[Roentgenological and pathological studies on the development of discitis in canine models]

Discitis was experimentally induced in 42 dogs by intradiscal injections of bacterial suspensions and sequentially studied by X-rays and histopathology up to 24 weeks. 1. A narrowing of the serpentine intervertebral disc space was seen roentgenologically in the Pseudomonas and E. coli groups. 2. Histologically, the acute inflammation began to subside in eight weeks, at which time new bone formation started to appear, and fusion of the adjacent vertebrae became apparent in eight weeks. The degree of the disease process was more advanced in the Staph. aureus group and less severe in the Pseudomonas group. The E. coli group lay in between. 3. The inflammatory process seemed to be confined in the disc for a week after the injection, during which time the cartilagenous cells in the nucleus pulposus underwent atrophy and degeneration. This resulted in direct exposure of the cartilagenous plate to the infection, causing invasion of the inflammatory process into the vertebral body. 4. The presence of the epiphyseal line, however, seemed to act as a barrier to hinder the inflammatory process invading the vertebral body.