ABSTRACT
Bone defects or fractures are increasing rapidly with age due to extra osseous factors such as the impaired reex of the elderly, their reduced proprioceptive efciency, reduced cushioning by fat, weakened musculature, by osseous factors such as the structural changes in the shape and size of the bone, and by deterioration of the condition of the bone material itself; it can also occur due to various reasons including degenerative, neoplasm, congenital defects, motor accident, osteoporosis, arthritis, surgical, and traumatic processes, which signicantly compromise quality of life. Another cause may be trauma [1]. Currently, millions of patients are suffering from bone and cartilage defects such as osteoarthritis and rheumatoid arthritis that affect the structure of freely movable (synovial) joints, such as the hip, knee, shoulder, ankle, and elbow, cause considerable pain in such joints, particularly weight-bearing joints like the hip and knee, and the effects on ambulatory function are quite devastating [7,8]. Generally, two types of methods are commonly used as standard procedure for the treatment of bone or cartilage defect: autologous transplantation in which cortical bone is selected for strength and mechanical support, while cancellous bone autografts are used to promote lattice formation and rapid bone regeneration; and allograft or xenograft transplantation in which allogenic bone has been successfully used in osseous reconstruction. Autograft promotes bone formation over its surface by direct bone bonding (osteoconduction) and induces local stem cells to differentiate into bone cells (osteoinduction) without any associated immune response; while in autologous bone grafting fresh cortical or trabecular bone or a combination of both are transplanted from one site in the body, such as the iliac crest, to another within the same patient [9-11]. However, these methods suffer from many problems such as less immunocompatibility, need of a secondary surgery, high cost, possible morbidity, limited quantity of donor tissue, possible transmission of donor pathogens, immunogenic responses, and high risks of infection [12]. Therefore, it is highly desired to synthesize articial organs and implants for replacement of injured and diseased hard tissues. Recently, researchers are trying to construct the articial bone with a large number of synthetic materials (metals, metal alloys, collagen, carbon-based materials, polymers, ceramics, and composites) and synthesized as bioactive materials that open new possibilities for clinical application, mainly in orthopedics and dentistry. However, the materials that can be used in successful treatment of bone cartilage defect should exhibit the following properties: excellent biocompatibility; resistance to degradation; be structurally, functionally, and mechanically equal to healthy bone; acceptable strength; low modulus to minimize bone resorption; low cost and cell adhesion; cell proliferation and differentiation for bone tissue regeneration; and high wear resistance to minimize wear-debris generation [13]. Figure 3.2 describes some unassembled parts for total hip replacement and presents broad criteria for orthopedic implant materials.
