Biomedical Engineering Reference
In-Depth Information
The UHMWPe cups articulating with smooth oxzr heads showed a 45%
wear reduction in comparison with CoCr heads under identical conditions.
Moreover, particle analysis of UHMWPE wear debris showed significantly
fewer particles.
6.3.3 Tantalum
Tantalum has an excellent corrosion resistance,
14
being among the most
biocompatible metals used for implantable devices.
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The high density
(16.6 g cm
-3
) and its poor mechanical properties preclude its use for the
fabrication of large components, however, it provides excellent fluoroscopic
visibility. Tantalum has been used successfully in sheets and plates for
cranioplasty and reconstructive surgery. recently, tantalum has gained interest
for the fabrication of scaffolds for bone ingrowth.
6.3.4 Magnetic materials
The magnetic field application in orthopaedics attracts the interest of scientists
and clinicians. Both static magnetic fields and pulsed electromagnetic fields
are used in combination with or without metallic magnetic materials implanted
into the body. In this sense, many medical applications range from their simple
use for retention, through maxillofacial, orthopaedics and fracture healing,
helping to maintain stability of joints like the elbow or shoulder.
a ferromagnetic material may be either hard, which means that once
magnetized it retains its magnetization even in the absence of magnetic
fields, that is a permanent magnet, or soft, meaning it is easy to magnetize
or demagnetize. an overview of their applications in medicine can be found
elsewhere.
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among hard magnetic materials are the modern permanent
magnets based on intermetallic compounds of rare earths and 3
d
transition
metals with very high magnetocrystalline anisotropy, such as nd
2
Fe
14
B and
smCo
5
. Typical examples of soft ferromagnetic materials are ferritic stainless
steels and Fe-Pt alloys. However, Fe-Pt alloys have both soft (< 39.5 at%
Pt) and hard (> 39.5 at% Pt) magnetic properties and can be used for the
fabrication of castable devices. In this system, the relatively large Pt content
makes them corrosion resistant.
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one of the main advantages of magnetic materials is that they allow the
application of forces
in situ
without physical contact. With regard to bone
growth, it is worth mentioning the use of magnetic materials in distraction
devices which are implanted in young patients diagnosed with bone tumour,
who have not completed their growth at the time of surgery. When the patient
grows, the implant is extended by activating a magnetic force. The lengthening
procedures, which do not require additional surgery, enable the patient to
reach skeletal maturity with no or very minimal leg length discrepancy
