Biomedical Engineering Reference
In-Depth Information
Clinical Need in Orthopedic Applications
Approximately 40% of the body is bone [1]. It plays an important role, protecting internal
organs and enabling body locomotion [5]. Autografts, allografts, xenographs (for periodon-
tal applications only), and biomaterials (synthetic grafts and bone-fillers) have been used
to repair bone defects that have damaged surface areas too large for self-repair. Autograph
implants (bone material that is transferred from one location to the other in the same
patient) have exhibited good clinical performance. However, the surgical procedure is lim-
ited by the amount of healthy tissue available coupled with additional damage at the site
where bone is harvested. Allograph and xenograph implants (where bone material from
another patient is transplanted and where bone material from another species is trans-
planted) address shortcomings in availability of material but introduce new problems—
infections and foreign body reactions [6]. Biomaterials are clinically safe and free from the
shortcomings addressed above. Metals, ceramics, and polymers have all been selected and
used in orthopedics [7]; however, their discussion is beyond the scope of this chapter, so I
recommend the reader consult the excellent review by Navarro et al. [7].
Tissue Engineering Approach to Biomaterials Development
Early biomaterials development was regarded as a means to an end (i.e., materials-focused
selection and application driven by appropriate inherent bulk properties matching the host
tissue site) solution where suitable materials were chosen or developed to replace absent,
damaged, or diseased host tissues. With the discovery of biomaterials, surface reaction
responses (even to bioinert surfaces), research focus shifted toward the development of bio-
materials bulk properties coupled with engineered surface reaction properties (e.g., match-
ing mechanical properties to host tissues while controlling wear, corrosion, and surface
dissolution characteristics). Since no implanted foreign objects are bioinert, biomaterials
Bio
materials
e past: Removal of damaged tissue
Biomaterials
e present: Replacement of damaged tissues
Implants
Transplants
1st 2nd 3rd
generations
Bio
materials
e future: Regeneration of medicine (tissue engineering)
Engineered tissues
Regenerative biomaterials
FIGURE 9.2
Shift in biomaterials development over the past 40 years [8].
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