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Orthopaedic Surgery Knee
Ceramic Total Knee Arthroplasty – An Update
a report by
F Benazzo,
1
F Macchi,
2
S Rossi
1
and P Dalla Pria
3
1. Orthopaedic and Traumatology Clinic, University of Pavia, Fondazione IRCCS Policlinico San Matteo;
2. Ceramtec Medical Product Division; 3. Lima-Lto, San Daniele del Friuli, Udine
Total knee arthroplasty (TKA) can be considered a reliable operation with since the early 1980s, experience with ceramic TKA has been almost
good, long-lasting clinical results.
1,2
However, it does have a weak point: its exclusively in Japan.
14–18
The Japanese experience was based on the use
polyethylene liner, whose wear triggers the well-known cascade of bone of Alumina; prosthetic designs were either cruciate-retaining or posterior-
resorption with debonding of the metallic components, leading to the stabilised; and the coupling was always ceramic–polyethylene. The first
failure of the implant.
3,4
Different materials – cross-linked polyethylenes – implants were performed by Oonishi
17,19
and produced by Kyocera Corp;
have been introduced to total joint implants for both the hip and the knee afterwards, other designs were presented, such as the Low Friction
in an attempt to resolve this problem. However, more time is needed to Anatomical (LFA; Kyocera Corp., Kyoto, Japan), now in its third edition,
demonstrate the efficacy of these improved materials in terms of wear.
5,6
the Kyoto Ceramics-1 (KC-1; Company Kyoto, Japan), the Yokohama
Different sterilisation processes have decreased the oxidation of the plastic Medical Ceramic Knee (YMCK; Kyocera Corp., Kyoto, Japan) and the
material and have shown their efficacy in reducing wear through decreased Bisurface (University of Kyoto).
delamination, but are not able to positively influence adhesive and abrasive
wear caused by the metal surface of the femoral component. Furthermore, In hip replacement, the ceramic components have a very simple design
studies on retrieved femoral components have shown their surfaces to be and shape with an axial-symmetrical structure – spheres and cones – with
more abrasive and ridged, which over time can increase the wear of the optimal contact conditions – spherical hinges and conic couplings – that
liner.
7
Finally, allergy to the metal ions released by the metallic component can tolerate high articular loads with a moderate tensional layer. In
of cobalt–chromium–molybdenum (CoCrMo) implants is an emerging issue, contrast, the designs required in TKA, in particular for the femoral
although its clinical relevance is still uncertain. As a result, current research component, and the contact conditions – the relevant differences
is focusing on new materials. Ceramic, whose resistance to abrasion and between the curvature of the femoral component and the polyethylene
better wettability and lubrication are well-known,
8
can play an important liner – need to be of an adequate size to avoid the stress forces at the
role in reducing wear – both adhesive and abrasive – and in increasing the edges of the femoral resections (traction stress) and at the points of
lifetime of the component. In addition, ceramic is totally inert, and thus can contact with the polyethylene (contact stress under the surface). Alumina
avoid the potential problem of allergy to metal ions. prostheses are therefore thicker than the equivalent metal implants and
thus require a larger bone resection. This problem was only partially
In this paper we will provide an update on the issue of ceramic TKAs. resolved with the introduction of Zirconia, while new designs have been
made possible by the introduction of BIOLOX delta.
20
Ceramic in Prosthetic Surgery
Ceramic components were introduced to total hip replacement in the The BIOLOX delta project sought to combine the resistance and
1970s in France by Dr Boutin, who used a ceramic–ceramic coupling for toughness of Zirconia with the better wear, resistance and toughness of
the first time.
9
The material employed for the heads and acetabular cups Alumina to create a composite material using an Alumina matrix; the
was Alumina (aluminum oxide, Al
2
O
3
), whose biocompatibility and desired end result was a material with good biocompatibility, chemical
optimal tribological features were immediately evident. However, the and hydrothermal stability, high resistance to wear and good mechanical
material was brittle and the engineering of the components was features (toughness and strength). To obtain these characteristics,
insufficient (the cups were cemented directly onto the bone); the particles of tetragonal Y-ZTP were uniformly distributed in the Alumina
breakage of several heads and the debonding of the cups from the bone matrix; a small percentage of chrome oxide (Cr
2
O
3
) was then added to
limited the spread of this initial component. Greater success was achieved counterbalance the reduction of hardness caused by the introduction of
in the early 1990s when the basic material was improved, with better
sinterisation, to create the 99.7% pure BIOLOX
®
, and again in 1994 with
the introduction of BIOLOX forte, which had better mechanical resistance
Francesco Benazzo is Chairman of the Orthopaedic and
Traumatology Clinic at the University of Pavia, Fondazione
due to the smaller dimensions of the grains, increased density and a more
IRCCS Policlinico San Matteo, a position he has held since
homogeneous structure. The main defect of Alumina is its low 2002. His previous positions in the same institution
toughness, or ability to withstand plastic deformations. In contrast,
include Clinical Assistant in the Section of Sports
Traumatology, Assistant Professor and Full Professor of
Zirconia (zirconium oxide, ZrO
2
, stabilised with yttria: Y-ZTP) is tougher;
Orthopaedics and Traumatology. Dr Benazzo is the
however, it is limited by its low hydrothermal stability and the fact that it
immediate Past President of the European Federation of
National Societies of Sports Traumatology (EFORT) and
cannot be coupled with itself due to its deformation characteristics.
10–12
also serves as President of the Scientific Committee of the Italian Society of Knee Surgery,
Arthroscopy, Sport, Cartilage and Orthopaedic Technology (SIGASCOT).
Ceramic was introduced to the field of knee arthroplasty by Langer in
E:
f.bennazzo@smatteo.pv.it
1973,
13
when it was used for unicompartimental implants. From then on,
© TOUCH BRIEFINGS 2007 59
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