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

Sagittal knee laxity is often quantified using arthrometers. Adding rotational laxity and compliance measurements is relatively new and could bring new information for anterior cruciate ligament (ACL) injury diagnosis. The DYNEELAX® is a new knee arthrometer able to evaluate simultaneously tibial translation and rotation. The purpose is to assess the sensitivity, reproducibility and repeatability of the DYNEELAX® with a prototype leg to provide 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 experienced operators and a group of two non-experienced operators. Repeatability is assessed throughout the study. The results showed that DYNEELAX® is poorly sensitive to the angle and the position of the displacement sensor, and the angle of the rotation sensor. It is a bit sensitive to positioning of patella and ankle supports. It is very sensitive to 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 the two non-experienced operators (p ​> ​0.229). Variation coefficients for intra-series are on average inferior to 5% for translation and rotation tests. Then, the DYNEELAX® presented encouraging results with a good accuracy and a good reliability but operators must be careful about positioning.