BIOLOX - Nanocomposite for Arthoplasty

Tribology and Arthroplasty
Competence in Ceramics
Material Properties
The Strengths of BIOLOX ® delta
Key Issues in Hip Arthroplasty
2
Osteolysis and aseptic
loosening are primarily
triggered by wear
particles, mostly of
polyethylene (left).
Osteolysis
Although total hip arthroplasty is one of
the most successful of all surgical procedures,
a number of open questions relating
to implant design and materials remain.
According to the Swedish Register, osteolysis
and aseptic loosening are responsible
for more than 75 percent of all revisions.
The bearing materials used and the volume,
size, and biological effects of wear particles
play a decisive role in the development
of these conditions. The second most frequent
complication is dislocation created
by prosthetic impingement and insufficient
joint stability.
Wear Particles
Particle disease, a condition first identified
by Willert, is triggered by polyethylene (PE)
wear particles. Even the new highly crosslinked
polyethylene (XPE) can produce
wear particles, which create a similar condition.
In addition, the fact that the particles
released are significantly smaller than
those associated with standard PE, some
concerns exist over the long-term biological
reaction to these smaller particles and
their increased surface area. In the case of
metal-on-metal articulations, the unavoidable
leaching of metal ions represents an
obvious risk.
Synovial Fluid Lubrication
We know today that there is no permanent
hydrodynamic state of lubrication in
artificial hip joints. The continuous shifting
between motion and rest and the frequent
generation of one-sided stress usually prevent
the formation of a permanent lubricating
film of synovial fluid. This makes the
wear resistance of the articulating materials
even more crucial.
Three states of lubrication
are observed in
total hip arthroplasty,
including fluid film lubrication
(A), mixed lubrication
(B) and boundary
lubrication (C). The especially
smooth and
hydrophilic surfaces of
ceramic components
help to ensure that the
wear-reducing lubrication
states A and B are
achieved more often
than in other bearings
(right).
A
B
C
Source: OA Dr. H. Hessler, Department of Traumatology,
General Hospital in Celle, Germany