Talus Bipartitus Etiology - Is Neonatal Infection Involved?

UNLABELLED: Talus bipartitus is a rare skeletal variation. Several causative factors have been proposed, but none of them seem to be convincing. We hypothesize that talus bipartitus may result from ossification disruption in neonatal period caused possibly by an infection. The observations supporting this link are discussed. The hypothesis is supported by two cases with symptomatic talus bipartitus illustrating the postulated connection. KEY WORDS: ankle, pain etiology, talus abnormalities, talus bipartitus.

Hox11 paralogous genes are required for formation of wrist and ankle joints and articular surface organization.

Limb skeletal elements are connected by distinct synovial joints, but the mechanisms regulating joint formation, diversity, and organization remain unclear. Previous studies showed that Hox11 mouse mutants have severe developmental defects in radius and ulna and tibia and fibula, but wrist and ankle joint formation and characteristics were not examined in detail. We now find that E11.5 and E12.5 triple Hox11aaccdd mutants exhibit a significant reduction in prospective carpal and tarsal mesenchyme. Although the mesenchyme became segmented into individual carpal and tarsal skeletal elements with further development, the elements were ill defined and the more proximal elements (radiale, ulnare, talus, and calcaneous) actually underwent involution and/or fusion. Wild-type carpal and tarsal elements displayed a thick articulating superficial zone at their outer perimeter that expressed genes typical of developing joint interzones and articulating cells, including Gdf5, Erg, Gli3, collagen IIA, and lubricin, and defined each element anatomically. In mutant wrists and ankles, the superficial zone around each element was thin and ill defined, and expression of several of those genes was low and often interrupted. These and other data provide novel and clear evidence that Hox11 paralogous genes regulate wrist and ankle joint organization and are essential for establishing carpal and tarsal element boundary and maintaining their articulating surface tissue.

[Development and biomechanics of the talocrural joint]. / Vývoj a biomechanika hlezenného kloubu.

We have studied the development of talocrural joint in fetuses, newborns and children. The results of the microscopical, anatomical and biomechanical studies are as follows: 1. The distal extremities of tibia and fibula are joint not only by the distal part of the tibiofibular syndesmosis, but also by an articulation (articulation tibiofibularis distalis). Its articular cavity communicates with the cavity of the talocrural joint and is visible on its arthrographic pictures. This articulation enables the mutual shift and rotation between distal extremities of tibia and fibula-during the plantar flexion fibula turns and shifts round tibia anteriorly, by the dorsal flexion posteriorly. 2. We recommend to preserve the possibility of mutual movements of tibia and fibula in all cases of the surgical treatment of talocrural injuries. 3. Analysis of prostheses of talocrural joint showed why they cannot be functionally successful. They do not respect the physiological movements, the small articulations of tarsus are overloaded. Pain, arthrosis and functional collapse results in these small articulations, because the prostheses change the axis of movements and the biomechanics at all. 4. We have defined conditions for a successful talocrural prosthesis. 5. Study of the topography of the attachment of the Achilles tendon showed, that it develops medially from the axis of the extremity and therefore rotates in the fetus the foot in the equinovarus position. The tendon shifts till the axis during the second half of fetal life. When this shift is temporarily stopped or slown down, the syndrome of pes equinovarus congenitus develops. We recommend the modification of the surgical treatment of pes equinovarus congenitus: transposition of the Achilles tendon in the axial position.

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 subtalar joint: embryology and morphology.

Several different aspects of the subtalar joint are studied. Embryology indicates that it is a recently acquired structure. The anterior subtalar joint does not have a uniform morphology, and it has been subdivided into three anatomical descriptions (ovoid, bean, and two part). To correct the confusion found in other papers, we intend to clearly describe the anatomy of the ligaments. The form and function of the retinacula, cervical ligament, and ligament of the canal are studied. The microscopic anatomy of ligaments is studied, dealing specifically with their innervation and the structure of their fibers.

[Morphogenetic factors and mechanisms in the articulation of limbs]. / Observations sur les facteurs et les mécanismes morphogénétiques des articulations des membres.

After excision or reorientation of a part of the tibia rudiment in the chick embryo, an articular head or a heterotopic joint may develop by regulation without direct or indirect participation of the interzonal mesenchyme. The undifferentiated cells which take part in the regulation arise from the prospective perichondrium: their proliferation, organization and incorporation are controlled by influences exerted by the adjacent parts of the skeletogenous blastema. Other experiments have been performed on the tibia rudiment in the attempt to modify the pressures exerted along the zeugopod by its growing skeleton. When the pressures are reduced, a joint can form between the distal end of the tibia and the proximal tarsal, which undergo fusion in normal development. As an effect of increased longitudinal pressures, fusion of the proximal tarsal and the proximal epiphysis of the 180 degrees inverted tibia may occur in spite of the interposition of a part of the interzonal mesenchyme of the knee. Our results stress the primary role seemingly exerted by the growing articular ends of the skeletal pieces during joint formation; under the conditions of our experiments, joint development does not seem causally related to any special morphogenetic property of the interzonal mesenchyme. In some joints, menisci, ligaments, fatty pads differentiate from parts of the interzonal mesenchyme which are apparently endowed with a special and early determination; it is still unknown, however, whether the interzonal mesenchyme also plays a more general role in all the joints.