If trabecular bone tissue has been lost due to severe fractures or disease, there is a necessity to construct biomechanically compatible artificial materials for the repair and reconstruction of human and animal cancellous bone defects. Ideally from a mechanical point of view artificial bone graft substitutes should have similar elastic properties.The soft tissue, regenerate of bone or callus and spongy bone tissue are capable of large elastic deformations. Spongy bone tissue is almost incompressible. The candidates for replacement materials are isotropic compositions on the basis of tricalcium phosphate and hydroxyapatite. Therefor a theory of large elastic deformations of incompressible isotropic materials can be used to interpret uni-axial load-displacement curves of replacement a single stored-energy function. Last is defined as a function of the invariants of strain.