Subchondral Stainless Steel Implants

An Experimental Investigation in Sheep

Abstract

In a previous investigation concerning reincorporation of avascular osteochondral autografts a discoloration was observed on the joint surface corresponding to the course of the inserted subchondral A0-screws. This study was performed to find out if the internal fixation material had any influence on the articular cartilage or bone. Stainless steel A0-screws of the A.I.S.I 316 type were inserted subchondrally in the proximal end of the tibia. At observation times of up to 8 months the ferroxyl test revealed no corrosion of the screws. The screws did not give rise to any local morphological reaction in the articular cartilage, and the cancellous bone around the screws showed only a slight increase in density, consisting of newly formed bone. It is suggested that the discoloration may be caused by diffusion into the tissue of haemoglobin or some breakdown product of haemoglobin that has not reached the stage of ionized iron.