One Digit Interruption: The Altered Force Patterns during Functionally Cylindrical Grasping Tasks in Patients with Trigger Digits

Most trigger digit (TD) patients complain that they have problems using their hand in daily or occupational tasks due to single or multiple digits being affected. Unfortunately, clinicians do not know much about how this disease affects the subtle force coordination among digits during manipulation. Thus, this study examined the differences in force patterns during cylindrical grasp between TD and healthy subjects. Forty-two TD patients with single digit involvement were included and sorted into four groups based on the involved digits, including thumb, index, middle and ring fingers. Twelve healthy subjects volunteered as healthy controls. Two testing tasks, holding and drinking, were performed by natural grasping with minimal forces. The relations between the force of the thumb and each finger were examined by Pearson correlation coefficients. The force amount and contribution of each digit were compared between healthy controls and each TD group by the independent t test. The results showed all TD groups demonstrated altered correlation patterns of the thumb relative to each finger. Larger forces and higher contributions of the index finger were found during holding by patients with index finger involved, and also during drinking by patients with affected thumb and with affected middle finger. Although no triggering symptom occurred during grasping, the patients showed altered force patterns which may be related to the role of the affected digit in natural grasping function. In conclusion, even if only one digit was affected, the subtle force coordination of all the digits was altered during simple tasks among the TD patients. This study provides the information for the future studies to further comprehend the possible injuries secondary to the altered finger coordination and also to adopt suitable treatment strategies.     

Manipulabilities of the index finger and thumb in three tip-pinch postures

Tip-pinch, in which the tips of the index finger and thumb pick up and hold a very fine object, plays an important role in the function of the hand. The objective of this study was to investigate how human subjects affect manipulabilities of the tips of the index finger and thumb within the flexion/extension plane of the finger in three different tip-pinch postures. The index finger and thumb of twenty male subjects, were modeled as linkages, based on measurement results obtained using two three-dimensional position measurement devices. The manipulabilities of the index finger and thumb were investigated in three tip-pinch postures, using three criteria indicating the form and posture of the manipulability ellipse of the linkage model. There were no significant differences (p > 0.05, ANOVA) in each criterion of each digit across the subjects, except for two criteria of the thumb. The manipulabilities of the index finger and thumb were separately similar across all subjects in tip-pinch postures. It was found that the manipulability for the cooperation of the index finger and thumb of all the subjects in tip-pinch depended on the posture of the index finger, but not on the posture of the thumb. In two-dimensional tip-pinch, it was possible that the index finger worked actively while the thumb worked passively to support the manipulation of the index finger.     

Directional Coordination of Thumb and Finger Forces during Precision Pinch

The human opposable thumb enables the hand to perform dexterous manipulation of objects, which requires well-coordinated digit force vectors. This study investigated the directional coordination of force vectors generated by the thumb and index finger during precision pinch. Fourteen right-handed, healthy subjects were instructed to exert pinch force on an externally stabilized apparatus with the pulps of the thumb and index finger. Subjects applied forces to follow a force-ramp profile that linearly increased from 0 to 12 N and then decreased to 0 N, at a rate of ±3 N/s. Directional relationships between the thumb and index finger force vectors were quantified using the coordination angle (CA) between the force vectors. Individual force vectors were further analyzed according to their projection angles (PAs) with respect to the pinch surface planes and the shear angles (SAs) within those planes. Results demonstrated that fingertip force directions were dependent on pinch force magnitude, especially at forces below 2 N. Hysteresis was observed in the force-CA relationship for increasing and decreasing forces and fitted with exponential models. The fitted asymptotic values were 156.0±6.6° and 150.8±9.3° for increasing and decreasing force ramps, respectively. The PA of the thumb force vector deviated further from the direction perpendicular to the pinching surface planes than that of the index finger. The SA showed that the index finger force vector deviated in the ulnar-proximal direction, whereas the thumb switched its force between the ulnar-proximal and radial-proximal directions. The findings shed light on the effects of anatomical composition, biomechanical function, and neuromuscular control in coordinating digit forces during precision pinch, and provided insight into the magnitude-dependent force directional control which potentially affects a range of dexterous manipulations.     

Medial pedicle reduction mammaplasty for severe mammary hypertrophy

Current options in reduction mammaplasty for severe mammary hypertrophy include amputation with free-nipple graft as well as the inferior pedicle and bipedicle techniques. Complications of these procedures include nipple-areola necrosis, insensitivity, and hypopigmentation. The purpose of this study was to determine whether medial pedicle reduction mammaplasty can minimize these complications. Twenty-three patients with severe mammary hypertrophy were studied. The medial pedicle successfully transposed the nipple-areola complex in 44 of 45 breasts (98 percent). Mean change in nipple position was 17.1 cm, and mean weight of tissue removed was 1604 g per breast. Nipple-areola sensation was retained in 43 of 44 breasts (98 percent) using a medial pedicle. Hypopigmentation was not observed, and central breast projection was restored in all patients. This study has demonstrated that medial pedicle reduction mammaplasty is a safe and reliable technique and should be given primary consideration in cases of severe mammary hypertrophy.     

Making digit patterns in the vertebrate limb

The vertebrate limb has been a premier model for studying pattern formation - a striking digit pattern is formed in human hands, with a thumb forming at one edge and a little finger at the other. Classic embryological studies in different model organisms combined with new sophisticated techniques that integrate gene-expression patterns and cell behaviour have begun to shed light on the mechanisms that control digit patterning, and stimulate re-evaluation of the current models.     

The Force Synergy of Human Digits in Static and Dynamic Cylindrical Grasps

This study explores the force synergy of human digits in both static and dynamic cylindrical grasping conditions. The patterns of digit force distribution, error compensation, and the relationships among digit forces are examined to quantify the synergetic patterns and coordination of multi-finger movements. This study recruited 24 healthy participants to perform cylindrical grasps using a glass simulator under normal grasping and one-finger restricted conditions. Parameters such as the grasping force, patterns of digit force distribution, and the force coefficient of variation are determined. Correlation coefficients and principal component analysis (PCA) are used to estimate the synergy strength under the dynamic grasping condition. Specific distribution patterns of digit forces are identified for various conditions. The compensation of adjacent fingers for the force in the normal direction of an absent finger agrees with the principle of error compensation. For digit forces in anti-gravity directions, the distribution patterns vary significantly by participant. The forces exerted by the thumb are closely related to those exerted by other fingers under all conditions. The index-middle and middle-ring finger pairs demonstrate a significant relationship. The PCA results show that the normal forces of digits are highly coordinated. This study reveals that normal force synergy exists under both static and dynamic cylindrical grasping conditions.     

Interplay between the molecular signals that control vertebrate limb development

Vertebrate limbs display three obvious axes of asymmetry. These three axes are referred to as proximal-distal (Pr-D; shoulder to digit tips), anterior-posterior (A-P; thumb to little finger), and dorsal-ventral (D-V; back of hand to palm). At a molecular level, it is now possible to define the signals that control patterning of each of the three axes of the developing limb. These signals do not work in isolation though but rather their activity must be integrated such that the various limb elements are coordinately formed with relation to these three axes. This review will provide an overview of the intricate medley amongst the molecular signals that serve to establish and coordinate patterning information along the three primary axes of the limb.     

Haptic-Motor Transformations for the Control of Finger Position

Dexterous manipulation relies on modulation of digit forces as a function of digit placement. However, little is known about the sense of position of the vertical distance between finger pads relative to each other. We quantified subjects'' ability to match perceived vertical distance between the thumb and index finger pads (d_y) of the right hand (“reference” hand) using the same or opposite hand (“test” hand) after a 10-second delay without vision of the hands. The reference hand digits were passively placed non-collinearly so that the thumb was higher or lower than the index finger (d_y = 30 or –30 mm, respectively) or collinearly (d_y = 0 mm). Subjects reproduced reference hand d_y by using a congruent or inverse test hand posture while exerting negligible digit forces onto a handle. We hypothesized that matching error (reference hand d_y minus test hand d_y) would be greater (a) for collinear than non-collinear d_ys, (b) when reference and test hand postures were not congruent, and (c) when subjects reproduced d_y using the opposite hand. Our results confirmed our hypotheses. Under-estimation errors were produced when the postures of reference and test hand were not congruent, and when test hand was the opposite hand. These findings indicate that perceived finger pad distance is reproduced less accurately (1) with the opposite than the same hand and (2) when higher-level processing of the somatosensory feedback is required for non-congruent hand postures. We propose that erroneous sensing of finger pad distance, if not compensated for during contact and onset of manipulation, might lead to manipulation performance errors as digit forces have to be modulated to perceived digit placement.     

贵州布依族、仫佬族和毛南族9对遗传性状的基因频率

对贵州布依族、仫佬族和毛南族1239例的9对遗传性状的基因频率进行了调查, 并对民族间基因频率差异进行显著性检验。结果显示: 卷舌和小指弯曲的显性基因频率高于隐性基因频率, 而叠舌、前额发际、发旋、耵聍、拇指类型、中指毛、环食指长则相反; 卷舌、叠舌、前额发际、耵聍、拇指类型、环食指长的基因频率在民族间差异较大, 而发旋、中指毛、小指弯曲则相对较小。     

Somatotopy of human hand somatosensory cortex as studied in scalp EEG

We recorded somatosensory evoked potentials (SEPs) in scalp EEGs during stimulation of the median nerve, the ulnar nerve and the individual digits in 3 normal subjects and in 1 epilepsy patients. In this patient we also measured SEPs from chronically indwelling subdural grid electrodes during electrocorticography (ECoG). We applied dipole modelling techniques to study the 3-dimensional intracerebral locations and time activities of the neuronal sources underlying stimulation of different peripheral receptive fields. The sources underlying median nerve SEPs were located an average of 10.8 mm lateral inferior to those underlying ulnar nerve SEPs. Digit SEP sources showed a somatotopic arrangement from lateral inferior to medial superior in the order thumb, index finger, middle finger, ring finger and little finger, with some overlap or reversal for adjacent digits. The average distance between thumb and little finger was 12.5 mm. Thumb, index finger and middle finger were clustered around median nerve cortical representation, whereas ring finger and little finger were arranged around ulnar nerve cortex. In the epilepsy patient, the source localizations obtained in scalp EEGs showed good agreement with those on ECoGs. We conclude that SEPs recorded in scalp EEGs can be used to study functional topography of human somatosensory cortex non-invasively.     

Fixed and random effects in the variation of the finger ridge count: a study of fragile-X families.

A maximum-likelihood scoring technique for analysis of pedigree data allows for the concurrent estimation of random and of fixed effects in a quantitative trait. We included both types of effects in genetic models, to study the sources of variation in finger ridge count in 54 large families affected with the fragile-X disorder. The fixed effects were represented by fragile X and sex, and the random effects by environmental and genetic variance. We found a significant effect of fragile X in the mean of the finger ridge count on the thumb (finger 1) and index finger (finger 2), which had the lowest heritability and a negligible nonadditive component of genetic variance. This was in contrast with ridge counts on fingers 3 and 4, which showed little fragile-X effect, but high heritability and a significant nonadditive component. A contrast in genetic properties for ridge counts on fingers 1 and 2, compared with these counts on the remaining three fingers, may be relevant to increased selection pressures on functions of the thumb and of the index finger in evolution of modern man. We have also demonstrated an important effect of fragile X in increasing the additive variance in covariance, especially between male pairs. These findings suggest that the effect of the fragile-X genotype in finger ridge count is additive and superimposed on the normal hereditary variations in this trait.     

Structured exploratory data analysis (SEDA) of finger ridge-count inheritance: II. Association arrays in parent-offspring and sib-sib pairs

Familial similarity of the dermatoglyphic trait values of finger ridge-count scores and pattern intensity index is examined for 125 nuclear families from the Velanadu Brahmin population of Southern India by the method of association arrays. This methodology assesses parent-offspring and sibship similarity through a collection of measures of dependence that is sensitive to a variety of nonlinear trends and stochastic relationships between trait values. The method is used in conjunction with various weights to determine the relationship between family size and the level and form of dependence. These analyses reveal that siblings are most strongly associated for ridge-counts of the middle digit and less associated for the thumb and fifth digit ridge-counts. Further, sibship similarity for ridge-counts increases with family size for the thumb and fifth digit but remains relatively constant over all family sizes for the middle finger. Family size effects are also observed for total ridge-counts of the left hand, right hand, and both hands combined, and for the pattern intensity index. These effects of family size may be due to the most pronounced changes occurring in the amniotic environment between the first and second pregnancy, which are most strongly manifested in the sibship associations of smaller families.     

Thumb reconstruction by free microvascular transfer of an injured index finger

Thumb reconstruction for amputation at the metacarpal phalangeal level was accomplished by microneurovascular transfer of the contralateral damaged index finger ray, including metacarpal phalangeal joint. This transfer accomplished a successful thumb restoration and removed a cumbersome index finger amputation stump, improving function in both hands. This case emphasizes the merits of spare part transfer in hand reconstructive surgery made possible by microneurovascular techniques.     

Three successful digital replantations in a patient after 84, 86, and 94 hours of cold ischemia time

Three successful digital replantations were performed on a patient after 84, 86, and 94 hours of prolonged cold ischemia time. Both the intraoperative and postoperative courses were smooth. Functional evaluation 8 months after operation revealed a normal speed of sensory recovery and nail growth. The atrophic changes in all three replants are mild. Total active movement was 45, 100, and 70 degrees in the replanted left thumb, left index finger, and right thumb, respectively. There is no cold intolerance. The overall functional result is satisfactory. Replantation of an amputated digit that is properly cooled immediately after injury should be attempted in selected patients even after prolonged ischemia time.     

Sixty-four cases of thumb and finger reconstruction using transplantation of the big toe skin-nail flap combined with the second toe or the second and third toes

The purpose of this article is to introduce the results of thumb and finger reconstruction using transplantation of the big toe wraparound flap combined with the second toe or the second and third toes. Between August of 1981 and December of 1998, in a series of 64 cases involving 58 patients with digitless hands, either (1) the thumb and index fingers were reconstructed by transplantation of a big toe wraparound flap combined with the adjacent second toe harvested from the ipsilateral foot; or (2) the thumb, index, and long fingers were reconstructed by transplantation of an ipsilateral big toe wraparound flap combined with the adjacent second and third toes. The phalanx of the new thumb was usually an iliac block. The success rate of this series was 92.2 percent. At long-term follow-up, the average static 2-point discrimination was less than 10 mm. The distance between the tip of the new thumb and the new index finger ranged from 6 to 10 cm (average, 8 cm). Opposition action was nimble and forceful. The patients could lift a 6- to 12-kg weight with their reconstructed digits. All patients were satisfied with their new hands and were able to use them in their daily activities. The transplants for reconstructing the thumb and fingers are harvested from the same foot in a procedure known as one-foot donation. Function of the bilateral digitless hand can be recovered with this procedure.     

Subjective magnitude of tactile roughness

The subjective experience of tactile roughness was judged by subjects using the method of absolute magnitude estimation (AME). The stimuli were 11 grades of sandpaper having particle diameters ranging from 16 to 905 mum. All of the estimates resulted in power functions when assigned numbers were plotted as a function of particle diameter. It was determined that on the finger pad of the index finger and the thumb there was no difference between the active and passive modes of stimulation and that there was no difference in roughness estimates made on the finger and on the thumb. When the finger and thumb were stimulated simultaneously, higher numbers were assigned for a given stimulus indicating the presence of a form of spatial summation at these sites. The pleasantness of the tactile sensation, as assessed using AME, was inversely related to the roughness estimates. Furthermore, hydration of the stratum corneum with water and three concentrations of surfactant solutions reduced the sensation of roughness below that of normally hydrated skin.     

Maternal effects on fingertip dermatoglyphics.

Significantly larger variation between sibships within families of male MZ twins than between sibships within families of female MZ twins, indicative of maternal influences, was found for 10 of 41 dermatoglyphic fingertip variables. Of these, five were thumb-related with the effect primarily on the thumb radial and ridge count (larger of radial and ulnar count). These same variables were previously found to have unequal variances in MZ twins of known placental type, and the results indicate maternal influences in singletons as well as twins for these variables. Although the total ridge count (TRC), previously shown to differ in MZ twins of known placental type (paralleling the thumb radial and ridge counts) did not reach significance, the trend indicated that the observed thumb changes may be reflected in the TRC as well. Little finger pattern type and ulnar counts also showed less variability in families of female MZ twins, but the interpretation is complicated by the concomitant differences in mean squares within-sibships for these little finger variables.     

Subjective magnitude of tactile roughness

The subjective experience of tactile roughness was judged by subjects using the method of absolute magnitude estimation (AME). The stimuli were 11 grades of sandpaper having particle diameters ranging from 16 to 905 microm. All of the estimates resulted in power functions when assigned numbers were plotted as a function of particle diameter. It was determined that on the finger pad of the index finger and the thumb there was no difference between the active and passive modes of stimulation and that there was no difference in roughness estimates made on the finger and on the thumb. When the finger and thumb were stimulated simultaneously, higher numbers were assigned for a given stimulus indicating the presence of a form of spatial summation at these sites. The pleasantness of the tactile sensation, as assessed using AME, was inversely related to the roughness estimates. Furthermore, hydration of the stratum corneum with water and three concentrations of surfactant solutions reduced the sensation of roughness below that of normally hydrated skin.     

Grasping behavior in tufted capuchin monkeys (Cebus apella): grip types and manual laterality for picking up a small food item

This study investigates prehension in 20 tufted capuchins (Cebus apella) in a reaching task requiring individuals to grasp a small food item fixed to a tray. The aim was twofold: 1) to describe capuchins' grasping techniques in detail, focusing on digit movements and on different areas of contact between the grasping fingers; and 2) to assess the relationship between grip types and manual laterality in this species. Capuchins picked up small food items using a wide variety of grips. In particular, 16 precision grip variants and 4 power grip variants were identified. The most frequently used precision grip involved the distal lateral areas of the thumb and the index finger, while the most preferred kind of power grip involved the thumb and the palm, with the thumb being enclosed by the other fingers. Immature capuchins picked up small food items using power grips more often than precision grips, while adult individuals exhibited no significant preference for either grip type. The analysis performed on the time capuchins took to grasp the food and withdraw it from the tray hole revealed that 1) precision grips were as efficient as power grips; 2) for precision grips, the left hand was faster than the right hand; and 3) for power grips, both hands were equally quick. Hand preference analysis, based on the frequency for the use of either hand for grasping actions, revealed no significant hand bias at group level. Likewise, there was no significant relationship between grip type and hand preference.     

Correction of pincer-nail deformity using dermal grafting

Pincer-nail syndrome has been described as distortion in the shape of the nails with excessive transverse curvature of the plate that increases from proximal to distal, leading to pinching and loss of soft tissue in the affected digit, resulting in severe pain. Many treatments have been recommended, but an effective long-term method that preserves the nail matrix has not been described. A method of dermal grafting under the nail matrix is described, and the results of treatment of six digits are reported. Five women and one man with an average age of 52 were treated. The affected digit was the thumb in four patients and the great toe in two patients. Follow-up averaged 25 1/2 months. The results were good in all cases with only one side of one nail remaining slightly curved. Pain was relieved in all cases, and complete adherence of the new nail plate occurred. Dermal grafting seems to provide excellent long-term treatment of the pincer-nail deformity with preservation of the nail matrix.