In 75 knee joints of 46 adult rabbits osteochondral defects of 4 mm diameter were placed by a drill reaching the cancellous bone. Twenty-three defects were left untreated, or closed by collagen foam or fibrin adhesive, or a combination of both. Fifty-two defects were closed with very small autologous cartilage fragments and a special fibrin adhesive. The adhesive differed from commercially supplied types by digested alpha chain of fibrinogen for increase in concentration, and by the addition of alpha-2-macroglobulin as protease-inhibitor. In most cases small pieces of collagen foam were added for hemostasis. In the first group of 23 joints observed over up to 40 weeks, no hyaline cartilage was found histologically in any of the defects. In the second group a rapid proliferation of chondrocytes appeared with development of hyaline cartilage with alcianblue-positive matrix. It resembled juvenile cartilage in its histologic appearance and with regard to the induction of ossification. The phenomenon is interpreted as a "second adolescence" of the adult cartilage induced by the rich nutritional and oxygen supply from the cancellous vessels, which resembles the environmental conditions before the forming of subchondral cortical bone at the end of the growth period. This method enabled us to achieve a complete closure of defects by hyaline cartilage on the very level of the surrounding articular surface.

No abstract

Conjoined twinning is a rare obstetric event that has fascinated physicians and laypersons alike for centuries. When this event occurs, early diagnosis, close prenatal management, and the proper route of delivery will assure the best possible outcome for mother and affected infants. Magnetic resonance imaging (MRI) is used both as an ancillary technique to the sonography for the antepartum diagnosis and in the preoperative planning for the surgical separation of conjoined twins. This report describes the MRI findings in conjoined twins of the thoraco-omphalopagus symmetricus type, a condition incompatible with extrauterine life. The twins were delivered at 21 weeks gestation. The MRI was used to evaluate the anatomic nature of the internal anomalies. These findings were then used to develop an autopsy approach plan that preserved the external phenotype. After dissection, the specimen was preserved by using polyethylene glycol and ultimately prepared for use as a teaching specimen.