Journal of orthopaedic research : official publication of the Orthopaedic Research Society
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Human mast cells (MC) exhibit two distinct phenotypes based on the protease content of their secretory granules. MC(TC) cells express tryptase, chymase, cathepsin G, and mast cell carboxypeptidase, while MC(T) cells express only tryptase. Both mast cell phenotypes were assessed near regions of osteolysis in uninfected failed joint implants by immunohistochemistry with antibodies to tryptase and chymase, and by in situ hybridization with anti-sense RNA probes for the respective mRNA molecules. ⋯ Most of these mast cells were aligned along the bone-prosthesis interface adjacent to loosened implants, suggesting involvement in the chronic inflammatory response that leads to bone resorption. Further ultrastructural evidence of mast cells in tissues from failed joint interface membranes was shown by transmission electron microscopy, and detection by staining after magnetic activated cell sorting. The presence of MC at the periprosthetic interface of eroded bone suggests MC degranulation and activity are associated with osteolysis in failed joint prostheses.
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Screw loosening can threaten pedicle screw fixation of the spine. Conical screws can improve the bending strength, but studies of their pullout strength as compared with that of cylindrical screws have shown wide variation. In the present study, polyurethane foam with two different densities (0.32 and 0.16 gm/cm3) was used to compare the pullout strength and stripping torque among three kinds of pedicle screws with different degrees of core tapering. ⋯ Conical core screws with effective foam compaction had significantly higher pullout strength and insertion torque than cylindrical core screws (p<0.05). The results of finite element analyses were closely related to those of the mechanical tests in both situations with or without foam compaction. This study led to three conclusions: polyurethane foam bone yielded consistent experimental results; screws with a conical core could significantly increase pullout strength and insertion torque over cylindrical; and finite element models could reliably reflect the results of mechanical tests.
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Defects in articular cartilage are often repaired with fresh osteochondral grafts. While fresh allografts provide viable chondrocytes, logistic limitations require surgical implantation within seven days of graft harvest. Here, we provide information on cold preservation of whole intact osteochondral materials that retains cartilage cell viability and function, and histologic and biochemical integrity for 28 days. ⋯ Cell function measures showed that the level of 35SO4 incorporation was suppressed in samples stored at 4 degrees C. However, no significant differences were seen among groups at 14, 21 or 28 days of cold preservation. This data has implications for tissue banking protocols for osteochondral allograft material obtained for transplantation suggesting that cold preserved allograft material be implanted within 28 days.