Biomedical Engineering Reference
In-Depth Information
Table 1
(continued)
Indication
Procedures or patients per year
Bladder
57 200
Ureter
30 000
Urethra
51 900
Hernia
290 000
Breast
261 000
Blood transfusions
18 000 000
Dental
10 000 000
high. Bone is one of the most common transplanted tissues, second only to
blood [18]. Hence, the need for new bone engineering strategies is quite ap-
parent although the tissue has a strong natural capacity for repair. Cartilage
has also been the focus of significant tissue engineering research for the last
decade given its lack of a self-repair ability when it is lost due to trauma,
disease, or congenital abnormalities. Cartilage is an avascular tissue, which
not only provides structural function as in the nose and ears, but the tis-
sue also acts as a cushion and lubricating surface for proper joint function.
Cartilage defects are not uncommon as over 1 million surgical procedures
are performed annually to correct defective cartilage, with a significant frac-
tion devoted to facial and dental restoration [19]. Like joint degeneration,
degenerative spinal disorders are also very common, with 5.7 million people
being diagnosed with intervertebral disc (IVD) degenerations every year in
the United States [20]. The IVD consists of a gelatinous nucleus pulposus en-
cased within a highly elastic annulus fibrosus attached to the bony vertebral
tissue. The disc is avascular, receives nutrients by passive diffusion, and lacks
the ability to self repair. The degeneration of nucleus pulposus, and subse-
quent disc herniation, often results in severe nerve compression symptoms
ranging from lower back pain to temporary paralysis [20, 21]. Indeed low
back pain is identified as one of the most common causes of musculoskeletal
impairment [21]. These are just few examples which show the socio-economic
necessity for tissue-engineered implants.
2
General Concepts in Tissue Engineering
Tissue engineering provides a solution to the earlier discussed inadequacies
of nonbiological replacements as well as allografts and autografts. Tissue en-
gineering approaches mainly consist of the following key components: cells,
biomaterial scaffolds and growth factors or other biological signals. Muscu-
