Quantitative analysis of the measuring capabilities of the KT-1000 knee ligament arthrometer.

The KT-1000 arthrometer was evaluated in vitro and in vivo to determine accuracy and quantify effects of potential error sources in clinical application. The KT-1000 arthrometer in vitro accuracy was evaluated by making 30 measurements of 13 known displacements (range, +15 to -15 mm). The effect of applied force on malalignment measurements was evaluated in vitro by making repeated measurements with force applied 5 degrees, 10 degrees, and 15 degrees from the vertical position. The effect of malpositioning the device along the joint line was evaluated in vivo by making repeated measurements 1 cm proximal and 1 cm distal to the joint line. The KT-1000 arthrometer was accurate in vitro (average error, 0.13 mm; SD, 0.12 mm). The range of measurements increased when the angle of force application was increased. Positioning the device 1 cm proximal to the joint line produced larger anterior translation measurements in vivo than those at the joint line (5.8 versus 5.4 mm), while positioning it 1 cm distal produced smaller measurements (4.4 mm). The KT-1000 arthrometer's accuracy indicates great potential for clinical application, but one must ensure that the displacing force is directed properly and the device is positioned accurately over the joint line.