The effect of knee position on the reproducibility of measurements taken from stress films: a comparison of four measurement methods

Abstract

We evaluated the accuracy of four different means of radiographic measurement of anteroposterior translation in the knee joint. The tests were performed in normal knees, in knees lacking the anterior cruciate ligament, and in knees lacking both anterior and posterior cruciate ligaments; the knees were obtained from cadavers. It is difficult to define landmarks and to perform exact measurements, and we sought to determine which of the four methods is the most accurate. In particular, we examined the effect of various degrees of rotation and flexion on the positional relationships of the landmarks of the tibia and the femur.

Fluoroscopic validation of electrogoniometrically measured femorotibial translation in healthy and ACL deficient subjects

“…The conclusions based on the results on a single cadaver knee experiment may not reflect the true validation. However, Wirz, von Stokar, Jakob (2000), using 3 cadaver specimens, showed similar results in that the dimension of error was 1.1 mm when using a centrally located point while measuring with varying degrees of axial rotation.…”

Anterior cruciate ligament assessment using arthrometry and stress imaging

“…Ideally, landmarks should be easily and unequivocally identifiable, and should not be highly dependent on subtle changes in knee rotation or flexion. Theoretically, posterior landmarks are the least dependent on knee flexion, since the center of knee flexion lies posterior to the midshaft axis [6][7][8]. Central landmarks are the least dependent on axial knee rotation, since they again are nearest to the center of rotational motion.…”

“…In a study by Lee et al, a method using the posterior Blumensaat's line and the anterior tibial plateau showed the best inter-rater and intra-rater reliability, with an intraclass correlation coefficient between 0.891 and 0.963 [6]. Wirz et al also compared multiple measurement protocols, specifically examining the effect of rotation and flexion on landmark position and reliability, as these represent common positioning errors [7]. They found that a Bcentral-peripheral^method was most consistent despite rotation or flexion-this method used the central tibial axis, compared to a parallel line positioned midway between the posterior aspects of both femoral condyles.…”

“…This is a device which holds the femur and tibia in a fixed position, and then applies a reproducible force to the posterior tibia, producing anterior tibial translation. Most authors use 150 N of force, roughly equivalent to 15 kg, but different protocols use anywhere from 50 to 250 N [2,6,7,16].…”

Comparison of 5 Different Methods for Measuring Stress Radiographs to Improve Reproducibility During the Evaluation of Knee Instability

“…14, 16 Wirz et al 16 recommended a central peripheral measuring method to determine the translation of the tibia after comparing 4 measurements methods.…”