To The Editor:
In the paper "Outcomes of Total Elbow Arthroplasty for Rheumatoid
Arthritis: Comparative Study of Three Implants" (2005;87:2439-2448),
Little,et al, compared their clinical results using the
Kudo implant (from 1993 to 1997) to those of two other implants. However,the authors did not specifically mention which type
of Kudo implant they used.
The type-4 Kudo prosthesis (Biomet UK) was first put on the market in 1988. The
humeral component was made of titanium alloy while the
ulnar component was made either of polyethylene alone or metal
-backed polyethylene. We have since learned that
this combination of implant materials was associated with deleterious consequencies-- massive wear of
titanium alloy resulting in severe metallosis as well as a high rate of
wear of the polyethylene.
In 1992, I asked
Biomet UK to modify the humeral component as
soon as possible by using
cobalt-chromium alloy instead of titanium alloy. At the same time I published interim
clinical results of the arthroplasty using the Type-4 prosthesis in 1994, and in that
report I described the specific problems (metallosis and subsequent
severe osteolysis) caused by the use of titanium alloy (1).
In January 1993, the Type-5 prosthesis became available for clinical use.
The humeral component was made of cobalt-chromium alloy
while the ulnar component was almost unchanged from that of Type-4. In
Japan, since the introduction of the Type 5 design, the Type-4 prosthesis was completely withdrawn
from the market. However, the situation in
Europe was quite different and the Type-4 prosthesis remained
on the market until 1997, along with marketing of Type-5.
This complicated situation was clearly shown in the report by Reinhard R.,
et al (2). They stated in that report that they had used the Type-4
prosthesis alone from 1990 to 1997. Besides this report, most of the
authors in the European literature clearly mentioned which type of Kudo
prosthesis (Type-4 or Type-5) had been used in their series.
At our institution, 107 elbows with the Type-5 prosthesis have been followed
for more than five years, the longest follow-up was 12 years. Of
these 107 elbows, six underwent revision because of loosening of the
all-polyethylene ulnar component. There was no ulnar component loosening in any of the elbows in which metal-
backed ulnar components were used.
There were no radiographic signs of
loosening of the humeral component in any of the 107 elbows. Even with these good results, we felt it necessary to increase the thickness of the
polyethylene of the metal-backed ulnar component, and, in fact, this
modification process is now under way.
At the final follow-up of
our series of the Type-5 prosthesis, the Kaplan-Meier survival rate is 91% at 11
years with revision arthroplasty as the end-point.
Lastly, I should like to mention that the
Type-4 design can be differentiated from the Type-5 design on the lateral
radiograph of the elbow; it is not possible to identify the difference between the two designs on the anteroposterior
radiograph alone.
References:
1. Kudo H, Iwano K, Nishino J. Cementless or hybrid total elbow
arthroplasty with titanium-alloy implants. A study of interim clinical
results and specific complications. J Arthroplasty. 1994;9:269-78.
2. Reinhart R, van der Hoeven M, de Vos MJ, Eygendaal D. Total elbow
arthroplasty with the Kudo prosthesis. Int Orthop.2003;27:370-2.
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