Faculty Bibliography

An acrylic-headed prosthesis was removed after 30 years and analyzed for material deterioration. Although the acrylic head showed some wear and minor corrosion of the cobalt-chromium stem was found, tissue responses were not significant, indicating that use of these materials is consistent with the long-time survival of a prosthesis

This case report of a myxoid chondrosarcoma of the os calcis is presented because of its rarity. The clinical, roentgenographic, and pathological features are discussed, and the difficulty in diagnosis is elaborated

Giant cell tumors of bone dissociated by collagenase digestion were found to be composed of four different cell types defined by morphology, growth in culture, and pattern of staining with monoclonal antibodies. Giant cells comprised an average of 0.8% of the cells recovered, with the remainder consisting of small stromal cells. Of the giant cells, 20-57% expressed Ia antigens, while all lacked IgG Fc receptors and five differentiation antigens associated with mature members of the monocyte-macrophage lineage (M phi S-1, M phi P-9, M phi P-15, M phi S-39, and 63d3). One antigen, M phi U-50, found on early monocytoid forms was expressed on Ia+ giant cells. 6-36% of the remaining stromal tumor cells formed a second subpopulation that assumed either a rounded or elongated shape in culture. These cells bore Ia antigens, IgG Fc receptors, and five antigens of the monocyte-macrophage lineage usually found on blood monocytes. However, these cells differed from monocytes or macrophages in that the antigen M phi R-17 generally found on tissue macrophages was absent, and the M phi U-50 antigen present on more primitive cells was well expressed. A very limited endocytic capacity was demonstrable. A third population of up to 24% of the tumor cells was defined by the presence of intense staining for Ia antigens but the absence of antigens of mature monocytes. A proportion of these cells expressed M phi U-50 and a minority had IgG Fc receptors. The two Ia(+) populations of stromal cells were not identifiable after 2 wk of culture, nor did tumor cells selected for the presence of Ia antigens proliferate in culture. A fourth population of cells lacked Ia and monocyte lineage antigens, but showed pronounced intracellular staining for acid phosphatase. These cells had a distinctive plump epitheloid to fibroblastoid morphology and were readily established in long-term culture where they gave rise to large multinuclear Ia(-) cells containing acid phosphatase. The possibility is discussed that the cell types of these tumors relate to various stages in the development of osteoclasts from precursors in the mononuclear phagocyte lineage.

Cyst formation in an infarcted bone, though rare, can be diagnosed with reasonable confidence when radiographs show an expanding lytic lesion confined by an intact but attenuated cortex. If the cortex is destroyed and a periosteal response or soft-tissue mass is present, malignant transformation should be suspected.

An unusual calcified soft tissue mass in the knee of an 18-month-old black male infant proved to be tumoral calcinosis. A relatively rare disorder of unknown etiology, this is one of the few reported cases of its occurrence in the knee. The diagnosis is one of exclusion. Because of their radiographic similarity, the differential diagnosis includes intracapsular and paraarticular chondroma, traumatic myositis ossificans, and calcinosis circumscripta