Pelvic pseudotumoral calcium pyrophosphate dihydrate deposition: an ultrastructural study.

We analyzed large periarticular calcifications of the hips and pubis in a woman with diffuse primary chondrocalcinosis, symptomatic in the knees. Serial articular and periarticular biopsies were obtained during surgery for osteoporotic hip fracture. Histologic examination showed diffuse nonbirefringent clumps in red alizarin stained cartilage, capsula and tendon. Scanning electron microscopy with microanalysis indicated a calcium/phosphorus atomic ratio of about 1. Transmission electron microscopy, electron diffraction and Raman spectroscopy assessed calcium pyrophosphate dihydrate (CPPD) in cartilage, synovia, capsula, tendon and muscle. The cause of these hard to observe, bulky CPPD periarticular deposits, which resembled basic calcium phosphate on radiography, is still unclear.