Biomedical Engineering Reference
In-Depth Information
Figure 8.3
The Birmingham hip. (Reproduced with kind
permission from Smith & Nephew, Memphis, TN, USA.
by Smith & Nephew.)
and, in many cases, bone graft will be used to replace the missing bone. In most
cases, the joint replacement implant will be specifically designed for use in a
revision case, which generally involves the use of longer stems for the femoral part
[23]. Revision of the acetabular part is a challenging surgical procedure where there
is extensive bone loss. A newer approach involves the use of blocks of tantalum,
which is a metal in the form of a porous structure that bone can grow into [24].
Hip resurfacing (Figure 8.3) is a newer alternative to the traditional design of hip
replacement implants, for use in young and active people. The resurfacing implant
has a cobalt chrome molybdenum alloy against cobalt chrome molybdenum alloy
bearing articulation, with a large diameter femoral head (typically 50mm). Hip
resurfacing implants have been found to operate under fluid-film lubrication,
under some conditions [25]. The femoral part is fixed to the bone with the use of
a peg instead of a stem which is used in the traditional femoral part. This means
that there is more preservation of the bone. Large diameter femoral heads are also
Ball
Soft layer
Rigid backing
material
Figure 8.4
Cushion form joint for the hip.
