Intracellular measurement of polyethylene particles. A histomorphometric study

A histological and histomorphometric study was carried out on pseudo-capsules retrieved from patients during revision surgery of cementless total hip replacement. Polyethylene loading and areal polyethylene particle size in different cells of the reticuloendothelial cell line were determined within the tissue by histomorphometry. In the reticuloendothelial cell line, foreign-body giant cells are considered to be the result of confluence of mononuclear macrophages caused by large particles or other unknown stimuli. The aim of this study was to investigate whether polyethylene particle size and polyethylene loading are different in mononuclear macrophages and foreign-body giant cells. The specimens were examined under the light-optical microscope with plain and polarized light. The polyethylene loading of 329 macrophages (mononuclear), 81 small foreign-body giant cells (2-5 visible nuclei), and 103 large foreign-body giant cells (6 or more visible nuclei) was determined and the intracellular polyethylene particle size analyzed by histomorphometry. The mean polyethylene loading was 13 +/- 8 microm2, 25 +/- 16 microm2, and 49 +/- 42 microm2, respectively. This difference was statistically significant (Student's t-test, P < 0.05). The mean polyethylene particle size was 2.34 +/- 3.2 microm2, 3.02 +/- 3.46 microm2, and 4.70 +/- 11.25 microm2, respectively. This difference was statistically significant between macrophages and large foreign-body giant cells (t-test, P < 0.05). The findings of this light-optical study show that the mean intracellular polyethylene particle size is greater in foreign-body giant cells. In addition, absolute polyethylene loading tends to be higher in foreign-body giant cells than in mononuclear macrophages.