[Cadmium-induced vertebral-column ankylosis in whitefish ]

In two healthy and two diseased whitefish (Coregonus Wartmanni) taken from Lake Constance (FRG), ankylosis of the vertebral column was investigated both roentgenologically and histologically. Subsequent to the collapse and necrosis of the "residual" spinal cord within the intervertebral spaces, the outside edges of the vertebral bodies come into direct contact. The compression and tensile forces that occur to an increased extent as a result of the instability, lead not only to a remodelling of the vertebral bodies, but also to the formation of spondylotic osteophytes at the edges of the vertebrae and, as a result of periosteal stimulation, to the development of cellular hyaline cartilage, which fills the intervertebral spaces. Finally, as a result of perichondral ossification, a bony ankylosis develops. The humping of the spine of the fish due to the stiffening and shortening of the vertebral column, is accompanied by a restriction in the animal's freedom of movement. Muscular atrophic processes and disordered food uptake give rise to poor growth and a reduction in the weight of the diseased fish. These remodelling processes in the spine resulting from instability are specific to the periosteum and may be equated with the changes seen in man in spondylosis deformans. The possible cause of this vertebral column ankylosis is cadmium poisoning. The accumulation of this heavy metal obviously leads primarily to an irreversible toxic degeneration of the cells of the chorda dorsalis.