The biocompatibility of alumina ceramic was tested by means of macrophage cultures, intraperitoneal (i.p.) and intramuscular (i.m.) application of powdered particles in rats, and by implantation of solid samples in the paravertebral muscles and the condylus femur. No acute cytotoxicity was found in macrophage cultures. The i.p. and i.m. application of powdered particles in the beginning showed a granulocytic reaction, later followed by a histiocytic reaction. Also, the morphological changes in the organs of reticulo histiocytic system (RHS) are shown. In the solid samples implantation, the fibrogenetic stimulus is measured by morphological analysis of the connective tissue membrane around the sample. The importance of the individual cell observation by transmission-electron microscope (TEM) examination is evidenced. The experimental results are compared to the environmental reaction of smaller animal-adapted prostheses and prostheses having been implanted in human patients. Good biocompatibility is confirmed by these investigations; also regarding central position of the macrophages, the environmental reaction due to implant material is shown.

Typical anterior spinal artery syndrome with initially severe pain and paraplegia with sensory disturbances occurred after a fall in a 36-year-old man with a history of lumbago. Multiple emboli of fibrocartilaginous material with nucleus pulposus cells were found in the foci of myelomalacia. The embolism of nucleus pulposus tissue originating from Schmorl's nodules was probably carried via the blood vessels of the neighbouring vertebral bodies with retrograde flow through the perispinal venous plexus into spinal cord veins and hence into the arteries of the spinal cord via veno-arterial anastomoses. A transitory increase in intra-abdominal pressure was probably the cause of the inversion of venous flow.

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