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Joint distraction promotes structural repair in patients with severe knee osteoarthritis

June 16, 2008

Joint distraction (the use of a surgical frame around a degenerated joint to strengthen and promote repair) promotes cartilage repair in severe end stage osteoarthritis (OA) of the knee, as demonstrated for the first time by data presented today at EULAR 2008, the Annual Congress of the European League Against Rheumatism in Paris, France.

In the study, an external fixation frame, with springs, was used to bridge the knee joint in 19 relatively young osteoarthritis patients (<60 years). The frame was then distracted by 5mm over a period of two months with the aim of promoting knee repair by removing mechanical stress on the knee. The functional ability and pain scores of the patients were poor before treatment (40% and 30% of the maximum WOMAC score), however, following joint distraction, both scores increased to more than 80%, equivalent to almost complete normalisation in terms of symptoms experienced.

MRI and digital x-ray evaluation carried out at baseline and at one year follow up showed evidence of cartilage repair. Cartilage volume and subchondral bone covered with cartilage increased by 50% and 40% respectively and mean cartilage thickness increased from baseline to one year follow up. Biomarkers of cartilage and bone (breakdown and synthesis), measured in serum and urine, demonstrated an increased level of turnover of cartilage and bone during distraction that returned to normal in the months after treatment, with a gradual increase for cartilage synthesis markers over time indicative of structural repair due to distraction.

Professor Floris Lafeber of the University Medical Center Utrecht, The Netherlands, who led the study, said, "We are delighted to report such an impressive outcome in the use of joint distraction for severe osteoarthritis of the knee. Positive results have been sustained over the two year follow up period, suggesting the potential for joint distraction to delay the need for a joint prosthesis in these relatively young patients. Our data are very promising, demonstrating the clinical efficacy and potential for structural repair. The logical next step should be the implementation of a prolonged prospective multi-centre study on the procedure."

Pain, functional disability, clinical condition and flexion of the joint were evaluated during two years of follow-up using a box-scale, a questionnaire (slightly modified WOMAC), and by physical examination. In addition, serum and urine samples were stored for biomarker evaluation and radiographs and MRIs were taken at regular intervals.

The knee (the largest joint in the body) is a common location for osteoarthritis, which causes painful joint damage and inflammation. This happens because the, as cartilage in the knee gradually roughens and thins, surrounding bone thickens to compensate and the synovium (surrounding membrane) swells, often producing extra fluid. The capsule and ligaments slowly thicken and shrink and muscles can weaken and thin, causing the knee joint to become unstable.

Osteoarthritis of the knee is twice as common in women as in men, mainly occurring in women over the age of 50. So far, no treatment has been available and end stage placement of a joint prosthesis is often inevitable. Delaying such joint replacement surgery and preserving the original joint, specifically in the light of the ageing population, offers significant social and economical potential.

European League Against Rheumatism