Exploratory analysis using machine learning algorithms to predict pinch strength by anthropometric and socio-demographic features.

Objectives. This study examines the role of different machine learning (ML) algorithms to determine which socio-demographic factors and hand-forearm anthropometric dimensions can be used to accurately predict hand function. Methods. The cross-sectional study was conducted with 7119 healthy Iranian participants (3525 males and 3594 females) aged 10-89 years. Seventeen hand-forearm anthropometric dimensions were measured by JEGS digital caliper and a measuring tape. Tip-to-tip, key and three-jaw chuck pinches were measured using a calibrated pinch gauge. Subsequently, 21 features pertinent to socio-demographic factors and hand-forearm anthropometric dimensions were used for classification. Furthermore, 12 well-known classifiers were implemented and evaluated to predict pinches. Results. Among the 21 features considered in this study, hand length, stature, age, thumb length and index finger length were found to be the most relevant and effective components for each of the three pinch predictions. The k-nearest neighbor, adaptive boosting (AdaBoost) and random forest classifiers achieved the highest classification accuracy of 96.75, 86.49 and 84.66% to predict three pinches, respectively. Conclusions. Predicting pinch strength and determining the predictive hand-forearm anthropometric and socio-demographic characteristics using ML may pave the way to designing an enhanced tool handle and reduce common musculoskeletal disorders of the hand.

First Experience of Plastination at 4150 Meters Above Sea Level, at the Altitude of La Paz, Bolivia / Primera Experiencia de Plastinación a 4150 Metros sobre el Nivel del Mar, en la Altura de La Paz, Bolivia

SUMMARY: Despite attempts to develop the plastination technique in Bolivia, standardized results have not yet been achieved that could be communicated via scientific publications. There is a great deal of misunderstanding around the technique, confusing it with classic techniques of inclusion in different types of resin, such as polyester and epoxy, but these protocols are not plastination. The aim of this work was to communicate the first standardized room-temperature plastination protocol with silicone in Bolivia, with the unique feature of doing so at the altitude of the city of La Paz, thus constituting the first communication of a plastination technique at 4,150 m.a.s.l. sub sede La Paz, La Paz, Bolivia.

En Bolivia, a pesar de los intentos en el desarrollo de la técnica de Plastinación, aún no se han alcanzado resultados estandarizados que pudieran ser comunicados por medio de publicaciones científicas. Existe una gran confusión al momento de desarrollar la técnica, confundiéndola con técnicas clásicas de inclusión en distintos tipos de reina, como poliéster y epoxy, pero no correspondiendo estos protocolos desarrollados a la técnica de plastinación. En este sentido, el objetivo de esta trabajo consistió en comunicar el primer protocolo estandarizado de plastinación a temperatura ambiente con silicona de Bolivia, con la particularidad de desarrollarlo en la altura de la ciudad de La Paz, constituyéndose, de esta manera, en la primera comunicación de una técnica de plastinación a 4.150 metros sobre el nivel del mar.

Nationwide Stature Estimation from Forearm Length Measurements in Montenegrin Adolescents / Estimación de la Estatura a Partir de Mediciones de la Longitud del Antebrazo en Adolescentes Montenegrinos

SUMMARY: The purpose of this research is to determine a regression equation for estimation of stature from forearm length measurements. This research was carried out on 1200 subjects (604 male and 596 female) among the population of Montenegrin adolescents. The stature and forearm length measurements were taken according to the ISAK protocol, and the data were analyzed statistically. Linear regression analysis determined the prediction of forearm length on the criterion variable a body height at the significance level of p <0.05. These relations are presented in the form of scatter diagram. Thereby, we obtained the coefficient of determination, the multiple correlation coefficients, the partial correlation coefficient, the regression, t-test and standardized beta coefficient. The results of this research study confirmed that forearm length reliably predicts stature in both sexes of Montenegrin adolescents and revealed a very useful finding for physical anthropologists and experts from related fields. It was confirmed that there is a correlation between forearm length and body height (males: 31.9 %, females: 33.3 %).

El propósito de esta investigación fue determinar una ecuación de regresión para la estimación de la estatura a partir de medidas de la longitud del antebrazo. Esta investigación se llevó a cabo en 1200 sujetos (604 hombres y 596 mujeres) entre la población de adolescentes montenegrinos. Las medidas de estatura y longitud del antebrazo se tomaron de acuerdo con el protocolo ISAK y los datos se analizaron estadísticamente. El análisis de regresión lineal determinó la predicción de la longitud del antebrazo en la variable de criterio una altura del cuerpo en el nivel de significación de p <0,05. Estas relaciones se presentan en forma de diagrama de dispersión. De tal manera obtuvimos el coeficiente de determinación, los coeficientes de correlación múltiple, el coeficiente de correlación parcial, la regresión, la prueba t y el coeficiente beta estandarizado. Los resultados de este estudio confirmaron que la longitud del antebrazo predice de manera confiable la estatura en adolescentes montenegrinos de ambos sexos y reveló un hallazgo muy útil para los antropólogos físicos y expertos en áreas relacionadas. Se confirmó que existe una correlación entre la longitud del antebrazo y la altura del cuerpo (hombres: 31,9 %, mujeres: 33,3 %).

Dissection, digitization, and three-dimensional modelling: a high-fidelity anatomical visualization and imaging technology.

Technological advances have enabled the development of a novel technique of dissection, digitization and three-dimensional modelling of skeletal muscle and other tissues including neurovascular structures as in situ over the last 25 years. Meticulous serial dissection followed by digitization is used to collect Cartesian coordinate data of the contractile and connective tissue elements throughout the entire muscle volume. The Cartesian coordinate can then be used to construct high-fidelity three-dimensional models that capture the spatial arrangement of the contractile and connective tissue elements as in situ enabling detailed studies of the arrangement of the fiber bundles and their attachment sites to aponeuroses, tendon, and bone. In the laboratory, we have concurrently developed a computational methodology to quantify architectural parameters, including fiber bundle length, pennation angle, volume, physiological cross-sectional area in three-dimensional space. In this paper, a flexor digitorum superficialis specimen will be used to demonstrate the high-fidelity outcomes of dissection, digitization, and three-dimensional modelling. This three-step methodology provides a unique opportunity to study muscle architecture in three dimensions, as in situ. Knowledge translation from the anatomy laboratory to the clinical setting has been highly successful.

Intramuscular aponeuroses and fiber bundle morphology of the five bellies of flexor digitorum superficialis: A three-dimensional modeling study.

Restoring balanced function of the five bellies of flexor digitorum superficialis (FDS) following injury requires knowledge of the muscle architecture and the arrangement of the contractile and connective tissue elements. No three-dimensional (3D) studies of FDS architecture were found in the literature. The purpose was to (1) digitize/model in 3D the contractile/connective tissue elements of FDS, (2) quantify/compare architectural parameters of the bellies and (3) assess functional implications. The fiber bundles (FBs)/aponeuroses of the bellies of FDS were dissected and digitized (MicroScribe® Digitizer) in 10 embalmed specimens. Data were used to construct 3D models of FDS to determine/compare the morphology of each digital belly and quantify architectural parameters to assess functional implications. FDS consists of five morphologically and architecturally distinct bellies, a proximal belly, and four digital bellies. FBs of each belly have unique attachment sites to one or more of the three aponeuroses (proximal/distal/median). The proximal belly is connected through the median aponeurosis to the bellies of the second and fifth digits. The third belly exhibited the longest mean FB length (72.84 ± 16.26 mm) and the proximal belly the shortest (30.49 ± 6.45 mm). The third belly also had the greatest mean physiological cross-sectional area, followed by proximal/second/fourth/fifth. Each belly was found to have distinct excursion and force-generating capabilities based on their 3D morphology and architectural parameters. Results of this study provide the basis for the development of in vivo ultrasound protocols to study activation patterns of FDS during functional activities in normal and pathologic states.

Old name, new face: A systematic analysis of flexor digitorum superficialis muscle with "chiasma antebrachii".

The gross anatomy of the forearm flexors, particularly that of the flexor digitorum superficialis (FDS) muscle, has been described and graphically illustrated in several anatomical books and atlases starting in the middle of the century before last. However, in anatomical dissection studies as well as in clinical-anatomical courses training muscle-specific targeted injections due to movement disorders such as dystonia or spasticity, it has become apparent that there is a need for a closer investigation of the complex construction of the FDS muscle. To this end, we studied the structure of the muscle bellies and tendons of FDS on 46 human body donates that have been used either in our dissection or clinical-anatomical training courses. With this, we demonstrate here the topographical configuration of the individual muscle belly for each of digits 2 through 5 and the exact paths of their tendons until their passing through the carpal tunnel. Furthermore, we demonstrate the presence of a chiasm of the FDS tendons for the digits 2 and 3, approximately 3-4 cm proximal of the carpal tunnel. Thus, we introduce herewith the terminology "chiasma antebrachii". These findings were confirmed in situ by imaging of fixed human body donates via MRI and corroborated by MRI and ultrasound imaging in two volunteers. Taken together, the present findings enable an updated understanding of the complex organization of the heads, bellies, and tendons of FDS that is relevant not only for anatomical teaching but also clinical interventions.

Morphologic observation for anomalous patterns of the flexor carpi radialis muscle and atypical insertions: a proposal for a new classification.

In the present study, four types of variations of the flexor carpi radialis with accessory muscular bundles were classified depending on the origin of the accessory muscular bundle and relationships with the bicipital aponeurosis, biceps brachii, pronator teres, and coracobrachialis. Six types of insertions of the tendon of the flexor carpi radialis were also divided according to their inserted positions on the carpal and metacarpal bones. An accessory muscular bundle of the flexor carpi radialis was found in 4 (1 female and 3 males) of 68 cadavers (5.88%), with five examples in 136 arms (3.68%). It was bilateral in one cadaver and unilateral (two on the right and one on the left) in three. The insertion of the flexor carpi radialis tendon was not only on the proximal surface of the base of the second metacarpal bone but also on the third metacarpal bone, the tubercle of the trapezium, and the scaphoid. These findings and classifications are important in anatomical education, and have important significances in clinical diagnosis and therapies.

Anomalous retrogressive palmaris longus.

An interesting case of unusual unilateral variant of palmaris longus (PL) tendon of forearm was noticed by us. We found two bellies of PL as well as their different insertions. These observations will help in understanding morphological variations of this muscle and its clinical implications. PL is a fusiform muscle in the superficial flexor group of muscles of forearm. It originates from medial epicondyle of humerus by common flexor tendon. We found PL having one origin, i.e., from medial epicondyle from common tendinous origin of flexor muscles and then it divided to form two bellies having two long tendons distally. Understanding of presence or absence or anomalies of PL is not only important for medical professionals but also for evolutionary biologists. Awareness of anatomy and variations of flexor tendons is important for health care practitioners for the correct diagnosis and management of pain, disease, and trauma of forearm and hand.

Résumé Nous avons remarqué un cas intéressant de variante unilatérale inhabituelle du tendon du long palmaire (PL) de l'avant-bras. Nous avons retrouvé deux ventres de PL ainsi que leurs différentes insertions. Ces observations aideront à comprendre les variations morphologiques de ce muscle et ses implications cliniques. Le PL est un muscle fusiforme du groupe des muscles fléchisseurs superficiels de l'avant-bras. Il provient de l'épicondyle médial de l'humérus par le tendon fléchisseur commun. Nous avons trouvé que le PL avait une origine, c'est-à-dire de l'épicondyle médial provenant de l'origine tendineuse commune des muscles fléchisseurs, puis il s'est divisé pour former deux ventres ayant deux longs tendons distalement. Comprendre la présence, l'absence ou les anomalies de PL est non seulement important pour les professionnels de la santé mais également pour les biologistes évolutionnistes. La connaissance de l'anatomie et des variations des tendons fléchisseurs est importante pour les praticiens de la santé afin de diagnostiquer et de gérer correctement la douleur, la maladie et les traumatismes de l'avant-bras et de la main. Mots-clés: Palmaris longus, greffe tendineuse, variation, contracture ischémique de Volkmann.

Typology of flexor carpi radialis muscle in human fetuses.

INTRODUCTION: The musculus flexor carpi radialis (FCR) is a muscle with an important function for the mechanics and physiology of the hand. Its isolation during intrauterine development occurs relatively late, which may result in the presence of high variability during the fetal period. The aim of this study is to determine the detailed typology of FCR in the fetal period based on the available material. MATERIAL AND METHODS: A total of 114 human fetuses (53 female, 61 male) aged between 117.0 and 197.0 days of fetal life were included in the study. The research material was derived from the collections of the Department of Anatomy, Medical University of Wroclaw. Fetuses were stored in typical conservation solvents. The study incorporated the following methods: anthropological, preparational, and image acquisition, which was obtained using an innovative digital microscope. Statistical analysis was performed using R software. RESULTS: The typology of FCR was determined based on the characteristics of the distal attachment of the investigated muscle. The statistical analysis revealed a predominance of type I in the examined fetal material - the attachment located on metacarpal bone II (about 82% of cases). Type IV (attachment to the 4th metacarpal bone) occurs with a frequency of less than 10% and the remaining types II and III occur with a frequency of 4-6%. The statistical analysis did not reveal bilateral or dimorphic differences in the prevalence of each FCR type. In respect of the collected anthropometric parameters, no statistically significant dimorphic differences were revealed. For a more complete description, the FCR proportionality index was introduced. The mean value of this index was 0.6 and was independent of the side or sex of the analyzed fetus. CONCLUSIONS: FCR in the fetal period is characterized by a stable course in both the proximal and distal attachments.

Gross anatomy of the craniolateral antebrachial muscles in kinkajou (Potos flavus, Carnivora): Intra- and interspecific variants within the family Procyonidae.

The kinkajou (Potos flavus) is a carnivoran that has special morphological adaptations in its thoracic limbs to climb threes and handling food. This study aimed to describe the craniolateral muscles of the antebrachium in P. flavus. Five specimens were used. The extensor carpi radialis longus and brevis were seen as two separate muscles. The extensor carpi ulnaris muscle can present two bellies with different insertions. An extensor digit III muscle was found. The P. flavus has anatomical variants on the craniolateral antebrachial muscles that were previously reported in other procyonids. Thus, those variants are phylogenetically related within the family Procyonidae, except the doubled bellies of the extensor carpi ulnaris muscle which is exclusive of P. flavus.

Morphological symmetry of the radius and ulna-Can contralateral forearm bones utilize as a reliable template for the opposite side?

The most important precondition for correction of the affected forearm using data from the contralateral side is that the left and right bone features must be similar, in order to develop patient-specific instruments (PSIs) and/or utilize computer-assisted orthopedic surgery (CAOS). The forearm has complex anatomical structure, and most people use their dominant hand more than their less dominant hand, sometimes resulting in asymmetry of the upper limbs. The aim of this study is to investigate differences of the bilateral forearm bones through a quantitative comparison of whole bone parameters including length, volume, bowing, and twisting parameters, and regional shape differences of the forearm bones. In total, 132 bilateral 3D radii and ulnae 3D models were obtained from CT images, whole bone parameters and regional shape were analyzed. Statistically significant differences in whole bone parameters were not shown. Regionally, the radius shows asymmetry in the upper section of the central part to the upper section of the distal part. The ulna shows asymmetry in the lower section of the proximal part to the lower section of the central part. Utilizing contralateral side forearm bones to correct the affected side may be feasible despite regional differences in the forearm bones of around 0.5 mm.

Relationship between the Branching Patterns of the Radial Nerve and Supinator Muscle.

The posterior interosseous nerve (PIN) innervates the posterior compartment muscle of the forearm and is a continuation of the deep branch of the radial nerve. The anatomic descriptions of PIN vary among different authors. This study investigated the distribution patterns of PIN and its relationships to the supinator muscle. This study investigated which nerves innervate the posterior compartment muscles of the forearm, the radial nerve, and the PIN, using 28 nonembalmed limbs. Also, the points where the muscle attaches to the bone were investigated. The measured variables in this study were measured from the most prominent point of the lateral epicondyle of the humerus (LEH) to the most distal point of the radius styloid process. For each specimen, the distance between the above two points was assumed to be 100%. The measurement variables were the attachment area of the supinator and branching points from the radial nerve. The attachment points of the supinator to the radius and ulna were 47.9% ± 3.6% and 31.5% ± 5.2%, respectively, from the LEH. In 67.9% of the specimens, the brachioradialis and extensor carpi radialis longus (ECRL) were innervated by the radial nerve before superficial nerve branching, and the extensor carpi radialis brevis (ECRB) innervated the deep branch of the radial nerve. In 21.4% of the limbs, the nerve innervating the ECRB branched at the same point as the superficial branch of the radial nerve, whereas it branched from the radial nerve in 7.1% of the limbs. In 3.6% of the limbs, the deep branch of the radial nerve branched to innervate the ECRL. PIN was identified as a large branch without divisions in 10.7% and as a deep branch innervating the extensor digitorum in 14.3% of the limbs. The anatomic findings of this study would aid in the diagnosis of PIN syndromes.

Correlation of hand functionality and grip strengths with anthropometric measurements.

BACKGROUND: Using objective anthropometric measurement data and anthropometric ratios, grip strength and hand functionality can be evaluated. OBJECTIVE: The aim of this study was to obtain anthropometric measurements regarding the forearm and hand, to evaluate the hand functionality in addition to hand and finger grip strengths, and to investigate the correlation between these values. METHODS: One-hundred eight-four subjects between 18 and 25 years were included in the study. Forearm and hand anthropometric measurements and ratios were measured. Hand and lateral grip strengths were evaluated. Jebsen Taylor Hand Function Test (JTHFT) was used to assess hand functionality. RESULTS: A statistically weak and consistently negative correlation between the ratios of forearm length to forearm/wrist circumferences and the ratio of hand length to metacarpal head circumference and hand-lateral grip strengths was found. There was a statistically weak and consistently negative correlation between these ratios and the subtests of JTHFT. It was shown that there was a statistically weak-moderate positive correlation between the hand-lateral grip strengths and JTHFT subtests. CONCLUSIONS: In conclusion, when evaluating grip strength and hand functionality, forearm and hand anthropometric measurements and ratios, which could affect the results, should be considered.

Myological variation in the forearm anatomy of Callitrichidae and Lemuridae.

The anatomy of the primate forearm is frequently investigated in terms of locomotor mode, substrate use, and manual dexterity. Such studies typically rely upon broad, interspecific samples for which one or two representative taxa are used to characterize the anatomy of their genus or family. To interpret variation between distantly related taxa, however, it is necessary to contextualize these differences by quantifying variation at lower hierarchical levels, that is, more fine-grained representation within specific genera or families. In this study, we present a focused evaluation of the variation in muscle organization, integration, and architecture within two speciose primate families: the Callitrichidae and Lemuridae. We demonstrate that, within each lineage, several muscle functional groups exhibit substantial variation in muscle organization. Most notably, the digital extensors appear highly variable (particularly among callitrichids), with many unique configurations represented. In terms of architectural variables, both families are more conservative, with the exception of the genus Callimico-for which an increase is observed in forearm muscle mass and strength. We suggest this reflects the increased use of vertical climbing and trunk-to-trunk leaping within this genus relative to the more typically fine-branch substrate use of the other callitrichids. Overall, these data emphasize the underappreciated variation in forearm myology and suggest that overly generalized typification of a taxon's anatomy may conceal significant intraspecific and intrageneric variation therein. Thus, considerations of adaptation within the forearm musculature should endeavor to consider the full range of anatomical variation when making comparisons between multiple taxa within an evolutionary context.

Compartments of the antebrachial fascia of the forearm: clinically relevant ultrasound, anatomical and histological findings.

PURPOSE: Acute compartment syndrome is defined as a limb-threatening condition caused by bleeding or oedema in a closed muscle compartment surrounded by fascia or bone. It is most commonly encountered in the forearm, which has three compartments: posterior, anterior and lateral. These are surrounded and closed in by the antebrachial fascia, formed by dense connective tissue that facilities their study on ultrasound and is key to fasciotomy treatment. The purpose of this study was to broaden existing ultrasound, anatomical and histological knowledge of the fascia of the forearm to facilitate their identification on ultrasound, with possible clinical and therapeutic applications. METHODS: The study was performed in 50 cryopreserved upper limbs from adult cadavers from the dissection room of the Faculty of Medicine and Health Sciences. They were examined on ultrasound and subsequent anatomical dissection and microscopy to study the fascia and its relationship with different muscles of the forearm compartments. RESULTS: Distinct anatomical relationships were observed on ultrasound and dissection between the fascia and the extensor carpi ulnaris, extensor digiti minimi, and anconeus muscle in the posterior compartment, and the flexor carpi radialis and flexor carpi ulnaris in the anterior compartment. They were isolated by the antebrachial fascia and had distinct relationships with the neurovascular structures. CONCLUSION: These results demonstrate that high-definition ultrasound enables us to locate the antebrachial fascia and particular muscles with a distinct relationship with neurovascular structures. This helps better identify these structures, facilitating diagnosis of any pathology in the area, with potential therapeutic and clinical applications.

The arcade of Frohse: a systematic review and meta-analysis.

PURPOSE: The structure of the proximal margin of the superficial layer of the supinator muscle is of high interest to many researches. Its tendinous appearance, called the arcade of Frohse, may be clinically important because of its close relationship to the deep branch of the radial nerve passing beneath it and is considered to be the cause of several syndromes. Given the importance of this structure, we aimed to provide a comprehensive and evidence-based review with meta-analytic techniques. MATERIALS AND METHODS: The meta-analysis was performed in adherence to the PRISMA guidelines. Three medical databases were searched in order to identify all potentially eligible articles. Included studies were assessed for quality and the extracted morphological and morphometric data from the relevant articles was analyzed with the use of random effects meta-analysis. RESULTS: A total of 20 studies were included into this meta-analysis. The pooled prevalence of the arcade of Frohse was calculated to be 66% within the adult population and 0% in the fetuses. Other variations regarding the arcade of Frohse were identified as very rare. Analysis of the morphometric parameters revealed the average proportions to be 23.22 mm for the length, 11.05 mm for the width and the mean thickness is 0.67 mm. CONCLUSIONS: The arcade of Frohse is a commonly found structure in adults and thoughtful knowledge of its texture and morphology is especially useful in neurology, neurosurgery, orthopedics, trauma surgery and hand surgery, because it is considered to be the most common source of compression for the deep branch of the radial nerve.

Fiber type composition of contiguous palmaris longus and abductor pollicis brevis muscles: Morphological evidence of a functional synergy.

The palmaris longus (PL) tendon is used in surgical opponensplasty to restore functional hand movements in thenar paralysis. Although successful PL autologous tendon transfer has been attributed to an established synergistic relationship between the PL and abductor pollicis brevis (APB) muscles in vivo, this functional relationship may be dependent on the quality of their spatial relationship and properties of their constituent muscle fibers. The purpose was to compare the proportion of type I and type II muscle fibers in the APB based on its contiguous morphological relationship with the PL tendon for indirect insight into their functional synergy, contractile capacity, and digastric arrangement. Twenty-four contiguous PL and APB specimens were harvested from the upper limbs (12 right and 12 left) of twelve formalin-embalmed cadavers (mean age: 74 ± 10 years). The fiber type composition of these muscles was determined by labeling serial cross sections with myosin heavy chain (MyHC) type I and type II monoclonal antibodies. The PL consisted of a relatively heterogeneous fiber type composition irrespective of the presence of a discrete (type I: 41 ± 11%; type II: 55 ± 12%; hybrid: 4 ± 3%) or rudimentary (type I: 49 ± 10%; type II: 45 ± 9%; hybrid: 6 ± 4%) tendinous connection with the APB. The APB fascicles arranged contiguously with the PL through a discrete tendon had significantly greater proportions of type II fibers (41 ± 19%) compared to those with rudimentary PL connections (type II: 15 ± 8%). Therefore, the APB fascicles arranged in a digastric relationship with the PL may have the capacity to produce more powerful contractions than those with rudimentary PL tendons based on the known contractile properties of type II muscle fibers. Knowledge of the spatial relationship between the PL and thenar musculature prior to PL autologous tendon transfer may be a useful indicator of the quality of established synergy in vivo.

The interosseous tuberosity of radius: a descriptive radiological and cadaveric anatomical study.

PURPOSE: The radius is described with a single tuberosity: the radial tuberosity. However, we hypothesize that there is a second tuberosity on the interosseous border of the radius: which we propose to call the interosseous tuberosity - Tuberositas interossea radii - (IT). METHODS: First, we analyzed all anteroposterior radiographs of the forearm (48 females, 54 males; 62 lefts and 40 rights) as well as CT scans (6 females, 7 males; 5 lefts and 8 rights) carried out during one year in our hospital. We evaluated the presence of IT, its length, thickness of the interosseous cortex at IT level, above and below compared with anterior, posterior and lateral bone cortices. In the second part of the study, we dissected cadaveric forearms to determine which ligaments and muscles were attaches on the IT. RESULTS: A total of 102 standard forearm radiographs and 13 CT-scans were analyzed. In all cases, an IT was present. The mean tuberosity length was 93.9 mm (+ / - 15.8), which corresponds to 37% (+ / - 5) of total radial length. IT corresponds to a significant thickening (7.6 mm than 4.2 mm and 4.3 mm below; p < 0.0001) of radial interosseous cortex. A total of 10 forearms were dissected. In all cases, we observed that IT served as an attachment for central band of interosseous membrane and for all extrinsic muscles of the thumb with the exception of the extensor pollicis longus. CONCLUSION: Tuberositas interossea radii exists, corresponds to a cortex thickening and may play a role in the stability of the forearm and the function of the thumb.

Optimal mass of the arm segments in throwing: A two-dimensional computer simulation study.

Producing a high release speed is important in throwing sports such as baseball and the javelin throw. Athletes in throwing sports might be able to achieve a greater throwing speed by improving the effectiveness of the kinetic chain. In this study a two-dimensional computer simulation model of overarm throwing was used to examine the effect of changes in forearm mass and upper arm mass on the release speed of a lightweight (58 g) projectile. The simulations showed that increasing the mass of the forearm decreases release speed, whereas increasing the mass of the upper arm initially increases release speed. For a given forearm mass there is an optimal upper arm mass that produces the greatest release speed. However, the optimal upper arm mass (5-6 kg) is substantially greater than that of an average adult (2.1 kg). These results suggest that athletes might be able to throw faster if they had a stronger tapering of segment mass along the length of their arm. A stronger taper could be readily achieved by attaching weights to the upper arm or by using hypertrophy training to increase the mass of the upper arm. High-speed overarm throwing is a complex three-dimensional movement and this study was a preliminary investigation into the effect of arm segment mass on throwing performance. Further simulation studies using three-dimensional throwing models are needed to generate more accurate insights, and the predictions of the simulation studies should be compared to data from experimental intervention studies of throwing sports.

The forearm and hand musculature of semi-terrestrial rhesus macaques (Macaca mulatta) and arboreal gibbons (fam.Hylobatidae). Part II. Quantitative analysis.

Nonhuman primates have a highly diverse locomotor repertoire defined by an equally diverse hand use. Based on how primates use their hands during locomotion, we can distinguish between terrestrial and arboreal taxa. The 'arboreal' hand is likely adapted towards high wrist mobility and grasping, whereas the 'terrestrial' hand will show adaptations to loading. While the morphology of the forearm and hand bones have been studied extensively, functional adaptations in the forearm and hand musculature to locomotor behaviour have been documented only scarcely. In this paper, we investigate the forelimb musculature of the highly arboreal gibbons (including Hylobates lar,Hylobates pileatus,Nomascus leucogenys,Nomascus concolor and Symphalangus syndactylus) and compare this with the musculature of the semi-terrestrial rhesus macaques (Macaca mulatta). Anatomical data from previous dissections on knuckle-walking bonobos (Pan paniscus) and bipedal humans (Homo sapiens) are also included to further integrate the analyses in the scope of catarrhine hand adaptation. This study indicates that the overall configuration of the arm and hand musculature of these primates is very similar but there are some apparent differences in relative size which can be linked to differences in forelimb function and which might be related to their specific locomotor behaviour. In macaques, there is a large development of wrist deviators, wrist and digital flexors, and m. triceps brachii, as these muscles are important during the different phases of palmi- and digitigrade quadrupedal walking to stabilize the wrist and elbow. In addition, their m. flexor carpi ulnaris is the most important contributor to the total force-generating capacity of the wrist flexors and deviators, and is needed to counteract the adducting torque at the elbow joint during quadrupedal walking. Gibbons show a relatively high force-generating capacity in their forearm rotators, wrist and digital flexors, which are important muscles in brachiation to actively regulate forward movement of the body. The results also stress the importance of the digital flexors in bonobos, during climbing and clambering, and in humans, which is likely linked to our advanced manipulation skills.