Morphological integration and shape covariation between the trapezium and first metacarpal among extant hominids.

OBJECTIVES: The shape of the trapezium and first metacarpal (Mc1) markedly influence thumb mobility, strength, and the manual abilities of extant hominids. Previous research has typically focused solely on trapezium-Mc1 joint shape. Here we investigate how morphological integration and shape covariation between the entire trapezium (articular and non-articular surfaces) and the entire Mc1 reflect known differences in thumb use in extant hominids. MATERIALS AND METHODS: We analyzed shape covariation in associated trapezia and Mc1s across a large, diverse sample of Homo sapiens (n = 40 individuals) and other extant hominids (Pan troglodytes, n = 16; Pan paniscus, n = 13; Gorilla gorilla gorilla, n = 27; Gorilla beringei, n = 6; Pongo pygmaeus, n = 14; Pongo abelii, n = 9) using a 3D geometric morphometric approach. We tested for interspecific significant differences in degree of morphological integration and patterns of shape covariation between the entire trapezium and Mc1, as well as within the trapezium-Mc1 joint specifically. RESULTS: Significant morphological integration was only found in the trapezium-Mc1 joint of H. sapiens and G. g. gorilla. Each genus showed a specific pattern of shape covariation between the entire trapezium and Mc1 that was consistent with different intercarpal and carpometacarpal joint postures. DISCUSSION: Our results are consistent with known differences in habitual thumb use, including a more abducted thumb during forceful precision grips in H. sapiens and a more adducted thumb in other hominids used for diverse grips. These results will help to infer thumb use in fossil hominins.

Sex Determination by the Machine Learning Algorithms Through Using Morphometric Measurements of the Carpal, Metacarpal, and Phalangeal Bones / Determinación del Sexo Mediante Algoritmos de Aprendizaje Automático Mediante el Uso de Mediciones Morfométricas de los Huesos del Carpo, el Metacarpo y las Falanges

SUMMARY: In the study, it was aimed to predict sex from hand measurements using machine learning algorithms (MLA). Measurements were made on MR images of 60 men and 60 women. Determined parameters; hand length (HL), palm length (PL), hand width (HW), wrist width (EBG), metacarpal I length (MIL), metacarpal I width (MIW), metacarpal II length (MIIL), metacarpal II width (MIIW), metacarpal III length (MIIL), metacarpal III width (MIIIW), metacarpal IV length (MIVL), metacarpal IV width (MIVW), metacarpal V length (MVL), metacarpal V width (MVW), phalanx I length (PILL), measured as phalanx II length (PIIL), phalanx III length (PIIL), phalanx IV length (PIVL), phalanx V length (PVL). In addition, the hand index (HI) was calculated. Logistic Regression (LR), Random Forest (RF), Linear Discriminant Analysis (LDA), K-nearest neighbour (KNN) and Naive Bayes (NB) were used as MLAs. In the study, the KNN algorithm's Accuracy, SEN, F1 and Specificity ratios were determined as 88 %. In this study using MLA, it is understood that the highest accuracy belongs to the KNN algorithm. Except for the hand's MIIW, MIIIW, MIVW, MVW, HI variables, other variables were statistically significant in terms of sex difference.

En el estudio, el objetivo era predecir el sexo a partir de mediciones manuales utilizando algoritmos de aprendizaje automático (MLA). Las mediciones se realizaron en imágenes de RM de 60 hombres y 60 mujeres. Parámetros determinados; longitud de la mano (HL), longitud de la palma (PL), ancho de la mano (HW), ancho de la muñeca (EBG), longitud del metacarpiano I (MIL), ancho del metacarpiano I (MIW), longitud del metacarpiano II (MIIL), ancho del metacarpiano II (MIIW), longitud del metacarpiano III (MIIL), ancho del metacarpiano III (MIIIW), longitud del metacarpiano IV (MIVL), ancho del metacarpiano IV (MIVW), longitud del metacarpiano V (MVL), ancho del metacarpiano V (MVW), longitud de la falange I (PILL), medido como longitud de la falange II (PIIL), longitud de la falange III (PIIL), longitud de la falange IV (PIVL), longitud de la falange V (PVL). Además, se calculó el índice de la mano (HI). Regresión logística (LR), Random Forest (RF), Análisis discriminante lineal (LDA), K-vecino más cercano (KNN) y Naive Bayes (NB) se utilizaron como MLA. En el estudio, las proporciones de precisión, SEN, F1 y especificidad del algoritmo KNN se determinaron en un 88 %. En este estudio que utiliza MLA, se entiende que la mayor precisión pertenece al algoritmo KNN. Excepto por las variables MIIW, MIIIW, MIVW, MVW, HI de la mano, otras variables fueron estadísticamente significativas en términos de diferencia de sexo.

Human thumb consists of three phalanges and lacks metacarpal? A morphometric study on the long bones of the hand.

PURPOSE: For many years, it was thought that the thumb consists of just two phalanges that differentiate it from the other four medial triphalangeal fingers. But there are some old reports that few former scientists believed the thumb has three phalanges and it lacked a metacarpal, and the thumb metacarpal is a phalanx. So this anthropometric study was carried out by investigating the morphology of the long bones of the hand and correlations between the thumb metacarpal and other miniature long bones of the hand. METHODS: We studied anterior-posterior X-ray images of the right hands of 80 individuals from 18 to 65 years old. The exploration targets were the length of all metacarpals (MC), proximal phalanges (PP), middle phalanges (MP), and distal phalanges (DP). Friedman Repeated Measures Analysis of Variance and Dunn's post hoc test were carried out to compare the means of all variables. The correlation between all quantitative factors was done by Spearman Rank Correlation (Spearman's Rho) coefficient. RESULTS: Our results showed that the length of the phalanges and the total length of the fingers are independent of the related metacarpal length (P < 0.001). Also, the thumb metacarpal length in comparison to all bones of the hand was significantly different from all long bones of the hand except the proximal phalanx of the middle finger (P = 1). CONCLUSION: Based on the morphology of the long bones of the hand and the high similarity between the thumb metacarpal and phalanges especially the proximal phalanx of the middle finger, it can be suggested that the current thumb metacarpal is a proximal phalanx of the thumb.

Ontogenetic changes to metacarpal trabecular bone structure in mountain and western lowland gorillas.

The trabecular bone morphology of adult extant primates has been shown to reflect mechanical loading related to locomotion. However, ontogenetic studies of humans and other mammals suggest an adaptive lag between trabecular bone response and current mechanical loading patterns that could result in adult trabecular bone morphology reflecting juvenile behaviours. This study investigates ontogenetic changes in the trabecular bone structure of the third metacarpal of mountain gorillas (Gorilla beringei beringei; n = 26) and western lowland gorillas (Gorilla gorilla gorilla; n = 26) and its relationship to expected changes in locomotor loading patterns. Results show that trabecular bone reflects predicted mechanical loading throughout ontogeny. Bone volume fraction, trabecular thickness and trabecular number are low at birth and increase with age, although degree of anisotropy remains relatively stable throughout ontogeny. A high concentration of bone volume fraction can be observed in the distopalmar region of the third metacarpal epiphysis in early ontogeny, consistent with the high frequency of climbing, suspensory and other grasping behaviours in young gorillas. High trabecular bone concentration increases dorsally in the epiphysis during the juvenile period as terrestrial knuckle-walking becomes the primary form of locomotion. However, fusion of the epiphysis does not take place until 10-11 years of age, and overall trabecular structure does not fully reflect the adult pattern until 12 years of age, indicating a lag between adult-like behaviours and adult-like trabecular morphology. We found minimal differences in trabecular ontogeny between mountain and western lowland gorillas, despite presumed variation in the frequencies of arboreal locomotor behaviours. Altogether, ontogenetic changes in Gorilla metacarpal trabecular structure reflect overall genus-level changes in locomotor behaviours throughout development, but with some ontogenetic lag that should be considered when drawing functional conclusions from bone structure in extant or fossil adolescent specimens.

Morphometric evaluation of second to fifth metacarpals for retrograde intramedullary headless screw fixation / Evaluación morfométrica del segundo al quinto metacarpianos para la fijación retrógrada con tornillos intramedulares sin cabeza

SUMMARY: Intramedullary headless screw fixation has come to the fore in the treatment of metacarpal fractures in recent years with its advantages. Our aim was to evaluate the metacarpal morphometry for retrograde intramedullary entrance and to determine the optimal entry point. Computed tomography images of 105 patients including 64 men and 41 women, were examined. Distal and proximal metacarpal widths, medullary cavity width, cortex thickness and the measurements of the optimal entry site in volar-dorsal and radio-ulnar directions were measured in both coronal and sagittal planes. In the sagittal plane, the second metacarpal had the widest proximal width (16.29 mm), distal width was greatest in the third metacarpal (14.34 mm) which was significantly different between the sexes (p<0.001). Third metacarpal had the widest medullary cavity width in the sagittal plane (4.12 mm). In the coronal plane, it was the second metarcarpal with the widest proximal (16.14 mm) and distal width (13.92 mm) and was also the longest (66.32 mm). Unlike the sagittal plane, the medullary cavity width in the coronal plane was at the widest (4.06 mm) in fifth metacarpal. The points determined for optimal entry were respectively (4.60 mm; 4.97 mm; 4.55 mm; 4.36 mm) in the dorsal-volar plane, close to the dorsal side. There was no significant difference between the sexes for optimal insertion point in the sagittal planes in all the measured metacarpals. Considering its three dimensional structure, metacarpal bones have irregular morphometric properties and these features differ in sagittal and coronal planes. The optimal entry site is located in the midline in the coronal plane, while it is located in the sagittal plane close to the dorsal part. Knowing these properties can reduce the complication rate by reducing entry attempts and help select the correct material.

RESUMEN: En los últimos años, debido a sus ventajas la fijación intramedular con tornillos sin cabeza ha pasado a primer plano en el tratamiento de las fracturas de los huesos metacarpianos. Nuestro objetivo fue evaluar la morfometría del hueso metacarpiano para la entrada intramedular retrógrada y determinar el punto de entrada óptimo. Se examinaron imágenes de tomografía computarizada de 105 pacientes, incluidos 64 hombres y 41 mujeres. Los anchos de los huesos metacarpianos distal y proximal, el ancho de la cavidad medular, el grosor de la cortical y las medidas del sitio de entrada óptimo en las direcciones palmar-dorsal y radioulnar se midieron en los planos coronal y sagital. En el plano sagital, el segundo hueso metacarpiano presentó el mayor ancho proximal (16,29 mm), el ancho distal fue mayor en el tercer hueso metacarpiano (14,34 mm), lo que fue significativamente diferente entre individuos de ambos sexos (p<0,001). El tercer metacarpiano tenía la cavidad medular más ancha en el plano sagital (4,12 mm). En el plano coronal, era el segundo hueso metarcarpiano con mayor ancho proximal (16,14 mm) y distal (13,92 mm) y también era el más largo (66,32 mm). A diferencia del plano sagital, el ancho de la cavidad medular en el plano coronal era más ancho (4,06 mm) en el quinto hueso metacarpiano. Los puntos determinados para la entrada óptima fueron respectivamente (4,60 mm; 4,97 mm; 4,55 mm; 4,36 mm) en el plano dorsal-volar, próximo del lado dorsal. No hubo diferencia significativa entre ambos sexos para el punto de inserción óptimo en los planos sagitales en todos los huesos metacarpianos medidos. Teniendo en consideración su estructura tridimensional, los huesos metacarpianos tienen propiedades morfométricas irregulares, y estas características difieren en los planos sagital y coronal. El sitio de entrada óptimo se encuentra en la línea mediana en el plano coronal, mientras que se ubica en el plano sagital cerca de la parte dorsal. Conocer estas propiedades puede reducir la tasa de complicaciones al disminuir los intentos de entrada y ayudar a seleccionar el material correcto.

Length of metacarpal and metatarsal bones in five Iranian sheep breeds and their associations with ungula measurements.

BACKGROUND: This study aimed to measure the length of metacarpal and metatarsal bones in five Iranian sheep breeds and to correlate the length of the bones with ungula measurements. Thoracic and pelvic limbs of 2-year-old, previously untrimmed, pastured Afshari, Moghani, Kurdi, Makoui, and Lori-Bakhtiari ewes, (n = 20 ewes per breed) were collected after slaughter. The following lengths were recorded in the metacarpal and metatarsal bones: from the margo proximalis lateralis to the lateral (L1) and medial (D1) cartilago physialis; from the margo proximalis lateralis to the margo abaxialis of the lateral (L2) and medial (D2) caput; from the cartilago physialis lateralis to the margo abaxialis of the lateral caput (X1); from the cartilago physialis medialis to the margo distalis of the caput ridge (X2) and from the margo axialis of cartilago physialis to the margo axialis of the lateral caput (X3). Additionally, measurements of the ungula including pars dorsalis length, pars mobilis lateralis and medialis height, pars dorsalis height to the ground and to the solea cornea, thickness of the solea in the pars dorsalis, pars mobilis lateralis and medialis, solea cornea length and angulus dorsalis were recorded in the medial and lateral digits of the thoracic and pelvic limbs. Data on length of the metatarsal and metacarpal bones were analysed using mixed model equations while Pearson correlations were calculated between metacarpal and metatarsal bones and ungula measurements. RESULTS: Lori- Bakhtiari and Moghani ewes had greater L1, L2, and D1 and D2 while X1, X2 and X3 was greater in Kurdi ewes (P < 0.05). Measurements such as L1, L2, D1 and D2 were greater in the metatarsal than in metacarpal bones (P < 0.05) and the opposite was observed for X1, X2 and X3 (P < 0.05). No asymmetry was observed between the lateral and medial measurements (P > 0.05). Low to moderate correlations were observed between bone and ungula measurements (P < 0.05). CONCLUSION: Under the conditions of this study, differences in metacarpal and metatarsal bone measurements were observed between breeds but no asymmetry was observed between lateral and medial bones. Results indicate an association between metacarpal and metatarsal bones ungula measurements. This could provide baseline information for the development and/or improvement of current ungula health protocols in the studied sheep breeds.

Homo naledi pollical metacarpal shaft morphology is distinctive and intermediate between that of australopiths and other members of the genus Homo.

Homo naledi fossils from the Rising Star cave system provide important insights into the diversity of hand morphology within the genus Homo. Notably, the pollical (thumb) metacarpal (Mc1) displays an unusual suite of characteristics including a median longitudinal crest, a narrow proximal base, and broad flaring intrinsic muscle flanges. The present study evaluates the affinities of H. naledi Mc1 morphology via 3D geometric morphometric analysis of shaft shape using a broader comparative sample (n = 337) of fossil hominins, recent humans, apes, and cercopithecoid monkeys than in prior work. Results confirm that the H. naledi Mc1 is distinctive from most other hominins in being narrow at the proximal end but surmounted by flaring muscle flanges distally. Only StW 418 (Australopithecus cf. africanus) is similar in these aspects of shape. The gracile proximal shaft is most similar to cercopithecoids, Pan, Pongo, Australopithecus afarensis, and Australopithecus sediba, suggesting that H. naledi retains the condition primitive for the genus Homo. In contrast, Neandertal Mc1s are characterized by wide proximal bases and shafts, pinched midshafts, and broad distal flanges, while those of recent humans generally have straight shafts, less robust muscle flanges, and wide proximal shafts/bases. Although uncertainties remain regarding character polarity, the morphology of the H. naledi thumb might be interpreted as a retained intermediate state in a transformation series between the overall gracility of the shaft and the robust shafts of later hominins. Such a model suggests that the addition of broad medial and lateral muscle flanges to a primitively slender shaft was the first modification in transforming the Mc1 into the overall more robust structure exhibited by other Homo taxa including Neandertals and recent Homo sapiens in whose shared lineage the bases and proximal shafts became expanded, possibly as an adaptation to the repeated recruitment of powerful intrinsic pollical muscles.

Age estimation from the biometric information of hand bones: Development of new formulas.

INTRODUCTION: In the judicial context of the age estimation of living individuals, a new method was recently proposed, based on the collection of biometric information on hand bones radiographs. The aim of this study was to apply this method to a large French sample to provide new tools for age estimation MATERIALS AND METHODS: The study sample consisted of metacarpals and proximal phalanges measurements of 1003 individuals aged less than 21 years. This sample was divided into two subgroups 1-12 and 13-21 years as the age of 13 is a relevant legal threshold for most European countries. A quadratic discriminant analysis was performed to identify the group to which an individual was most likely to belong. Age estimation formulas were also constructed from linear models: for each subgroup and the total sample. RESULTS: The belonging of an individual to the 1-12 or 13-21 subgroup was determined with a correct classification rate of 89.8%. Age estimation formulas became less precise with age, with a mean absolute error ranging between 11 and 21 months. CONCLUSION: We proposed a two-step procedure for age estimation: firstly, the identification of the age group to which the individual is most likely to belong, and secondly, the age estimation of this individual by applying the appropriate formula.

Current Opinions on the Management of Non Thumb Metacarpal Fractures.

Metacarpals are unique bones that support the finger to aid hand function. Metacarpals are also the commonest bones to get fractured in the hand. Historically, most metacarpal fractures were managed conservatively. Due to increased patient expectations as well as advancements in diagnosis and osteosynthesis, various surgical options are now available for metacarpal fractures. The goal of operative management of metacarpal management is no longer limited to achieving clinical or radiological union. To restore hand function to a preinjury level, the surgeon must achieve adequate anatomical reduction and stable fixation with minimal soft tissue damage. Similar to tendon repair, to start early active motion should be the goal after metacarpal fracture fixation. Intraoperative consideration should also include minimizing soft tissue damage and avoiding tendon, ligament or capsular entrapment. The aim of this article is to explain the principles of surgical management, the different options available for metacarpal fractures, the techniques, pearls, advantages and disadvantages of each technique, so the surgeon can choose the ideal option to achieve the best result.

Dorso-palmar elongation of the diaphysis of the third metacarpal bone in prehistoric Jomon people.

This study investigated cross-sectional morphological differences in the diaphysis of the third metacarpal bone (MC3) between prehistoric Jomon hunter-gatherers and modern Japanese people. Overall, 179 skeletal remains of 119 individuals (73 men and 46 women) from the Middle-to-Final Jomon period (3500 BC-500 BC) and 60 modern Japanese people (35 men and 25 women) were included in the analysis. Analyses were performed at the mid-shaft of the MC3 using linear measurement, elliptic Fourier analysis, and cross-sectional geometric properties. The standardized polar section modulus (ZpSTD) indicated sexual differences in both populations. The right MC3 was generally stronger than the left side. There was no populational difference in the ZpSTD in both sexes. In both men and women, the cross-sectional shape of the MC3 was relatively larger in the dorso-palmar direction than in the radioulnar direction in the Jomon population compared to the modern Japanese population. Sexual differences in cross-sectional shape were recognized only in the Jomon population, with the dorso-palmar elongation being greater in Jomon men than in women (particularly when comparing the left MC3). There was a significant side difference in the diaphyseal shape among Jomon women, with the right MC3 being relatively larger in the dorso-palmar direction. These findings were consistent, although skeletal remains of the Jomon population were excavated from different regions. Differences in the diaphyseal cross-sectional shape between populations suggest differences in habitual loading on MC3 associated with differences in subsistence behavior. Furthermore, differences in diaphyseal shape and strength between Jomon men and women suggest sexual division of labor, with men performing bimanual tasks and women performing unimanual tasks.

Locomotion on the edge: Structural properties of the third metacarpal in Thoroughbred and Quarter Horse racehorses and feral Assateague Island ponies.

The elongated, distally tapered limbs of horses are adapted for high-speed locomotion. Because these traits are artificially selected for in modern racehorses, they operate at a morphological extreme with a high risk of fracture. Racehorses are subject to different training and racing regimes depending on their breed and gait, and are therefore an interesting model to examine bone functional adaptation under variable biomechanically intense conditions. This study compares bone structural properties in the third metacarpal (MCIII) of Thoroughbred (n = 9) and Quarter Horse (n = 11) racehorses, using feral Assateague Island ponies (n = 6) as an untrained/unraced outgroup, to determine whether structural properties reflect variable racing and training regimes. Geometric section properties and bone mineral densities were determined using peripheral quantitative CT at two diaphyseal sites and through the distal epiphysis. Diaphyseal strength of the MCIII in all three breeds does not differ relative to body size, but in the mid-diaphyseal region Thoroughbreds have higher antero-posterior relative to medio-lateral bending strength than Quarter Horses, as well as higher bone mineral densities in left MCIII epiphyses (particularly in the lateral condyle). Interestingly, all breeds have lower bone mineral densities in the lateral versus medial condyle, an inherent structural feature that may influence predisposition to fracture when running around turns. Our results suggest that despite subtle differences in bone structure between different racehorse breeds, basic morphology of the third metacarpus is relatively similar among racing and non-racing horses, possibly reflecting intense selection (natural and artificial) across domestic equids for similar structural features within distal limb elements.

The implications of thumb movements for Neanderthal and modern human manipulation.

Much research has debated the technological abilities of Neanderthals relative to those of early modern humans, with a particular focus on subtle differences in thumb morphology and how this may reflect differences in manipulative behaviors in these two species. Here, we provide a novel perspective on this debate through a 3D geometric morphometric analysis of shape covariation between the trapezial and proximal first metacarpal articular surfaces of Neanderthals (Homo neanderthalensis) in comparison to early and recent humans (Homo sapiens). Results show a distinct pattern of shape covariation in Neanderthals, consistent with more extended and adducted thumb postures that may reflect habitual use of grips commonly used for hafted tools. Both Neanderthals and recent humans demonstrate high intraspecific variation in shape covariation. This intraspecific variation is likely the result of genetic and/or developmental differences, but may also reflect, in part, differing functional requirements imposed by the use of varied tool-kits. These results underscore the importance of holistic joint shape analysis for understanding the functional capabilities and evolution of the modern human thumb.

Rudimentary, "functionless" first metapodials of Canis latrans: Variation and association in length with longer, functional metapodials.

A tenet of evolutionary theory is that phenotypic variation of a trait is inversely related to the intensity of stabilizing selection pressure. Among homologous bones, such as metapodials, a rudimentary, "nonfunctional" bone is expected to be more variable in length than nonrudimentary bones. This study compares variation and association in length among metapodials using 277 adult skeletons of Canis latrans. Canis latrans has a short, "functionless" first metacarpal (mc1) and "rudimentary, vestigial" first metatarsal (mt1). Results show that among the 10 metapodials, mt1 has the highest variation in length; other metapodials do not differ significantly from one another in their variation. Correlation coefficients for length of mc1 and mt1 with their ipsilateral metapodials 2-5 are significantly lower than coefficients for all other ipsilateral pairs. The correlation coefficient between left and right mt1 is significantly the lowest among all bilateral pairs of metapodials. Results are interpreted as follows. Mt1's high variation and low association in length are the outcome of less intense stabilizing selection pressure compared with other metapodials. The nonsignificant difference for variation in length between mc1 and metapodials 2-5 may be that mc1 is functional for development of a pollical dewclaw that helps restrain small prey.

Prevalence and Risk Factors of Carpal Tunnel Syndrome in Japanese Aged 50 to 89 Years.

Background: Carpal tunnel syndrome (CTS) is the most common entrapment neuropathy worldwide, but there are few reports investigating its prevalence using subjects diagnosed by both clinical symptoms and nerve conduction studies (NCSs) in a population-based cohort. This study aimed to determine the epidemiology of CTS diagnosed by sensory disturbance findings and NCSs using a randomly sampled resident population. Methods: Subjects aged between 50 and 89 years were randomly sampled from the basic resident registry of a rural Japanese town. Subjects indicating a history of CTS surgery in a written questionnaire were classified as having past CTS. Subjects with both sensory disturbance of the median nerve area and delays in NCSs were diagnosed as having present CTS. Subjects with past or present CTS were judged as affected with CTS. We calculated the prevalence of CTS and investigated for possible risk factors. Results: Seventeen subjects (14 female and 3 male) were affected with CTS among 379 enrolled subjects. Adjusting these results to Japanese population values, the weighted prevalence of CTS was 4.7% (female: 7.2%, male: 1.8%) in the Japanese population aged 50 to 89 years. Statistically significant positive correlations were found between CTS and female, higher BMI, rheumatoid arthritis, and trigger digit. In females affected with CTS, third metacarpal length was significantly shorter than in those without CTS. Conclusions: This epidemiological study clarified the prevalence of CTS among Japanese seniors as 4.7%. Female, higher BMI, rheumatoid arthritis, trigger digit, and shorter third metacarpal length in females were risk factors for CTS.

Correlation between musculoskeletal structure of the hand and primate locomotion: Morphometric and mechanical analysis in prehension using the cross- and triple-ratios.

Biometric ratios of the relative length of the rays in the hand have been analyzed between primate species in the light of their hand function or phylogeny. However, how relative lengths among phalanges are mechanically linked to the grasping function of primates with different locomotor behaviors remains unclear. To clarify this, we calculated cross and triple-ratios, which are related to the torque distribution, and the torque generation mode at different joint angles using the lengths of the phalanges and metacarpal bones in 52 primates belonging to 25 species. The torque exerted on the finger joint and traction force of the flexor tendons necessary for a cylindrical grip and a suspensory hand posture were calculated using the moment arm of flexor tendons measured on magnetic resonance images, and were compared among Hylobates spp., Ateles sp., and Papio hamadryas. Finally, the torques calculated from the model were validated by a mechanical study detecting the force exerted on the phalanx by pulling the digital flexor muscles during suspension in these three species. Canonical discriminant analysis of cross and triple-ratios classified primates almost in accordance with their current classification based on locomotor behavior. The traction force was markedly reduced with flexion of the MCP joint parallel to the torque in brachiating primates; this was notably lower in the terrestrial quadrupedal primates than in the arboreal primates at mild flexion. Our mechanical study supported these features in the torque and traction force generation efficiencies. Our results suggest that suspensory or terrestrial quadrupedal primates have hand structures that can exert more torque at a suspensory posture, or palmigrade and digitigrade locomotion, respectively. Furthermore, our study suggests availability of the cross and triple-ratios as one of the indicators to estimate the hand function from the skeletal structure.

Three-dimensional modelling of computed tomography images of limb bones in gazelles (Gazella subgutturosa).

The objective of the present study was to model in 3D the detailed morphometric features of the thoracic and pelvic limb bones of the gazelle (Gazella subgutturosa), whose natural habitat is only in the Sanliurfa province, by using multidetector computerized tomography (MDCT) images. Materials from 14 (7 male and 7 female) dead gazelles were collected from the Harran University Veterinary Medicine Faculty clinics during or after treatment. MDCT images of the gazelles were taken and saved as DICOM (Digital Imaging and Communications in Medicine) files. MIMICS 20.1 software was used to generate a 3D reconstruction of the data, and morphological and morphometrical evaluation was performed. In respect of morphological features, the combined metacarpus (Mc) III and metacarpus Mc IV were the main weight-bearing metacarpal bone, while Mc II and Mc V were rudimentary. On the femur, the lateral condyle was bigger than the medial condyle at the caudodistal end and the medial wing of the trochlea femoris was larger than the lateral. As with the thoracic limb, the combined metatarsus (Mt) III and metatarsus Mt IV were the main weight-bearing metacarpal bone and they displayed a synostosis structure. There was no secondary metatarsus in the gazelles' pelvic limb. Based on digital measurements, the tibia was the longest bone of the gazelles' skeletal system, and there was a statistically significant sexual dimorphism throughout the skeleton at the levels of p < .05, p < .01 and p < .001. As a result, the present study's findings are useful as reference data for further studies on anatomy, surgery and archaezoology, while also being useful for classifying species and for forensic sciences.

Anatomy, Morphometry and Radiography in the thoracic limb bones of the Patagonian Huemul Deer (Hippocamelus bisulcus).

The aim of this study was to provide morphometric, anatomic and radiographic data of the thoracic limb bones of the Patagonian Huemul (Hippocamelus bisulcus) including a functional interpretation of this, as a reference for clinical use, biomedical research and teaching purposes. Currently, the Patagonian huemul deer is in danger of becoming extinct due to multiple causes. Research carried out for its conservation has focused mainly on its ecology and pathology, leaving gaps in biological knowledge, which is basic and important for its comprehension. This study was conducted to reveal the gross osteology and radiology features of the thoracic limb bones of the Patagonian huemul deer. The osteological findings suggest the presence of powerful flexor muscles in the scapulohumeral and elbow joints, useful to cushion the jumps. Also, the principal nutrient foramen of Patagonian huemul differs in position with respect to domestic ungulates, which may be important to consider during surgical procedures. Finally, the radiographic data can provide new information about the tissue loading conditions in Patagonian huemul, so that this new knowledge can be of great importance for a better understanding of mechanically induced or adaptive changes in bone produced by habitat or other ecological phenomena.

Management of Metacarpal and Phalangeal Fractures in the Athlete.

Metacarpal and phalangeal fractures are common injuries in athletes and occur frequently in contact and ball-handling sports. They usually result after direct hits from other players or athletic equipment. The fractures often are minimally displaced and require a short period of immobilization followed by early range of motion for expeditious return to play. Unstable or intra-articular fractures may require operative fixation. Open reduction and internal fixation afford the most stability while allowing for early rehabilitation. Athletes represent a unique population, and treatment of these fractures requires consideration of specific sport, timing of injury, and level of play.

Changes in the skeletal dimensions of the digits of the thoracic limb of Holstein cows after maturation.

The 12 left digits of the thoracic limb of Holstein female cows were obtained from a slaughterhouse, and 13 linear measurements of skeletal specimens of the digits of the thoracic limb were used in this study. Bivariate plots, regressions and correlation analyses were performed to assess the relationships between osteometric data and age, and between osteometric data and body size. The geometric mean (GM) of the metacarpal size was used as a proxy of body weight. The results of the regression analysis demonstrated that the length and the width of the distal phalanx were significantly correlated with age, whereas those of other bones were not. In addition, the correlations of the distal phalanx tended to be higher with age than with the GM of the metacarpal size, and their skeletal measurements tended to be longer in older animals than in younger animals. These findings suggest that the distal phalanx is slightly elongated and enlarged in its solear aspect with increasing age in skeletally mature cows. Moreover, although the side difference in the distal phalanx between the lateral and medial digits did not increase significantly with age, the solear aspect of the distal phalanx tended to be rougher, and deformation of the flexor tubercle tended to be more pronounced in the medial digit compared with the lateral digit. Therefore, in the distal phalanx of the front feet, the skeletal deformation with age and asymmetrical bone development might be related to the pathogenesis of claw horn lesions, as in the hind feet.

Relation between muscle architecture and first metacarpal morphology, and its implications for human hand evolution.

Previous studies have proposed that our ability to produce and use stone tools was the primary selective pressure explaining the evolution of the human hand. Derived traits in humans include a robust first metacarpal and longer thumbs relative to the other fingers. Along with other anatomical peculiarities, humans can exert forceful precision and have powerful grips, and can resist loads during tool production and use. Despite this biomechanical explanation for the morphology of the human hand, limited work has been done on the soft tissue and, therefore, the relationship between the hand bones and the muscles most heavily relied upon during tool-related behaviours still requires thorough investigation. For this purpose, we have dissected 23 forearms and hands of fresh human cadavers of known sex and age at death, and dissected all the muscles attached at the first metacarpal (the first dorsal interosseous, opponens pollicis, and abductor pollicis longus muscles). Variations in physiological cross-sectional area, muscle mass, and fibre length were compared with metacarpal anatomy. In no case bone traits were a significant predictor of muscle features. In contrast, sex and age predicted muscle architecture in several cases, thus substantially affecting the functional analysis based on linear measurements of this bone. The data, therefore, failed to provide a deductive framework for predicting muscle recruitment based on measurements of bone from the fossil record.