Selection of knee radiographs for trials of structure-modifying drugs in patients with knee osteoarthritis: a prospective, longitudinal study of Lyon Schuss knee radiographs with the definition of adequate alignment of the medial tibial plateau.

OBJECTIVE: The quality of medial tibial plateau (MTP) alignment, which is assessed by measuring the distance between the anterior and posterior margins (intermargin distance [IMD]) of the tibial plateau, and the reproducibility of alignment in serial radiographs are suggested to be key elements in determining the accuracy and sensitivity to change in knee radiographs in patients with tibiofemoral osteoarthritis (OA). We evaluated the influence of both MTP alignment and radiograph superimposition on the sensitivity to change in radiographic joint space narrowing (JSN) in knee OA. METHODS: The study group comprised 106 patients with knee pain (73 with OA). Lyon schuss radiographic images of the knee were obtained twice (at baseline [month 0] and 12 months later), using a standardized radiographic procedure. Computerized measurement of the IMD for the assessment of MTP alignment was compared with the grading of MTP alignment by 2 observers using a 5-point scale (excellent, good, fair, poor, bad). To obtain the rate of JSN, computerized measurement of the joint space width was performed at month 0 and month 12. The sensitivity of the joint space width to change over 1 year was evaluated by the standardized response mean (SRM). RESULTS: The mean (+/-SD) IMD was 1.2 +/- 0.9 mm. The correlation between scoring and computer measurement of MTP alignment was highly significant. The cutoff value for satisfactory alignment (excellent or good) was an IMD of 1.2 mm at month 0 and/or month 12. CONCLUSION: The quality of MTP alignment at both baseline and the end point highly influences the sensitivity to change in radiographic JSN in knee OA. To obtain relevant data, only radiographs showing an IMD of

Lyon Schuss radiographic view of the knee. Utility of fluoroscopy for the quality of tibial plateau alignment.

OBJECTIVE: The "Lyon schuss" (LS) view is a fluoroscopically assisted radiographic technique of the knee in flexion. The quality of medial tibial plateau (MTP) alignment is a key element for accuracy and sensitivity to change of knee radiography. We collected data on the geometry of the osteoarthritic (OA) knee when positioned under fluoroscopy according to the LS protocol, then applied the results to develop an angulation standard for a nonfluoroscopically guided examination, and evaluated the performance of fluoroscopic and nonfluoroscopic alternatives for good alignment of the MTP. METHODS: 1. For 50 patients with knee pain (100 knee radiographs): Standardized radiographic procedure under fluoroscopy (LS view and lateral weight-bearing radiograph of the 2 knees); measurement of the tibial plateau inclination with the horizontal (TPI-h); evaluation of the quality of MTP alignment; assessment of the mean x-ray beam angle to obtain satisfactory MTP alignment. 2. For 30 patients with knee OA: LS radiograph of the knee performed without fluoroscopy, using a fixed 11 degrees downward x-ray beam angle (mean value of the angle obtained in the first part of the study) and standardized procedure; then assessment of the quality of MTP alignment. RESULTS: With the fluoroscopically assisted protocol, MTP alignment was satisfactory in 88% of cases. The mean x-ray beam angle was 11.2 degrees downward (SD 3.3 degrees, range 4-22 degrees ) and was unrelated to sex, height, weight, body mass index, and joint space width. The mean TPI-h was 19.6 degrees (SD 6.9 degrees, range 3-35 degrees ). Beam angle and TPI-h were correlated only in the satisfactorily aligned radiographs. In the 30 knees radiographed using a standardized procedure without fluoroscopy, the MTP alignment was satisfactory in 60% of cases. CONCLUSION: Fluoroscopy is useful to obtain satisfactory MTP alignment in LS radiographs because of large interindividual variations in anatomy of the knee.