Bone graft/substitutes

Bone is one of the few tissues capable of self-regeneration during skeletal deficiency, but this regeneration is limited by the nature and size of the defect. In general, skeletal deficiency occurs as a result of trauma, tumor, bone disease, or abnormality. In the case of severe fracture, bone will not heal by itself. For this reason, artificial bone substitutes may be required to restore routine function without damaging living tissue, and the selection of the bone graft substitute is the most important factor for better performance in vivo. 

Ideally, bone substitute materials should be replaced by mature bone without transient loss of mechanical support. Unfortunately, at present there is no material available fulfilling these requirements. Consequently, mechanically unstable bone defects ought to be stabilised with a non-resorbable metallic fixation made from stainless steel or titanium and the bone defect filled with a bone graft substitute. While the mechanical properties of the bone graft substitute are of minor importance, much more important it is to optimise the resorption rate of the bone graft substitute to minimise the time required for bone healing (Bohner, 2010). To control the resorption rate several strategies such as modification of the... 

State-of-the-art materials for resorbable calcium orthophosphate bioceramics as bone graft substitutes are still TCPs, either as the low temperature modification (0-TCP) or one of the high temperature modifications (a-TCP, a -TCP). The P-TCP is stable below 1125 °C. The a-TCP exists up to 1475 °C, and above this temperature up to the melting point at 1756 °C the a -TCP modification is stable (Figure 4.22). 

Bohner, M. (2010) Resorbable biomaterials as bone graft substitutes. Mater. Today, 13 (1/2), 24-30. 

Damien CJ and Parsons JR (1991) Bone graft and bone graft substitutes. A review of current technology and applications. J Appl Biomater 2 187-208. 

OoNiSHi H, Kushitani S, Yasukawa E, Iwaki H, Hench LL, Wilson J andTsuji E (1997) Particulate bioglass compared with hydroxyapatite as a bone graft substitute. Clin Orthop Rel Res 334 316-325. 

The efficacy of Osteoset as a bone graft substitute has been questioned [32] and the evidence base for use in treating diabetic ulcer infections is sparse but anecdotally UK and USA centres are reporting positive results. This is clearly an area for further research. 

Kelly CM, Wilkins RM, Gitelis S, Hartjen C, Watson JT, Kim PT. The use of a surgical grade calcium sulfate as a bone graft substitute results of a multicentre trial. Clin. Orthop. Relat. 2001 382 42-50. 

Holmes R., Mooney V., Bucholz R., and Tencer A. 1984. A coralline hydroxyapatite bone graft substitute. 

Sartoris D.J., Gershuni D.H., Akeson W.H., Holmes R.E., and Resnick D. 1986. Coralline hydroxyapatite bone graft substitutes Preliminary report of radiographic evaluation. Radiology 159 133-137. 

Wolford L.M., Wardrop R.W., and Hartog l.M. 1987. Coralline porous hydroxylapatite as a bone graft substitute in orthognathic surgery. /. Oral. Maxillofacial. Surg. 45 1034-1042. 

Holmes, D.E., Bucholz, R.W., and Mooney, V. 1986. Porous hydroxyapatite as a bone graft substitute in metaphyseal defects, /. Bone Jnt. Surg., 68,904-911. 

K. Gorna, S. Gogolewski, Preparation, degradation, and calcification of biodegradable polyurethane foams for bone graft substitutes,... 

S.N. Parikh, Bone graft substitutes past, present, future, J. Postgrad. Med. 48 (2002) 142-148. 

The particular advantage of porous HA is that it permits ingrowth of tissue into the pores, providing biological fixation of the implant. The minimum pore size necessary is -100 pm. When used as a bone graft substitute, the porous HA should mimic the framework (or... 

Key words putty, cement, bone graft substitute, calcium phosphate, injectable. 

A few million patients every year need a bone graft or bone graft substitute to repair a bone defect resulting from an injury or a disease. A large number of bone graft substitutes can be used unprocessed or processed allogenic bone, animal-derived bone substitutes and synthetic bone substitutes, mostly ceramics. ... 

Even though the first studies dealing with ceramic bone substitutes are more than 100 years old, it was only in the 1970s that research soared." In the early days, studies were focused mainly on porous blocks and granules." However, the discovery of calcium phosphate cements (CPC) in 1982-1983 opened up a new era in which the handling properties of bone graft substitute became of paramount importance. 

Designing ceramics for injectable bone graft substitutes 29... 

When the composition of a bone graft substitute has been optimized to achieve adequate handling, physico-chemical, and biological properties, other problems might arise and render the project non-feasible non-availability of raw materials, poor product shelf-Ufe, or difficulty with sterilizing die product. These aspects are discussed in the next paragraphs. 

Another important trend in the future will be the improvement in the biological properties of bone substitutes, the aim being to transform a bone defect into new mature bone as fast as possible. This implies that the focus will be set on resorbable materials that possess an open-porous structure allowing cells to invade the structure. Another potential focus could be set on osteoinductive ceramics. A number of authors have indeed observed that ceramic bone graft substitutes implanted under the skin or in muscles are filled or coated with bone over time. However, despite very intensive research, there is only a poor understanding of the mechanisms leading to osteoinduction, and as a result, it is not possible at the moment to design an osteoinductive ceramic. 

A last trend is to add minute amounts of foreign ions into ceramic bone graft substitutes to improve their biological behaviour. Most efforts have been set on Si, but other ions have been looked at such as Mg, Na, Sr, or Even... 

Chan C, Thompson I, Robinson P, Wilson J, Hench L. Evaluation of Bioglass/ dextran composite as a bone graft substitute. Int J Oral Maxillofac Surg. 2002 Feb 31(1) 73-7. 

Bucholz RW. Nonallograft osteoconductive bone graft substitutes. Clin Orthop. 2002 Feb(395) 44-52. 

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