Osteoarthritis (OA) is the fourth most common debilitating condition among women and the eighth most common among men in Western countries. At least 50 per cent of the population over 65 has radiographic evidence of osteoarthritis and more than 10 per cent have major disabilities as a result. Approximately 5 per cent of this population will require total hip replacement surgery. Non-medical management of the condition involves weight loss, exercise and physiotherapy.
Palliative medical interventions use paracetamol as a first choice analgesic. An NSAID should only be used if paracetamol is ineffective or is there is significant inflammation involved. When given regularly in full doses, NSAIDs have an analgesic and anti-inflammatory effect, but they are generally more useful in rheumatoid arthritis than OA, although they can benefit patients with severe OA.
Of course, there are significant risks associated with long-term use of NSAIDs, particularly in the elderly. GI bleeding is the most serious side effect, but NSAIDs may also worsen cardiac disease and renal impairment in the elderly. However, NSAID tolerance varies widely. Cox-2 inhibitors are licensed for pain relief in OA. Where cox-2 therapy is used, they may be combined with H2-receptor antagonists or proton pump inhibitors to reduce GI effects. Finally, in the treatment progression of OA, is joint replacement therapy, although most patients with OA typically do not need it.
Corticosteroids are sometimes used intra- and peri-articularly in patients with localised inflammation, but they have only short-term benefits (typically three to six weeks) and are recommended for use infrequently or as an adjunctive therapy.
Viscosupplementation or synovial fluid replacement therapy using hyaluronan became available on the GMS in February. It has been licensed for clinical use in OA treatment in much of Europe since 1995 and in the US since 1997.
The Director of the Canadian Centre for Activity and Ageing, Dr Robert Petrella, was in Dublin recently to talk about the benefits of viscosupplementation.
“The OA disease process is initiated through an inflammatory process in which joint cartilage is involved. Within the joint there is a milieu of material, of synovial fluid, which has a composition which allows patients to perform normal movements like walking, that create impacts on joints. But as the disease process continues, we know that the synovial fluid changes in its characteristics,” Dr Petrella explained.
Eventually, he said, the patient will develop cartilage and bone changes which are irreversible.
Viscosupplementation is a process which tries to reintroduce a normal milieu within the synovial fluid in the joint space, altering its properties such that it can withstand different kind of stress.
Synovial fluid is made up of various chains of hyaluronan. It is responsible for the viscous properties observed in the fluid. Hyaluranon is a dynamic molecule. It changes in its configuration and its physicochemical properties, depending on what types of stressors are being placed on the joint.
“If you were to sample a joint after a high level of bouncing activity, for example, in a basketball or volleyball player, you’ll see that there is a shift in the molecules’ composition to a more dynamic form, with a more viscous property, as opposed to what you would find in someone who has just been sitting around or gently walking,” Dr Petrella explained.
“There are a number of products that try to mimic what should be in the joint. They vary in their molecular weight and in their concentration. The idea behind all of them is that, if you can mimic what the joint needs, you would be able to forestall the progression of arthritis to the irreversible bone and cartilage changes, but also you could enable patients to function in a more normal way,” according to the doctor.
All of the products are introduced as a liquid gel, intra-articularly injected into the joint space, he commented, but stressed that there is a dosing aspect involved.
“The beauty of this material is that because it is natural, it can be introduced at any time and has no accumulative effects. So patients come back in, have another series of three injections, and get a repeat of symptom relief for a similar period,” Dr Petrella said.
“An area of very active investigation is the change in synovial fluid composition or its characteristics as the condition progresses. What we would like, but don’t have now, is a way or a marker to determine at what stage a patient may be in the disease progress” he commented.
“More importantly right now, we know that this is a process that starts very early and continues to develop until the end of the joint’s life. We can introduce this product at any time in the disease process. Even patients who are waiting for a total knee joint replacement can still have about a 60 per cent improvement in their symptoms if they have viscosupplementation injections, even if they have very late stage arthritis. We really don’t have any other options in that case. Patients are typically waiting considerable periods before they will have the replacement surgery. I know in Ireland the wait can be two years or more but in the interim patients actually do very well with this therapy,” he said.
“It’s safe to use viscosupplementation if a patient has a co-morbidity such as cardiovascular problems or GI disease, or are taking NSAIDS for arthritis. The big issue about viscosupplementation is awareness,” according to Dr Petrella. “I think there is a lack of awareness of the therapy as an option, particularly in Ireland, where it has just been introduced.
Dr Petrella’s role as Director at the Canadian Centre for Activity and Ageing at the University of Western Ontario is to oversee its activities as a clearing house for community-based programmes and laboratory-based research into activity-related disease.
Dr.Robert Petrella was in Ireland to address a meeting to discuss the treatment of OA, chaired by Dr. Doug Veale, consultant rheumatologist,St Vincent’s University Hospital.