Sensitivity, repeatability and reproducibility study with a leg prototype of arecently developed knee arthrometer: The DYNEELAX®

Sagittal knee laxity is often quantified using arthrometers. Adding rotational laxity and compliance measurementsis relatively new and could bring new information for anterior cruciate ligament (ACL) injury diagnosis. TheDYNEELAX® is a new knee arthrometer able to evaluate simultaneously tibial translation and rotation. Thepurpose is to assess the sensitivity, reproducibility and repeatability of the DYNEELAX® with a prototype leg toprovide accurate instructions before using it in clinical practice. Sensitivity is studied by varying 7 parameters(positioning and sensors), and reproducibility by repeating measurement series with a group of two experiencedoperators and a group of two non-experienced operators. Repeatability is assessed throughout the study. Theresults showed that DYNEELAX® is poorly sensitive to the angle and the position of the displacement sensor, andthe angle of the rotation sensor. It is a bit sensitive to positioning of patella and ankle supports. It is very sensitiveto the tightening of the patella and ankle supports. It exists a significant difference only between groups (p <0.001), but there is no significant difference between the two experienced operators (p > 0.215), or between thetwo non-experienced operators (p > 0.229). Variation coefficients for intra-series are on average inferior to 5% fortranslation and rotation tests. Then, the DYNEELAX® presented encouraging results with a good accuracy and agood reliability but operators must be careful about positioning.