Response to Letter to the Editor on “The Impact of Imaging Modality on the Measurement of Coronal Plane Alignment After Total Knee Arthroplasty

Abstract

We would like to thank Drs. Kim and Scott for their interest in our article and their insightful comments. We agree with the points that they have raised. Unfortunately, as the methodology described in their article had not been published before our submission, we were unable to account for and comment on their findings in our investigation [1]. We agree that prior investigations have demonstrated the impact of lower extremity rotation on standard measurements of limb and component alignment [2,3]. We have recognized this to be a limitation of our study in the Discussion of our article, and certainly differences in lower extremity rotation could account for the discordances seen in comparison of these 2 imaging modalities. However, we also feel that weight bearing likely plays a role in the differences seen between the standing, hip-knee-ankle and supine, scout computed tomography images. Clarke et al [4] have shown that there is a trend toward an increased varus alignment when moving from a supine to standing position, and thus we must also account for the impact of weight bearing on coronal alignment measurements.