TEM observation of seven retrieved total knee joints made of Co‐Cr‐Mo and Ti‐Al‐V alloys

Abstract

We demonstrate that a myriad of fine particles produced by the abrasion of both cobalt‐chromium‐molybdenum (Co‐Cr‐Mo) and titanium‐aluminum‐vanadium (Ti‐Al‐V) alloys accumulate in the synovial cells next to surgical implants made from these alloys. The metallic particles were of various sizes, and were observed within the lysosomes. Energy dispersive X‐ray spectroscopy studies revealed that the fine spherical particles consisted solely of Cr, and that other larger particles were composed of the Co‐Cr‐Mo alloy. We measured the size of the metallic particles using the public domain NIH image program, and found that most of the fine spherical particles were 10–15 nm in diameter (n=1000). Eighty percent of the large particles were 30–35 nm in length and 20–25 nm in width (n=300). In addition, EDS examination clarified that all of the fine particles of the Ti‐Al‐V alloy were composed of that alloy. For this alloy, when discounting the larger particles, the fine metal deposits were 20–25 nm in length and 10–15 nm in width (n=1000).

From these findings, we conclude that the Co‐Cr‐Mo alloy is easily corroded and that Co is released from the cells. In contrast, the Ti‐Al‐V alloy is very stable and does not corrode, although the Ti‐Al‐V alloy does produce particles that are smaller than those produced by the Co‐Cr‐Mo alloy.