A scanning electron microscopic study of wear in the plastic components of prosthetic knee and hip joints

The polyethylene surfaces of four metal on plastic prosthetic knee joints were compared with those of four hip joint replacements, by the use of scanning electron microscopy. The acetabular components of the hip joints showed concentric machining marks, but were generally smooth, and in some areas plastic deformation of the articular surface was evident after 24 months' use. In contrast, the tibial components of knee joints removed after 12 to 22 months showed deep scoring and pitting near the centre of their articular surfaces. This appeared to be due to abrasion by a third material, possibly fragments of cement, which sometimes became embedded in the joint surface. These results indicate that wear in prosthetic knee joints may be much more rapid than in hip joint replacements made from similar materials.