Copyright © 2009 by The Journal of Bone and Joint Surgery, Inc.
Commentary & Perspective
Commentary & Perspective by
Thomas K. Fehring, MD*,
OrthoCarolina Hip and Knee Center, Charlotte, North Carolina
Posted September 2009
This is another in the series of excellent studies by the
authors in which they compare all-polyethylene tibial components with another
form of total knee prosthesis1,2. In this prospective randomized trial,
the authors compared a cruciate-substituting rotating-platform design and a
fixed-bearing design that had an all-polyethylene tibial component. The
strength of this study is that it is prospective and randomized and only one
patient was lost to follow-up. The authors have shown that there is no significant
difference between designs—admittedly, after a very short-term of follow-up (i.e.,
a mean of forty-two months). This was a fairly homogeneous group of patients: 97%
were men with a broad age range from sixty to eighty-five years. It should be
recognized that this cohort is somewhat dissimilar to the group of patients in
whom mobile bearings are usually advocated, that is, a heterogeneous group of
patients who are younger than seventy years of age.
The authors sought to determine if there would be an outcome
difference at the time of short-term follow-up, and secondly, if there would be
a difference in implant survival at the time of long-term follow-up. I believe
that the authors have clearly achieved their first goal, as the results showed
no difference between these implants at the time of short-term follow-up. However,
it will be many years before they can answer their second question. The
rotating-platform design has attracted the attention of surgeons who are trying
to solve the problem of osteolysis in young, active patients. Unfortunately the
cohort in this study group is elderly, with an average age of seventy-two
years. Ten years from now, this cohort will have an average age of eighty-two. Therefore,
I am concerned that when the authors reevaluate these patients at that time, they
still may not be able to answer the question that is of real interest to the
reader: Which design is superior with regard to wear and osteolysis in active
patients?
While this particular question may not be answered, this study
does point out the advantages of the monoblock all-polyethylene tibial
component. In an era of decreased health-care resources, the authors have once
again shown that this component is a reasonable choice. It is less costly and
has the added advantage of being associated with diminished nonarticular wear as
compared with the wear seen in other designs, such as the rotating-platform
design or the modular fixed-bearing design. The one disadvantage that keeps the
monoblock all-polyethylene tibial component from being widely utilized in the
marketplace by most surgeons is the very fact that it is nonmodular. The loss
of intraoperative flexibility because of its nonmodular design should be
weighed against the issue of backside wear, resultant osteolysis, and the
economics of contemporary arthroplasty.
I have used all-polyethylene designs for patients who are
older than seventy years of age for the last fifteen years and have found that
osteolysis is not an issue, and I have never had to revise one of these
implants because of instability. This paper confirms my observation that all-polyethylene
tibial components are a sound design and represent a fiscally responsible choice
in a period of diminishing health-care resources. This design should be
considered as a viable alternative for the treatment of arthritis in elderly
patients.
*The author did not receive any outside funding or grants in support of his research for or preparation of this work. The author, or a member of his immediate family, received, in any one year, payments or other benefits in excess of $10,000 or a commitment or agreement to provide such benefits from a commercial entity (DePuy).
References
1. Gioe TJ, Stroemer ES, Santos ERG. All-polyethylene and metal-backed tibias have similar outcomes at 10 years: a randomized level I [corrected] evidence study. Clin Orthop Relat Res. 2007;455:212-8. Erratum in: Clin Orthop Relat Res. 2007;458:249.
2. Gioe TJ, Bowman KR. A randomized comparison of all-polyethylene and metal-backed tibial components. Clin Orthop Relat Res. 2000;380;108-15.
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