Trabecular bone anisotropy and orientation in an Early Pleistocene hominin talus from East Turkana, Kenya.

Among the structural properties of trabecular bone, the degree of anisotropy is most often found to separate taxa with different habitual locomotor modes. This study examined the degree of anisotropy, the elongation, and primary orientation of trabecular bone in the KNM-ER 1464 Early Pleistocene hominin talus as compared with extant hominoid taxa. Modern human tali were found to have a pattern of relatively anisotropic and elongated trabeculae on the lateral aspect, which was not found in Pan, Gorilla, Pongo, or KNM-ER 1464. Trabecular anisotropy in the fossil talus most closely resembled that of the African apes except for a region of high anisotropy in the posteromedial talus. The primary orientation of trabeculae in the anteromedial region of KNM-ER 1464 was strikingly different from that of the great apes and very similar to that of modern humans in being directed parallel to the talar neck. These results suggest that, relative to that of modern humans, the anteromedial region of the KNM-ER 1464 talus may have transmitted body weight to the midfoot in a similar manner while the lateral aspect may have been subjected to more variable loading conditions.

Internal architecture of the talus.

BACKGROUND: Ideally, bone has the external shape and internal architecture best adapted to its function. The internal architecture of the talus should reflect its functional adaptations. The purpose of this study was to evaluate the orientation of lamellae to account for its role in transmission of various forces. METHOD: Twenty-five pairs of dry adult human tali were sectioned in various planes and dissected grossly to study the internal architecture of the talus. RESULTS: Two sets of lamellae were observed in the body of the talus. One set was descending from the posterior two-thirds of the lateral part of trochlear surface onto the posterior calcaneal facet of the talus. These lamellae were in the form of vertical perforated interconnected plates. The second set of trabeculae originated from medial part of trochlear surface and anterior third of the lateral part. The neck of the talus showed the continuity of sagittal plates extending from the body to the head, which was occupied by stacked curved plates extending from infero-medial to the supero-lateral part of the head. CONCLUSION: We identified two sets of lamellae which we believe reflect the lines of forces of weightbearing through the talus. CLINICAL RELEVANCE: These findings may help in better understanding of fracture lines in the talus,which could improve internal fixation techniques, and the design of talar prostheses.

[Electron microscopic and immunohistochemical studies on chondroblastoma].

Six clinically and patho-histologically proven cases of chondroblastoma were studied with electron microscopic and immunohistochemical methods. The tumor tissues of chondroblastoma exhibited biphasic pattern i.e., chondroid and cellular area. In the chondroid area, small and round tumor cells contained many filaments in the cytoplasm and small processes in the cell wall. Many glycogen granules were present in the tumor cells in some cases. Intercellular matrix was immunohistochemically positive for S-100 protein and showed fine collagen fibers were very similar to those of articular and epiphysial cartilage. Many portions of mitochondria, cell wall and matrix of chondroblastoma tissue clearly exhibited calcification but were not definitely ossification. In the cellular area, tumor cells were composed of small immature mesenchymal and clear large degenerated tumor cells, histiocytes with lysosomes and osteoclast-like multinuclear giant cells. Immunohistochemical studies in the cellular area revealed that there were many tumor cells positive for lysozyme, alpha 1-antitrypsin and alpha 1-antichymotrypsin. In the transitional zone between chondroid and cellular area, degenerated tumor cells were found. The chondroblastoma was composed of chondroid and histiocytic areas which were very similar to those of chondromyxoid fibroma. The present study appears to demonstrate that chondroblastoma originates from a mixture of chondrocytic and histiocytic tumor cells but not from articular and epiphysial cartilage.

[Ultrastructure of the substantia spongiosa of the femur head and talus]. / Substrukturen in der Substantia spongiosa des Caput femoris und des Talus.

The results of the SEM examination of the zone between the cartilage and the spongeous substances are described precisely. For the first time, W. Lierse examined the 'tensulae' of calcium-collagen lamellae by light microscopy. The examination of this zone was initiated by the fact that the hydrodynamic flow can take place in the calcified zone of the cartilage which is filled with synovial fluid and that the calcified zone adheres to the subchondral substantia corticalis. The subchondral corticalis is characterized by funnel-like indentations with a high number of calcium-collagen and chondrocyte 'tensulae' which are up to now uncounted. The special aim was to locate the separation of the space of adipose and arterial supplies.

Hyaline cartilage changes in diastrophic dwarfism.

Hyaline cartilage of the talus of a diastrophic dwarf was studied by light and transmission electron microscopy before and after proteoglycan extraction or digestion, glycogen digestion, and enzyme marking. The nuclei of the chondrocytes were as a rule large and round and the cytoplasm contained large vacuoles. Best's carmine stained the cytoplasm of most cells red; after diastase digestion the cytoplasm remained unstained. This suggested that the cells contained glycogen. This observation was complimented by the ultrastructural demonstration of large amounts of glycogen. Cell scars were frequent. The shape and state of activity of the cells as well as the development of intracytoplasmic organelles showed great variability. The matrix showed many areas of degeneration and a general dearth of sulphated acid mucopolysaccharides. A lacey pattern of unmasked collagen fibers was frequently seen. Collagen fibers showed a great variability in diameter and often appeared frayed when examined by electron microscopy. These observations suggest an enzymatic deficiency in chondrocyte mucopolysaccharide and glucose metabolism. The techniques we used when added to biochemical studies should prove useful in the investigation of human dwarfism.