MAST-CELLS IN LOOSENING OF TOTALLY REPLACED HIPS

This study evaluated mast cells in tissue around loose total hip impla nts. interface acid pseudocapsular tissues were obtained from 6 patien ts with a loose hip prosthesis. Mast cells were labeled with monoclona l mouse antihuman antibodies against tryptase and chymase in avidin-bi otin-peroxidase complex staining and were quantitated morphometrically by means of a semiautomatic Kontron image analyzer. Almost all mast c ells in situ were chymase-positive and tryptase-positive connective ti ssue cells. The mean number of such cells per mm(2) of tissue increase d in this rank order: interface (9.98 +/- 5.03 cells) < pseudocapsule (15.85 +/- 4.99 cells) < control knee synovium (25.08 +/- 8.64 cells). Mast cells in periprosthetic tissue, in contrast to normal knee synov ial tissue, exhibited granule release. Mast cells around loose hip pro stheses appeared to be activated by connective tissue mast tells. Thes e were found in diminished numbers and in a degranulated state in the interface tissue between implant and bone. Mast cell activation in loc o may thus lead to significant focal production and/or release of proi nflammatory mast cell mediators. Prevention of mast cell activation (d egranulation) could prove useful in the postponement of loosening of t he totally replaced hip.