An Experimental Study on Bipolar Endoprosthesis

Abstract

The purpose of this study is to investigate the histopathological findings of the acetabulum and the femur after insertion of a bipolar endoprosthesis. The surgery was carried out on the left hip joint of 20 mongrel adult dogs. The canines were divided into two groups. One of the groups was operated on under the assumption that the femoral neck was fractured, without any damage to the acetabular cartilage. This group was labelled the RC-group (Remaining Cartilage group). Second group was operated on under the assumption that there was damage to the acetabular cartilage caused through coxarthrosis, in this case the canine's acetabular cartilage was removed. This group was labelled the EC-group (Eliminating Cartilage group). Three years after the surgery, microscopic findings of RC-group's acetabulum showed cartilage remaining with decreasing safranin-0 stain. Microscopic findings of the EC-group's acetabulum that were observed at three years after the operation showed fibrocartilage stained by safranin-O in the deep layer. On the femur side, the section known as the "radiopaque line" in X-rays, showed thick bone trabeculae in the bone marrow. On the outside of the outer head and the inside of the bearing insert, minimal wear was only observed. Fixed strength between the stem and the femur, measured by a tensile tester, increased with passage of time. It is concluded based on this study that in the RC-group acetabular cartilage showed minimal microscopic changes for a long time after the surgery and that in the EC-group, fibrocartilage, stained partly by safranin-O, was revealed, covering over the subchondral bone.