SHAPE OF WEAR PARTICLES FOUND IN HUMAN KNEE JOINTS AND THEIR RELATIONSHIP TO OSTEOARTHRITIS

Objective. To analyse and compare the shape of wear particles found-in healthy-and osteoarthritic human knee joints for monitoring the progr ess of osteoarthritis, the long-term prognosis and to evaluate therape utic regimens. Method. Joint particles from seven patients with normal cartilage in all compartments of the knee joint, 12 patients with fib rillation of less than half the cartilage thickness (grade 1), Seven p atients with fibrillation of more than half the cartilage thickness (g rade 2) and four patients with erosions down to bone (grade 3) were an alysed. A total of 565 particles were extracted from synovial fluid sa mples by ferrography and analysed in a scanning electron microscope. A number of numerical descriptors, i.e. boundary fractal dimension, sha pe factor, convexity and elongation, were calculated for each particle image and correlated to the degree of osteoarthritis using non-parame tric tests. Results. Experiments demonstrated that there were signific ant differences between the numerical descriptors calculated for wear particles from healthy and osteoarthritic knee joints (P < 0.01), sugg esting that the particle shape can be used as an indicator of the join t condition. In particular, the-fractal dimension of the particle boun dary was shown to correlate directly with the degree of osteoarthritis . Conclusion. Numerical analysis of the shape of wear particles found in human knee-joints may provide a reliable means for the assessment o f cartilage repair after surgical or conservative treatment of osteoar thritis.