Massive wear of a steel ball head by ceramic fragments in the polyethylene acetabular cup after revision of a total hip prosthesis with fractured ceramic ball

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Abstract
The purpose of this case study of severe metallosis is to draw the attention of orthopedic surgeons to extremely serious results of this kind in the event of the fracture of the ceramic ball in a total hip prosthesis. Eleven months after implantation of a KJF hip prosthesis with an aluminum oxide ceramic ball in combination with a polyethylene acetabular cup, fracture of the ceramic ball was observed. After examining the polyethylene cup during the revision operation, the operating orthopedic surgeon merely replaced the fractured ceramic ball with a metal ball head made of stainless steel. Twenty-five months after this procedure, radiography revealed massive wear of the steel ball head with resulting severe metallosis of the surrounding tissues. All prosthetic components therefore had to be removed. Careful examination of the removed prosthetic components clearly showed that sharp-edged ceramic particles originating from the fractured ceramic ball had become embedded in the bearing surface of the polyethylene cup. These tiny ceramic fragments, ranging from 0.05 to 2 mm, were too small to be seen by the operating surgeon's unaided eye. It is these extremely hard ceramic fragments that were responsible for the massive wear of the steel ball head, the hardness of which is approximately ten times less than that of aluminum oxide ceramic. The fracture of the ceramic ball further resulted in damage to the metal taper of the stemmed femoral component. In cases of this kind it is consequently absolutely essential to remove both the polyethylene cup and the ball head, and — if necessary — the femoral component as well.