X-ray technologists' reproducibility from automated measurements of the medial tibiofemoral joint space width in knee osteoarthritis for a multicenter, multinational clinical trial

Abstract

Objective: To determine the reproducibility of x-ray technologists, 26 in North America (NA), 24 in Europe (EU), in reliably repositioning patient's osteoarthritic (OA) knees, from computerized measurements of minimum joint space width (JSW) and reproducibility in joint repositioning, during their training for the clinical trial.

Methods: Technologists from 12 NA and 12 EU clinical radiology units received identical training, at one site on each continent, in performing the fluoroscopically assisted semiflexed knee examination and in quality control criteria (QCC) for film acceptance. Subjects recruited were 129 in NA and 70 in EU, with both knees radiographed for some subjects. Each technologist radiographed 5 OA knees and repeated the process on the same knees 2 to 7 days later. Minimum medial JSW was measured at a single center on digitized images with computer software that corrected for radiographic magnification. Technologists' reproducibility in joint repositioning and JSW measurement was determined from the difference between test and retest.

Results: In all, only 3/50 technologists failed qualification criteria with a repeat-film JSW difference > 0.50 mm. The mean, standard deviation (SD) of the difference in JSW between test/retest for 146 NA film-pairs of -0.020 (0.16) mm was not statistically different from that in 120 EU film-pairs: -0.001 (0.18) mm. In NA and EU 45% of examinations achieved high quality, i.e., JSW difference between repeat films < 0.1 mm, and 92% achieved excellent to good quality with a difference between repeat films < 0.3 mm. NA and EU technologists' reproducibility was unaffected by subject's sex, age, and degree of JSW loss. Reproducibility in joint reposition for all technologists was excellent.

Conclusion: Between-continent precision of JSW measurements from all accepted pairs of semiflexed views was excellent to very good and similar to the high technical quality achieved in the authors' original report. The value of training incorporating both test/retest radiographs and film QCC is essential for the high technical quality required for multinational clinical trials.