EVOLUTION OF BONE TRANSPLANTATION - MOLECULAR, CELLULAR AND TISSUE STRATEGIES TO ENGINEER HUMAN BONE

Bone defects occur in a wide variety of clinical situations, and their reconstruction to provide mechanical integrity to the skeleton is a n ecessary step in the patient's rehabilitation. The current gold standa rd for bone reconstruction, the autogenous bone graft, works well in m any circumstances. However, autograft reconstruction, along with the a vailable alternatives of allogenous bone graft or poly(methylmethacryl ate) bone cement, do not solve all instances of bone deficiency. Novel materials, cellular transplantation and bioactive molecule delivery a re being explored alone and in various combinations to address the pro blem of bone deficiency. The goal of these strategies is to exploit th e body's natural ability to repair injured bone with new bone tissue, and to then remodel that new bone in response to the local stresses it experiences. In general, the strategies discussed in this paper attem pt to provide the reconstructed region with appropriate initial mechan ical properties, encourage new bone to form in the region, and then gr adually degrade to allow the new bone to remodel and assume the mechan ical support function. Several of the concepts presented below are alr eady finding clinical applications in early patient trials.