The intervertebral discs are the joints of the spinal column. They have a primarily mechanical role in transmitting loads through the spine and providing flexibility to the spinal column (allowing bending, flexion and torsion). The disc has a complex structure. It contains very few cells embedded in an extracellular matrix. These cells have the essential function of maintaining and repairing the matrix by synthesising matrix macromolecules and synthesising proteinases for matrix breakdown. Disc function is dependent on a balance between matrix synthesis and matrix breakdown. When this balance is in place, damaged discs can be restored by cellular repair responses.

When there is an imbalance between matrix synthesis and matrix breakdown, the matrix composition and organisation alters and the cellular repair responses are inadequate. The degraded matrix can no longer carry load effectively. Some of the cells become necrotic. The endplate of the disc calcifies and disc degeneration begins. Discs degenerate far more rapidly than other tissues. With prolonged disc degeneration, blood vessels and nerves penetrate the previously avascular and aneural disc giving rise to discogenic pain. This, in turn, causes further disc degeneration which alters the spinal mechanics and leads to painful and disabling conditions.

Degenerative changes can cause the disc to herniate which leads to sciatica and low back pain. This results in a loss of mobility and employment. It is a burden both financially and in terms of human suffering. In the long term, degenerative changes in the disc can cause spinal stenosis (narrowing of the spinal canal). Spinal stenosis is a major cause of pain and disability in the elderly. Its incidence is rising exponentially as the population ages. Disc degeneration is a multifactorial and heterogenous disease that is hugely detrimental to both individuals and populations. It is significant in around 10% of teenagers and more than 70% of people over 50 years. 5-10% of disc-denegeration-related cases become chronically disabled. This is often coupled with depressive illness which further decreases the quality of life for the patient and his/her family.

The diagnosis and treatment of painful degenerative disc disease remains one of the most controversial topics in the spine literature. There are few objective criteria for diagnosis. For 80% of back pain patients there is no clear diagnosis linking symptoms with pathological changes. Spinal stensosis can be diagnosed once the condition has advanced to a situation where surgery is required, but there are currently no early diagnostic tests which would allow preventative interactions. Because of poor knowledge of the aetiopathogenesis of these disorders, there is no clinical consensus on indications or methods of treatment. Thus, treatments vary widely with surgery the only medical intervention on offer. Surgery is generally effective for spinal stenosis but many elderly patients are unable to undergo surgery. Surgical interventions for back pain are 25 times more frequent in some parts of the US, and 10 times more frequent in Germany, than in the UK.

Without clear diagnostic criteria, treatment will remain poorly targeted with low efficacy. Gene therapy, whole disc prostheses, and hydrogel, tissue and cell implants are being developed, but it has not been proven that the nutritional, biochemical and mechanical state of the tissues is able to support such interventions. New diagnostic techniques are urgently required to meet this need or patients will be subjected to unsuccessful, expensive and possibly harmful interventions.

The reasons for the dramatic degenerative changes in the disc are poorly understood, but ageing is the biggest determinant. There have been many epidemiological studies over the past 30 years. They have revealed heavy physical work, truck-driving and smoking as risk factors for back problems, based on an 'injury' paradigm. This model implies that overloading results in structural damage which leads to disc degeneration causing symptomatic conditions. This model does not, however, examine the biological capacity of the musculoskeletal system to adapt to external exposures. In addition, improvements in the workplace and ergonomic interventions have not resolved the problem of disc degeneration-associated pain and disability, rather the incidence is increasing arithmetically. This may be explained by population studies over the last decade which have shown a genetic predisposition to back pain problems. Although disc degeneration is strongly genetic, degenerative changes are an outcome of interactions between genetics, age and cumulative exposure to environmental factors.

The objectives of the EURODISC project are to examine the interplay of ageing, genotype and environmental factors in disc matrix degeneration. This information will be used to provide a knowledge-based classification scheme for clinical diagnosis which will aid in targeting appropriate treatment and surgical interventions. Because of the complex nature of disc degeneration-related disorders, a multidisciplinary approach is necessary to identify what causes the intiation and progression of degenerative changes in the intervertebral disc. EURODISC involves close and co-operative associations between clinical personnel, spinal surgeons, research scientists and industry. It is the first project to adopt such an approach. The involvement of laboratory-based scientists, geneticists and epidemiologists with clinicians involved in diagnosis and treatment of spinal disorders will ensure efficiency in transfer of (1) diagnostic criteria and (2) understanding of pathogenesis of disc degeneration between research fndings and users. This will not only allow better targeted and more direct treatment for specific disorders, but it will also allow identification of those at risk and promote preventative education in avoiding occupation and life-style risks. The direct involvement of the laboratory-based scientists with surgeons and companies involved in developing diagnostic microelectrodes and intervertebral disc prostheses will ensure direct transfer of research results to the clinic and to industry.