Lyon Schuss, fixed flexion radiographs provide similar reproducibility for joint space width but differences in joint space narrowing

Lyon Schuss (LS) and fixed flexion (FF) radiographs provide similar reproducibility in the measurement of joint space width, but the LS view is much more sensitive in evaluating joint space narrowing in osteoarthritis (OA) knees, according to a recent head-to-head trial. The analysis included 161 women aged >=40 years and in good general health. Sixty-two patients had radiographic OA at baseline and 99 were age- and sex-matched controls without OA. Patients and controls were similar in age...

Lyon Schuss (LS) and fixed flexion (FF) radiographs provide similar reproducibility in the measurement of joint space width, but the LS view is much more sensitive in evaluating joint space narrowing in osteoarthritis (OA) knees, according to a recent head-to-head trial.

The analysis included 161 women aged >=40 years and in good general health. Sixty-two patients had radiographic OA at baseline and 99 were age- and sex-matched controls without OA. Patients and controls were similar in age (57.2 years vs 56.0 years, respectively), but had substantial differences in body mass index (36.9 vs 25.1, respectively) and in Western Ontario and McMaster Universities OA Index pain scores (6.3 vs 1.0, respectively).

The OA and control knees were imaged twice on the same day with LS and FF views at baseline and at 12 months. The investigators measured minimum joint space width using a computer, and assessed medial tibial plateau alignment from the distance between anterior and posterior margins of the medial tibial plateau (intermargin distance). Reproducibility of measurements of minimum joint space width and sensitivity to change were evaluated.

Joint space width in healthy knees did not vary with either view over 12 months. However, in OA knees, the 2 views differed significantly in detecting mean 12-month joint space narrowing (0.22 mm with the LS view, P=.0002; -0.01 mm with the FF view, P=.92). At both baseline and 12-month examinations, mean intermargin distance was approximately twice as large in the FF view as in the LS view (1.9 mm vs 0.9 mm; P<.0001).

"These findings have practical implications: an interval of only 12 months was sufficient to detect joint space narrowing with the LS, but not FF, view of OA knees," the authors wrote. "In an observational study, increasing the duration of follow-up or the sample size may overcome the limitations of the FF technique. However, in a clinical trial attempting to demonstrate slowing of joint space narrowing by a structure modifying drug for OA, those limitations would require exposure of a larger number of subjects to possible adverse effects of the test drug than use of the LS protocol." (Graverand M-P, et al. Ann Rheum Dis 2008;67:1562-1566.)