As the population ages, the number of operations performed on bone is expected to increase. Diseases such as arthritis, tumours, and trauma can lead to defects in the skeleton requiring an operation to replace or restore the lost bone. Surgeons can use autografts, allografts, and/or bone graft substitutes to restore areas of bone loss. Surgical implants are also used in addition or in isolation to replace the diseased bone. This review considers the application of available bone grafts in different clinical settings. It also discusses recently introduced bioactive biomaterials and highlights the clinical difficulties and technological deficiencies that exist in our current surgical practice.

Both temporary and permanent orthopedic implants have, by default or design, surface chemistry, and topography. There is increasing evidence that controlling nanodisorder can result in increased osteogenesis. Block co-polymer phase separation can be used to fabricate a nanotopography exhibiting a controlled level of disorder, both reproducibly and cost-effectively. Two different topographies, produced through the use of block co-polymer phase separation, were embossed onto the biodegradable thermoplastic, polycaprolactone (PCL). Analysis of the topography itself was undertaken with atomic force microscopy, and the topography's effect on human osteoblasts studied through the use of immunocytochemistry and fluorescence microscopy. Planar controls had a surface roughness 0.93 nm, and the substrates a high fidelity transfer of a disordered pattern of 14 and 18 nm. Cytoskeletal organization and adhesion, and increased expression of Runx2 were significantly greater on the smallest nanotopography. Expression of osteopontin and osteocalcin protein, and alizarin red staining of bone nodules were greatest on the smallest feature nanopatterns. Highly osteogenic, disordered nanotopographies can be manufactured into thermoplastics in a rapid and cost-effective way through the use of block co-polymer phase separation. Osteogenic topographies reproducibly and cost-effectively produced have a potentially useful application to the fields of implant technology and regenerative orthopedics. ß

Will stem cell research reverse the projected sevenfold increase in primary and revision knee replacements expected in the United States between 2005 and 2030? A focus on prevention and treatment of osteoarthritis may end the need for primary joint replacements. A more likely scenario can be described as slow and incremental changes in the prevention and treatment of osteoarthritis, accompanied by the continuing development of implant technology. Since the discovery of stem cells in the 1950s, research has increased exponentially. Expanded autologous chondrocytes, and more recently ex vivo expanded skeletal stem cells, are currently injected into osteochondral defects in the hope of regenerating cartilage and halting progression towards osteoarthritis. In addition, mesenchymal stem cells are being injected into human joints as a treatment for osteoarthritis despite a lack of quantitative research. Concurrently, stem cell research continues to contribute to chemical and topographical advancements in implant design. Advances in co-culture techniques mean it is possible that biologic articular replacements will develop prior to the cessation of the need for arthroplasty and radically change the nature of joint replacements. Whether it is through implant design or a potential cure for the pain attributable to osteoarthritis, as we hope to show in this 'forward look article', it is our opinion that stem cells will certainly impact future joint replacement.

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