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.

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.

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 (Z_pSTD) indicated sexual differences in both populations. The right MC3 was generally stronger than the left side. There was no populational difference in the Z_pSTD 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.

Reproducibility of Metacarpal Bone Mineral Density Measurements Obtained by Dual-Energy X-Ray Absorptiometry in Healthy Volunteers and Patients With Early Arthritis

Reduction in cortical bone mineral density at diaphysis of metacarpal bones of the hand, evaluated by dual X-ray radiogrammetry, has a bad prognostic value in patients with early arthritis. Nevertheless, this technique is hardly accessible in clinical practice. By contrast, evaluation of cortical bone mineral density at that location has not been previously assessed by conventional dual X-ray absorptiometry. The aim of this study is to evaluate the reproducibility of bone mineral density measurements at diaphysis of metacarpal bones using conventional dual X-ray densitometry in a population of healthy volunteers and patients with early arthritis. Nondominant hand dual X-ray densitometry was performed at three consecutive times with complete hand replacement in 27 subjects: 10 early arthritis and 17 healthy volunteers. Three different evaluators analyzed the 3 measurements of second to fourth metacarpal bones. To assess the reproducibility and accuracy of the measurements, intra- and interobserver agreement degrees, intra- and interclass correlation coefficients, smallest difference detectable assessment, and Bland Altman graphs were calculated. The coefficients of variation obtained for the different metacarpal evaluations were 2.25%, 2.91%, 2.85%, and 2.07% for metacarpal-2, metacarpal-3, metacarpal-4, and mean metacarpal-second to fourth, respectively, with a smallest difference detectable of 0.028, 0.034, 0.028, and 0.03 g/cm², respectively. The mean intra- and interobserver correlation coefficients between of metacarpal second to fourth were 0.990 (95% confidence interval [CI]: 0.982-0.995) and 0.995 (95% CI: 0.991-0.997), respectively. As expected, women had lower bone mineral density at metacarpal bones, especially after menopause. The results obtained in this study show an excellent reproducibility of bone mineral density measurements at diaphysis of metacarpal bones of the hand, measured by conventional dual X-ray densitometry, in a mixed population of healthy subjects and patients with early arthritis. This is of great interest for longitudinal studies in patients with early arthritis.

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 (Z_pSTD) indicated sexual differences in both populations. The right MC3 was generally stronger than the left side. There was no populational difference in the Z_pSTD 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.

Trabecular architecture of the capitate and third metacarpal through ontogeny in chimpanzees (Pan troglodytes) and gorillas (Gorilla gorilla)

Chimpanzees (Pan troglodytes) and gorillas (Gorilla gorilla) both knuckle-walk in adulthood but are known to develop their locomotor strategies differently. Using dentally defined age-groups of both Pan and Gorilla and behavioral data from the literature, this study presents an internal trabecular bone approach to better understand the morphological ontogeny of knuckle-walking in these taxa. Capitate and third metacarpal bones were scanned by μCT at 23-43 μm resolution with scaled volumes of interest placed centrally within the head of the capitate and base of the third metacarpal. Trabecular measures related to activity level (size-adjusted bone volume/total volume, trabecular number, and bone surface area/bone volume) met expectations of decreasing through ontogeny in both taxa. Degree of anisotropy did not show statistical support for predicted species differences, but this may be due to the sample size as observed changes through ontogeny reflect expected trends in the capitate. Analyses of principal trabecular orientation corroborated known behavioral differences related to variation of hand use in these taxa, but only Pan showed directional patterning associated with suggested wrist posture. Assessment of allometry showed that the trabecular bone of larger animals is characterized by fewer and thinner trabeculae relative to bone size. In combination, these findings confirm the efficacy of trabecular bone in reflecting locomotor ontogeny differences between closely related taxa. These techniques show promise for use within the hominin fossil record, particularly for taxa hypothesized to be arboreal in some capacity.

Metacarpal trabecular bone varies with distinct hand-positions used in hominid locomotion

Trabecular bone remodels during life in response to loading and thus should, at least in part, reflect potential variation in the magnitude, frequency and direction of joint loading across different hominid species. Here we analyse the trabecular structure across all non-pollical metacarpal distal heads (Mc2-5) in extant great apes, expanding on previous volume of interest and whole-epiphysis analyses that have largely focused on only the first or third metacarpal. Specifically, we employ both a univariate statistical mapping and a multivariate approach to test for both inter-ray and interspecific differences in relative trabecular bone volume fraction (RBV/TV) and degree of anisotropy (DA) in Mc2-5 subchondral trabecular bone. Results demonstrate that whereas DA values only separate Pongo from African apes (Pan troglodytes, Pan paniscus, Gorilla gorilla), RBV/TV distribution varies with the predicted loading of the metacarpophalangeal (McP) joints during locomotor behaviours in each species. Gorilla exhibits a relatively dorsal distribution of RBV/TV consistent with habitual hyper-extension of the McP joints during knuckle-walking, whereas Pongo has a palmar distribution consistent with flexed McP joints used to grasp arboreal substrates. Both Pan species possess a disto-dorsal distribution of RBV/TV, compatible with multiple hand postures associated with a more varied locomotor regime. Further inter-ray comparisons reveal RBV/TV patterns consistent with varied knuckle-walking postures in Pan species in contrast to higher RBV/TV values toward the midline of the hand in Mc2 and Mc5 of Gorilla, consistent with habitual palm-back knuckle-walking. These patterns of trabecular bone distribution and structure reflect different behavioural signals that could be useful for determining the behaviours of fossil hominins.

Inverse remodelling algorithm identifies habitual manual activities of primates based on metacarpal bone architecture

Previously, a micro-finite element (micro-FE)-based inverse remodelling method was presented in the literature that reconstructs the loading history of a bone based on its architecture alone. Despite promising preliminary results, it remains unclear whether this method is sensitive enough to detect differences of bone loading related to pathologies or habitual activities. The goal of this study was to test the sensitivity of the inverse remodelling method by predicting joint loading histories of metacarpal bones of species with similar anatomy but clearly distinct habitual hand use. Three groups of habitual hand use were defined using the most representative primate species: manipulation (human), suspensory locomotion (orangutan), and knuckle-walking locomotion (bonobo, chimpanzee, gorilla). Nine to ten micro-computed tomography scans of each species ([Formula: see text] in total) were used to create micro-FE models of the metacarpal head region. The most probable joint loading history was predicted by optimally scaling six load cases representing joint postures ranging from [Formula: see text] (extension) to [Formula: see text] (flexion). Predicted mean joint load directions were significantly different between knuckle-walking and non-knuckle-walking groups ([Formula: see text]) and in line with expected primary hand postures. Mean joint load magnitudes tended to be larger in species using their hands for locomotion compared to species using them for manipulation. In conclusion, this study shows that the micro-FE-based inverse remodelling method is sensitive enough to detect differences of joint loading related to habitual manual activities of primates and might, therefore, be useful for palaeoanthropologists to reconstruct the behaviour of extinct species and for biomedical applications such as detecting pathological joint loading.

A longitudinal comparison of appendicular bone growth and markers of strength through adolescence in a South African cohort using radiogrammetry and pQCT

To compare growth patterns and strength of weight- and non-weight-bearing bones longitudinally. Irrespective of sex and ethnicity, metacarpal growth was similar to that of the non-weight-bearing radius but differed from that of the weight-bearing tibia. Weight- and non-weight-bearing bones have different growth and strength patterns.

INTRODUCTION

Functional loading modulates bone size and strength.

METHODS

To compare growth patterns and strength of weight- and non-weight-bearing bones longitudinally, we performed manual radiogrammetry of the second metacarpal on hand-wrist radiographs and measured peripheral quantitative computed tomography images of the radius (65%) and tibia (38% and 65%), annually on 372 black and 152 white South African participants (ages 12-20 years). We aligned participants by age from peak metacarpal length velocity. We assessed bone width (BW, mm); cortical thickness (CT, mm); medullary width (MW, mm); stress-strain index (SSI, mm³); and muscle cross-sectional area (MCSA, mm²).

RESULTS

From 12 to 20 years, the associations between metacarpal measures (BW, CT and SSI) and MCSA at the radius (males R² = 0.33-0.45; females R² = 0.12-0.20) were stronger than the tibia (males R² = 0.01-0.11; females R² = 0.007-0.04). In all groups, radial BW, CT and MW accrual rates were similar to those of the metacarpal, except in white females who had lower radial CT (0.04 mm/year) and greater radial MW (0.06 mm/year) accrual. In all groups, except for CT in white males, tibial BW and CT accrual rates were greater than at the metacarpal. Tibial MW (0.29-0.35 mm/year) increased significantly relative to metacarpal MW (- 0.07 to 0.06 mm/year) in males only. In all groups, except white females, SSI increased in each bone.

CONCLUSION

Irrespective of sex and ethnicity, metacarpal growth was similar to that of the non-weight-bearing radius but differed from that of the weight-bearing tibia. The local and systemic factors influencing site-specific differences require further investigation. Graphical abstract.

Systemic patterns of trabecular bone across the human and chimpanzee skeleton

Aspects of trabecular bone architecture are thought to reflect regional loading of the skeleton, and thus differ between primate taxa with different locomotor and postural modes. However, there are several systemic factors that affect bone structure that could contribute to, or be the primary factor determining, interspecific differences in bone structure. These systemic factors include differences in genetic regulation, sensitivity to loading, hormone levels, diet, and activity levels. Improved understanding of inter-/intraspecific variability, and variability across the skeleton of an individual, is required to interpret properly potential functional signals present within trabecular structure. Using a whole-region method of analysis, we investigated trabecular structure throughout the skeleton of humans and chimpanzees. Trabecular bone volume fraction (BV/TV), degree of anisotropy (DA) and trabecular thickness (Tb.Th) were quantified from high resolution micro-computed tomographic scans of the humeral and femoral head, third metacarpal and third metatarsal head, distal tibia, talus and first thoracic vertebra. We found that BV/TV is, in most anatomical sites, significantly higher in chimpanzees than in humans, suggesting a systemic difference in trabecular structure unrelated to local loading regime. Differences in BV/TV between the forelimb and hindlimb did not clearly reflect differences in locomotor loading in the study taxa. There were no clear systemic differences between the taxa in DA and, as such, this parameter might reflect function and relate to differences in joint loading. This systemic approach reveals both the pattern of variability across the skeleton and between taxa, and helps identify those features of trabecular structure that may relate to joint function.

Low second to fourth digit ratio in Dupuytren disease

The ratio of the lengths of the second and fourth digits (2D:4D) has been described as reflecting endogenous prenatal androgen exposure. In general, 2D:4D is lower in men than in women and has potential as a biomarker or predictor for various diseases, athletic ability, and academic performance. Dupuytren disease has digital flexion contractures and is known to predominate in men, but the pathogenesis of the disease remains unclear. To clarify the relationships between Dupuytren disease and endogenous androgens, we performed a retrospective analysis of hand radiographs to investigate 2D:4D in Dupuytren disease. The study included male patients with Dupuytren disease (n = 22) and a control group (n = 18) of male patients with carpal tunnel syndrome. Only unaffected hands, without contractures or osteoarthritis, were evaluated for the purpose of radiographic assessment. The lengths of the phalanx and metacarpal bones in the second and fourth digits were measured by 2 independent observers who each performed 2 sets of measurements separated by a minimum 1-week interval. The 2D:4D was calculated separately for the phalanges and metacarpals, and a combined (phalanx + metacarpal) 2D:4D was also calculated. The reliability of the observer measurements was established using the intraclass correlation coefficient, and both the intra- and interobserver reliability showed excellent agreement. We found that compared with control group, the Dupuytren disease group had significantly lower phalanx and combined 2D:4D. These findings suggest that endogenous prenatal androgens could contribute to the development of Dupuytren disease, leading to its characteristic clinical presentation predominantly in men and affecting the ulnar rays.

Manual Loading Distribution During Carrying Behaviors: Implications for the Evolution of the Hominin Hand

The human hand is unparalleled amongst primates in its ability to manipulate objects forcefully and dexterously. Previous research has predominantly sought to explain the evolution of these capabilities through an adaptive relationship between more modern human-like anatomical features in the upper limb and increased stone tool production and use proficiency. To date, however, we know little about the influence that other manipulatively demanding behaviors may have had upon the evolution of the human hand. The present study addresses one aspect of this deficiency by examining the recruitment of the distal phalanges during a range of manual transportation (i.e., carrying) events related to hominin behavioral repertoires during the Plio-Pleistocene. Specifically, forces on the volar pad of each digit are recorded during the transportation of stones and wooden branches that vary in weight and size. Results indicate that in most instances, the index and middle fingers are recruited to a significantly greater extent than the other three digits during carrying events. Relative force differences between digits were, however, dependent upon the size and weight of the object transported. Carrying behaviors therefore appear unlikely to have contributed to the evolution of the robust thumb anatomy observed in the human hand. Rather, results suggest that the manual transportation of objects may plausibly have influenced the evolution of the human gripping capabilities and the 3rd metacarpal styloid process.

Evaluation of mean echogenicity of tendons and ligaments of the metacarpal region in neonatal foals: A preliminary study

The aims of this research were to evaluate mean echogenicity (ME) of the deep and superficial digital flexor tendons (DDFT and SDFT), the interosseous muscle (IM), and the accessory ligament of the deep digital flexor tendon (ALDDFT) of the metacarpal region in neonatal foals, and determine the effect of sex, side and body weight on this quantitative ultrasonographic evaluation. Thirteen orthopedically sound neonatal foals were examined. Four areas of study (1A, 1B, 2A, 2B) were identified. Transverse scans of the DDFT, SDFT, IM and ALDDFT were obtained, recorded, and analyzed. The most echogenic structures were the ALDDFT and DDFT, while the SDFT was significantly less echogenic than all other structures (P<0.05). No influence of sex, forelimb, or body weight was observed. The echogenicity of the tenodesmic structures of foals partially overlapped that reported in the metacarpal region in adult horses, except for IM.

Morphometrics of the human thumb metacarpal bone: interest for developing an osseointegrated prosthesis

INTRODUCTION

Amputation of the thumb presents a serious insult to the hand and diminished quality of life for a patient physically, vocationally, and possibly psychologically. The aim of this study was to define the geometry of the thumb metacarpal in order to help create a standardized set of transcutaneous osseointegrated prostheses to treat patients who have suffered amputation of the thumb at the level of the metacarpophalangeal joint.

MATERIALS AND METHODS

A total of 80 metacarpals from 46 cadavers were studied. All soft tissues were removed and the thumb metacarpals were imaged using computed tomography. Three-dimensional models were constructed using images from the coronal, sagittal, and axial planes. Using HyperMesh™ CAD software, the bones were analyzed for overall length, radius of curvature, medullary canal diameter, cortical thickness, and distance to the isthmus, defined as the narrowest portion of the intramedullary canal.

RESULTS

The average length of the first metacarpal was 47.6 mm (±3.3 mm, 39.2-56.9 mm). The average radius of curvature was 55.5 mm (±10.7 mm, 33-78.9 mm). Inner bone diameter, measured in two axes, was 10.5 mm (±1.3 mm, 5.4-18.7 mm) for the major axis and 7.7 mm (±0.9 mm, 4.3-17.8 mm) for the minor axis. The average cortical thickness was 1.4 mm (±0.3 mm, 0.7-3.1 mm). The distance to the center of the isthmus from the distal end had an average length of 21.3 mm (±1.9 mm, 17-25 mm).

CONCLUSIONS

Using these findings a standardized set of intramedullary stems can be developed as a base for a transcutaneous osseointegrated prosthesis, helping to create a reliable method for treating patients with amputated thumbs.

The Hand of Cercopithecoides williamsi (Mammalia, Primates): Earliest Evidence for Thumb Reduction among Colobine Monkeys

Thumb reduction is among the most important features distinguishing the African and Asian colobines from each other and from other Old World monkeys. In this study we demonstrate that the partial skeleton KNM-ER 4420 from Koobi Fora, Kenya, dated to 1.9 Ma and assigned to the Plio-Pleistocene colobine species Cercopithecoides williamsi, shows marked reduction of its first metacarpal relative to the medial metacarpals. Thus, KNM-ER 4420 is the first documented occurrence of cercopithecid pollical reduction in the fossil record. In the size of its first metacarpal relative to the medial metacarpals, C. williamsi is similar to extant African colobines, but different from cercopithecines, extant Asian colobines and the Late Miocene colobines Microcolobus and Mesopithecus. This feature clearly links the genus Cercopithecoides with the extant African colobine clade and makes it the first definitive African colobine in the fossil record. The postcranial adaptations to terrestriality in Cercopithecoides are most likely secondary, while ancestral colobinans (and colobines) were arboreal. Finally, the absence of any evidence for pollical reduction in Mesopithecus implies either independent thumb reduction in African and Asian colobines or multiple colobine dispersal events out of Africa. Based on the available evidence, we consider the first scenario more likely.

Polar histograms of curvature for quantifying skeletal joint shape and congruence

The effect of articular joint shape and congruence on kinematics, contact stress, and the natural progression of joint disease continue to be a topic of interest in the orthopedic biomechanics literature. Currently, the most widely used metrics of assessing skeletal joint shape and congruence are based on average principal curvatures across the articular surfaces. Here we propose a method for comparing articular joint shape and quantifying joint congruence based on three-dimensional (3D) histograms of curvature--shape descriptors that preserve spatial information. Illustrated by experimental results from the trapeziometacarpal joint, this method could help unveil the interrelations between joint shape and function and provide much needed insight for the high incidence of osteoarthritis (OA)--a mechanically mediated disease whose onset has been hypothesized to be precipitated by joint incongruity.

Locked intramedullary nail: metacarpal geometry study in adults

BACKGROUND

Ideal fixation for metacarpal fracture should provide immediate stability to allow early rehabilitation. Locked intramedullary nail may fulfill the need. Metecarpal geometry has to be studied in order to design the locked intramedullaly nail.

OBJECTIVE

To study metacarpal geometry in adult cadaver for locked intramedullary nail design.

MATERIAL AND METHOD

Radiographs of metacarpals taken from 50 embalmed adult cadavers were measured for essential parameters for locked intramedullary nail design. Total length, proximal metaphyseal width, distal metaphyseal width, isthmus width and medullary canal width were measured. The parameters were analyzed by descriptive statistic.

RESULTS

The average total lengths were rangedfrom 44.53 to 65.42 mm. The average metaphyseal widths ofmetacarpal bone were between 11.42 to 16.42 mm. The average medullary canal widths were between 3.05 to 6.74 mm. The extreme small (less than 3 mm) medullary canals were found in index, middle, ring and small metacarpals.

CONCLUSION

The results of our study provide crucial preliminary data for locked metacarpal nail design for adult patient.

[The anatomical basis of the formation of the pedicled bone grafts on the upper extremity]

The study of the vascular bed of the upper extremities was performed by the method of anatomical preparation of 24 formalin-fixed cadaver specimens from 5 men and 7 women and by the injection of black latex into the arterial bed of 4 male and 4 female cadavers (16 specimens). The arteries, directly feeding the bones, and the arteries that provide blood supply to the muscles, attached to the bones, were studied. M. pectoralis major, m. pronator teres, m. pronator quadratus, mm. lumbricalis and interosseus were examined. These studies were followed by the experimental surgeries during which bone grafts on vascular pedicle were formed and moved. It was found that the feeding arteries of the bone grafts on musculo-vascular pedicle were: on the clavicula--the branches of a. thoracoacromialis, on the brachium--muscular branches of a. brachialis, on the proximal parts of forearm bones--muscular branches of a. radialis and ulnaris, on the distal parts of forearm bones--the branches of a. interosseous anterior, on the metacarpal bones--the branches of aa. metacarpalis palmaris and dorsalis. The size of the bone transplants is determined by the size of the defect of recipient field and varies from 3 to 8 cm. The displacement of vascularised bone graft can be made over the distance from 4 to 8 cm.

Trabecular bone structure correlates with hand posture and use in hominoids

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

[Phenotypic features in autistic individuals: the finger length ratio (2D:4D), hair whorl, and hand dominance]

OBJECTIVE

The aim of this study was to compare the finger length ratio (2D:4D), hair whorl direction, and hand, foot, and eye dominance in autistic and healthy individuals, and to investigate the phenotypic characteristics of autism.

MATERIALS AND METHODS

The study included 37 males diagnosed with autistic disorder and 121 healthy males, all aged 4-18 years. The length of the index and ring fingers of both hands--from the proximal bend of the metacarpophalangeal joint to the fingertips--was measured with digital calipers and the index-ring finger (2D:4D) ratio was determined. The distance between hair whorls, their perpendicular distance from the mid-sagittal line, and their direction of rotation were calculated in the autism and control groups. Hand, foot, and eye dominance were determined in both groups. The findings were evaluated using SPSS v.15.0.

RESULTS

The autism group had a greater number of hair whorls than the control group. The distance between hair whorls and the mid-sagittal line was longer in those with left hand and left eye dominance. A significant difference in the 2D:4D ratio of the right and left hands between the 2 groups was not observed.

CONCLUSION

The autism group had more hair whorls than the control group and the hair whorls in the autistic individuals with left hand and left eye dominance were located further from the mid-saggital line. We think that these novel findings might contribute to the determination of the phenotypic features specific to autism.

Topography and morphological anatomy of nutrient foramina in human metacarpal bones and their clinical implications

PURPOSE

To study the morphological and topographic anatomy of nutrient foramina and to determine the foraminal index of metacarpal bones.

MATERIALS AND METHODS

The study consisted of 438 unpaired, human metacarpal bones of unknown age and sex. Nutrient foramina in each of the bones were grossly identified in relation to their number and location. The foraminal index was calculated by applying the Hughes formula. A digital vernier caliper was used to perform the measurements.

RESULTS

Among our specimens, 93.1% of metacarpals had single foramen, 2% had double foramina, 0.3% of the bones had triple foramina and in 4.6% of cases the foramen was absent. The mean foraminal indexes of the 1st, 2nd, 3rd, 4th and 5th metacarpal were 60.1, 53, 43.1, 43.7 and 45.9 respectively.

CONCLUSION

It was observed that the morphology and topography of nutrient foramina vary among different metacarpals. In 1st and 2nd metacarpals, foramina were more common at the medial surface and in other metacarpals, mostly seen on the lateral surface. The knowledge about these foramina is important in certain surgical procedures to preserve the circulation. This data is important to the plastic surgeon for microvascular bone transfer surgeries.

Three-dimensional quantitative comparative analysis of trapezial-metacarpal joint surface curvatures in human populations

PURPOSE

Trapezial-metacarpal (TM) joint surfaces appear to be shallower in Asian than in white postmortem specimens, and the frequency of TM osteoarthritis seems to be substantially lower in Asian TM joints. This study tested the hypothesis that there are significant differences among human populations in TM joint surface curvature and that populations of Asian descent have less curvature than those of recent European descent.

METHODS

The sample included trapeziums and first metacarpals from skeletons of 80 individuals of recent European and Asian descent and from skeletons of 34 African and 9 Australian aboriginal individuals. We scanned the surfaces using a laser digitizer to generate 3-dimensional models of each articular surface. We calculated dorsovolar, radioulnar, and root mean square curvatures by fitting modeled quadric surfaces to the TM joint surfaces. We tested pairwise comparisons of mean curvatures between populations for statistical significance using a standard resampling method (ie, bootstrapping). We also made pairwise comparisons of mean curvatures between males and females for a combined African and European sample.

RESULTS

Mean dorsovolar metacarpal curvature was significantly higher in the European sample than in the Asian, African, and Australian samples. Mean root mean square curvature of the trapezial surface was significantly higher in the European sample than in the Asian sample. The European sample had the highest root mean square and dorsovolar trapezial curvatures of all the populations. We found no significant differences between male and female specimens.

CONCLUSIONS

A tendency toward higher mean dorsovolar curvature of both the metacarpal and trapezial surface in the European sample may help to explain the higher frequency of TM osteoarthritis reported in Europeans.

CLINICAL RELEVANCE

The greater TM curvatures affect basal thumb joint mechanics in thumb opposition and therefore may be a factor in the development of osteoarthritis at this joint in Europeans.

A new alternative to quantify finger rotation: angles between the axis of flexed fingers and the axis of third metacarpal bone

OBJECTIVE

To determine whether the proposed angle, formed between the axis of middle and distal phalanges of each of flexed fingers and the axis of the third metacarpal bone was symmetrical between both hands in adult population.

MATERIAL AND METHOD

Thirty-one volunteers (12 males and 19 females) having normal and uninjured hands with an average age of 38 years underwent a fluoroscopic examination of their hands. All volunteers put their hands in a special positioning device that passively held the metacarpophalangeal and proximal interphalangeal joints in full flexion with distal interphalangeal joint in full extension. Fluoroscopic images were then taken and angles were digitally measured.

RESULTS

Mean angles of the flexed index, middle, ring and small fingers compared to the third metacarpal bone were -4.07 (SEM = 1.041), 5.22 (SEM = 0.889), 12.91 (SEM = 1.009) and 23.11 (SEM = 1.370) degrees, respectively. The angles were statistically symmetrical between both hands (p = 0.838, 0.546, 0.620 and 0.641, respectively). The genders had no effect on the symmetry (p > 0.3). The differences between angle of each finger and the angle of the middle finger were also found to be statistically symmetrical.

CONCLUSION

Side-to-side comparison of the angle formed between the axis of flexed fingers and the third metacarpal bone measured from radiographic images can be used as an additional alternative to determine the finger rotation. The angular relationship between each finger with respect to the middle finger can also be used to purposefully reduce x-ray beam projection variation.

Variation in childhood skeletal robustness is an important determinant of cortical area in young adults

A better understanding of bone growth will benefit efforts to reduce fracture incidence, because variation in elderly bone traits is determined primarily by adulthood. The natural variation in robustness was used as a model to understand how variable growth patterns define adult bone morphology. Longitudinally acquired hand radiographs of 29 boys and 30 girls were obtained from the Bolton-Brush study for 6 time points spanning 8 to 18 years of age. Segregating individuals into tertiles based on robustness revealed that the biological activity underlying bone growth varied significantly with the natural variation in robustness. For boys, slender metacarpals used an osteoblast-dependent growth pattern to establish function, whereas robust metacarpals used an osteoclast-dependent growth pattern. In contrast, differences in biological activity between girls with slender and robust metacarpals were largely based on the age at which the marrow surface changed from expansion to infilling. Importantly, cortical area for slender metacarpals was as much as 19.7% and 32.2% lower than robust metacarpals for boys and girls, respectively, indicating that robustness was a major determinant of adult cortical area. Finally, after accounting for robustness and body weight effects, we found that the inter-individual variation in cortical area was established as early as 8 years of age. While variation in the amount of bone acquired during growth has primarily been attributed to factors like nutrition, exercise, and genetic background, we showed that the natural variation in robustness was also a major determinant of cortical area, which is an important determinant of bone mass. This predictable relationship between robustness and cortical area should be incorporated into clinical diagnostic measures and experimental studies.

Metacarpal thickness, width, length and medullary diameter in children--reference curves from the First Zürich Longitudinal Study

SUMMARY

Metacarpal thickness (T), width (W), length (L) and medullary diameter (M) were measured in 3,121 X-rays from 231 healthy Caucasian children aged 3 to 19 years and analysed for bone age, age, height, weight and gender-related characteristics, showing highly differentiated growth patterns with prepubertal dips. Reference data for the four metacarpal measures are presented.

INTRODUCTION

The aim of the study was to create and explore a reference database for metacarpal T, W, L and M in children.

METHODS

Three thousand one hundred twenty-one left-hand X-rays (1,661 from boys) from 231 healthy Caucasian subjects (119 boys) aged 3 to 19 years were analysed by BoneXpert, a programme for automatic analysis of hand X-rays and bone age (BA; in years).

RESULTS

In boys, growth of T, W and L shows a prepubertal decrease from BA 7 to 13 and then accelerates again. In girls, the same is seen only for T starting from BA 8 to 11, whereas W and L grow at a declining rate. M shows steady growth until BA 10.5 in girls and BA 13.5 in boys and then grows smaller in both. W is greater in boys from BA 6 onwards, while L is greater in girls from BA 9 to 13 and T from BA 11 to 14. BA is reflected best by L until start of puberty and by T and L thereafter.

CONCLUSION

T, W, L and M show highly differentiated growth patterns. These reference data provide a basis for further research into skeletal development and the management of hormone therapies in children.

Methodological considerations for analyzing trabecular architecture: an example from the primate hand

Micro-computed tomographic analyses of trabecular bone architecture have been used to clarify the link between positional behavior and skeletal anatomy in primates. However, there are methodological decisions associated with quantifying and comparing trabecular anatomy across taxa that vary greatly in body size and morphology that can affect characterizations of trabecular architecture, such as choice of the volume of interest (VOI) size and location. The potential effects of these decisions may be amplified in small, irregular-shaped bones of the hands and feet that have more complex external morphology and more heterogeneous trabecular structure compared to, for example, the spherical epiphysis of the femoral head. In this study we investigate the effects of changes in VOI size and location on standard trabecular parameters in two bones of the hand, the capitate and third metacarpal, in a diverse sample of nonhuman primates that vary greatly in morphology, body mass and positional behavior. Results demonstrate that changes in VOI location and, to a lesser extent, changes in VOI size had a dramatic affect on many trabecular parameters, especially trabecular connectivity and structure (rods vs. plates), degree of anisotropy, and the primary orientation of the trabeculae. Although previous research has shown that some trabecular parameters are susceptible to slight variations in methodology (e.g. VOI location, scan resolution), this study provides a quantification of these effects in hand bones of a diverse sample of primates. An a priori understanding of the inherent biases created by the choice of VOI size and particularly location is critical to robust trabecular analysis and functional interpretation, especially in small bones with complex arthroses.

Estimating peak strains associated with fast exercise in Thoroughbred racehorses

REASONS FOR PERFORMING STUDY

The third metacarpal bones (MC3) of racing Thoroughbreds are a common site for bone damage. The midshaft dorsal cortex (DC) of MC3 thickens in response to fast exercise. It is not clear if it changes to a shape and size that limits the peak bone strains to a range associated with normal loading in other species.

OBJECTIVES

To relate the proportionate size of the DC cortex in racehorses exercising at racing speed to surface strains, and test whether the DC reached a plateau that was sustained through subsequent exposures to racing speed exercise.

METHODS

Standardised lateral MC3 radiographs were taken weekly for 2-5 years in 40 racehorses in race training (16-19 m/sec). DC, medulla (M), and palmar cortex (PC) thickness were measured. at 2.5 cm distal to the nutrient foramen. An index (RI) of the relative thickness of the DC was calculated for each radiograph (RI = [DC+PC]/ M multiplied by [DC/ PC]) and used to calculate strains at 12 m/sec from an equation published previously.

RESULTS

Mean time to plateau in DC thickness was 501 days, mean increase in DC was 3.9 mm on the left and 3.7 mm on the right. Rate of change was 8.8 microm/day on the left, and 8.4 microm/day on the right during this time. In most horses the medulla width did not change between the first and last measurements so these bone growth rates reflect periosteal bone growth on the DC surface. No further significant change in DC or RI was found, once they had reached a plateau. Mean DC thickness at the plateau was 14.7 mm on the left and 14.9 mm on the right. Mean RI at the plateau was 3.7. This equated to peak microstrains at 12 m/sec of -2492 and suggests that strains much greater than 3000 microstrains occur at racing speed in most horses.

CONCLUSIONS

Experienced racehorses are likely to be exposed to peak strains beyond the normal limit for adult mammalian bone to resist without damage and strains associated with very fast exercise may not be sufficient stimulus to induce further bone modelling in these horses.

POTENTIAL RELEVANCE

Strains occur in the bones of experienced racehorses at a higher level than normal for other mammalian bones. Hence there may be other mechanisms operating in this particular bone in racehorses that protects the bone from failure when exposed to the high strains associated with fast exercise speeds. Investigation of such mechanisms may provide an insight on how to reduce the likelihood of damage to this bone during very fast exercise.

Careful climbing in the Miocene: the forelimbs of Ardipithecus ramidus and humans are primitive

The Ardipithecus ramidus hand and wrist exhibit none of the derived mechanisms that restrict motion in extant great apes and are reminiscent of those of Miocene apes, such as Proconsul. The capitate head is more palmar than in all other known hominoids, permitting extreme midcarpal dorsiflexion. Ar. ramidus and all later hominids lack the carpometacarpal articular and ligamentous specializations of extant apes. Manual proportions are unlike those of any extant ape. Metacarpals 2 through 5 are relatively short, lacking any morphological traits associable with knuckle-walking. Humeral and ulnar characters are primitive and like those of later hominids. The Ar. ramidus forelimb complex implies palmigrady during bridging and careful climbing and exhibits none of the adaptations to vertical climbing, forelimb suspension, and knuckle-walking that are seen in extant African apes.

The great divides: Ardipithecus ramidus reveals the postcrania of our last common ancestors with African apes

Genomic comparisons have established the chimpanzee and bonobo as our closest living relatives. However, the intricacies of gene regulation and expression caution against the use of these extant apes in deducing the anatomical structure of the last common ancestor that we shared with them. Evidence for this structure must therefore be sought from the fossil record. Until now, that record has provided few relevant data because available fossils were too recent or too incomplete. Evidence from Ardipithecus ramidus now suggests that the last common ancestor lacked the hand, foot, pelvic, vertebral, and limb structures and proportions specialized for suspension, vertical climbing, and knuckle-walking among extant African apes. If this hypothesis is correct, each extant African ape genus must have independently acquired these specializations from more generalized ancestors who still practiced careful arboreal climbing and bridging. African apes and hominids acquired advanced orthogrady in parallel. Hominoid spinal invagination is an embryogenetic mechanism that reoriented the shoulder girdle more laterally. It was unaccompanied by substantial lumbar spine abbreviation, an adaptation restricted to vertical climbing and/or suspension. The specialized locomotor anatomies and behaviors of chimpanzees and gorillas therefore constitute poor models for the origin and evolution of human bipedality.

One-year change in the second metacarpal bone mass associated with menopause nutrition and physical activity

OBJECTIVES

To clarify the annual changes and effects of nutrition and physical activity on bone mass at the second metacarpal using computed X-ray densitometry.

DESIGN

Population-based prospective follow-up study.

MEASUREMENTS

Bone mass measurements and assessments of nutritional intake, exercise habits, and health status were conducted twice with a one-year interval.

PARTICIPANT

269 Japanese women aged 40 - to -80 - years old.

RESULTS

The annual change rate among subjects who started menopause during the observation period was -4.2 +/- 4.9%. Bone mass subsequently continued to decrease 3% annually until 6 years after menopause. Subjects who consumed high levels of milk or calcium in the first year showed no substantial decrease in bone mass among the post-menopausal subjects. Premenopausal subjects who began or continued exercise evidenced increased bone mass, and peri-menopausal subjects who continued exercise or a high level of daily physical activity showed inhibited bone loss.

CONCLUSION

Second metacarpal bone changed by menopause, nutrition and physical activity similar with other bone site presented in the previous studies.

[Trapezio second metacarpal joint: anatomical study and clinical matters]

INTRODUCTION

An unusual dislocation of the column of the thumb associated with a fracture of the base of the second metacarpal inspired an anatomical study of the trapeziosecond metacarpal joint.

MATERIALS AND METHODS

Forty-five dissections of the palmar aspect of trapeziometacarpal joint aimed at focusing on palmar ligaments and tendons reinforcing the joints.

RESULTS

Trapeziosecond metacarpal joint is a constant little diarthrosis reinforced by a palmar ligament stressed between the crest of the trapezium and the base of the second metacarpal. The tendon of flexor radialis carpi muscle is an active link due to strong vinculae to trapezium bone and distal attachment to the bases of both second and third metacarpals.

CONCLUSION

The connections between the trapezium and the base of the second metacarpal bone play a role in the treatment of thumb instability and their mechanical importance is illustrated in our original clinical observation.

An additional radial wrist extensor and its clinical significance

The knowledge of anatomical variations in the antebrachial and dorsal regions of the arm and hand are useful in hand surgery. The extensor carpi radialis intermedius and extensor carpi radialis accessorius are two classic variants described for the radial wrist extensors, in the antebrachial region. We report an additional extensor carpi radialis muscle taking origin from the common extensor origin, between the extensor carpi radialis longus and extensor digitorum communis. The tendon of the variant muscle divides below the abductor pollicis longus and becomes attached to the base of the second and third metacarpal bone. Due to its considerable size and independent origin from the lateral epicondyle, we suggest the present variation should be named extensor carpi radialis tertius. The clinical significance of the present variation is discussed.

Orang-like manual adaptations in the fossil hominoid Hispanopithecus laietanus: first steps towards great ape suspensory behaviours

Morphological and biometrical analyses of the partial hand IPS18800 of the fossil great ape Hispanopithecus laietanus (=Dryopithecus laietanus), from the Late Miocene (about 9.5Ma) of Can Llobateres (Catalonia, Spain), reveal many similarities with extant orang-utans (Pongo). These similarities are interpreted as adaptations to below-branch suspensory behaviours, including arm-swinging and clambering/postural feeding on slender arboreal supports, due to an orang-like double-locking mechanism. This is confirmed by the long and highly curved phalanges of Hispanopithecus. The short and stout metacarpals with dorsally constricted heads, together with the dorsally extended articular facets on proximal phalanges, indicate the persistence of significant degrees of palmigrady. A powerful grasping capability is indicated by the great development of basal phalangeal tubercles, the marked insertions for the flexors on phalangeal shafts and the large pits for the collateral ligaments. The morphology of the Hispanopithecus long bones of the hand indicates a unique positional repertoire, combining orthogrady with suspensory behaviours and palmigrade quadrupedalism. The retention of powerful grasping and palmigrady suggests that the last common ancestor of hominids might have been more primitive than what can be inferred on the basis of extant taxa, suggesting that pronograde behaviours are compatible with an orthograde bodyplan suitable for climbing and suspension.

The structure of the cushions in the feet of African elephants (Loxodonta africana)

The uniquely designed limbs of the African elephant, Loxodonta africana, support the weight of the largest terrestrial animal. Besides other morphological peculiarities, the feet are equipped with large subcutaneous cushions which play an important role in distributing forces during weight bearing and in storing or absorbing mechanical forces. Although the cushions have been discussed in the literature and captive elephants, in particular, are frequently affected by foot disorders, precise morphological data are sparse. The cushions in the feet of African elephants were examined by means of standard anatomical and histological techniques, computed tomography (CT) and magnetic resonance imaging (MRI). In both the forelimb and the hindlimb a 6th ray, the prepollex or prehallux, is present. These cartilaginous rods support the metacarpal or metatarsal compartment of the cushions. None of the rays touches the ground directly. The cushions consist of sheets or strands of fibrous connective tissue forming larger metacarpal/metatarsal and digital compartments and smaller chambers which were filled with adipose tissue. The compartments are situated between tarsal, metatarsal, metacarpal bones, proximal phalanges or other structures of the locomotor apparatus covering the bones palmarly/plantarly and the thick sole skin. Within the cushions, collagen, reticulin and elastic fibres are found. In the main parts, vascular supply is good and numerous nerves course within the entire cushion. Vater-Pacinian corpuscles are embedded within the collagenous tissue of the cushions and within the dermis. Meissner corpuscles are found in the dermal papillae of the foot skin. The micromorphology of elephant feet cushions resembles that of digital cushions in cattle or of the foot pads in humans but not that of digital cushions in horses. Besides their important mechanical properties, foot cushions in elephants seem to be very sensitive structures.

Identification of two accessory muscle bundles with anomalous insertions in the flexor side of the right forearm

During dissection practice held at Kyorin University School of Medicine in 2004, two anomalous muscles were observed on the Rt-forearm-flexor-side of an 83-year-old man. The results of this investigation are reported. One accessory muscle originated from the tendinous insertion of the biceps brachii and medial epicondyle. After passing through the deep layer of the pronator teres, it became tendinous, passing towards the trapezium and second metacarpal base. Its two origins fused superficial to the ulnar artery distal to the cubital fossa, and it merged with the deep region of the pronator teres. More distally, the accessory muscle formed a belly before again becoming tendinous and bifurcated, one branch attaching to the trapezium and the other fusing with the belly of the second accessory muscle. These findings suggested that this accessory muscle was similar to Gantzer's muscle. The other accessory muscle arose distal to the origin of the flexor pollicis longus and inserted onto the second metacarpal base. In addition, from the distal side of its origin, a small muscle bundle was formed and became tendinous. It fused with the insertion tendon of the first accessory muscle to the trapezium. The second accessory muscle was thought to be deep radial carpal flexor.

Metacarpal sexual determination in a Spanish population

Anthropologists and forensic pathologist determine the sex of skeletons by analyzing quantitative and qualitative characters in the bone remains. Generally, the skull and os coxae are the elements most used, but they are not always preserved. In such cases, the investigator needs to have available other techniques based on different remains. The aim of the present work is to develop and describe discriminating functions for sex determination in a recent Spanish population using metacarpal morphology. A sample of bones corresponding to a contemporary Spanish population deposited at the Complutense University of Madrid (UCM) was analyzed. This sample comprised 697 metacarpals, corresponding to 79 adult individuals (37 men and 42 women). These allowed us to obtain 120 unifactorial discriminant functions. We selected the 10 equations, one for each metacarpal from both hands, that provided the best sexual discrimination. The correct sex classification rank progressed from 81%, for right (R) metacarpals IV and V, to 91%, for left (L) metacarpal II. The results suggest that metacarpals are structures that can be used for sex determination in paleoanthropological and forensic identifications.

[The trapezio-metacarpal joint: the strain of the ligaments as a function of the thumb position. Study on an enlarged model]

INTRODUCTION

The aim of this paper was to develop an enlarged anatomical model of the trapezio-metacarpal joint in order to measure the strains on the ligaments when this joint was passively moved in several directions under constant loading.

MATERIAL AND METHOD

A model of the two first rays of the hand was made in polystyrene, at a X3 enlargement, and the ligaments substituted by rubber bands with well characterized mechanical properties so as to reproduce the actual ratio of stiffness (approximately = 10) of the different tissues (bones and ligaments) found in real life. The first metacarpal was moved in 6 directions as described by Ebskov (1970) and Pieron (1973, 1980) using a small spring exerting a constant force (1.5 N) tilted at 30 degrees with respect to the transverse plane. The strain was measured between two white marks for each model ligament and each direction respectively, and the percentage of lengthening was calculated. A statistical study was performed using the non-parametrical Test of Wilcoxon in order to compare the ligament strains obtained in the different directions of loading.

RESULTS

The largest strains were observed in the intermetacarpal ligament and in the anterior oblique ligament reaching 26 to 39% in direction J (posteromedial) and in direction L (posterolateral). Deformations of the two parts of the dorsoradial ligament and of the posterior oblique ligament were equal or inferior to 12% and were observed in the other 4 directions: D, F, K, I (Anterolateral, maximal anteposition, anteromedial, medial) and their combinations.

CONCLUSION

. These data may be useful for helping the understanding of the biomechanics of the basal joint of the thumb. Nevertheless, we are dealing here with a simplified model, which must be considered with caution if the results are to be applied to the living joint.

The effect of the epiphyseal growth plate on the length of the first metacarpal in triphalangeal thumb

PURPOSE

Triphalangeal thumb is characterized as a congenital difference of the thumb with an extra phalanx. Additional thumb length is attributed mostly to the extra phalanx. The influence of the epiphyseal plate positions on growth in congenital hand anomalies is unclear. The purpose of this article was to compare the length of the first metacarpal in triphalangeal thumbs with the length of the same bone in normal thumbs and to investigate the influence of the often aberrant metacarpal epiphyseal plates on the length of the triphalangeal thumb metacarpal during growth.

METHODS

The positions of the epiphyseal plate and the relative length of the first metacarpal were examined retrospectively in 37 patients with triphalangeal thumb. Ratios of the measurements were calculated (metacarpal II/metacarpal I) and compared with a normal population. Subjects were divided into 3 groups based on the position of the epiphyseal plate (double, proximal, distal).

RESULTS

The distally placed growth plate was the most common variety, present in 22 of patients, followed by the proximal position in 14, and double epiphyseal plates in 6. All ratios of patients with triphalangeal thumb were significantly smaller than those of a normal population, indicating a longer first metacarpal in this condition. First metacarpals in triphalangeal thumb with double epiphyses grew disproportionately more than those of a normal population, whereas those with distal epiphyses grew disproportionately less than normal. First metacarpals with proximal epiphyses grew at the same rate as normal first metacarpals.

CONCLUSIONS

In this study population the most common growth plate location was distal whereas the most common location in the normal population is proximal. The different positions of the epiphyseal plates correlate with growth differences in patients with triphalangeal thumb.

SCINTIGRAPHIC EVALUATION OF THE PROXIMAL METACARPAL AND METATARSAL REGIONS IN CLINICALLY SOUND HORSES

In recent years, pain arising from the proximal metacarpal and metatarsal regions has become well recognized as a cause of lameness and various disease entities have been identified. However, our knowledge of normal patterns of radiopharmaceutical uptake is limited, making interpretation of images problematic. It is therefore important to characterize normal patterns of radiopharmaceutical uptake at specific sites to ensure valid interpretation of images in clinical cases with subtle lesions. The purpose of this study was to describe the pattern of radiopharmaceutical uptake in the proximal metacarpal and proximal metatarsal regions in clinically sound horses. Scintigraphic images from 64 clinically normal horses were evaluated. All the images were assessed subjectively. The lateral, dorsal, and plantar scintigraphic images were assessed qualitatively using horizontal line profiles through the proximal metacarpal and proximal metatarsal regions. Mean ratios of radiopharmaceutical uptake were calculated from three regions of interest sited over the proximal metacarpal and proximal metatarsal regions and a reference site. In 78% of forelimbs the peak of radiopharmaceutical activity was at the dorsal to central portion of the proximal metacarpal region. Seventy-five per cent of the dorsal plane profiles of activity were symmetrical, with the highest peak over the medial to central portion of the proximal metacarpal region. In 80% of hindlimb lateral images the peak radiopharmaceutical activity was at the central to plantar aspect of the proximal metatarsal region. All (100%) plantar image profiles of activity were symmetrical, with the highest peak being over the lateral portion of the proximal metatarsal region. There was no significant left and right variation between sites for mean ratios on the lateral and dorsal images of the proximal metacarpal region. However, using lateral images the mean ratios from all regions of the right proximal metatarsal were greater than left (dorsal P = 0.003, plantar P < 0.0001 and whole proximal metatarsal, P = 0.0006). There was no significant variation in mean ratios between left and right on plantar images. However, the mean ratio for the lateral proximal metatarsal region was significantly greater than for the medial proximal metatarsal regions (P < 0.0001). There was no significant effect of age. Left/right symmetry of radiopharmaceutical uptake was shown in the proximal metacarpal region. However, there was a significant difference between left and right proximal metatarsal regions. There was higher radiopharmaceutical uptake in the right proximal metatarsal region than the left, which agrees with previous studies of the tarsal and metatarsophalangeal joints. There were differences in the pattern of radiopharmaceutical uptake between the forelimbs and hindlimbs. In the forelimbs maximum radiopharmaceutical uptake was located at the dorsal to central portion of the proximal metacarpal region in the lateral image, with peak activity over the medial to central portion of the proximal metacarpal region on dorsal images. In the hindlimbs the maximum radiopharmaceutical uptake was at the central to plantar aspect of the proximal metatarsal region in the lateral image, with peak activity over the lateral portion of proximal metatarsal region on plantar images. The results of this study support the hypothesis that there would be a standard pattern of radiopharmaceutical uptake across the proximal metacarpal and l metatarsal regions, but the pattern of uptake observed would be different in the proximal metacarpal region compared with the proximal metatarsal region. There was left/right symmetry of radiopharmaceutical uptake in the proximal metacarpal region. However, there was a significant difference between left and right proximal metatarsal regions, with higher radiopharmaceutical uptake in the right. There was no variation of radiopharmaceutical uptake pattern with age.

[Anatomy of the splint bones and their surrounding area particularly in consideration of fascial attachments]

This study concerns the vestigial metacarpal and metatarsal bones, so called splint bones. The soft tissues, which stabilize the splint bones were carefully examined. The palmar metacarpal/plantar metatarsal fascia, the metacarpal/metatarsal interosseous ligaments and the fibres, which exit distally from the splint bone, were examined in depth. Cadaveric distal limbs were collected from 5 slaughtered or euthanized horses. The legs were examined both, microscopically and macroscopically. The palmar metacarpal/plantar metatarsal fascia is a very stable structure, which connects the splint bone with its environment. The connection between splint and McIII/MtIII, established through the metacarpal/ metatarsal interosseous ligaments, showed impressive differences between specimens examined. Macroscopic examination of the soft tissue in the distal region showed a band structure, which originates from the distal end of the splint bone and extends in dorsal and distal direction towards the proximal sesamoid bone.

Metacarpal index and bone mineral density in healthy African-American women

Bone mineral density (BMD) reference data of non-Caucasian women is scarce but greatly needed for African-American women. The objective of this study was to establish a metacarpal normative reference database for African-American women using digital X-ray radiogrammetry (DXR) and hand radiographs and compare these values to existing Caucasian data. Two hundred and fifty healthy African-American women between the ages of 20 and 79 years old, 14 of whom were excluded, were recruited to participate from four different clinical sites. The study population was recruited in approximately equal number into the following groups: 20-29, 30-39, 40-49, 50-59, 60-69 and 70-79 years of age. A radiograph was acquired of each subject's non-dominant hand. The radiographs were scanned and analyzed using radiogrammetric techniques, and the BMD, MCI (Metacarpal Index), bone width and cortical thickness were calculated. The regression curve that best fit the data was a second order polynomial. The BMD and MCI of young adult women (20-40 years of age) were used to calculate T-score parameters. The young reference BMD and MCI with their associated standard deviations were found to be 0.6045 g/cm2+/-0.0529 g/cm2 and 0.5096 and 0.0792, respectively. However, the MCI was found to be approximately 2.5% lower (-0.0118) compared to Caucasian women. The African-American metacarpal BMD was found to be 3.5% (0.0207 g/cm2) higher across all ages when compared to existing Caucasian reference data acquired in a similar way. The differences were found to be entirely due to larger bone size, cortical diameter and bone width in the African-American women.

The cross-sectional geometry of the hand and foot bones of the hominoidea and its relationship to locomotor behavior

Cheiridia are valuable indicators of positional behavior, as they directly contact the substrate, but systematic comparison of the structural properties of both metacarpals and metatarsals has never been carried out. Differences in locomotor behavior among the great apes (knuckle-walking vs. quadrumanous climbing) can produce biomechanical differences that may be elucidated by the parallel study of cross-sectional characteristics of metacarpals and metatarsals. The aim of this work is to study the cross-sectional geometric properties of these bones and their correlation with locomotor behavior in large-bodied hominoids. The comparisons between bending moments of metacarpals and metatarsals of the same ray furnished interesting results. Metacarpals III and especially IV of the knuckle-walking African apes were relatively stronger than those of humans and orangutans, and metatarsal V of humans was relatively stronger than those of the great apes. Interestingly, the relative robusticity of the metacarpal IV of the quadrumanous orangutan was between that of the African apes and that of humans. The main conclusions of the study are: 1) cross-sectional dimensions of metacarpals and metatarsals are influenced by locomotor modes in great apes and humans; 2) interlimb comparisons of cross-sectional properties of metacarpals and metatarsals are good indicators of locomotor modes in great apes and humans; and 3) the results of this study are in accord with those of previous analyses of plantar pressure and morphofunctional traits of the same bones, and with behavioral studies. These results provide a data base from which it will be possible to compare the morphology of the fossils in order to gain insight into the locomotor repertoires of extinct taxa.

Evaluation of subchondral bone mineral density associated with articular cartilage structure and integrity in healthy equine joints with different functional demands

OBJECTIVE

To determine and correlate subchondral bone mineral density and overlying cartilage structure and tensile integrity in mature healthy equine stifle (low magnitude loading) and metacarpophalangeal (high magnitude loading) joints.

ANIMALS

8 healthy horses, 2 to 3 years of age.

PROCEDURE

Osteochondral samples were acquired from the medial femoral condyle (FC) and medial trochlear ridge (TR) of the stifle joint and from the dorsal (MC3D) and palmar (MC3P) aspects of the distal medial third metacarpal condyles of the metacarpophalangeal joint. Articular cartilage surface fibrillation (evaluated via India ink staining) and tensile biomechanical properties were determined. The volumetric bone mineral density (vBMD) of the underlying subchondral plate was assessed via dual-energy x-ray absorptiometry.

RESULTS

Cartilage staining (fibrillation), tensile moduli, tensile strength, and vBMD were greater in the MC3D and MC3P locations, compared with the FC and TR locations, whereas tensile strain at failure was less in MC3D and MC3P locations than FC and TR locations. Cartilage tensile moduli correlated positively with vBMD, whereas cartilage staining and tensile strain at failure correlated negatively with vBMD.

CONCLUSIONS AND CLINICAL RELEVANCE

In areas of high joint loading, the subchondral bone had high vBMD and the articular cartilage surface layer had high tensile stiffness but signs of structural wear (fibrillation and low failure strain). The site-dependent variations and relationships in this study support the concept that articular cartilage and subchondral bone normally adapt to physiologic loading in a coordinated way.

Functional trade-offs in the limb bones of dogs selected for running versus fighting

The physical demands of rapid and economical running differ from the demands of fighting in ways that may prevent the simultaneous evolution of optimal performance in these two behaviors. Here, we test an hypothesis of functional trade-off in limb bones by measuring mechanical properties of limb bones in two breeds of domestic dog (Canis lupus familiaris L.) that have undergone intense artificial selection for running (greyhound) and fighting (pit bull) performance. The bones were loaded to fracture in three-point static bending. To correct for the effect of shear, we estimated the shear stress in the cross section and added energy due to shear stress to the tensile energy. The proximal limb bones of the pit bulls differed from those of the greyhounds in having relatively larger second moments of area of mid-diaphyseal cross sections and in having more circular cross-sectional shape. The pit bulls exhibited lower stresses at yield, had lower elastic moduli and failed at much higher levels of work. The stiffness of the tissue of the humerus, radius, femur and tibia was 1.5-2.4-fold greater in the greyhounds than in the pit bulls. These bones from the pit bulls absorbed 1.9-2.6-fold more energy before failure than did those of the greyhounds. These differences between breeds were not observed in the long bones of the feet, metacarpals and metatarsals. Nevertheless, the results of this analysis suggest that selection for high-speed running is associated with the evolution of relatively stiff, brittle limb bones, whereas selection for fighting performance leads to the evolution of limb bones with relatively high resistance to failure.

Musculoskeletal responses of 2-year-old Thoroughbred horses to early training. 6. Bone parameters in the third metacarpal and third metatarsal bones

AIM

To determine the effect of a known training regimen on the size and mineral content of the third metacarpal (Mc3) and third metatarsal (Mt3) bones of 2-year-old Thoroughbred horses trained on racetracks.

METHODS

Mc3 and Mt3 of seven horses trained on grass and sand tracks were scanned at several sites using conventional quantitative and peripheral computed tomography (CT). Bone dimensions and density in the diaphysis and epiphysis were compared with those from seven untrained horses. Calcein label was injected in two clusters, during Weeks 9 and 12. The extent and rate of diaphyseal modelling was determined by confocal fluorescent microscopic examination of thin plane parallel sections of the mid-metacarpal region.

RESULTS

Volumetric bone mineral density (BMDv) of the epiphysis was markedly higher and of the diaphysis was slightly higher in trained compared with untrained horses, but greater bone size in the trained horses had the greatest effect on an index of bone strength. Active osteons, defined as Haversian systems containing calcein label, were fewer, of smaller diameter at the time of calcein injection, and had a greater bone apposition rate in trained than in untrained horses.

CONCLUSIONS

Conventional training of 2-year-old Thoroughbred racehorses over a 13-week period had a significant effect on bone size, density and strength index when compared to untrained horses.

CLINICAL RELEVANCE

Bone responded rapidly to early training. The data provide reference values and sites for use in longitudinal studies of commercial training regimens.

Bilateral asymmetry in the limb bones of the chimpanzee (Pan troglodytes)

There is much debate in behavioral primatology on the existence of population-level handedness in chimpanzees. The presence or absence of functional laterality in great apes may shed light on the origins of human handedness and on the evolution of cerebral asymmetry. The plasticity of long bone diaphyses in response to mechanical loading allows the functional interpretation of differences in cross-sectional geometric. While left-right asymmetry in upper limb diaphyseal morphology is a known property in human populations, it remains relatively unexplored in apes. We studied bilateral asymmetry in 64 skeletons of wild-caught chimpanzee using the humerus, second metacarpal, and femur. The total subperiosteal area (TA) of the diaphyses was measured at 40% of maximum humeral length and at the midshaft of the metacarpals and femora using external silicone molds. Overall, the TA values of the left humeri were significantly greater than the right, indicating directional asymmetry. This effect was even greater when the magnitude of difference in TA between each pair of humeri was compared. The right second metacarpals showed a tendency toward greater area than did the left, but this did not reach statistical significance. The lack of asymmetry in the femur serves as a lower limb control, and suggests that the upper limb results are not a product of fluctuating asymmetry. These findings imply behavioral laterality in upper limb function in chimpanzees, and suggest a complementary relationship between precision and power.

The ossification of the metacarpal and phalangeal bones in human foetuses

An evaluation was made of the ossification level of the metacarpal and phalangeal bones in human foetuses of both sexes from the 4th to the 9th month of gestation. Our results indicate that ossification of phalangeal bones 1 to 5 always started at the distal end of the phalanx and endochondral ossification prevailed in the proximal phalanx of the thumb.

The analysis of population structure based on morphometric dimensions of metacarpal bones (the Island of Krk, Croatia)

The aim of this study was to investigate: 1) a possibility of using the morphometric dimensions of metacarpal bones for approximation of biological distances, and 2) a relationship of biological matrices, based on the morphometric dimensions of metacarpal bones to other biological (dermatoglyphic, genetic), bio-cultural (migration) and geographic variables. The morphometry of the metacarpal bones was performed according to Barnett and Nordin procedure and biological distances were estimated using Mahalanobis D2 method. Population structure was assessed through Mantel's permutation test using E2 genetic distances for classical serogenetic markers, DA genetic distances for HLA, DSW genetic distances for STRs, geographic distances expressed in kilometres, and migration kinship matrix estimated according to the method proposed by Malécot and modified by Morton. This study clearly indicated the need for applying factorial analytical approach to study the factor structure of morphometric variables that may be measured on six metacarpal bones as well as the need for conducting complex family and segregation analyses to address not only the intriguing issue of genetic vs. ecological impact onto the bone mineral turnover, but also to test the hypothesis of major gene control in determining bone mineral density.