OSTEOARTHRITIS OF THE HIP - AGREEMENT BETWEEN JOINT SPACE WIDTH MEASUREMENTS ON STANDING AND SUPINE CONVENTIONAL RADIOGRAPHS

Objective-To assess the effect of standing position on joint space wid th (JSW) measurements of the hips with and without osteoarthritis (GA) on pelvic radiographs. Methods-Adult patients aged 18 or more had pel vic anteroposterior conventional radiographs standing and supine perfo rmed by a single radiologist in the same radiology unit according to s tandardised guidelines. JSW measurements in mm were made by a single r eader blind to patients' identity and type of view, using a 0.1 mm gra duated magnifying glass directly laid over the radiograph, at the narr owest point for OA hips or at the vertical joint space for non-GA hips . Agreement of JSW between both views was assessed using the Bland and Altman graphical analysis. Results-JSW was greater on than supine rad iographs, for example, 7.1% for OA hips. Mean (SD) differences and lim its of agreement (mm) between both views were 0.08 (0.27) and -0.46 to 0.62 for the 70 non-OA hips, 0.02 (0.31) and -0.60 to 0.64 for the 46 OA hips. Corresponding 95% confidence intervals of mean differences w ere 0.02, -0.14 mm and -0.07, -0.11 mm. Conclusions-Measurements of JS W of the hip on pelvic standing and supine radiographs are concordant. Changes less than or equal to 0.64 mm between the two views are simil ar or inferior to radiological progression of GA.