Contribution to morphological knowledge of the development of the human incudo-mallear joint.

At the time of birth, the incudo-mallear joint is completely developed. OBJECTIVE. To study the development of the incudo-mallear joint in human embryos and fetuses. MATERIALS AND METHODS. In all, 46 temporal bones with ages between 9 mm and newborns were studied. The preparations were cut in a series and dyed using Martins' trichrome technique. RESULTS. The incudo-mallear joint acquires the characteristics of a saddle joint at 10 weeks of development. The cartilage that covers the articular surfaces is formed by different strata that develop successively: the superficial stratum at 14 weeks, the transitional between 15 and 19 weeks, and the radial from 20 weeks. The subchondral bone develops between weeks 25 and 28 by the mechanisms of apposition and extension of the periosteal and endosteal bones, but it is not until week 30 that it completely covers the articular surfaces, consisting of bone fascicles whereby the lines of force will be transmitted. The articular capsule is formed as from the inter-zone. The surface zone develops the capsular ligament, and the internal surface develops the synovial membrane. Even though it is not consistent, the primordium of the meniscus is seen at 18 weeks.