Histologic evaluation of response to implantation of polyvinilidine plates in dogs and rats.

The effect of implantation of polyvinilidine spinal plates was studied when placed on spinous processes of 11 mixed breed dogs and when placed within the thoracolumbar musculature of 12 male white rats. Specimens were also obtained from soft tissues adjacent to polyvinilidine plates 2 to 3 months after clinical surgery to repair spinal subluxations in three dogs. A similar pattern of dense, organized fibrous tissue interspersed with focal congregations of lymphocytes, plasma cells, and multinucleated giant cells was observed in the dog experiment, rat experiment, and in all clinical cases. Birefringent debris with polarization patterns identical to small slivers of polyvinilidine was associated with the observed reactions. It would appear that either a chemical or physical characteristic of the plates elicited this foreign body reaction. Grooving the inner surface of the plates, which is performed to increase the friction grip when applied to spinous processes, may make the surface texture of the plate more reactive or it may predispose the surface of the plate to minute fragmentation ("wear products").