Biomedical Engineering Reference
In-Depth Information
9.2 Themost common causes for total hip replacement revisions in theUS from
2005 to 2006. (Adapted from Bozic et al. [27].)
An ideal bone implant should not only temporarily replace missing bone, but
also provide a framework to regenerate and heal host bone and orthopedic soft
tissue around it. On the one hand, bone implants should have sufficient
mechanical strength to connect severed/fractured bone segments, blood vessels,
nerves and other soft tissue and support physiological loads. On the other hand,
bone implants should have suitable surface chemistry to successfully integrate
into the host tissue. In other words, they should be bio/cyto-compatible, not
stimulate foreign body reactions or inflammation, and encourage new tissue
growth (not just bone, but also blood vessels, nerves, etc., as such tissues are
crucial for the maintenance of healthy bone throughout a person's life). How-
ever, current conventional implants display continual problems in these areas
leading to implant failure [29, 30]. Of paramount importance, at some point
during failure, a lack or separation of bone from the implant leads to failure,
which may be because conventional implants usually have poor initial bone
growth on the surface of the implant and/or lead to poor maintenance of healthy
juxtaposed bone intended to firmly fix the implant for the patient's lifetime.
Secondly, wear debris generated from articulating components of implants
becomes lodged between the implant and surrounding tissue, thus leading to
bone cell death and bone loss. Thirdly, infection also leads to poor bone
regeneration or even death of bone tissue. Last but not least, stress and strain
imbalances between an implant and surrounding tissue lead to bone loss, implant
loosening, and eventually failure.
One way to overcome many of these shortcomings of current bone implants is
to stimulate rapid initial bone regeneration and maintain such healthy juxtaposed
bone over long periods of time in order to fix an implant firmly between
