TO THE EDITOR:
Morawski et al. provided important data in "Polyethylene Debris in Lymph Nodes after a Total Hip Arthroplasty. A Report of Two Cases" (77-A: 772—776, May 1995). However, the authors mentioned the metallic debris very briefly and did not mention cement debris at all. Thus, the workup for their second patient (Case 2) included only light microscopy for the detection of polyethylene. I want to call attention to the fact that cemented metal-on-polymer endoprostheses generate wear particles that are consistent with all of their components and that these particles can disseminate through the lymphatic system.
Wear debris disease, which is not limited to the periprosthetic region, has been described in humans as well as in animal models2. In addition to polyethylene debris, metallic debris has been reported recently in lymph nodes1,3,5. According to Schmalzried et al.6, staining with oil red O is a less specific test compared with polarized light microscopy.
I suggest that lymph nodes removed for cancer-staging purposes from patients who have had a total joint replacement be evaluated with light microscopy (including oil-red-O staining), electron microscopy, and energy-dispersive x-ray analysis.
Cobi Lidor, M.D., Ph.D.: Department of Orthopaedic Surgery, Sapir Medical Center, Kfar Saba 44281, Israel
Dr. Morawski, Dr. Coutts, Dr. Handal, Dr. Luibel, Dr. Santore, and Dr. Ricci reply:
We agree that lymph nodes removed for cancer-staging purposes from patients who have had a total joint replacement should be evaluated with light microscopy (including oil-red-O staining), electron microscopy, energy-dispersive x-ray analysis, and polarized light microscopy. Electron microscopic studies were performed on both of the patients reported on in our article. Tissue freshly fixed in glutaraldehyde was not available, and, therefore, formalin-fixed tissue was used. The results were judged to be generally non-contributory because of the presence of fixation artefacts.
Polarized light microscopy and staining with oil red O appear to be complementary procedures, and both may be used in studies of this type. Only a very limited amount of material was available for study for our second patient (Case 2), and light microscopy revealed no evidence of metallic debris that needed precise identification. Therefore, detailed investigation with energy-dispersive x-ray analysis was not done. Additionally, specimens from our first patient (Case 1) did not demonstrate methylmethacrylate or barium suggestive of cement particles on energy-dispersive x-ray analysis. We agree that all components (metal, cement, and polyethylene) must be considered possible causes of debris generation and, therefore, of debris that has migrated into distant lymph nodes.
We appreciate Dr. Lidor's comments and hope that additional patients will become available for our study in the future.
David R. Morawski, M.D.: Fox Valley Orthopaedic Associates, 2525 Kaneville Road, Geneva, Illinois 60134
Richard D. Coutts, M.D.; Edgar G. Handal, M.D.; Richard Santore, M.D.: Arthritis Surgery Center, 7920 Frost Street, Suite 200, San Diego, California 92123
Joseph Luibel, M.D.: Department of Pathology, Sharp Memorial Hospital, 7901 Frost Street, San Diego, California 92123
John L. Ricci, Ph.D.: Department of Engineering, Hospital for Joint Diseases, 301 East 17th Street, New York, N.Y. 10003