Radiographic assessment of osteoarthritis: comparison between existing methodologies.

Radiographic sensitivity for quantifying the rate of change in joint space width (JSW) for DMOAD trials, is influenced by the following, which vary between methodologies for imaging hip, knee and hand. Radio-anatomical plane of measurement JSW measurement precision is improve when the (i) joint is in a normal functional position, (ii) X-ray beam is centred on the joint space and (iii) plane of measurement is orthogonal to the beam and articular surfaces, and parallel to the film. Measuring instrument Manual methods, e.g. callipers with graduated magnifying lens or digitisation tablets, suffer from observer variability but are practical and can reliably measure JSW. Computer-based techniques provide precise and accurate JSW measurements. Site of measurement Minimum JSW may lie within the joint's load transmitting region. JSW area and mean area assess the entire JS width. Radiographic magnification This effect is present in hip and knee radiographs and when not corrected, requires increased study numbers. Type of X-ray unit Microfocal radiography's improved spatial resolution increases measurement precision and can decrease study numbers.