Reproducibility of measurements of axial patellar views at 30°

Abstract

Introduction Different types of studies and radiographic parameters have been established to diagnose potential patellofemoral alterations; one of the most commonly used of these is the axial patellar view at 30°. Purpose To assess the reproducibility of patellar measurements on axial patella X-rays at 30°. Materials and methods In 23 patients we performed 2 axial X-rays of the same patella, at a fixed 30° angle; both films were obtained with the same technique, at an interval of 5min between them. The 3 most frequently used parameters were used to measure alterations in patellofemoral alignment: Laurin's lateral patellofemoral angle, Sasaki and Yagi's lateral deviation and Merchant's congruence angle. These measurements were taken by one same observer in all radiographs. A statistical analysis was made of the results, comparing each measurement on the 2 radiographs and analyzing the intraclass correlation coefficient. Results We found very good concordance levels with an intraclass correlation coefficient for the three angles studied greater than 0.90. Conclusions The technique described boasts a high degree of reproducibility.