ABSTRACT
Bone is a fascinating tissue whose composition and properties vary with age, sex, diet, health, and disease. (Many additional details on bone may be found in Chapter 3.) Bone represents an immense and dynamic con guration of extracellular proteins and minerals that play an important role in calcium and phosphate homeostasis, blood cellular component formation, organ protection, and structural support against gravity (Shoback et al. 2007). Histologically, bone is considered a type of connective tissue consisting of a collagen framework infused with predominantly calcium and phosphate salts. Proper precipitation and crystallization of these salts result in the formation of hydroxyapatite, a mineral compound responsible for giving bone its rigidity. The isoform of collagen that predominates in bone is type I collagen (Bringhurst et al. 2008), and it
29.1 Introduction ..........................................................................................................................509 29.1.1 Bone Structure ..........................................................................................................509 29.1.2 Bone Cells ................................................................................................................. 511 29.1.3 Bone Loss ................................................................................................................. 512
29.2 Biomaterials .......................................................................................................................... 512 29.3 Biomaterials for Bone Repair ............................................................................................... 513
29.3.1 Metals and Alloys ..................................................................................................... 513 29.3.2 Ceramic Biomaterials ............................................................................................... 514 29.3.3 Polymeric Biomaterials ............................................................................................ 514 29.3.4 Bone Cements ........................................................................................................... 515
29.4 Bone Grafts ........................................................................................................................... 516 29.4.1 Autografts ................................................................................................................. 516 29.4.2 Allografts .................................................................................................................. 516 29.4.3 Xenografts ................................................................................................................ 517 29.4.4 Synthetic Grafts ........................................................................................................ 517
29.5 Bone Tissue Engineering ...................................................................................................... 518 29.5.1 Scaffold-Based Approach ......................................................................................... 518 29.5.2 Selected Bone Scaffold Systems ............................................................................... 519 29.5.3 Scaffold Requirements.............................................................................................. 521 29.5.4 Scaffolds with Cells and Growth Factors ................................................................. 522 29.5.5 Biocompatibility and Osteocompatibility In Vitro ................................................... 523 29.5.6 Scaffold Degradation, Bone Repair, and Regeneration In Vivo ............................... 523
29.6 Summary .............................................................................................................................. 525 References ...................................................................................................................................... 526
comprises over 90% of the nonmineralized portion of bone matrix. Collagen, which, weight for weight, is as strong as steel, consists of a triple helix of three polypeptides bound tightly together.
