Accuracy and Reproducibility of Radiographic Knee Joint Space Narrowing Measurements Referenced to the Mid-Coronal Plane

Abstract

Introduction: Knee joint space narrowing (JSN) is a primary outcome measure in the progression of knee osteoarthritis and its treatment. JSN is most frequently determined from radiographs relying on the radiographic shadow of the anterior or posterior margins of the tibial plateau. Several studies address the confounding issues related to use of the anterior and posterior margins of the tibial plateau. An alternative strategy is to identify the mid-coronal plane of the tibial plateau and use that as a reference for measuring JSN. Methods: Radiographs with precisely defined changes in joint space width (JSW) were created from CT imaging of cadaver knees. The mid-coronal plane of the knee was used to measure JSW and calculate JSN. Radiographs and data from the Osteoarthritis Initiative study were used to assess reproducibility and compare mid-coronal plane measurements of JSN to previously reported methods. Results:The average absolute error in the measured versus known medial JSN was below 0.2 mm. The reproducibility was similar to previously published methods. There was a strong correlation between the mid-coronal plane measurements of JSN and JSN calculated using previously reported methods. There were several discrepancies between the two methods, suggesting that JSN for individual cases may depend on the method used to measure JSN. Discussion: This study describes an alternative to using the margins of the tibial plateau when calculating JSN. JSN measurements based on the mid-coronal plane of the knee, where cartilage changes are more likely to occur, may have advantages.

Characterization of the mid-coronal plane method for measurement of radiographic change in knee joint space width across different levels of image parallax

“…The purpose of this paper is to fully characterize a novel "midcoronal plane" (MCP) method 18 that minimizes the effect of parallax on DJSW measurements. The method involves placement of a tibial reference line for JSW measurement, representative of the mid-coronal plane (Fig.…”