[Methods for evaluating chondroprotective agents].

Abstract

A number of compounds have "chondroprotective" effects in animals or chondrocyte cultures. However, in humans, these drugs have not been convincingly shown to prevent, delay, arrest, or repair structural cartilage lesions due to osteoarthritis. In clinical trials, the main evaluation criterion should be the time-course of cartilage lesions. One parameter for assessing cartilage lesions is cartilage thickness, which can be measured at the site of greatest joint space loss using compasses and a magnifying glass. Alternatively, joint space surface area in the abnormal zone can be determined by automatic analysis of digitalized images. Use of echotomographic sections obtained using an intraarticular probe inserted during arthroscopy of the knee has been advocated. External measurements by magnetic resonance imaging or ultrasonography are technically difficult and most have been found inadequate during validation studies. Clinical trials should also include a clinical assessment of therapeutic benefits, without which chondroprotection would be pointless. Duration of these trials should be two to four years, since cartilage loss occurs slowly in osteoarthritis: mean values of 1/4 mm per year, with wide variations, have been reported at the hip and knee. A randomized, double-blind, placebo-controlled design should be used.