[A study of the menisci of the knee by scanning electron microscopy (author's transl)]. / Les ménisques du genou. Etude en microscopie électronique à balayage et corrélation biomécanique.

Sixty menisci have been studied by scanning electron microscopy. In the frontal plane of the middle third of the meniscus, two distinct parts can be discerned - a central part corresponding to the medial two thirds and a peripheral part corresponding to the lateral third. Collagen fibres can be arranged in four different ways; radial fibres in the central portion; a marginal area underlying each surface of the meniscus made up of mixed collagen fibres; circumferential fibres in the peripheral part and a fascicular layer of fibres made up of loose connective tissue arising from the articular capsule and penetrating into the circumferential fibrous layer. The authors consider that the radial fibres are best adapted to pressure, whilst circumferential fibres are submitted to traction forces; the marginal areas are best adapted to gliding forces. Both menisci comprise a single functional unit.

Knee menisci. Correlation between microstructure and biomechanics.

Light and scanning electron microscopy techniques were used to define the microstructure of human knee menisci. Two structurally different regions were shown: a mesial part that included the innermost two thirds and a peripheral part formed by the remaining outer one third. The organization of collagen bundles of the mesial part demonstrated a radial pattern. Those of the peripheral part were larger and circumferential. The articular surfaces of the mesial part were lined by thinner bundles parallel to the surface, while the outer portion was covered by synovium. This structural organization suggested specific biomechanical functions: mainly compression mesially with tension peripherally and a direct translation of forces from the inner wedge-shaped part to the outermost region. The covering layer is well suited for surface to surface motion. Outward displacement of the menisci by the femoral condyles is resisted by solid anchorage of the peripheral circumferential fibers to the intercondylar bone. The resistance to such displacement would force the femoral condyles inwards. Such an organization of menisci has implications in knee joint stability and in the pathology of meniscal injuries.

[Cp2V] migration along an octatetrayne chain: from the monometallic complex (Cp2V(2-4eta-tBuC triple bond C2-C triple bond CC triple bond CtBu)] to the dimetallic complex.

The oxidative addition of one equivalent of [Cp2V] (4) to the tetrayne ligand tBuC triple bond CC triple bond CC triple bond CC triple bond CtBu (5) gives the monometallic complex [Cp2V(3-4eta-tBuC triple bond C-C2-C triple bond CC triple bond CtBu)] (7). Compound 7 reacts further with a second equivalent of [Cp2V] to give the dimetallic complex [(Cp2V)2(1-2eta:7-8eta-tBuC2-C triple bond CC triple bond C-C2tBu)] (8), which involves a shift of the first coordinated [Cp2V] unit from the internal C3-C4 to the external C1-C2 positions on the alkynyl ligand. Compound 8 is also directly obtained by the addition of two equivalents of [Cp2V] to 5. Reversibly, reaction of 8 with 5 leads to 7. This exchange reaction between 7 and 8 by adding successively 5 and 4 has been monitored by EPR spectroscopy. By contrast, the oxidative addition of one or two equivalents of [Cp2V] to the tetrayne ligand PhC triple bond CC triple bond CC triple bond CC triple bond CPh (6) gives the homodimetallic complex [(Cp2V)2(1-2eta:7-8eta-PhC2-CC triple bond CC triple bond C-C2-Ph)] (9). Both monometallic and dimetallic complexes 7, 8, and 9 have been characterized by X-ray diffraction. Magnetic moment measurements for 8 and 9 from 300 to 4 K indicated a weak antiferromagnetic J exchange coupling of -12.5 and -4.1 cm(-1), respectively.