ACCURACY AND PRECISION OF JOINT SPACE WIDTH MEASUREMENTS IN STANDARD AND MACRORADIOGRAPHS OF OSTEOARTHRITIC KNEES

Objectives-To improve the reproducibility and accuracy of joint space width (JSW) measurement as an assessment of cartilage loss in patients with osteoarthritis (OA) of the knee by determining how precision and accuracy of JSW measurement were altered by a computerised method of measurement, correction for radiographic magnification, radiography of the knee in the standing semiflexed view, and high definition macrora diography of the knee in the semiflexed view-taking JSW measurements f rom standard radiographs of OA knees in the extended view as the stand ard for comparison. Methods-Twenty five OA and 10 non-arthritic knees were radiographed in the extended view and minimum JSW was measured ma nually. Conventional and x 5 macroradiographs were taken in the semifl exed view. All radiographs were taken twice on the same day and repeat ed two weeks later. Automated computerised measurement of minimum JSW was obtained from digitally stored images of all radiographs. Results- For medial compartment JSW measurements, computerised was more accurat e than manual, correction for radiographic magnification improved prec ision and accuracy, measurements in the semiflexed view were more prec ise and accurate, and macroradiography increased measurement precision . For the lateral compartment JSW measurements, correction for radiogr aphic magnification improved precision and accuracy, and the semiflexe d view improved precision only. Conclusions-Protocols defining radiogr aphic and mensural procedures are essential for quality control of kne e radiography in the semiflexed view to permit accurate and reproducib le measurement of JSW. Macroradiography provides greater precision of JSW measurement.