Biomedical Engineering Reference
In-Depth Information
Figure 8.5
PFC sigma fixed bearing
knee system cruciate retaining. (Re-
produced with kind permission from
DePuy International Ltd, Leeds, UK.
by DePuy International Ltd.)
An alternative to the use of a total knee replacement implant is the use of a
unicondylar (or unicompartmental) implant. This is used where damage to the
joint surface of the natural knee is confined to either the medial or lateral side of
the knee. The materials used are the same as for the total knee system, with fixed
and mobile bearings also available [30].
Alternative materials in knee replacement implants include the use of titanium
nitride coatings or Oxinium for the femoral part. Highly cross-linked polyethylene
has been used for the tibial part [31]. Future development may involve the use
of cushion form joints, which have so far been confined to laboratory simulator
studies [32, 33].
8.3.4
Ankle Joint Replacement
The ankle joint consists of the proximal articulating surfaces of the talus and the
distal ends of the tibia and fibula. Arthritis in the ankle is less frequent than that
of the hip and knee and therefore the use of ankle joint replacement implants is
less. However, the smaller number of ankle joint replacements performed can also
be attributed to the designs not being as successful as those for the hip and knee.
The surgical procedure for ankle joint replacement is also more challenging as the
