Volar Pad Research Articles

The active von Frey filament test: A new technique to evaluate hand tactile sensation in continuous variable units

The von Frey filament test (vF) is a mainstay of clinical examination. However, its results can be affected by touch speed and other potentially confounding factors. Moreover, the differences between two adjacent filament levels are too large to detect subtle changes. Active vF (AvF) was developed to induce in-depth sensory change. The present study hypothesized that AvF produces different patterns of fingertip sensation; consequently, it could be used as a new assessment tool for neural impairment. The aim of the study was to provide preliminary normative comparative vF and AvF data. This study prospectively examined 32 healthy participants, using AvF and vF. The index and the fifth finger volar pad were examined using AvF and vF, without visual stimulation. The correlation between AvF and vF measurements was evaluated. In addition, differences according to innervation zone, right versus left hand, and gender, and the correlation between AvF values and subjects’ age were analyzed. Mean AvF value was significantly higher and had greater variance than vF (111.3 ± 46.9 vs. 24.1 ± 9.8; P < 0.01). The Spearman correlation coefficient between AvF and vF was 0.341. Values were similar in the index and fifth fingers and right and left hands. However, values were significantly different between women and men. The correlation between age and AvF values was 0.259. AvF provided more precise values, with continuous units for tactile sensation, excluding tester-dependent factors. Furthermore, AvF and vF values may not be correlated.

Manual dexterity of mice during food-handling involves the thumb and a set of fast basic movements.

The small first digit (D1) of the mouse's hand resembles a volar pad, but its thumb-like anatomy suggests ethological importance for manipulating small objects. To explore this possibility, we recorded high-speed close-up video of mice eating seeds and other food items. Analyses of ethograms and automated tracking with DeepLabCut revealed multiple distinct microstructural features of food-handling. First, we found that mice indeed made extensive use of D1 for dexterous manipulations. In particular, mice used D1 to hold food with either of two grip types: a pincer-type grasp, or a "thumb-hold" grip, pressing with D1 from the side. Thumb-holding was preferentially used for handling smaller items, with the smallest items held between the two D1s alone. Second, we observed that mice cycled rapidly between two postural modes while feeding, with the hands positioned either at the mouth (oromanual phase) or resting below (holding phase). Third, we identified two highly stereotyped D1-related movements during feeding, including an extraordinarily fast (~20 ms) "regrip" maneuver, and a fast (~100 ms) "sniff" maneuver. Lastly, in addition to these characteristic simpler movements and postures, we also observed highly complex movements, including rapid D1-assisted rotations of food items and dexterous simultaneous double-gripping of two food fragments. Manipulation behaviors were generally conserved for different food types, and for head-fixed mice. Wild squirrels displayed a similar repertoire of D1-related movements. Our results define, for the mouse, a set of kinematic building-blocks of manual dexterity, and reveal an outsized role for D1 in these actions.

Barrels of Monkeys: Effects of Long‐term Ethanol Storage on Volar Fat Pad Morphology

Museum fluid collections preserve tissues from endangered and protected species for study. Tissues are often fixed in 10% buffered formalin to halt metabolic activities and transferred to a solution of ethanol for long term storage. This process, however, forces water from the tissues and has been shown to alter the morphology of preserved specimens in ways that may influence the biological interpretation of results. The degree to which fluid preservation alters morphology is linked to multiple biological and methodological factors and should therefore be examined prior to functional analysis. This study was conducted as part of an evaluation of mammalian volar pad morphology and comprises two analyses. In the first, a sample of rats (Rattus norvegicus) is utilized to evaluate longitudinal changes in the dimensions of the volar pads across fixation in 10% buffered formalin and preservation in 70% ethanol for one year. In the second, a cross‐sectional sample of fresh primate volar pads from varying species is compared to a corresponding sample from museum specimens fixed in 10% buffered formalin and preserved in 70% ethanol. No significant changes to the measured dimensions of the volar pads are present across stages of fixation and preservation, nor are significant differences evident between fresh and preserved specimen groups. These findings are likely related to the anhydrous nature of the volar fat pads and their confined position between major joints.Support or Funding InformationThis work was funded by NSF Doctoral Dissertation Improvement Grant #1128861.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

The tenth member of stout newt (Amphibia: Salamandridae: Pachytriton): Description of a new species from Guangdong, southern China.

Field surveys of less-explored forests often lead to discoveries of new amphibian species. During a series of field surveys in early 2017 at Mt. Lianhua (the Lotus Mountain) of Lianhuashan-Baipenzhu Provincial Nature Reserve in southern China, we found an undocumented population of stout newt, genus Pachytriton. Based on its distinct morphological characters and large genetic divergence from congeners (uncorrected p-distance &gt; 5% in either mitochondrial nd2 or cytb sequences), we describe this population as the tenth species of the genus: Pachytriton airobranchiatus sp. nov. It can be distinguished from other members of Pachytriton by a combination of the following morphological characters: prominently elevated distal end of the epibranchial bone showing as two conspicuous protruding bulges behind the head; dorsal coloration can be either spotted or unspotted; bright orange dots absent on dorsum; costal grooves absent between axilla and groin; fingers I and toe I slender, do not forms a volar pad; dorsal tips of fingers and toes brown; and tips of fore- and hind limbs could contact when limbs adpressed against body flank. Phylogenetic analysis grouped the new species with P. wuguanfui, P. xanthospilos, and P. changi. Currently, the new species is known from the type locality and an adjacent mountain peak at about 1000 m elevation. It inhabits small montane streams in broadleaf forests near the top of the mountain.

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.

Digital diabetes?

S Yohannes, et al. Dermatoglyphics in diabetes: a prospective diagnostic aid and early preventive tool. Pages 50– 51. We have friction ridges on the skin of our finger tips – our fingerprints. These develop on the smooth fetal volar pads. The patterns formed vary according to the rate of hand growth versus volar pad regression. Genetic factors influence the timing of these events and thus the ultimate fingerprint pattern, so family members, particularly identical twins, share a similar pattern type. However, in each person the exact arrangement of the friction ridges and any subsequent scarring mean that their fingerprints are unique. Intrauterine undernutrition has been linked to adult type 2 diabetes1 which is often strongly inherited, so it seems logical to consider if fingerprints, also influenced by these factors, can be used as a marker for risk of future diabetes. In people born during the Dutch hunger period (1943–47), with adjustment for age, sex, parental diabetes and adult anthropometry, fingerprint mean dermatoglyphic ridge count difference between fingertips 1 and 5 (Md15) was associated with prevalent diabetes odds ratio of 1.37 (1.02–1.84). ‘Among 42 sibling pairs discordant for diabetes, the diabetic sibling had higher Md15 by 3.5 (0.6–6.3) after multivariable adjustment.’2 However, many paths lead to diabetes, with different genetic factors and different effects of nutrition inside or outside the womb. There are probably hundreds of versions of diabetes. So, in this issue of Practical Diabetes, Yohannes et al. are right to point out that very carefully controlled studies are needed. Patients have a practical issue: ‘I had to have my fingerprints done recently. The guy was all cheery and polite… until I had to show him my hands. He asked what all the “dots” on my left hand fingers were from so we had a little conversation about diabetes, the pump, testing… Then, he says, “oh, well that's going to make the prints bad and there's nothing I can do about it. The prints probably won't turn out and you'll have to come back up here to do it again”.’3 Small scars on the fingertips should not invalidate fingerprint testing; indeed, it may make people more readily identifiable!

An investigation of ecological correlates with hand and foot morphology in callitrichid primates

Studies of primate taxonomy and phylogeny often depend on comparisons of limb dimensions, yet there is little information on how morphology correlates and contributes to foraging strategies and ecology. Callitrichid primates are ideal for comparative studies as they exhibit a range of body size, limb proportions and diet. Many callitrichid species exhibit a high degree of exudativory, and to efficiently exploit these resources, they are assumed to have evolved morphologies that reflect a level of dependence on these resources. We tested assumptions by considering measurements of limb proportion and frictional features of the volar surfaces in preserved specimens of 25 species with relation to published life history and ecological data. The degree of exudativory and utilization of vertical substrates during foraging were found to correlate both with size and with size-corrected foot and hand dimensions. Smaller species, which engage in greater degrees of exudativory, had proportionally longer hands and feet and more curved claw-like tegulae (nails) on their digits to facilitate climbing on vertical substrates. The density of patterned ridges (dermatoglyphs) on the volar surfaces of the hands and feet is higher in more exudativorous genera, suggesting a role in climbing on vertical tree trunks during foraging. Dermatoglyph comparisons suggest that ridges on the soles and palms may facilitate food procurement by enhancing frictional grip during exudate feeding. Volar pad features corroborate taxonomic relationships described from dental morphology.

Study of Flexion Creases and Ridges Patterns in Patients with Congenital Anomalies of Aplasia and Hypoplasia of Thumb

Present study was carried out on 120 hands in which 60 hands were anomalous having aplasia and hypoplasia of thumb as cases and 60 hands were normal hands as control were studied. Aim of this study was to find out any ridges abnormalities in anomalous hands as ridges differentiation is closely associated with embryogenesis of limbs. Second aim is to find out any specific association between aplasia and hypoplasia of thumb and formation of thenar crease because of close association between presence of thenar volar pad and thenar crease during development of hand. We evaluated fingertip patterns palmar pattern, position of axial triradius, and type of flexion creases either transverse type, transitional type normal type (having distal, proximal transverse and thenar creases) and presence or absence of thenar crease.Results of this study showed in aplasia of thumb there is increase in frequencies of unknown pattern, absence of axial triradius and absence of thenar crease while in hypoplasia of thumb there is increase in frequencies of arches pattern, shifting of axial triradius distally, some cases showed absence of thenar crease and some caseshaving poorly formed thenarcrease.Conclusion of this study shows development of anomalous hand influences development of epidermis and so ridges pattern and formation of thenar crease associated with presence of thenar volar pad In aplasia of thumb there is absence of thenar volar pad so there is no formation of thenar crease.

Pulp nonfiction: microscopic anatomy of the digital pulp space.

The volar pad of the fingertip provides a very stable yet sensitive surface that gives the hand the ability to pinch and grasp. The focus of this study was to advance understanding of the anatomical features of the digital pulp space. The unusual features of the fingertip pulp space include prominent collagen fiber cords and a branching continuous fine vasculature. Prominent collagen fiber cords radiating out from beneath the epidermal basement membrane are like the cords of a parachute, which directly attach to the periosteum of the distal phalanx. Those collagen fiber cords are responsible for the firm attachment of the fingertip to the distal phalanx. There is a fine patent vasculature within the pulp space. Also contained in the capsule are numerous lobules of fat, which contribute to some elasticity of the fingertip. Principles of treatment for injuries or infections of the digital pulp should attempt to preserve this anatomical construct so that the firmness and vascular supply of the fingertip are maintained and not disrupted.

Intraspecific Variation in the Vocalizations and Hand Pad Morphology of Southern Lesser Bush Babies (Galago moholi): A Comparison with G. senegalensis

Previous studies have shown the taxonomic value of vocal repertoires and hand (volar) pad characteristics in the classification of cryptic nocturnal primates such as bush babies. However, no study included quantitative comparisons within the geographical range of any one species. We investigated levels of intraspecific variation in calls and hand pad characteristics of the southern lesser bush baby (Galago moholi), using the northern lesser bush baby (Galago senegalensis) for interspecific comparisons. Examination of calls recorded from different regions along a transect of 1500 km across southern Africa revealed low levels of intraspecific variation in Galago moholi, whereas comparisons with homologous call-types in G. senegalensis revealed them to be significantly different. Volar pad measurements across the ranges of both species also showed low levels of intraspecific variation and relatively high interspecific variation. These findings demonstrate that vocal and volar pad characteristics can be used as consistent measures of difference between species that look almost identical. These methods provide a practical means of distinguishing between cryptic species, whether in the field, in captivity, or, in the case of volar pads, of preserved specimens.

The use of hand morphology in the taxonomy of galagos

Measurements of volar (hand) pad area were made for 244 specimens, representing 12 species and 4 genera of galagos (sub-family Galaginae). When corrected for body weight, statistically significant differences were identified, at both the genus and species levels in the areas of the volar pads. Most informative, in terms of taxonomic differences, were measurements of two of the five pads; interdigjtal pad number 4 and thenar pad number 5. Closely related species were distinguishable on the basis of these measurements. The thick-tailed galago (Otolemur crassicaudatus) was separate from Garnett's galago (O. garnettii) and the specific status of the silver greater galago (O. argentatus) was supported. Likewise, the two needle-clawed galagos (Euoticus elegantulus andE. pallidus), recently separated on mitochodrial DNA grounds, were found to differ significantly in their volar pad morphology. These studies show that comparative studies of volar hand pad morphology provide a novel approach to the re-assessment of galago taxonomy, and may be applicable also in taxonomic studies of other prosimian groups.

EMG of the human flexor pollicis longus muscle: implications for the evolution of hominid tool use.

Modern humans possess a distinct and well-developed flexor pollicis longus muscle, an extrinsic thumb flexor which is "either rudimentary or absent" in great apes (Straus, 1942, p. 228). Previous workers (e.g., Napier, 1962; Susman, 1988) have related the origin of a well-developed flexor pollicis longus muscle to the acquisition of precision grasping and stone tool making capabilities in early hominids. The proposed functional association between flexor pollicis longus activity, precision grasping, and stone tool manufacture has, however, never been tested experimentally. This study uses electromyographic techniques (EMG) to investigate the role of flexor pollicis longus during a variety of tool making, tool using, and manipulatory behaviors in order to determine the functional and evolutionary significance of the human flexor pollicis longus muscle. Our results indicate that flexor pollicis longus is recruited during forceful tool using and stone tool making behaviors, regardless of the power or precision grip used to hold the tool. In particular, both stone tool use and stone tool making employing three- and four-jaw chuck precision grips elicit consistently high levels of FPL activity. Flexor pollicis longus activity increases most when resistance is increased to the thumb's volar pad during these hammering, cutting, and knapping behaviors. In contrast, we observed relatively low levels of flexor pollicis longus activity during the fine manipulation of food items, the making of slender wooden probes, and the use of these probes as tools. The paleontological, archaeological, and experimental data suggest that a well-developed flexor pollicis longus muscle functioned initially in the hominid lineage to stabilize the terminal pollical phalanx against loads applied to the thumb's apical pad during the frequent and forceful use of unmodified stones as tools.

Reference values for touch sensibility thresholds in healthy Nepalese volunteers.

A hundred and thirty-six apparently healthy volunteers between the ages of 16 and 67 were used to determine normative thresholds of tactile sensibility in the Nepali adult population. Tactile sensibility thresholds on standardized sites on hands and feet were assessed for two sensory tests: Semmes-Weinstein monofilaments (SWM) and moving-point discrimination (M2PD). Results are reported as the proportion of subjects able to feel a given threshold. The effect of age, sex, side, occupation, smoking habit and alcohol consumption on the results was examined with quantile regression. On the hand 200 mg seemed an appropriate threshold for 'normal' touch sensibility measured with monofilaments. About 99% (95% confidence interval 97-100) of individuals could detect this filament at all sites. A similar proportion could discriminate two points 4 mm apart which were moved from proximal to distal on the volar pad of the distal phalanx of the index and little finger. For the sole of the foot the thresholds were 2 g and 8 mm. Variability of results was greatest at the heel. Normal thresholds for tactile sensibility were higher than those published for the North American population. Monofilament thresholds suitable for screening were 200 mg (log number 3 center dot 61) and 2 g (log number 4 center dot 31) for hand and foot, respectively. For moving 2-point discrimination on the hand this threshold was 4 mm.

Dermal ridge development on the volar pads of the rat (Rattus norvegicus) and comparative study of pattern formation using inbred strains

The development of dermal ridges, ridge configurations, and volar pad contours was investigated in the volar skin of the rat (Rattus norvegicus). The ridged structures corresponding to the epidermal ridges of primates exist only at the epidermal-dermal junction in the rat. Dermal specimens were prepared by treatment with alkaline solution and examined by toluidine blue staining and scanning electron microscopy, together with histological sections. Differentiation of dermal ridges began on day 18 of gestation on the palm followed by the sole. Ridges increased in number with advancing age. The process was complete approximately 2-3 days after birth, and sweat ducts began to develop simultaneously. As dermal ridges present various configurational patterns on palmar interdigital pad III, pattern formation on this pad was inspected in fetuses of three inbred strains possessing different pattern types, and in the hybrid progeny derived from them. Patterns and pad forms appeared to be under genetic control. It was revealed that the ridge arrangements, i.e., whorls, triradii, comb-like patterns, and others, are closely related to the pad contours during the developmental period, as hypothesized in primates.

Dermatoglyphic development on the volar pads of rats with chromosome abnormalities.

Dermatoglyphic abnormalities are often observed in patients with chromosome aberrations, but no similar observations have been made in animals. In the present study, palmar dermatoglyphics were examined in 4 rats with chromosome anomalies. Reciprocal translocations were induced by gamma-irradiation; the animals used were obtained from among offspring with abnormal karyotypes that were derived from the original mutant rats. As the epidermal surface of the volar pad of the rat is flat, dermatoglyphic characteristics were observed on the dermal surface following staining with toluidine blue. Unusual ridge configurations were found in some of them, suggesting that dermatoglyphic development in the rat reflects, to some extent, an abnormal chromosome constitution.

Anthropological dermatoglyphics: A review

AbstractResearch in dermatoglyphics having direct interest and application to anthropology has continued to grow since the turn of the century. Anthropological dermatoglyphics can offer important perspectives in viewing the nature and significance of human variation. Several forefronts of ongoing research are reviewed. First, methodology continues to improve definition and classification of variables. A second line of inquiry deals with hereditary aspects. Inheritance models, both monogenic and polygenic, have been proposed. Single locus systems seem to have limited application, as in the transmission of triradial excess or deficiency illustrated by the missing c triradius. Polygenic inheritance has been demonstrated in quantitative phenotypic expressions exemplified by the total finger ridge‐count. Exciting recent research employing the “field concept” has discovered a small number of developmental factors which correspond well with earlier findings on volar pad development and dermatoglyphic features. Maternal and other environmental effects have been shown to operate on dermatoglyphic expression. Human population studies using dermatoglyphics began with early racial descriptions and currently utilize multivariate procedures for detecting evolutionary processes. Congruence testing between dermatoglyphics and other biological distance measures is also an active endeavor. In this connection, dermatoglyphic variable selection has become important in recognizing that different variables might well be useful in micro‐ and macroevolutionary situations. Finally, dermatoglyphic analysis has. been applied to primate studies. Although this area has not kept pace with human studies, primate work has been crucial for the important matters of taxonomic assessment and functional dermatoglyphics.

Changes in primate Pacinian corpuscles following volar pad excision and skin grafting. A preliminary report.

Human fingertip avulsion injuries were simulated by excising volar digital pads in stump-tailed monkeys. Half the defects were covered with split-skin grafts from the forearm, and half with full-thickness grafts of fingertip skin. Innervated pacinian corpuscles were found in the center of these grafts 3 months after the operation. The site of origin of these corpuscles is undefined. Denervation and devascularization of pacinian corpuscles resulted in alterations of their gross architecture, size, and innervation. The possibility exists that these alterations result from a dynamic adaptation of pacinian corpuscles to environmental stress.

The primary application of an island pedicle flap in thumb and index finger injuries.

The use of a primary neurovascular pedicle flap to resurface the avulsed thumb and index volar pad has been reported. This seems an ideal procedure to provide durable cover and a good quality of sensation in one stage of surgery. Results have been better with thumb than index reconstruction.

Neurovascular Island Pedicle—Extension in Usage

1. With traumatic loss of the terminal volar pad of a thumb or index digit, the neurovascular island pedicle can serve as an immediate or secondary replacement in preference to a free graft or cross-finger pedicle. 2. A thumb reconstruction with pedicle covering alone has disadvantages of non-critical sensation and susceptibility to ulceration. Improved functional results are obtained when critical sensation and durability are secured by a neurovascular island flap. This supplemental measure sanctions the reconstruction of a thumb by pedicle and bone-graft procedures.