The quest for the perfect artificial bone substitute has proven to be much like the search for the Holy Grail. Although numerous materials have been developed and tested, none have simultaneously achieved all of the criteria desirable in a suitable graft. A primary concern has been the cost of manufacturing of most substances, followed by the engineering troubles of maintaining a material with high compressive strength that will not crack or deform under forces in multiple planes. Materials with high strength are often premade and cannot be resized for individual purposes without great difficulty. On the other hand, materials that can be shaped in real time are often lacking in strength, or release large amounts of heat while curing, which may be damaging to nearby structures. Furthermore, to enhance fusion rates, the material must be amenable to vascularization and colonization by osteoblasts and other support cells.
Jakus et al1 report on the development of “Hyperelastic” bone (HB), a material which they believe may come to be a standard of artificial bone substitute. They highlight the benefits of their material as being readily 3-D printable and osteoregenerative without the need for additional growth factors. The material they describe is a combination of 90% hydroxyapatite and 10% polycaprolactone (HAPCL) or poly (lactic-co-glycolic acid; HAPGL), which when combined with a trivalent solvent solution can be readily 3-D printed into a variety of shapes at room temperature. These materials had high elasticity, and were capable of tolerating strain of over 36.1%. When put under cyclical compression, a structure mimicking midfemoral shaft could tolerate up to 650 N of longitudinal force before exhibiting any evidence of deformation.
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