The work relates to the introduction of a relatively thick layer (~few mm), strongly attached to the
surface of a denser (conventional) implant material (see Fig.1). This layer is highly porous, being
composed of an array of metallic fibres bonded together. Bone growth into such material is known to
occur readily. The fibres are made of a magnetic material, such as ferritic stainless steel (which
has good biocompatibility). This field will cause the fibre array to distort elastically, as the
fibres become magnetised along their length and tend to align parallel to the field axis, which in
turn will impose mechanical strain on the in-growing bone tissue. Such mechanical deformation is known
to be highly beneficial in promoting bone growth, providing the associated strain lies in a certain range
(~1000 microstrain). Preliminary work, involving both model development and experimental studies
on the effect of imposed magnetic fields on such bonded fibre network materials, has suggested that
levels of strain in the therapeutically beneficial range could indeed be induced in this way, using
field strengths no greater than those already employed for diagnostic purposes. While the magnetic
induction of strain in growing bone tissue would be a short term measure to encourage rapid in-growth,
there would be other (long term) benefits from such a design. By controlling the thickness of the
porous layer, it should be possible to tailor the overall stiffness of the component to match that
of bone, allowing the bone surrounding the implant to be strained during normal exercise. In the
presence of such straining, the bone (adjacent to the implant) will remain healthy throughout its lifetime.
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