Calcium pyrophosphate dihydrate crystal deposition patterns in the triangular fibrocartilage complex

To define the patterns of calcium pyrophosphate dihydrate (CPPD) crystal deposition in the triangular fibrocartilage complex (TFCC), we examined the wrists of five adult, fresh-frozen cadavers using light and scanning electron microscopy and the wrist radiographs of 10 patients with a clinical diagnosis of CPPD disease. The radiographs consistently showed mineral deposits near or on the proximal and distal surfaces of the radial half of the TFCC. Light and electron microscopy showed that CPPD crystals formed distinct clusters sharply demarcated from uninvolved fibrocartilage. The density of crystal packing within clusters varied with the sharpness of demarcation of the clusters from the surrounding tissue. TFCC defects were consistently found in the vicinity of CPPD crystals, and degeneration of the articular cartilage on the ulnar half of the proximal surface of the lunate was associated with CPPD crystal deposition in the radial half of the TFCC. These observations suggest that degenerative tears of the TFCC and degeneration of the articular cartilage of the lunate are associated with CPPD crystal deposits in the TFCC.