Radiographic assessment. Introduction: existing methodology

Plain radiograph is the most accepted imaging technique to assess structural changes of osteoarthritis and it is proposed as 'surrogate' of outcome of the disease process. The existing radiographic methodology is well standardized with respect to its technique for investigation of hip, knee and hand joints, including advice on the most appropriate views, patient positioning, X-ray beam alignment, quality control. Quantitation of joint space narrowing is currently proposed as the primary variable in studies of disease progression for hip and knee, while semi-quantitation of this same parameter or of bone changes by published atlases have to be intended as secondary variables, or outcomes in hand studies. Unfortunately, the review of studies that evaluated the longitudinal rate of joint space narrowing indicates that the yearly change may be very small (<0.1 mm/year) and of doubtful clinical significance. This underlines the need for further refinement in the definition of the radiographic outcome in prospective clinical trials.