The diamond concept--open questions.

In the Trauma and Orthopaedic discipline, tissue engineering attempts to convert scientific knowledge into new products and methods of treatment in order to advance the repair, replacement, or regeneration of tissues such as bone, cartilage, tendon and ligament. Currently, tissue engineering strategies are based mainly on cell and tissue-based approaches. We have previously reported that the standard tissue engineering approach to provide solutions for impaired fracture healing, bone restoration and regeneration must include the utilisation of growth factors, scaffolds, mesenchymal stem cells and an optimal mechanical environment (diamond concept). These strategies are already benefiting patients, but as our understanding of the physiological processes increases, a number of questions come up requiring clarification and answers. In this article, important issues which continue to remain obscured are discussed.