The simian crease: Relationship to various genetic disorders.

The creases of the palm have been of interest for clinicians, anthropologists, and palmists for hundreds of years, but the variations in them have only been studied during the past 50 years. The simian crease, aptly named for its resemblance to the palmar creases of nonhuman simian primates, has received recognition clinically and anthropologically owing to its abnormal appearance and confounding cytogenetic etiology. Given the rarity of these palmar creases but also their usefulness in diagnosing congenital disorders, discussion of cases of those disorders could provide clinicians with further helpful diagnostic knowledge. This review of the literature focuses on the history, embryology, genetic and hereditary origins, and clinical significance of simian creases for the benefit of the diagnosing clinician. Clin. Anat. 32:1042-1047, 2019. © 2019 Wiley Periodicals, Inc.

The missing segment of the autopod 1st ray: new insights from a morphometric study of the human hand.

Whether the 1st segment of the human autopod 1st ray is a 'true' metapodial with loss of the proximal or mid phalanx or the original basal phalanx with loss of the metacarpal has been a long-lasting discussion. The actual knowledge of the developmental pattern of upper autopod segments at a fetal age of 20-22 weeks, combined with X-ray morphometry of normal long bones of the hand in the growing ages, was used for analysis of the parameters, percentage length, position of epiphyseal ossification centers and proximal/distal growth rate. The symmetric growth pattern in the fetal anlagen changed to unidirectional in the postnatal development in relation to epiphyseal ossification formation. The percentage length assessment, the distribution of the epiphyseal ossification centers, and differential proximal/distal growth rate among the growing hand segments supported homology of most proximal segment of the thumb with the 2nd-5th proximal phalanges and that of the proximal phalanx of the thumb with the 2nd-5th mid phalanges in the same hand. Published case reports of either metanalysis of 'triphalangeal thumb' and 'proximal/distal epiphyseal ossification centers' were used to support the applied morphometric methodology; in particular, the latter did not give evidence of growth pattern inversion of the proximal segment of the thumb. The presented data support the hypothesis that during evolution, the lost segment of the autopod 1st ray is the metacarpal.

The origin of human handedness and its role in pre-birth motor control.

The vast majority of humans are right-handed, but how and when this bias emerges during human ontogenesis is still unclear. We propose an approach that explains postnatal handedness starting from 18 gestational weeks using a kinematic analysis of different fetal arm movements recorded during ultrasonography. Based on the hand dominance reported postnatally at age 9, the fetuses were classified as right-handed (86%) or left-handed, in line with population data. We revealed that both right-handed and left-handed fetuses were faster to reach to targets requiring greater precision (i.e., eye and mouth), with their dominant (vs. non-dominant) hand. By using either movement times or deceleration estimates, handedness can be inferred with a classification accuracy ranging from 89 to 100% from gestational week 18. The reliability of this inference hints to the yet unexplored potential of standard ultrasonography to advance our understanding of prenatal life.

Growth and shaping of metacarpal and carpal cartilage anlagen: application of morphometry to the development of short and long bone. A study of human hand anlagen in the fetal period.

A histological and morphometric analysis of human metacarpal and carpal anlagen between the 16th and 22nd embryonic weeks was carried out with the aim of studying the establishment of the respective anlage architecture. No differences in the pattern of growth were documented between the peripheral and central zones of the metacarpal epiphyses and those of the carpals. The regulation of longitudinal growth in long bone anlagen occurred in the transition zone between the epiphysis and the diaphysis (homologous to the metaphyseal growth plate cartilage in more advanced developmental stage of the bone). Comparative zonal analysis was conducted to assess the chondrocyte density, the mean chondrocyte lacunar area, the paired chondrocyte polarity in the orthogonal longitudinal and transverse planes, and the lacunar shape transformation in the metacarpal. In transition from epiphysis to diaphysis chondrocyte density decreased and mean lacunar area increased. No significant differences in the chondrocyte maturation cycle were observed between proximal/distal metacarpal epiphyses and the carpal anlagen. The number of paired chondrocyte oriented along the growth vector was significantly higher in both proximal/distal transition zones between epiphysis and diaphysis. Human metacarpals shared with experimental models (like mice and nonmammal tetrapods) an early common chondrocyte maturation cycle but with a different timing due to the slower embryonic and fetal developmental rate of human anlagen.

A radiological investigation on the hand development in human fetuses throughout the fetal period and an evaluation performed in terms of its clinical importance hand development / Investigación radiológica sobre el desarrollo de la mano en fetos humanos a lo largo del período fetal y una evaluación realizada en términos de su importancia clínica en el desarrollo de la mano

It was aimed in this study that the morphometric development of the hand in human fetuses throughout the fetal period be radiologically investigated and the clinical importance of this period be evaluated. A total of 50 fetuses with no external pathology or anomaly, and the ages of which varied between 20-40 gestational weeks were incorporated into the study. The fetuses were separated into groups according to gestational weeks, trimesters and months. After the general external measurements of the fetuses were performed, mammography and hand radiographies of the fetuses were shot in the way that their hands would be in a pronational position. Afterwards, the morphometric measurements of the hands were performed with the help of a digital caliper through the hand radiographies that were shot. The averages and standard deviations of the measured parameters were determined according to gestational weeks, trimesters and months. There was a significant correlation between the measured parameters and the gestational age (p<0.001). Additionally, it was observed that there was some difference among the groups in the comparison of the measured parameters involving trimesters and months (p<0.05). We are of the opinion that in evaluating the clinical studies regarding the morphometric development of the hand throughout the fetal period and in determining the pathologies and variations related to the fetal hand development, the data obtained in our study will be of use to the clinicians engaged in gynecology, and forensic medicine as well as those involved in this field.

Se investigó radiológicamente el desarrollo morfométrico de la mano en fetos humanos a lo largo del período fetal y se evaluó la importancia clínica de este período. La muestra consistió en 50 fetos de 20 a 40 semanas de gestación, sin patología externa o anomalía. Los fetos se dividieron en grupos según las semanas, trimestres y meses de gestación. Después de las mediciones externas generales de los fetos se realizaron mamografías y radiografías de mano de los fetos en posición de pronación. Posteriormente, las mediciones morfométricas de las manos se realizaron en las radiografías con la ayuda de un calibre digital. Hubo una correlación significativa entre los parámetros medidos y la edad gestacional (p <0,001). Adicionalmente, se observó que hubo una diferencia entre los grupos en la comparación de los parámetros medidos según los trimestres y meses (p <0,05). Consideramos que al evaluar los estudios clínicos sobre el desarrollo morfométrico de la mano a lo largo del período fetal y la determinación de patologías y variaciones relacionadas con el desarrollo de ésta, serán de utilidad para los clínicos intervinientes en las áreas de ginecología y medicina forense.

Palmar Creases: Classification, Reliability and Relationships to Fetal Alcohol Spectrum Disorders (FASD).

A normal human palm contains 3 major creases: the distal transverse crease; the proximal transverse crease; and the thenar crease. Because permanent crease patterns are thought to be laid down during the first trimester, researchers have speculated that deviations in crease patterns could be indicative of insults during fetal development. The purpose of this study was twofold: (1) to compare the efficacy and reliability of two coding methods, the first (M1) classifying both "simiana" and Sydney line variants and the second (M2) counting the total number of crease points of origin on the radial border of the hand; and (2) to ascertain the relationship between palmar crease patterns and fetal alcohol spectrum disorders (FASD). Bilateral palm prints were taken using the carbon paper and tape method from 237 individuals diagnosed with FASD and 190 unexposed controls. All prints were coded for crease variants under M1 and M2. Additionally, a random sample of 98 matched (right and left) prints was selected from the controls to determine the reliabilities of M1 and M2. For this analysis, each palm was read twice, at different times, by two readers. Intra-observer Kappa coefficients were similar under both methods, ranging from 0.804-0.910. Inter-observer Kappa coefficients ranged from 0.582-0.623 under M1 and from 0.647-0.757 under M2. Using data from the entire sample of 427 prints and controlling for sex and ethnicity (white v. non-white), no relationship was found between palmar crease variants and FASD. Our results suggest that palmar creases can be classified reliably, but palmar crease patterns may not be affected by fetal alcohol exposure.

Congenital hand anomalies: etiology, classification, and treatment.

Congenital hand anomalies have a wide range of presentations and functional consequences. Understanding and treatment of these deformities require an understanding of embryology of upper-extremity development. In this report, common anomalies of the hand and upper extremity have been reviewed according to the International Federation for Societies for Surgery of the Hand classification system. We examine the epidemiology, etiology, functional consequences, and current treatments available for each anomaly.

Formation of normal interdigital web spaces in the hand revisited: implications for the pathogenesis of syndactyly in humans and experimental animals.

The creation of the normal web spaces has been attributed to apoptosis. This paper presents evidence that lysosomal-mediated cell death and extracellular matrix degradation are important events in addition to cell death by apoptosis. The author proposes the use of the term interdigital cell death- extracellular matrix degradation instead of interdigital apoptosis. Furthermore, the concept of web creation by differential growth is introduced along with the discussion of the latest research in molecular biology and genetics on the topic.

Variation of the proximal insertion of the abductor digiti minimi muscle: correlation with Guyon's canal syndrome? Case report and literature review.

We describe the case of an original insertion and course of the abductor digiti minimi muscle on the medial part of the palmaris longus tendon. The anomalous muscle was only present on the left side. Various studies have reported the frequency of anomalous muscles in approximately 22 to 35% of hands and it was in majority an anomalous abductor digiti minimi muscle. The knowledge of this original insertion is important because it can sometimes be correlated with ulnar nerve compression at Guyon's canal. But Guyon's canal syndrome is less common than carpal tunnel syndrome, and the incidence of ulnar nerve compression in relation with anomalous muscle is approximately 2.9% of cases. It is possible to diagnose the anomalous muscle through ultrasound or MRI. This variation should be taken into consideration by surgeons during surgical procedures for ulnar nerve decompression at Guyon's canal and when performing anteromedial approach to the wrist between flexors tendons and ulnar bundle.

Accessory head of flexor pollicis longus muscle in fetuses and adult cadavers and its relation to anterior interosseous nerve.

This study was conducted to examine the accessory head of flexor pollicis longus muscle (ahFPL) and its relation with the anterior interosseous nerve (AIN) in human fetuses and adult cadavers. Ninety fetus forearms and 52 adult cadaver forearms were dissected to evaluate the incidence, morphology, and innervation of the ahFPL. The ahFPL was observed in 29/90 (32%) of the fetus forearms and 20/52 (39%) of the adult cadaver forearms. The overall side incidence was 34.5% (49/142) among total forearms examined. On the other hand, the population incidence of ahFPL was 42% (19/45) in fetuses while it was 50% (12/24) in adult cadavers. So, the overall incidence in humans was 44.9% (31/69) in the population studied. Compression of the AIN in the forearm by the ahFPL is known as one of the causes of the anterior interosseous nerve syndrome (AINS). So, the relation of ahFPL with the AIN was evaluated, and in light of previous classifications a modified new classification is proposed. The most common relation detected in this study was Type IVa (71.4%) (AIN and its branches coursed posterior to the ahFPL). While Type I was not observed in this study, the incidences of Type II, Type III, and Type IVb (all AIN branches 'without AIN itself' coursed posterior to the ahFPL) were 2%, 14.3%, and 12.3%, respectively. The Types I, IVa, and IVb are thought to be associated with complete or incomplete types of AINS and Type III with incomplete type of AINS only.

Morphogenesis of the human palma arch using three-dimensional geometric modeling.

The hand goes through complex morphological modifications during embryogenesis. The goal of this study was to use geometric modeling to study the morphometric modifications of the palmar arch. Five embryos were used for the study (sizes: 15, 17, 23, 30, and 44 mm). After digitalization of histologic sections (Sony DXC-930P 3CCD camera, Leica Qwin) and segmentation of the metacarpal cartilaginous matrices (Winsurf 4.3 software), geometric modeling and calculations were performed using MSC.Patran 2005r2 software. Correlations (r > 0.99) were found between embryo size and metacarpal volume, metacarpal surface, and the surface of the modeled palmar arch. The growth of the palmar arch is nonhomothetic. Significant reduction (P = 0.05) in the divergence of the 2nd, 3rd, 4th, and 5th metacarpals was observed. Deepening of the palmar arch is correlated with embryo size and age (r > 0.99). Geometric modeling allows 3D rendering of histologic sections and thus quantitative description of the morphogenesis. The results of this study support the hypothesis that opposition of the thumb in correlation with deepening of the palmar arch appears early in embryological development. It constitutes a specific morphological characteristic that appears very early in the human phylum. The fact that the human thumb is naturally in opposition in the resting position is a consequence of this morphogenesis. The thumb's resting position has received little attention in clinical settings and should be considered as the reference position for biomechanical analysis of the thumb column.

An original histological method for studying the volar skin of the fetal hands and feet.

AIMS: The human fetal period of life is when there is complete development of the dermatoglyphic pattern. However, to date not enough is known about the differentiation of the papillary terrain during prenatal life and which mechanisms are involved in this differentiation. The aims of the present study are to contribute to the clarification of the embryogenesis of the papillary ridges and to compare their development on the hands and feet. METHODS: The hands and feet of 35 human embryos and fetuses were examined in the present study. We used a new and original method of orientation. The right hand with right foot or left hand with left foot of each embryo/fetus were placed together into one paraffin block. Three different planes of orientation were used. RESULTS: Volar pad development and papillary ridge formation are identical on hands and feet, but the developmental stages on feet lag one week behind those of hands. Papillary ridge embryogenesis follows the cranio-caudal developmental direction. After developmental week 14 the configuration of the future dermatoglyphic pattern has already ocurred at the dermo-epidermal junction. We consider the 6(th) month of prenatal development to be the gestational age when the papillary ridge development is completed. CONCLUSION: Our observations lead to the conclusion that the increased vascularization of dermis considerably affects papillary ridge formation.

Dorsal dimelia: report of two cases with an emphasis on the variation of phenotypic expression and a search for candidate causative genes.

Dorsal dimelia is a form of duplication along the dorsoventral axis of the developing limb. Previous authors reporting on this rare entity have stated that the essential feature of the deformity is the presence of double or circumferential nail at the tip of the finger and that the aetiology is probably related to a mutation of Engrailed-1 (En-1). In this paper we report on two cases to demonstrate that the deformity in humans may be fully or partially expressed, with or without the double nail deformity, respectively. We also reviewed reported cases in humans and experimental animals and searched our two cases for candidate causative genes within the En-1 pathway.

The digital venous drainage in the human embryonic hand.

The histogenesis and morphology of the digital venous drainage in human embryonic and fetal hands, aged from 6 to 12 weeks, were studied by light microscopy in 18 fingers. In the sixth week, capillaries could be identified around the cartilaginous models of the phalanges. By the ninth week, the neurovascular bundles were identifiable in the palmar part of the finger. In 12 week fetuses, all of the superficial and deep vascular venous system could be seen easily in the palmar aspect of the finger in positions similar to those in the adult hand. However, the arch systems, present on the dorsum of the finger in the adult hand, were not yet differentiated.

Embryology of the hand and upper extremity.

As a universal means of communication and a critical tool for survival, the human hand is of extraordinary importance to our evolutionary survival. As the product of countless overlapping chemical signals, the upper extremity is highly dependent on a multifactoral web of genetic and environmental factors. At the molecular level, specialized signaling centers guide limb development along 3 spatial limb axes: (1) proximodistal, (2) anteroposterior, and (3) dorsoventral. Within the growing limb bud, the 3 main signaling centers are (1) the apical ectodermal ridge, (2) the zone of polarizing activity, and (3) the nonridge ectoderm. Cells within these signaling centers govern the process of limb differentiation via secretion of various chemical messengers. Although each aspect of extremity growth seems directly dependent on a process-specific mechanism, overall limb development relies on the proper interaction of these countless protein factors. Here, we review the macroscopic development of the upper limb and discuss the complex mechanisms underlying differentiation of the human hand.

Congenital hand differences: embryology and classification.

Congenital hand differences affect approximately 1 in 500 persons and present unique diagnostic and classification challenges. The embryology of the hand and upper extremity is discussed, including the molecular basis for patterning of the upper limb. The Swanson/International Federation of Societies for Surgery of the Hand classification system is described, along with a discussion of the difficulties in classifying congenital hand differences based on morphology or etiology.

Failure of differentiation part I: Syndactyly.

Syndactyly is one of the two most common congenital hand anomalies, the other being polydactyly. Traditionally, syndactyly is considered simple when only skin is involved; complex when there is bone connection; complete when the web involvement includes the nail folds; incomplete or partial when the nail folds are not involved, but when the web depth is distal to its normal position; and complicated when there are multiple tissue abnormalities. This article discusses the various types of syndactyly, the current state of known genetic mechanisms, and the author's preferred surgical techniques for correction.

Duplication.

Congenital limb duplications include pre- and post-axial polydactyly, central polydactyly, and the mirror-hand spectrum. Treatment of these duplications constitutes a significant functional and aesthetic challenge for the reconstructive hand surgeon. This article provides an inclusive review of the embryologic and molecular mechanisms underlying these deformities and focuses on their clinical treatment. The anatomic variation, classification, surgical treatment, and outcomes of surgical intervention are reviewed for each of the disorders of duplication.