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Understanding the Effects of Wear Particles: Lessons Learned from Postmortem Retrievals

Dr. Deborah Hall, Robbins and Jacobs Family Biocompatibility and Implant Pathology, Laboratory of the Department of Orthopedic Surgery, Rush University Medical Center

Total hip and knee replacements have been successful in treating the disability caused by severe osteoarthritis. However, over time joint prostheses do wear and even loosen, producing particulate wear debris.  Analysis of postmortem retrieved prostheses, their surrounding tissues, and select remote organs have been most beneficial to understanding the mechanisms of wear and potentially adverse tissue reactions associated with particulate debris. The purpose of this lecture is to highlight the contributions of three postmortem retrieval studies to the current understanding of the generation and dissemination of particulate wear debris and the potential effects on local tissues and remote organs.  Joint prostheses, thoracic and abdominal organ samples, and bone marrow cores were obtained postmortem from patients who had previously undergone hip or knee replacement surgery.  Undecalcified plastic embedded sections of the implants with surrounding bone as well as paraffin embedded hematoxylin & eosin stained sections of the organs and marrow samples were prepared and studied using light and scanning electron microscopy.  Wear particles in the tissues were identified using polarized light, energy dispersive x-ray analysis and laser Raman microprobe spectroscopy. The bearing surfaces of the implants were examined with light microscopy at magnifications of 10-50X. The results of the first retrieval study revealed that design changes in third generation cementless acetabular components significantly reduced backside wear of the polyethylene bearing surface and the incidence of osteolysis in periacetabular bone (p≤0.014).  The second retrieval study identified systemic distribution of metal and polyethylene particles to the liver, spleen and abdominal lymph nodes of patients with total hip and knee implants. The results of the third study indicated that prosthetic wear can disseminate from the local site of generation to bone marrow throughout the body.  These results stress the importance of reducing particle generation at both bearing and non-bearing surfaces of joint replacement prostheses. Wear particles were shown to be disseminated to remote organs and throughout the marrow and retained for the life time of the joint replacement patient. Improved prosthetic designs and material wear properties can lengthen implant durability and aid in minimizing the amount of wear particles produced.

Bio:  Deborah Hall is a research scientist in the Robbins and Jacobs Family Biocompatibility and Implant Pathology Laboratory of the Department of Orthopedic Surgery at Rush University Medical Center. With over 27 years experience in the field of orthopaedic reconstructive surgery, Deborah studies retrieved orthopedic implants and their surrounding tissues.  Applying histologic, radiographic and electron microscopic techniques, Deborah analyzes retrieved implants for evidence of degradation, wear and corrosion products, and their effects on host tissues. The postmortem orthopedic implant and tissue procurement program, which Deborah leads, is one of the largest programs of its kind.  In addition, Deborah is also a principle investigator conducting histological and biomechanical studies of newly developed bone graft substitutes.

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