Abstract
Despite the earlier work on the bone cement interface in successful Charnley stems lasting 20 years, there is still controversy explaining success and failure of cemented stems. Is it possible to analyse cemented stems histo-pathologically over the whole length of the prosthesis, to show where loosening might start or where the osseous structure resists components' failure?
The purpose of this analysis was to develop histo-pathological procedures, to provide information about bony integration or fibrous encapsulation.
This study took place over the past 12 years. Fourteen femoral stems from autopsies, 2 to 26 years post implant - Charnley, Exeter and Muller prosthesis. All clinically and radiologically sound, patients died for reasons unrelated to the implant.
Sections were cut in a complete sequence and analysed using a new microscope, the HIIFL microscope, ZOW Munich; thin sections were processed using embedding in epoxy-resin and bloc-staining in alkaline fuchsine. The sequence of sections was performed using a wet-grinding cutting process, ZOW Munich.
The analysis resulted in a very simple and unique experience. Independent of how long the implant was in place, there was no or nearly no radiolucent line in the X-ray. In defined compartments, surprisingly, cancellous bone was preserved and in many cases stiffened by bone cement. Bone to cement contacts without interposition of fibrous tissue. The findings might influence the operating techniques in the future. The results were fully coincident to findings in animal experiments of earlier work, including the secondary medullary cavity.
