Topographical anatomy of the pronator teres muscle and median nerve: a study using histological sections of human fetuses.

The median nerve passes through the humeral and ulnar heads of the pronator teres muscle (PT), although variations such as absence of the ulnar head may exist. We observed histological sections of the upper extremity from 24 embryos and fetuses. In the early stage, the PT extended between the radius and the medial epicondyle of the humerus, but no candidate for the ulnar head was found. In mid-term fetuses, the ulnar margin of the PT was attached to the elbow joint capsule. Moreover, in late-stage fetuses, a small deep part of the PT arose from the thick joint capsule of the humero-ulnar joint near the coronoid process of the ulna. This joint capsule also provided the most proximal origin of the flexor digitorum profundus muscle. Therefore, we considered fetal PT origin from the capsule as a likely candidate for the ulnar head. Consequently, the PT seemed to develop from a single anlage through which the median nerve passed, but later - possibly after birth - a small PT origin from the joint capsule appeared to obtain an aponeurosis connecting the muscle fiber to the ulna. This secondary change in PT morphology might explain the muscle variation seen in adults.

Radiological investigation and clinical evaluation of the morphometric development of the forearm in human fetuses / Investigación radiológica y evaluación clínica del desarrollo morfométrico del antebrazo en fetos humanos

Fetal period of time during which the fetus grows rapidly and the organs are formed. The prenatal and postnatal analyses of the fetal structure provide information as to fetal growth, growth retardation, gestational age and congenital malformations. The development of the skeletal system during the intrauterine period takes place in an orderly manner as it also does in other systems. It was aimed that the morphometric development of the forearm in human fetuses during the period between 20-40 gestational weeks be radiologically investigated and that its clinical importance be evaluated, as well. A total of 100 fetal forearms (50 fetuses: 23 male, 27 female), the ages of which varied between 20-40 gestational weeks, without having any external pathology or anomaly were incorporated into the study. The fetuses were separated into groups according to weeks, trimesters and months. After the general external measurements of the fetuses had been performed, the mammographies and forearm radiographies of the fetuses were shot in the way that the forearms would remain in a prone position. Morphometric measurements pertaining to forearm structures were taken from the forearm radiographies that were shot with the help of a digital compass. Later on, the morphometric measurements in question were statistically evaluated. The mean values and the 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). In the comparison of the measured parameters between trimesters and months, it was observed that there was a statistically significant difference between the groups (p<0.05). Separately, it was also determined that there was no statistically significant difference in the comparison of the parameters, which was made between genders and right-left forearms (p>0.05). As for the results obtained in our study, we are of the opinion that the data obtained during this study period will be beneficial for the involved clinicians, such as those in charge of gynecology, radiology, forensic medicine and perinatology, in terms of evaluating the clinical studies related to the morphometric development of the forearm throughout the fetal period, in determining the fetal age and sex, and also in determining the pathologies and variations regarding the development of fetal skeletal system.

El período fetal es el tiempo en el cual el feto crece rápidamente y se forman los órganos. Los análisis prenatal y postnatal de la estructura fetal proporcionan información sobre el crecimiento fetal, el retraso de crecimiento, la edad gestacional y las malformaciones congénitas. El desarrollo del sistema esquelético, como también el de otros sistemas durante el período intrauterino, avanza de manera ordenada. Se investigó radiológicamente el desarrollo morfométrico del antebrazo en fetos humanos durante el período comprendido entre 20-40 semanas gestacionales y se evaluó su importancia clínica. Un total de 100 antebrazos fetales (50 fetos: 23 de sexo masculino, 27 de sexo femenino), cuya edad varió entre 20-40 semanas de gestación, sin patología externa o anomalía, fueron incluidos en el estudio. Los fetos fueron separados en grupos de semanas, trimestres y meses. Después de realizar las mediciones externas generales de los fetos, las mamografías y las radiografías fueron realizadas de tal manera que los antebrazos permanecieran en pronación. Las radiografías de las medidas morfométricas correspondientes a las estructuras del antebrazo se tomaron con apoyo de una compás digital; posteriormente, las medidas fueron tratadas estadísticamente. Los valores medios y las desviaciones estándar de los parámetros medidos se determinaron de acuerdo con las semanas de gestación, los trimestres y los meses. Hubo una correlación significativa entre los parámetros medidos y la edad gestacional (p <0,001). En la comparación de los parámetros medidos entre los trimestres y los meses, se observó una diferencia estadísticamente significativa entre los grupos (p <0,05). Se determinó también que no hubo diferencias estadísticamente significativas en la comparación de los parámetros, que se realizó entre los sexos y los antebrazos derecho-izquierdo (p> 0,05). En cuanto a los resultados de nuestro estudio, los datos obtenidos durante este período de estudio serán beneficiosos para los clínicos, como también para profesionales de las áreas de ginecología, radiología, medicina forense y perinatología, en la evaluación de estudios clínicos relacionados con el desarrollo morfométrico del antebrazo durante todo el período fetal, determinación de la edad y el sexo fetal, así como en la determinación de variaciones en el desarrollo del sistema esquelético fetal.

Median artery of the forearm in human fetuses in northeastern Brazil: anatomical study and review of the literature.

A persistent median artery is a rare anomaly. It accompanies the median nerve along its course in the forearm and is of variable origin. It is associated with other local anatomical variations and may contribute significantly towards formation of the superficial palmar arch. In embryos, it is responsible mainly for the blood supply to the hand. The objective of this study was to research the frequency, type (forearm or palmar) and origin of the median artery in fetuses, correlating its presence with sex and body side. Red-colored latex was injected into 32 brachial arteries of human fetuses until its arrival in the hand could be seen. Twenty-four hours after the injection, the median arteries were dissected without the aid of optical instruments. Among the 32 forearms dissected, the median artery was present in 81.25 % (26) of the cases, and it was found more frequently in females and on the left side. Regarding origin, most of the median arteries originated in the common interosseous artery (38.5 %) and anterior interosseous artery (34.6 %). The mean length of the median arteries was 21.1 mm for the palmar type and 19.8 mm for the forearm type. The median artery has a high rate of persistence. It is important to be aware of this anatomical variation, since its presence may give rise to difficulties during routine surgical procedures on the wrist. Its presence may cause serious functional complications in the carpal tunnel, anterior interosseous nerve, round pronator syndromes, and ischemia of the hand.

Preaxial polydactyly of the upper limb viewed as a spectrum of severity of embryonic events.

Preaxial polydactyly (PPD) is a common congenital abnormality and its classification varies among geneticists and hand surgeons. For example, the triphalangeal thumb, preaxial polysyndactyly, and the mirror hand deformity are considered as forms of PPD only in the genetics literature. Preaxial polydactyly is an error in the anteroposterior axis of the development of the upper limb. In this paper, the development of this axis is detailed and all molecular events that are known to lead to PPD are reviewed. Finally, based on the review, PPD is viewed as a spectrum of severity of embryonic events.

Hypothesis: terminal transverse limb defects with "nubbins" represent a regenerative process during limb development in human fetuses.

BACKGROUND: Terminal transverse limb defects with nubbins occur in one arm at one of several levels (distal humerus, proximal forearm, wrist, and at the metacarpal-phalangeal joint in the hand). The associated nubbins contain osteocartilaginous tissue and small nails and are not associated with evidence of amnion disruption. METHODS: We present affected newborn infants whose terminal transverse limb defects are at one of these three levels: proximal forearm, elbow, or metacarpal-phalangeal joint. RESULTS: We hypothesize that the presence of residual digit-like structures reflects a regenerative process that has occurred during limb development in these infants. DISCUSSION: Only limited regeneration of digit-like structures can occur in the human fetus.

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.

Occurrence and fate of palmar type of median artery.

BACKGROUND: The median artery represents a persistent part of the embryonic arterial axis of the upper extremity. It appears mainly as two types: an antebrachial type and a palmar type. The palmar type is of major clinical significance. METHOD: This study was undertaken to investigate the incidence and fate of the palmar type of the median artery in 19 cadavers. The occurrence was 15.8% and of this two incidences (5.2%) were on the right side and four (10.6%) were on the left side. On the right side, the artery originated from the ulnar and joined with the superficial palmar arch or anterior interosseous artery and communicated with the radial artery. CONCLUSIONS: This study concludes that palmar type of median artery is found at a higher incidence than the antebrachial type and that it may be involved in the pronator teres syndrome, carpal tunnel syndrome and anterior interosseous syndrome.

Three-dimensional ultrasound examination of the fetal hands: normal and abnormal.

PURPOSE: To assess particular features of fetal hand evaluation using three-dimensional ultrasound, and to determine whether any advantage is offered by three-dimensional over two-dimensional ultrasound in fetal hand evaluation. METHODS: Three-dimensional fetal data were collected prospectively from 44 hands in 40 fetuses from a predominantly high-risk patient population. All had a concurrent two-dimensional ultrasound examination of the hands. Diagnoses from two- and three-dimensional ultrasound examinations were compared and additional information from the three-dimensional volume assessment was noted. Three-dimensional assessment of distal forearm bones, wrist position, finger configuration and number of metacarpals and digits was recorded. RESULTS: Hands were appropriately identified as normal (32/32) or abnormal (12/12) by both two- and three-dimensional ultrasound. Three-dimensional ultrasound provided additional information when compared to two-dimensional ultrasound in both normal and abnormal hands, including the provision of three orthogonal planes with one volume acquisition, allowing rotation of the volume so that hands could be evaluated in planes not possible during two-dimensional imaging, assessment of a hand with loosely curled fingers as normal, the ability to evaluate thumb and fingers simultaneously, and improved assessment of abnormal hands. CONCLUSIONS: Three-dimensional ultrasound offers the potential to provide greater information in fetal hand evaluation for both normal and abnormal hands.

Explaining certain human limb anomalies and the limb-hematopoiesis community of syndromes using a model of determination.

Disturbances of determination, the process of limitation of developmental potential, can cause structural as well as histologic anomalies. A polar coordinate model (PCM) developed from studies in animals, in which determination depends upon positional information arranged along polar coordinates, can be used to explain certain classes of human limb anomalies. Under the model, interference with this system primarily affects distal patterning. If the radial area is distal to the zone of polarizing activity in embryological development, as it appears to be, the PCM explains the teratologic equivalence of preaxial duplications and deficiencies in certain circumstances and the prevalence of ulnar dimelias in forearm duplications. Also, failures of hematopoiesis can be considered late problems with determination and may be markers for abnormalities of a determinative process that also has earlier developmental consequences. Abnormalities of retinoic acid morphogen receptors would be one possible mechanism. This would provide a rationale for the known association of postnatal hematologic problems with developmental anomalies preferentially affecting the radial area. Syndromes with limb and hematopoietic problems may well be a community of determinative disorders.

Formation of extensor digitorum muscle proportions before and after birth.

Studies on the formation of the extensor digitorum muscle morphological characteristics were carried out on material of 85 human fetuses (42 males and 43 females), 16 to 36 weeks old, and 45 adults (31 males and 14 females). Intermediary conclusions were drawn on probable changes occurring in the morphological formation of the muscle after birth, as a result of comparing proportions of the muscle at the fetal stage with its form in adults. In this work, the anthropometric method of study and statistical analysis of results have been applied. Analysis of the results in the fetal group has shown that all metrical characteristics of the muscle reach their maximum values at the end of the investigated ontogenetic space. This is, naturally, a consequence of evolution and growth of all fetal body measures, including elongation of forearms. However, the evolution of the individual muscle characteristics is not regular and though the direction of this growth is similar, its extent varies, and also differs slightly in sexual groups. Comparison of the values of muscle indices for 9 month old fetuses with the same indices for adults shows that relative dimensions of all investigated muscular characteristics decrease during the post-natal period except the relative length of the tendon.