Harlan C. Amstutz, M.D. is the founding director of the Joint Replacement Institute, Professor Emeritus and former Chief of Orthopaedic Surgery at the University of California at Los Angeles. Dr. Amstutz is recognized worldwide as a preeminent orthopaedic surgeon and researcher in the field of joint replacement.
Harlan Amstutz, M.D.
JRI Research
The staff of JRI is engaged in various research studies, including: improving long term joint replacement durability by selective use of new replacement bearing technology, histological characterization of implant fixation, relationship between wear debris and aseptic loosening.
Metal-on-Metal Surface Arthroplasty Failures: Lessons from Implant Retrieval Studies
by Pat Campbell, Ph.D.
Introduction
With the use of metal-on-metal bearings, surface arthroplasty is again being performed in a growing number of centers. Now that the problems faced by metal-polyethylene can be solved by the metal-on-metal surface arthroplasties (MMSA), it is important to understand which failures may be preventable thorough optimized patient selection and surgical techniques. Implant retrieval studies help to achieve this.
Implant Retrieval Analysis of Metal-On-Metal Surface Arthroplasties
Revised MMSAs have been submitted to our implant retrieval laboratory by a number of surgeons from the US and worldwide. Six different kinds are now included and all of the components were made from cast cobalt chromium alloy. Each implant is photographed, and selected cases are submitted to the J. Vernon Luck Orthopaedic Research Center Wear Lab for the measurement of wear. Then each femoral component is sectioned using a water-cooled cut-off saw. This provides sections that can be examined for the thickness and distribution of the cement mantle, and the degree of cement penetration into cancellous bone. The viability and remodelling of the bone is determined from multiple decalcified sections in which the orientation is carefully preserved for later correlation with the fixation interfaces. Routine histological sections of the periprosthetic tissues are examined for the nature of the cells and tissues and for wear particles. The results of these studies are reviewed with the clinical and radiographic histories of each case.
Findings
Some of the important findings from the analysis of over 180 cases are:
femoral neck fracture is the main cause for failure
most of the fractures are associated with technical failures
cement fixation is highly variable
thermal necrosis from cement can heal by appositional new bone
avascular necrosis causing failure is uncommon
wear increases when the components are inserted improperly
lymphocytes are common in the soft tissues but failures from metal sensitivity are rare
Surgeons wishing to submit implants for analysis can contact the lab at 213 742 1134 or pcampbell@LAOH.UCLA.edu
Copyright 2005 Joint Replacement Institute Los Angeles, CA · (213) 484-7600 · JRIinfo@dochs.org
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