, but not in the other bones: the proximal epiphyses of the stylopod bones develop considerably during growth, while the distal epiphyses, which are involved in load distribution in the elbow and knee joints, are already massive in juveniles. We attribute this pattern to a weight-bearing adaptation already present in young specimens. Among adults of the same species, bone robustness increases with body mass, so that heavier specimens display stouter bones allowing for a better mechanical load distribution. While this robustness variation is significant for the humerus only, all the other bones appear to follow the same pattern. This is particularly visible in the ulna and tibia, but less so in the femur, which suggests that the forelimb and hindlimb adapted differently to high body mass support. Robustness analyses, while significant for the humerus only, suggest more robust long bones in Asian elephants than in African savanna elephants. More specifically, GMMs and qualitative comparisons indicate that three bones are clearly distinct when comparing the two species: in E. maximus the humerus, the ulna and the tibia display enlarged areas of muscular insertions for muscles involved in joint and limb stabilization, as well as in limb rotation. These results suggest a higher limb compliance in Asian elephants, associated with a higher dexterity, which could be linked to their habitat and foraging habits., (© 2023 The Authors. Journal of Anatomy published by John Wiley & Sons Ltd on behalf of Anatomical Society.)

Purpose: The surgical management of proximal humeral fractures remains challenging. Anatomical reduction of the fracture has been reported as the keystone for a sufficient surgical fixation and successful outcome. However, mostly there is no example of its premorbid state. Literature suggests that the mirrored contralateral side can be used as a reconstruction template. But is this a correct technique to use? The purpose of this study is to define anatomical variation between humeri based on gender and side comparison., Methods: Two different statistical shape models of the humerus were created and their modes of variation were described. One model contained 110 unpaired humeri. The other model consisted of 65 left and corresponding right humeri., Results: The compactness of the statistical shape model containing 110 humeri showed that two principal components explain more than 95% of the variation and the generalization showed that a random humerus can be described with an accuracy of 0.39 mm. For only three parameters, statistically significant differences were observed between left and right. However, comparing the mean of the different metrics on the humeri of men and women, almost all were significant., Conclusion: Since there were only small differences between left and right humeri, using the mirrored contralateral side as a reconstruction template for fracture reduction can be defended. The variable anatomy between men and women could explain why locking plates not always fit to the bone., (© 2023. The Author(s) under exclusive licence to SICOT aisbl.)

Skeletal pneumaticity is a key feature of extant avian structure and biology, which first evolved among the non-flying archosaurian ancestors of birds. The widespread presence of air-filled bones across the postcranial skeleton is unique to birds among living vertebrates, but the true extent of skeletal pneumaticity has never been quantitatively investigated-hindering fundamental insights into the evolution of this key avian feature. Here, we use microCT scans of fresh, frozen birds to directly quantify the fraction of humerus volume occupied by air across a phylogenetically diverse taxon sample to test longstanding hypotheses regarding the evolution and function of avian skeletal pneumatization. Among other insights, we document weak positive allometry of internal air volume with humeral size among pneumatized humeri and provide strong support that humeral size, body mass, aquatic diving, and the presence or absence of pneumaticity all have independent effects on cortical bone thickness. Our quantitative evaluation of humeral pneumaticity across extant avian phylogeny sheds new light on the evolution and ontogenetic progression of an important aspect of avian skeletal architecture, and suggests that the last common ancestor of crown birds possessed a highly pneumatized humerus.

The Miocene Caragua fossil fauna in northern Chile contains a considerable number (7) of articulated partial skeletons tentatively assigned to Caraguatypotherium munozi (Notoungulata, Mesotheriidae), which presents up to 40% body size difference. Since either inter- and intra- specific wide size range has been observed in the Mesotheriidae family in general, we wanted explore the ontogenic stage signature of the sample, by carrying out the first comprehensive paleohistological description of the appendicular system in Notoungulata. Results show that: 1) they can be classified as subadults and adults, based on the presence of bone tissues typical of ceased somatic growth; 2) there is a notorious inter-skeletal variation on bone growth rates (skeletal modularity), particularly, the humerus showed a slower diameter growth and less remodelling than the femur, resulting as a better element for ontogenetic analyses; 3) marked cyclical growth is observed, characterised by fast early ontogenic continuous growth, and subsequent fast/slow stratified bone tissue layering. In general, such growth pattern suggests that C. munozi had a similar ontogenetic growth process as other modern mammals, that it should also be influenced by other sex-related, ecological and environmental factors. Likely related to the presence of rapid climatic variations, due to orogenic uplift and concomitant re-organization of the drainage processes along the western tectonic front of the Central Andes at that time., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2023 Campos-Medina et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

The forelimb is involved in many behaviours including locomotion. Notably, the humero-ulnar articulation, implicated in the elbow joint, is of particular importance for both mobility and stability. Functional constraints, induced in part by environmental plasticity, are thought to drive an important part of the bone shape as bone directly responds and remodels in response to both muscle and external forces. In this context, the study of subterranean moles is of particular interest. These moles occupy a hard and heavy medium in comparison with air or water, requiring a powerful body structure to shear and shift the soil. Their general morphology is therefore adapted to digging and to their subterranean lifestyle. The various morpho-functional patterns, which drive diverse abilities according to the environment, are likely targets of natural selection and it is, therefore, useful to understand the relationships between the bone shape and their function. Here, we quantify, through 3D geometric morphometric methods, the interspecific variability in the morphology of the ulna and humerus of three Talpa species, including the new species Talpa aquitania, to infer their potential consequence in species digging performance. We also quantify shape covariation and morphological integration between the humerus and the ulna to test whether these bones evolve as a uniform functional unit or as more or less independent modules. Our results show that interspecific anatomical differences in the humerus and ulna exist among the three species. Shape changes are mostly located at the level of joints and muscle attachments. As the species tend to live in allopatry and the fossorial lifestyle induces strong ecological constraints, interspecific variations could be explained by the properties of the environment in which they live, such as the compactness of the soil. Our results also show that the humerus and ulna are highly integrated. The covariation between the humerus and ulna in moles is dominated by variation in the attachment areas and particularly of the attachment areas of shoulder muscles concerning the humerus, which affect the mechanical force deployed during locomotion and digging. This study also highlights that in the new species, T. aquitania, variations in anatomical structure (general shape and joints) exist and are related to the locality of collect of the individuals., (© 2022 The Authors. Journal of Anatomy published by John Wiley & Sons Ltd on behalf of Anatomical Society.)

Introduction: An understanding of the sagittal plane morphology of the humerus is relevant during surgical fixation of humeral fractures but is not well described in the literature. The purpose of this study was to better characterize the native sagittal plane morphology of the humerus., Materials and Methods: 170 patients with uninjured full length lateral humerus radiographs were retrospectively evaluated. The angle between the proximal humeral diaphyseal axis and the distal humeral diaphyseal axis was identified and measured. The proximal axis was defined by two points equidistant from the anterior and posterior cortex 10 mm and 100 mm distal to the metaphyseal flare, and the distal axis by two points at 10 mm and 50 mm proximal to the capitellum/trochlea. The relative location of the center of rotation of angulation (CORA) was calculated as a percentage of humeral length., Results: 114 radiographs were included in the analysis (66 right humeri, 48 left humeri). The average apex posterior angulation was 6.5 +/- 2.9°. The CORA occurred at an average of 80% (SD+/-13%) of the length of the humerus (proximal to distal). Total humeral length and absolute distance to CORA were greater in males compared to females (364 ± 50 mm versus 326 ± 30 mm; p<0.001; 290 ± 68 mm versus 260 ± 48 mm; p=0.003), but there were no significant sex differences with respect to magnitude of the apex posterior angulation (p=0.077) or location of CORA as a percentage of total humeral length (p=0.916). There were no statistically significant associations between age and total humeral length (p=0.056), distance to CORA (p=0.130), location of CORA as percentage of total humeral length (p=0.753), or magnitude of angulation (p=0.075)., Conclusion: An apex posterior bow consistently exists in the distal one-quarter of the humerus that is consistent across ages and between sexes. This normal anatomic bow is important to recognize to avoid an extension malreduction and has implications for implant fit and contouring., Competing Interests: Declaration of Competing Interest The authors declare that neither they, their immediate families, nor any research foundation with which they are affiliated received any financial payments or other benefits from any commercial entity related to the subject of this article., (Copyright © 2022. Published by Elsevier Ltd.)

This study examined the emergence and characteristics of bilateral asymmetry of the upper limb during development in a medieval agricultural population from Hungary, and investigated the agricultural activity-types in a bioarchaeological and biomechanical context. The skeletal remains of 169 nonadult individuals were selected from the cemetery of Bátmonostor-Pusztafalu, providing 134 cases for humeral diameter and length, 70 cases for radial length and 62 cases for ulnar length measurements. Biological age was estimated by using tooth eruption. Age groups were defined on the basis of the development of motor skills in children. Statistical analyses included correlation, Chi-square test, Fisher analysis and ANOVA. Our investigation revealed that the frequency of asymmetry increased significantly during growth with a shift to the right side in all measurements and reached adult-like distribution in early childhood. The bilateral asymmetry increased with age in humeral length, while other measurements revealed no change. The magnitude of asymmetry decreased with age in humeral diameter, but remained constant in other measurements. Our observations strengthen the hypothesis that right-sided asymmetry develops gradually during growth. Our findings also illustrate the effects of medieval agricultural labour on upper limb asymmetry: mechanical loading has various effects during development both on the magnitude and on direction of asymmetry.

Background: In our literature review, we did not encounter any study examining the supracondylar process (SP) and the supratrochlear foramen (STF) with a three-dimensional (3D) reconstruction method. The present study aimed to evaluate SP and STF morphologically by employing the 3D reconstruction method and emphasize their clinical significance., Materials and Methods: The research was carried out on dried human humeri of unknown sex and without pathological alterations. A total of 81 humeri (42 right, 39 left) were obtained from the Departments of Anatomy of Gazi University Faculty of Medicine and Lokman Hekim University Faculty of Medicine. The morphometric measurements of SP and STF were made with a digital vernier calliper. The computed tomography images acquired for radiological evaluation were analysed with the 3D reconstruction method., Results: The narrower distal medullary canal widths of humeri with STF were found to be statistically significant. No statistically significant difference was found between the transverse diameters (TD), vertical diameters (VD), the distance of the medial edge to the medial epicondyle, and the distance of the lateral edge to the lateral epicondyle of the supratrochlear foramen of the right and left humeri., Conclusions: The supracondylar process is often evaluated by mistake as a pathological condition of the bone, not as a normal anatomical variation. Knowing different shapes and dimensions, e.g. the TD and VD distance in which STF emerges, can assist in avoiding the misinterpretation of radiographs.

Age-related changes in bone microstructure can inform our understanding the biology of both extant and fossil birds, but to date, histological work in birds, and particularly work using high-resolution 3D imaging, has largely been restricted to limited growth stages. We used minimally destructive synchrotron radiation-based X-ray computed tomography to visualise and measure key morphological and histological traits in 3D across development in the domestic duck and ring-necked pheasant. We use these measurements to build on the database of key reference material for interpreting bone histology. We found that growth patterns differed between the two species, with the ducks showing rapid growth in their lower limbs and early lower limb maturation, while pheasants grew more slowly, reflecting their later age at maturity. In the pheasant, both walking and flight occur early and their upper and lower limbs grew at similar rates. In the duck, flight and wing development are delayed until the bird is almost at full body mass. Through juvenile development, the second moment of area for the duck wing was low but increased rapidly towards the age of flight, at which point it became significantly greater than that of the lower limb, or the pheasant. On a microstructural level, both cortical porosity and canal diameter were related to cortical bone deposition rate. In terms of orientation, vascular canals in the bone cortex were more laminar in the humerus and femur compared with the tibiotarsus, and laminarity increased through juvenile development in the humerus, but not the tibiotarsus, possibly reflecting torsional vs compressive loading. These age-related changes in cortical bone vascular microstructure of the domestic duck and pheasant will help understanding the biology of both extant and fossil birds, including age estimation, growth rate and growth patterns, and limb function., (© 2022 The Authors. Journal of Anatomy published by John Wiley & Sons Ltd on behalf of Anatomical Society.)

Background: Although sex can be determined with high accuracy in forensic anthropology, additional parameters are still required., Aim: To estimate with known simple statistical methods, the usability of the bi-humerus/maximum pelvic breadth ratio in sex estimation., Subjects and Methods: Bi-humerus breadth and maximum pelvic breadth were measured using the topogram images (196 males, 171 females), the ratio between them was calculated. We examined the usability of the ratio of the distance between the lateral edges of the right and left humeral heads to the maximum distance between the two most lateral parts of the iliac crests in sex estimation., Results: There was significant difference in the bi-humerus breadth and "bi-humerus breadth/maximum pelvic breadth" according to sex. The greatest breadth of the pelvis was higher in females, yet the difference was not statistically significant. The ratio yielded 80.6%-90.3% accuracy for females and 73.6%-74.7% for males, depending on arm position., Conclusions: The obtained data may contribute to the development of formulas created with metric measurements used in sex estimation. This can be used as a parameter to help in estimating the sex of skeletal remains found as a whole or excavated without losing their integrity, and also in the reconstruction of body structure.

Background: Medial ulnar collateral ligament (UCL) repair utilization is increasing in recent years, bolstered by shorter rehabilitation and satisfactory clinical outcomes. Although previous literature has illustrated the importance of tunnel position on restoring graft isometry in reconstruction, there remains a paucity of literature guiding anchor placement in UCL repair. The purpose of this study is to design a 3-dimensional (3D) elbow model to understand the effect of anchor location on UCL repair isometry., Methods: A 3D computer model of an elbow joint was created using computed tomographic and magnetic resonance imaging MRI scans from a single patient. The humeral and ulnar attachments of the UCL were plotted using 3 methodologies: (1) geometric cloud mapping and (2) quantitative measurements from the anatomic studies by Camp et al and (3) Frangiamore et al. A 3.5-mm-diameter clockface was placed on each attachment site, which allowed for simulation of 12 distinct 1.75-mm deviations in anchor position. The 3 models were ranged through 0°-120° at 10° increments, and the 3D distances were measured between the ligament centroids. The humeral and ulnar anchors were sequentially repositioned around the clockfaces, and construct lengths were again measured to evaluate changes in isometry. A paired Student t test was performed to determine if there was a significant difference in isometry between the humeral and ulnar anchor deviations., Results: Using method 1, the UCL repair length at 90° of elbow flexion was 26.8 mm. This construct underwent 13.6 mm of total excursion for a 46.4% change in length throughout its arc of motion. Method 2 produced a 19.3-mm construct that underwent 0.8 mm of excursion for a 3.9% length change throughout the arc. Method 3 produced a 24.5-mm construct that underwent 2.3 mm of excursion for a 9.4% length change. Identifying ligament footprints using the quantitative anatomic measurements from Camp et al and Frangiamore et al improved construct isometry through 120° of flexion (length changes of 3.9% and 9.4%, respectively) when compared to using the geometric cloud technique alone (46.4% length change). Humeral anchor deviations produced a significant increase in repair construct excursion compared with ulnar anchor deviations (P < .001)., Conclusion: When performing UCL repair, small deviations in humeral anchor position may significantly influence ligament repair isometry. Using quantitative anatomic data may help identify anchor positions with improved repair isometry. Particularly when addressing detachments of the humeral footprint, surgeons should be critical of the humeral anchor position in order to restore native anatomy and optimal biomechanics., (Copyright © 2022 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.)

The evolution of complex morphological structures can be characterized by the interplay between different anatomical regions evolving under functional integration in response to shared selective pressures. Using the highly derived humeral morphology of talpid moles as a model, here we test whether functional performance is linked to increased levels of evolutionary integration between humerus subunits and, if so, what the strength is of the relationship. Combining two-dimensional geometric morphometrics, phylogenetic comparative methods, and functional landscape modeling, we demonstrate that the high biomechanical performance of subterranean moles' humeri is coupled with elevated levels of integration, whereas taxa with low-performance values show intermediate or low integration. Theoretical morphs occurring in high-performance areas of the functional landscape are not occupied by any species, and show a marked drop in covariation levels, suggesting the existence of a strong relationship between integration and performance in the evolution of talpid moles' humeri. We argue that the relative temporal invariance of the subterranean environment may have contributed to stabilize humeral morphology, trapping subterranean moles in a narrow region of the landscape and impeding any attempt to reposition on a new ascending slope., (© 2022 The Authors. Evolution published by Wiley Periodicals LLC on behalf of The Society for the Study of Evolution.)

Background: Variable neck-shaft angle (NSA) stemmed humeral components have been incorporated into certain implant designs to better re-create normal anatomy in total shoulder arthroplasty (TSA). The purpose of this study was to determine if premorbid glenohumeral joint anatomy is better restored with a fixed- vs. variable-NSA prosthesis., Methods: A randomized controlled trial was performed including 50 patients with osteoarthritis indicated for primary anatomic TSA. Patients were randomized preoperatively to receive either a variable- (n = 26) or fixed-NSA (n = 24) prosthesis. Humeral neck cut in the variable-NSA group matched the patient's anatomic neck, with prosthetic NSA of 127.5°, 132.5°, and 137.5° available. Fixed-NSA cuts were made with an intramedullary guide of 132.5°. Preoperative and postoperative radiographs were evaluated for specific radiographic anatomic variables: NSA, head thickness, tuberosity-to-head height, head offset, articular arc, greater tuberosity offset, and center of rotation (COR). Postoperative radiographic criteria were compared between groups., Results: No differences were found between groups in demographics or preoperative radiographic measures. When comparing average difference in preoperative and postoperative measurements in the fixed-NSA group, the humeral head offset from the humeral shaft axis significantly decreased by 1.4 mm (P = .046), and the COR moved superiorly (3.0 mm, P = .002) without significant medialization or lateralization. In the variable angle group, humeral head offset decreased but did not reach significance (1.2 mm, P = .091), and the COR also moved superiorly (2.9 mm, P < .001) without significant medialization or lateralization. All remaining radiographic parameters did not significantly change from pre- to postoperative imaging. In comparing the fixed- and variable-NSA groups' net change from the premorbid measurements, no significant differences were found in tuberosity-to-head height, head offset, or COR position in both the horizontal and vertical planes., Conclusions: Both fixed- and variable-NSA anatomic TSA humeral components demonstrate adequate restoration of premorbid anatomy radiographically., (Copyright © 2022 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.)

Background: Surgery for humeral shaft fractures is associated with a high risk of iatrogenic radial nerve palsy (RNP). Plausible causes are difficult anatomical conditions and variants., Methods: We performed a cadaveric study with 23 specimens (13 female and 10 male Caucasian donors) to assess the course and anatomy of the radial nerve (RN) with its branches alongside the humeral shaft. The accuracy of identification of the RN in the surgical field was analyzed by measuring the location, course, diameter, and form of each nerve and vessel of interest., Results: The RN is not a single structure running alongside the humeral shaft; at least 4 parallel structures crossed the dorsal humerus in all subjects. The RN was accompanied by 2 vessels and at least 1 other nerve, which we named the musculocutaneous branch (MCB). With an oval profile and an average diameter of 3.1 mm (range, 2.6 to 3.8 mm), the MCB was thinner but, in some cases, close to the average diameter of 4.7 mm (range, 4.0 to 5.2 mm) of the RN, which had a round profile. Both accompanying vessels had similar diameters: 3.5 mm (range, 2.6 to 4.2 mm) for the radial collateral artery and 4.0 mm (range, 2.9 to 4.4 mm) for the medial collateral artery. In 20 (87%) of the cases, the RN ran proximal to and in 3 (13%) of the cases, distal to the MCB. Furthermore, a distal safe zone of at least 110 mm (range, 110 to 160 mm) was found, measured from the radial (lateral) epicondyle proximally., Conclusions: The RN does not cross the dorsal humerus alone, as often stated in anatomical textbooks, but runs parallel to vessels and at least 1 nerve branch with a similar appearance. Thus, for reliable preservation of the RN, we recommend identification and protection of all crossing structures in posterior humeral surgeries 110 mm proximal to the radial epicondyle., Competing Interests: Disclosure: The Disclosure of Potential Conflicts of Interest forms are provided with the online version of the article ( http://links.lww.com/JBJS/H53 )., (Copyright © 2022 by The Journal of Bone and Joint Surgery, Incorporated.)

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., (© 2022 Anatomical Society.)

Evaluation of the bony anatomy of the glenohumeral joint is frequently required for surgical planning and subject-specific computational modeling and simulation. The three-dimensional geometry of bones is traditionally obtained by segmenting medical image datasets, but this can be time-consuming and may not be practical in the clinical setting. The aims of this study were twofold. Firstly, to develop and validate a statistical shape modeling approach to rapidly reconstruct the complete scapular and humeral geometries using discrete morphometric measurements that can be quickly and easily measured directly from CT, and secondly, to assess the effectiveness of statistical shape modeling in reconstruction of the entire humerus using just the landmarks in the immediate vicinity of the glenohumeral joint. The most representative shape prediction models presented in this study achieved complete scapular and humeral geometry prediction from seven or fewer morphometric measurements and yielded a mean surface root mean square (RMS) error under 2 mm. Reconstruction of the entire humerus was achieved using information of only proximal humerus bony landmarks and yielding mean surface RMS errors under 3 mm. The proposed statistical shape modeling facilitates rapid generation of 3D anatomical models of the shoulder, which may be useful in rapid development of personalized musculoskeletal models., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Introduction: It has been well established that the subscapularis is divided in two different parts with a tendinous insertion at its superior two-thirds and a muscular attachment on its inferior third. The objective of this cadaveric study was to follow the muscular insertion of the subscapularis medially in order to determine the origin of this inferior muscle insertion and whether a subscapularis minor can be individualized MATERIALS AND METHODS: Twenty-six shoulders from thirteen fresh-frozen cadaveric specimens (5 males and 8 females; mean age, 74.4 years) were dissected in our anatomy lab. The humeral insertion of the subscapularis was then analyzed, and the inferior muscular part of the insertion was identified. The muscle fibers were followed medially until their scapular origin which was recorded as line drawings and photographs. We measured the dimensions of both the humeral insertion and of the scapular origin of the fibers going to the muscular portion., Results: In all cases, the fibres going to the tendinous portion and those going to the muscular portion of the insertion had a different orientation. The fibres going to the muscular portion of the humeral insertion did not originate from the subscapularis fossa but on the glenoid neck and in a depression at the infero-lateral part of the scapular pillar. The mean length of the superior tendinous portion of the humeral insertion was 3.42 cm (± 0.43 cm); the mean length of the inferior muscular portion of the humeral insertion was 1.88 cm (± 0.80 cm). The mean length of the scapular origin in the depression at the infero-lateral part of the scapular pillar of the fibres going to the muscular portion of the humeral insertion was 3.7 cm (± 0.17 cm)., Conclusion: The fibres of the subscapularis do not all originate from the subscapularis fossa. An additional origin exists at the inferior part of the glenoid neck and in a depression at the infero-lateral part of the scapular pillar. The fibers which originate at this location all insert on the humerus at the muscular portion of the subscapularis humeral insertion. This portion however does not seem to correspond to the so-called subscapularis minor which has been previously described., (© 2021. The Author(s) under exclusive licence to SICOT aisbl.)

Stemless humeral components for shoulder arthroplasty represent the fourth generation of modern prosthetic shoulder implants. Because of their metaphyseal fixation, the implantation technique is rather straightforward and preserves the humeral canal from violation. Substantial benefits have been highlighted with such a design, including less perioperative morbidity, independence from the proximal humeral anatomy, preservation of bone stock, ease of potential revision surgeries, and limited risk of complex periprosthetic fractures. Initially conceived to better re-create the center of rotation of the humeral head in anatomic arthroplasties, their use has been successfully extended to reverse total shoulder arthroplasty. Provided that contraindications are respected (eg, poor proximal humeral bone quality, proximal humerus fractures, patients who are elderly and/or overweight), short-term and midterm functional outcomes as well as postoperative complications appear to be similar to those of traditional stemmed implants, without increased risk of loosening of the humeral component.

Background: Tricipital aponeurosis (TA) has gained attraction as a constant and reliable landmark to identify the location of radial nerve in the setting of fracture distal humeri. The aponeurosis itself shows variant anatomical patterns. In this study, we intend to provide a comprehensive description and functional classification of observed anatomical variations with possible clinical implications., Materials and Methods: Sixty arms belonging to 30 adult cadavers were studied. TA was examined grossly to document variations in its shape and classified accordingly. Subsequently, length and breadth of TA were measured. The distance of the radial nerve (RN) from the point of confluence and from the lateral border of TA was also measured (tricepso-radial distance [TRD]). These distances were correlated with the different patterns of TA obtained., Results: Based on the shape of the proximal apex of TA or point of confluence and frequency of their occurrence, we propose a new classification of 4 patterns for the TA anatomy. Pattern I: classically seen as the triangular proximal apex (76.67%); pattern II: tongue shaped or blunt proximal apex (18.33%); pattern III: bifurcated or dual proximal apex (3.33%); pattern IV: as the absence of TA (1.67%). The mean of length and breadth of TA was 16.58 ± 2.05 cm and 3.61 ± 0.61 cm, respectively. The mean distance of RN from point of confluence and lateral border of TA was 3.57 ± 0.19 cm and 2.04 ± 0.56 cm, respectively. The length, breadth of TA and TRD differs amongst the different patterns of TA., Conclusions: Anatomical variations in the shape and size of TA are frequently encountered. The proposed, hitherto undescribed, classification may make operating surgeon aware of these morphological variations and help prevent iatrogenic injury to RN. Such classification is simple and unique; however, its success relies upon universal acceptance.

Lacking fur, living in eusocial colonies and having the longest lifespan of any rodent, makes naked mole-rats (NMRs) rather peculiar mammals. Although they exhibit a high degree of polymorphism, skeletal plasticity and are considered a novel model to assess the effects of delayed puberty on the skeletal system, scarce information on their morphogenesis exists. Here, we examined a large ontogenetic sample (n = 76) of subordinate individuals to assess the pattern of bone growth and bone microstructure of fore- and hindlimb bones by using histomorphological techniques. Over 290 undecalcified thin cross-sections from the midshaft of the humerus, ulna, femur, and tibia from pups, juveniles and adults were analyzed with polarized light microscopy. Similar to other fossorial mammals, NMRs exhibited a systematic cortical thickening of their long bones, which clearly indicates a conserved functional adaptation to withstand the mechanical strains imposed during digging, regardless of their chisel-tooth predominance. We describe a high histodiversity of bone matrices and the formation of secondary osteons in NMRs. The bones of pups are extremely thin-walled and grow by periosteal bone formation coupled with considerable expansion of the medullary cavity, a process probably tightly regulated and adapted to optimize the amount of minerals destined for skeletal development, to thus allow the female breeder to produce a higher number of pups, as well as several litters. Subsequent cortical thickening in juveniles involves high amounts of endosteal bone apposition, which contrasts with the bone modeling of other mammals where a periosteal predominance exists. Adults have bone matrices predominantly consisting of parallel-fibered bone and lamellar bone, which indicate intermediate to slow rates of osteogenesis, as well as the development of poorly vascularized lamellar-zonal tissues separated by lines of arrested growth (LAGs) and annuli. These features reflect the low metabolism, low body temperature and slow growth rates reported for this species, as well as indicate a cyclical pattern of osteogenesis. The presence of LAGs in captive individuals was striking and indicates that postnatal osteogenesis and its consequent cortical stratification most likely represents a plesiomorphic thermometabolic strategy among endotherms which has been suggested to be regulated by endogenous rhythms. However, the generalized presence of LAGs in this and other subterranean taxa in the wild, as well as recent investigations on variability of environmental conditions in burrow systems, supports the hypothesis that underground environments experience seasonal fluctuations that may influence the postnatal osteogenesis of animals by limiting the extension of burrow systems during the unfavorable dry seasons and therefore the finding of food resources. Additionally, the intraspecific variation found in the formation of bone tissue matrices and vascularization suggested a high degree of developmental plasticity in NMRs, which may help explaining the polymorphism reported for this species. The results obtained here represent a valuable contribution to understanding the relationship of several aspects involved in the morphogenesis of the skeletal system of a mammal with extraordinary adaptations., (© 2021 Anatomical Society.)

Bats show a remarkable ecological diversity that is reflected both in dietary and foraging guilds (FGs). Cranial ecomorphological adaptations linked to diet have been widely studied in bats, using a variety of anatomical, computational and mathematical approaches. However, foraging-related ecomorphological adaptations and the concordance between cranial and postcranial morphological adaptations remain unexamined in bats and limited to the interpretation of traditional aerodynamic properties of the wing (e.g. wing loading [WL] and aspect ratio [AR]). For this reason, the postcranial ecomorphological diversity in bats and its drivers remain understudied. Using 3D virtual modelling and geometric morphometrics (GMM), we explored the phylogenetic, ecological and biological drivers of humeral morphology in bats, evaluating the presence and magnitude of modularity and integration. To explore decoupled patterns of variation across the bone, we analysed whole-bone shape, diaphyseal and epiphyseal shape. We also tested whether traditional aerodynamic wing traits correlate with humeral shape. By studying 37 species from 20 families (covering all FGs and 85% of dietary guilds), we found similar patterns of variation in whole-bone and diaphyseal shape and unique variation patterns in epiphyseal shape. Phylogeny, diet and FG significantly correlated with shape variation at all levels, whereas size only had a significant effect on epiphyseal morphology. We found a significant phylogenetic signal in all levels of humeral shape. Epiphyseal shape significantly correlated with wing AR. Statistical support for a diaphyseal-epiphyseal modular partition of the humerus suggests a functional partition of shape variability. Our study is the first to show within-structure modular morphological variation in the appendicular skeleton of any living tetrapod. Our results suggest that diaphyseal shape correlates more with phylogeny, whereas epiphyseal shape correlates with diet and FG., (© 2020 Anatomical Society.)

Human ribs are thought to be less affected by mechanical strain at the microscopic level than limb bones, implying that rib remodelling better reflects bone physiological homeostasis. Here, we test the hypothesis that rib tissue will be well vascularized and thus enhance susceptibility to metabolic influence. An intra-skeletal comparison of bone vascular canal density was conducted using a macropod animal model adapted to bipedal habitual hopping. The right humerus, ulna, radius, femur, tibia, fibula, a mid-thoracic and upper-thoracic rib of an eastern grey kangaroo (Macropus giganteus) were sectioned at the midshaft, from which histological sections were prepared. Bone vascularity from a maximum of 12 mm 2  of sub-periosteal parallel-fibred and lamellar bone was recorded, resulting in a total of 2047 counted vessels. Vascular canal density data were corrected by cortical width, maximum length, and midshaft circumference robusticity indices computed for each bone. The fibula consistently had the highest vascular canal density, even when corrected for maximum length, cortical width and midshaft circumference robusticities. This was followed by the mid- and upper-thoracic ribs. Vascularity differences between bones were relatively consistent whether vascular canal density was controlled for by cortical width or midshaft circumference robusticities. Vascular canal density and robusticity indices were also positively and negatively correlated (p < 0.05). Results confirm that the ribs are well vascularized, which facilitates bone metabolic processes such as remodelling, but the fibula also appears to be a well vascularized bone. Future research investigating human bone metabolism will benefit from examining thoracic rib or fibula samples.

Joint mobility is a key factor in determining the functional capacity of tetrapod limbs, and is important in palaeobiological reconstructions of extinct animals. Recent advances have been made in quantifying osteological joint mobility using virtual computational methods; however, these approaches generally focus on the proximal limb joints and have seldom been applied to fossil mammals. Palorchestes azael is an enigmatic, extinct ~1000 kg marsupial with no close living relatives, whose functional ecology within Australian Pleistocene environments is poorly understood. Most intriguing is its flattened elbow morphology, which has long been assumed to indicate very low mobility at this important joint. Here, we tested elbow mobility via virtual range of motion (ROM) mapping and helical axis analysis, to quantitatively explore the limits of Palorchestes' elbow movement and compare this with their living and extinct relatives, as well as extant mammals that may represent functional analogues. We find that Palorchestes had the lowest elbow mobility among mammals sampled, even when afforded joint translations in addition to rotational degrees of freedom. This indicates that Palorchestes was limited to crouched forelimb postures, something highly unusual for mammals of this size. Coupled flexion and abduction created a skewed primary axis of movement at the elbow, suggesting an abducted forelimb posture and humeral rotation gait that is not found among marsupials and unlike that seen in any large mammals alive today. This work introduces new quantitative methods and demonstrates the utility of comparative ROM mapping approaches, highlighting that Palorchestes' forelimb function was unlike its contemporaneous relatives and appears to lack clear functional analogues among living mammals., (© 2021 Anatomical Society.)

Cigarette smoking is the largest cause of preventable deaths, and a known risk factor for musculoskeletal issues including rotator cuff tendon tears. Tendon degeneration is believed to be due in part to changes in tendon cell health and collagen structure. Several studies have demonstrated that exposure to nicotine negatively impacts tendon healing, but surprisingly, nicotine exposure was shown to increase rat supraspinatus tendon stiffness. In order to address this seeming contradiction, the objective of this study was to comprehensively investigate the effects of long-term (18 weeks) exposure of nicotine on tendon-to-bone microstructural properties in a rat model. We hypothesized that long term subcutaneous nicotine delivery would lead to diminished tendon mechanical properties, decreased bone microstructure in the humeral head, and altered tendon cell morphology compared to age-matched control rats receiving saline. Results demonstrated a small decrease in tendon size and stiffness, with decreased cell density in the tendon midsubstance. However, no differences were found in the enthesis fibrocartilage or in the underlying subchondral or trabecular bone. In conclusion, our study revealed limited effects of nicotine on the homeostatic condition of the supraspinatus tendon, enthesis, and underlying bone. Future studies are needed to ascertain effects of other components of tobacco products.