Dynamic laxity evaluation

Abstract

Dynamic laxity tests as the pivot shift test are superior over static laxity tests in simulating the complex multiplanar kinematics of the knee, simulating the “giving way” feeling of the patient and test specificity. However, the pivot shift is known to have a high inter-rater variability and the grading is subjective. Therefore, over the last two decades, several authors have aimed to overcome these restrictions by quantifying the pivot shift test. Different methods are used to quantify the pivot shift and include lateral anterior tibial translation (ATT), tibial rotation, and acceleration of the tibia in the reduction phase. These methods are reliable, and lateral ATT and acceleration of the reduction phase are accurate in distinguishing different pivot shift grades. In the literature, several measurement systems are used to quantify the pivot shift grades and include navigation systems with three-dimensional models, radiological imaging (i.e., radiographs and open MRIs), radiostereometric analysis, electromagnetic devices, inertial sensors, and skin markers, and some can be used in the clinical setting. Despite the development of quantitative measuring systems, the exact way of performing the test varies among examiners. Some studies have used mechanized pivot shifts to overcome this variability, whereas others have suggested using a standardized pivot shift. Recently, measurement systems as electromagnetic devices, inertial sensor, and skin markers have been used in the clinical setting. With the quantification of the pivot shift, an important step forward has been made towards the ultimate goal of objectively and reliably evaluating the dynamic laxity in the clinical setting.