The pathophysiology of intervertebral disc degeneration has been extensively studied. Various factors have been suggested as influencing its aetiology, including mechanical factors, such as compressive loading, shear stress and vibration, as well as ageing, genetic, systemic and toxic factors, which can lead to degeneration of the disc through biochemical reactions. How are these factors linked? What is their individual importance? There is no clear evidence indicating whether ageing in the presence of repetitive injury or repetitive injury in the absence of ageing plays a greater role in the degenerative process. Mechanical factors can trigger biochemical reactions which, in turn, may promote the normal biological changes of ageing, which can also be accelerated by genetic factors. Degradation of the molecular structure of the disc during ageing renders it more susceptible to superimposed mechanical injuries.

This review supports the theory that degeneration of the disc has a complex multifactorial aetiology. Which factors initiate the events in the degenerative cascade is a question that remains unanswered, but most evidence points to an age-related process influenced primarily by mechanical and genetic factors.

Polymethylmethacrylate remains one of the most enduring materials in orthopaedic surgery. It has a central role in the success of total joint replacement and is also used in newer techniques such as percutaneous vertebroplasty and kyphoplasty.

This article describes the current uses and limitations of polymethylmethacrylate in orthopaedic surgery. It focuses on its mechanical and chemical properties and links these to its clinical performance. The behaviour of antibiotic-loaded bone cement are discussed, together with areas of research that are now shedding light upon the behaviour of this unique biomaterial.

Failure of bone repair is a challenging problem in the management of fractures. There is a limited supply of autologous bone grafts for treating nonunions, with associated morbidity after harvesting. There is need for a better source of cells for repair. Mesenchymal stem cells (MSCs) hold promise for healing of bone because of their capacity to differentiate into osteoblasts and their availability from a wide variety of sources. Our review aims to evaluate the available clinical evidence and recent progress in strategies which attempt to use autologous and heterologous MSCs in clinical practice, including genetically-modified MSCs and those grown on scaffolds. We have compared various procedures for isolating and expanding a sufficient number of MSCs for use in a clinical setting.

There are now a number of clinical studies which have shown that implantation of MSCs is an effective, safe and durable method for aiding the repair and regeneration of bone.

The mammalian growth plate is a complex structure which is essential for the elongation of long bones. However, an understanding of how the growth plate functions at the cellular level is lacking. This review, summarises the factors involved in growth-plate regulation, its failure and the consequence of injury. We also describe some of the cellular mechanisms which underpin the increase in volume of the growth-plate chondrocyte which is the major determinant of the rate and extent of bone lengthening. We show how living in situ chondrocytes can be imaged using 2-photon laser scanning microscopy to provide a quantitative analysis of their volume. This approach should give better understanding of the cellular control of bone growth in both healthy and failed growth plates.