Development and morphogenesis of human wrist joint during embryonic and early fetal period.

The development of the human wrist joint has been studied widely, with the main focus on carpal chondrogenesis, ligaments and triangular fibrocartilage. However, there are some discrepancies concerning the origin and morphogenetic time-table of these structures, including nerves, muscles and vascular elements. For this study we used serial sections of 57 human embryonic (n = 30) and fetal (n = 27) specimens from O'Rahilly stages 17-23 and 9-14 weeks, respectively. The following phases in carpal morphogenesis have been established: undifferentiated mesenchyme (stage 17), condensated mesenchyme (stages 18 and 19), pre-chondrogenic (stages 19 and 20) and chondrogenic (stages 21 and over). Carpal chondrification and osteogenic processes are similar, starting with capitate and hamate (stage 19) and ending with pisiform (stage 22). In week 14, a vascular bud penetrates into the lunate cartilaginous mold, early sign of the osteogenic process that will be completed after birth. In stage 18, median, ulnar and radial nerves and thenar eminence appear in the hand plate. In stage 21, there are indications of the interosseous muscles, and in stage 22 flexor digitorum superficialis, flexor digitorum profundus and lumbrical muscles, transverse carpal ligament and collateral ligaments emerge. In stage 23, the articular disc, radiocarpal and ulnocarpal ligaments and deep palmar arterial arch become visible. Radiate carpal and interosseous ligaments appear in week 9, and in week 10, dorsal radiocarpal ligament and articular capsule are evident. Finally, synovial membrane is observed in week 13. We have performed a complete analysis of the morphogenesis of the structures of the human wrist joint. Our results present new data on nervous and arterial elements and provide the basis for further investigations on anatomical pathology, comparative morphology and evolutionary anthropology.

[The development of the wrist joint in the fetal period]. / El bilegi ekleminin fetal dönemdeki gelisimi.

OBJECTIVES: This study was designed to investigate the development and anatomical features of the wrist joint, particularly the scapholunate ligament and triangular disc in the fetal period and to identify possible congenital variations. METHODS: The study included 16 wrist joints of eight fetuses aborted at ages 8 to 14 weeks. The samples had no macroscopically discernible anomalies. Tissue specimens were fixed in 10% formalin solution, embedded in paraffin, and mounted on a microtome to obtain 5-micron sections in the coronal plane. Following staining with hematoxylin and eosin, conventional light microscopic examinations were performed. RESULTS: Organization of the carpal ligaments in the wrist joint began on the radial side in the 9th week. In the 10th week, the scapholunate ligament was formed; a membranous structure was observed, which lied from the interfacet prominence of the radius to the scapholunate ligament and divided the wrist joint into two cavities. The triangular disc formation began to appear at this stage. During the 11th and 12th weeks, the membranous structure underwent regression from the dorsal to the volar aspects, and at the end of the 14th week, the wrist joint became a single cavity. Also noted was the development of fibrous appearance of the scapholunate ligament and the triangular disc into fibrocartilage. Vascular areas were identified on the radial rather than the ulnar side of the scapholunate ligament, but vice versa for the triangular disc. Bicompartmental structure seemed to persist in the wrist joint of a 14-week-old fetus. CONCLUSION: In this study, we demonstrated that the scapholunate ligament and the triangular disc were not homogeneous in the fetal period in terms of vascularity and cellularity. We speculate that a plica-like membranous structure may persist in the wrist joint as a remnant of the fetal life. An accurate knowledge of the anatomy is necessary for the treatment planning and arthroscopic interpretation of the wrist joint.

Prenatal development of arm posture.

Fetal arm posture was studied longitudinally in 10 uncomplicated pregnancies using real-time ultrasound. Observation were performed at four weekly intervals from 12 to 36 weeks, and at 38 weeks. The percentage of assessments with optimal visualization of elbow, wrist and fingers was 84% at 12 weeks and more than 90% thereafter (range 92-98%). There was a clear developmental trend towards increased flexion. Flexion of the elbow occurred frequently from 12 weeks onwards with an increased incidence at 16 weeks, that in the fingers from 20 weeks onwards and from 28 weeks to term age in the wrist. All three trends were statistically significant. There was considerable intra-individual consistency in terms of the ages at which flexion increased. In fact the increase of flexion occurred one session later in only 6/30 registrations. The combined data of the elbow, wrist and fingers revealed preferential arm posture at 12 weeks with the elbow flexed and the wrist and fingers extended. From 16 to 28 weeks, the predominant posture consisted of elbow flexion, wrist extension and finger flexion and complete flexion thereafter. The development of fetal arm posture does not comply with a proximo-distal trend in that there was first an increase in flexion at the elbow, followed by the fingers and finally the wrist. The implications of our findings for understanding the prenatal development of the central nervous system and subsequent postural adjustments to extrauterine life are discussed.

The evolution of the distal radio-ulnar joint.

The pectoral girdle and the distal radio-ulnar joint have evolved over a period of 400 million years. Clinical circumstances exist that may represent atavistic development in modern man. Current understanding of this complex area does not explain all clinical situations.

[Embryology of the human carpal bones (triangular cartilage, central carpal bone, morphogenesis of the scaphoid)]. / Embryologie des os du carpe humain (cartilage triangulaire, os central du carpe, morphogenèse du scaphoïde).

Wax reconstructions according to Born's methods were performed from serial 10-micron sections of the wrists of human embryos (B. Tardif) to study the triangular cartilage and central bone of the carpus. A subsequent morphological study of the adult scaphoid bone was conducted in the light of embryological data. The triangular cartilage was observed in 4 of 38 carpi of embryos with a craniocaudal length of 40 to 69 mm, flatten between the ulna and triquetrum, on the inferior surface of the mesenchymal bud of the triangular ligament. The central bone of the carpus is constant in the embryo, between the inferior surface of the radial chondrification centre, capitatum, trapezium and trapezoid. In one case, the two wrists of the same embryo presented two central nuclei, leading to the distinction of two different formations:--the constant C2 embryonic central bone, trapped between capitatum, trapezoid and trapezium, which participates in the constitution of the scaphoid by fusion with the radial chondrification centre;--the C1 central bone, a rare supernumerary bone in adults, close to the inferolateral angle of the lunatum, on the dorsal surface of the carpus. These embryological data support. Westoll's theory concerning the filiation of the thoracic limb since the fin of crossopterygians, with deviation of the mechanical axis related to the development of weightbearing on the ground. The scaphoid bone must to be assimilated to a cube, but to an irregular tetrahedron, composed of two inverted pyramids joined by their bases. The inferior pyramid, articulating with he trapezium, trapezoid and capitatum, is concerned by morphological variations of the bone, which can present variable configurations between the two extreme morphotypes: the massive type and the strangulated type. The inferior pyramid, constituting the scaphoid, is derived from the central cartilage and presents the same relations. Variations of the volume of this inferior part of the bone are related to the more or less marked regression of this chondrification centre of the embryonic carpus. These variations of the bone can be expressed in terms of a scaphoid index, by calculating the relationship between the greatest dimension and the width of the narrowed portion.

Development of the human wrist joint ligaments.

BACKGROUND: Many studies have been published on the development of the human wrist joint, but scant attention has been given to the development of the wrist joint ligaments. Moreover, traditional description of wrist anatomy usually depict only the superficial capsular fibers of the wrist joint. The only ligamentous structure to receive much attention is the articular disc of the wrist joint, which has been described as a fibrocartilaginous structure extending from the medial edge of the lower end of the radius to the ulnar styloid process. METHODS: In the present report, we synthesize our observations in the wrist joint ligaments in 35 serially sectioned human embryonic and fetal hands (16 embryos and 19 fetuses). RESULTS: The interosseous intercarpal ligaments are organized from the mesenchyme, which, until O'Rahilly's stage 23, fills the intercarpal spaces. These ligaments are not individually distinguishable until the 9th week of development. The collateral ligaments begin to form in O'Rahillys's stage 22 and are completely formed by the end of week 10. The palmar radiocarpal and ulnocarpal ligaments (beginning with the palmar radiocarpal ligament) begin to form in O'Rahilly's stage 23 and are fully developed by the end of week 10. At this time, development of the dorsal radiocarpal ligament begins; this process is completed by the end of week 13. The articular disc which is initially formed of a single element, first appears in O'Rahilly's stage 23 and its organization is completed at week 10 of development. CONCLUSIONS: We establish the morphogenetic time-table of the wrist joint ligaments. Our descriptive findings may help explain carpal motion and the origin of wrist injuries.

[Evaluation of cartilaginous wrist development in the human during the prenatal period]. / Ocena Rozwoju Nadgarstka Chrzestnego u czlowieka w okresie prenatalnym.

The aim of the work was to assess the development of human chondral wrist in the prenatal period with regard to cartilaginous buds topography, histologic structure and development of article fissures in each month of intrauterine life. The performed examination covered 89 fetuses from 2nd to 9th month of prenatal life. Altogether 178 wrists were examined. The age of the fetuses was estimated on the clinical data, body mass, and crown-rump length base. Fetuses with developmental anomalies were excluded. At the beginning the material for microscopy was fixed and decalcified, next it was embedded in paraffin and cut on the microtome in a frontal plane. Preparations were stained by Van Gieson method, hematoxylin, and eosin. They were microscopied. I found that most of 2 month-old fetuses had 8 wrist bones buds. They were arranged in two rows: proximal and distal. Some of the examined fetuses had accessory bud that joined navicular bone during development process. Occasionally, 3, 4, 5, and 6 month-old fetuses revealed one chondral element with 2 or 3 differentiation foci in place of navicular, lunar and triangular bones. I disclosed no differences in histological development of wrist bone buds. (Fig. 1-4). There was a layer of thickened cells with mitotic figures at buds periphery in 2 and 3 month-old fetuses. A large amount of intercellular substance was in the central part. A reduced density of cells was seen in peripheral parts as well as in central parts, being viewed in intercellular substance, of buds in the 4th month of intrauterine life. Plane mesenchymal cells were observed on the surface of the buds, they created tracts forming layers, which may correspond to synovial membrane structure. The homogeneous substance staining yellow by Van Gieson method, what may be synovial membrane secretion, was found in 5 month-old fetuses. Reduction of cells from the periphery of buds had continued in 6th month. Cells forming buds resembled chondral, had light cytoplasm and central karyon, and fell into pairs. During further evolution it was observed that there was an increase of intracellular substance, formation of pairs and groups of chondral cells up to high differentiation. In 8th and 9th month of intrauterine life cells appeared like mature hyaline cartilage. Also chondral canaliculi including blood vessels were detected in the buds. Article fissures forming processes were observed already from 2nd month of intrauterine life and terminated their action in 5th month in the majority of fetuses. The evolution of distal radioulnar articular disc was seen, too. Mesenchyma being rich in cells was not differentiated in 2 month-old fetuses but during the evolution it changed into connective tissue band adhering to styloid process of ulna from one side and to head of radius from the other. Among forming article discs connective tissue fibres were found to be typical of chondral cells in 7, 8 and 9 month-old fetuses.

The formation of human synovial joint cavities: a possible role for hyaluronan and CD44 in altered interzone cohesion.

During fetal development, cavitation occurs within the primitive skeleton along planes destined to become the articular surfaces of synovial joints. A histochemical study of human fetal limbs was undertaken to identify the cell types involved in this cavitation and the possible role of interactions between cells and extracellular matrix. Cryostat sections were stained with antibodies to CD68, factor VIII related antigen, prolyl hydroxylase, beta 1 integrin, VCAM-1, proliferating cell nuclear antigen, chondroitin-4 sulphate, chondroitin-6-sulphate, hyaluronan synthase and CD44. Similar sections were reacted for uridine diphosphoglucose dehydrogenase (UDPGD) and acid phosphatase activity. Hyaluronan was demonstrated using an aggrecan core protein hyaluronan binding region probe. Macrophages were present prior to cavitation in the periphery of joint interzones but not at the presumptive joint line in the central interzone. Fibroblastic cells were present throughout. Absence of local VCAM-1 expression indicated that cavitation was temporally distinct from full fibroblast-like synoviocyte differentiation. CD44 was expressed by interzone cells at all stages. Staining for hyaluronan and hyaluronan synthase, but not chondroitin sulphates was present in the interzone before and at the time of cavitation. UDPGD activity was increased in a narrow band of cells at the presumptive joint line prior to cavitation. These findings suggest that joint cavitation is dependent on the behaviour of fibroblastic cells and/or adjacent chondrocytes, rather than macrophages. Since UDPGD activity is involved in hyaluronan synthesis, it is proposed that joint cavitation is facilitated by a rise in local hyaluronan concentration in an area of tissue where cohesion is dependent on the interaction between cellular CD44 and extracellular hyaluronan. As proposed by Toole et al. (1984) such a local rise in hyaluronan concentration may lead to a switch from intercellular cohesion to dissociation, leading to tissue cavitation.

The development of cartilaginous wrist in human fetuses.

Wrist bones were studied in fetuses aged 9 to 24 weeks. In fetuses aged 9 weeks the primordia of all wrist bones are present. The joint cavities begins to form early in the 3rd month.

The anatomy of the palmar scaphotriquetral ligament.

The palmar ligaments of the wrist were dissected in 15 adult cadaver wrists and demonstrated by MRI in three. Ten fetal wrists (10 to 19 weeks' gestation) were studied in histological sections. The palmar scaphotriquetral ligament was found in them all. Its attachment to the triquetrum is substantial but that to the scaphoid is thin and fan-shaped, its fibres interdigitating with those of the radioscaphocapitate ligament. The contribution of the ligament to carpal stability has yet to be studied, but it may help to support the head of the capitate when the wrist is dorsiflexed.

Embryologic development and variations in the anatomy of the ulnocarpal ligamentous complex.

Eighteen fetal hand specimens were reviewed in an effort to clarify variations in reports of the ligamentous anatomy of the ulnar side of the wrist. Sizes ranged from 45 mm crown-rump length (CRL) to 325 mm CRL. Representative coronal sections from the 2779 sections available were reviewed. Significant variations in size of triquetral attachment and thickness and consistency of the ulnocarpal ligamentous complex (UCLC) were observed. Each of the specimens exhibited one of four UCLC variations: (1) 5 of 18 (28%) with an average CRL of 187 mm had a dense, thin UCLC, with a focal triquetral attachment; (2) 7 of 18 (39%) with an average CRL of 209 mm had a focal, dense attachment of a thick UCLC to the triquetrum; (3) 5 of 18 (28%) with an average CRL of 220 mm exhibited a thick, dense UCLC with a broad attachment to the triquetrum; and (4) 1 of 18 (5%) with a CRL of 166 mm was unique, with a loose, areolar UCLC broadly attached to the triquetrum.

Histologic structure of the articular disk of the human distal radioulnar joint.

A histologic study of the structure of the articular disk of the distal radioulnar joint in humans was performed on 57 disks from 37 fresh cadavers that included fetuses and individuals up to age 65 years. The specimens were stained with hematoxylin and eosin, orcein, and Mallory and Mann-Dominici's methods, and studied with the light microscopy. It was found that the disks of adults were basically formed of the so-called fibrocartilagenous tissue composed of an intercellular substance in which there were interwoven wavelike collagen fiber bundles and between them three specific types of cells: (1) rather sparse fibrocytes mostly situated in dorsal and palmar margins, (2) predominant and constant chondroid cells dispersed throughout the disk, and (3) less-frequent real chondocytes distributed mostly in the central parts. This basic tissue is modified according to the age of the subjects and functional requirements. In fetuses and newborns, it is almost completely fibrous and very cellular, while in adults, it is more cartilaginous with significantly reduced cellularity. The structure of various parts of disks is adapted to the functional stresses exerted on them. In central parts exposed to pressure, the tissue is more cartilaginous, while peripheral, massive margins, subjected mostly to traction, are built in a ligamentlike pattern. The ulnar and carpal surfaces are adapted to the gliding movements of the ulna and carpus. It is concluded that the articular disk in humans, which is basically of fibrocartilagineous nature, is a dynamic structure biomechanically, predetermined and changing with aging.

Radioscapholunate ligament: a gross anatomic and histologic study of fetal and adult wrists.

The radioscapholunate ligament was studied using fifty-four dissected adult cadaver wrists. Four of these wrists had arterial perfusions with colored latex and serial sections were made of twenty-one wrists from fetuses ranging in size from 23 to 230 millimeters crown-rump length. The radioscapholunate ligament was consistently identified between the long and short radiolunate ligaments, emerging through the palmar capsule of the radiocarpal joint. It was found to be a neurovascular structure surrounded by synovial tissue with vascular origins from the anterior interosseous and radial arteries and a neural origin from the anterior interosseous nerve. On entering the radiocarpal joint it attaches proximally to the interfacet prominence on the articular surface of the radius and distally to form the proximal membrane of the scapholunate interosseous ligament system. We found no anatomic evidence that this structure should be considered a ligament in a traditional mechanical sense. However, this structure may be clinically important as the vascular supply of the scapholunate interosseous ligament, as well as a sensory pathway from the scapholunate articulation.

The articular disc of the wrist. Limits and relations.

The relationship between the discus articularis and its contiguous structures has been analyzed in 18 serially sectioned fetal hands. From this study, it can be concluded that these elements do not seem to be an extensive fibrous system emerging from the radius and reaching the metacarpal V, as it has been said, but a complex of clearly differentiated structures, of which further morphological details are given.

[The cubito-carpal region in gibbons]. / La région cubito-carpienne chez le gibbon.

As a continuation of our studies concerning the structure and fetal development of the human carpal articular disc (KAUER, 1968, 1975, 1976) we have investigated the disc-homologue in the Gibbon. For this purpose we have used the serial sectioned hand of a late-fetal specimen. The stratigraphical position of the os Daubentonii has been established comparing the situation in the Gibbon with that of the human ulno-carpal region. The homology presumed by others of the os Daubentonii with the cartilaginous primordium frequently found in the developing carpal articular disc in man, was found questionable. We have tried to give the os Daubentonii a functional interpretation as a sesamoid bone supporting the mechanical loaded pronation and supination of the hand in the Gibbon.