Bone replacement as a major challenge in the field of orthopaedic surgery Essay

The principal functions of the skeleton are to provide a case to support the organ-systems and to find out the orientation and limits of body movement. Bone provides an anchoring point for most skeletal muscles and ligaments.
Bone tissue can undergo spontaneous regeneration and remodel its micro and macrostructure. This regeneration can be accomplished by balancing osteogenic process (bone forming) and osteoclastic (bone removing) process. Bones can easily adapt to new mechanical environment by changing the equilibrium conditions between osteogenesis and osteoclasis.
Bone replacement is a major challenge in the field of orthopaedic surgery. Bone graft is the second most frequently transplanted tissue next to blood (Giannoudis, et al., 2005). Approximately, 500,000 bone graft surgeries are done per year in United Stated. This in turn results in 2.2 billion procedures being carried out for the bone replacement. Worldwide 2.5 billion dollars have been spent on the bone graft surgeries (C. Laurencin, et. al., 2005). Therefore, there is a need to develop bone replacement procedures which is economically feasible. This can be done by using scaffolds from a biological source for the replacement of bone in the orthopaedic surgeries. i. e. biocomposites can be used for bone replacement.
The best standard of treatment for the bone tissue defects is the use of autografts (patient's own tissue). This method of treatment is followed in 58% of cases (R. James, et. al., 2011). But, it also has drawbacks including limited supply and additional surgery must be performed for bone extraciron from the donor. Therefore, an alternative method to autograft bone treatment is allografts (tissue from another patient). This method approximately contributes for 34% of the current bone grafts methods followed (L.G. Zhang et. al., 2014). This also has limitations such as availability, disease transmission from the donor and risks of infection. The limitations of autograft method and allograft method for the treatment of bone defects can be overcome by the use of synthetic bone scaffolds.
The evolution of bone graft biomaterials can be classified into four levels of generations.
The first generation bone grafts include, metals and alloys which have excellent mechanical properties but are not bioresorbable and are not bioactive. The first generation bone graft materials have limited lifetime and hence need to be removed and replaced surgically after a time period.
The second generation bone grafts includes, bioactive ceramics and bioresorbable polymers (A. Ficai, et. al., 2011). The major disadvantages of polymeric scaffolds are that, they lack bioactivity and sufficient mechanical properties while ceramic scaffolds are too brittle and hence cannot be used for load bearing applications (V. Guarino, et. al., 2012).
The third generation bone grafts are composite scaffolds which combine mechanical strength, stiffness and osteoconductivity of ceramics with the elasticity, flexibility, toughness and resorbability of the polymers (N.G. Sahoo, et. al., 2013).
Fourth generation bone grafts are polymer-ceramic composite scaffolds. Their main advantages include incorporation of osteogenic cells (osteoblasts, osteoclasts and osteoprogenitor cells), growth factors or bone morphogenetic proteins, used alone or in combination (A. Ficai, et. al., 2011).