THE APPLICATION OF ATOMIC-FORCE MICROSCOPY FOR THE DETECTION OF MICROCRYSTALS IN SYNOVIAL-FLUID FROM PATIENTS WITH RECURRENT SYNOVITIS

Synovial fluid from 33 patients with inflammatory arthritis was examin ed with a polarized light microscope (PLM) and an atomic force microsc ope (AFM). Two samples were imaged with a transmission electron micros cope (TEM) to determine calcium/phosphate ratios and identify microcry stals of calcium pyrophosphate dihydrate and octacalcium phosphate. Ad ditional correlative x-ray diffraction studies were performed on sever al samples including purified hydroxyapatite and sodium chloride cryst als. Monosodium urate, calcium pyrophosphate dihydrate, hydroxyapatite , octacalcium phosphate, and cholesterol crystals were identified with AFM. AFM images of these microcrystals revealed detailed surface topo logy, including lattice parameters and structural irregularities at th e crystals' surface. These features were consistent with those obtaine d by TEM and x-ray diffraction studies. In addition, AFM images reveal ed that some specimens contained microcrystals that were undetected by PLM and/or TEM. These results suggest that AFM may provide a simple y et powerful technique for the detection of microcrystals in synovial f luid taken from patients with crystal-induced arthritis. (C) 1995 by W .B. Saunders Company