Our classic outcome scores increasingly fail to distinguish interventions or to reflect rising patient demands. Scores are subjective, have a low ceiling and score pain rather than function. Objective functional assessment tools for routine clinical use are required. This study validates inertial sensor motion analysis (IMA) by differentiating patients with knee versus hip osteoarthritis in a block-step test. Step up and down from a block (h=20cm, 3 repetitions) loading the affected (A) and unaffected (UA) leg was measured in n=59 subjects using a small inertial sensor (3D gyro and accelerometer, m=39g) attached onto the sacrum. Patients indicated for either primary unilateral THA (n=20; m/f=4/6, age=69.4yrs ±9.8) or TKA (n=16;m/f=7/9;age=67.8yrs ±8.2) were compared to healthy controls (n=23;m/f=13/10;age=61.7yrs ±6.2) and between each other to validate the test's capacity for diagnostics and as an outcome measure. The motion parameters derived (semi-) automatically in Matlab for both legs were: front-back (FB-) sway and left-right (LR-) sway (up and down); peak-to-peak accelerations (Acc) during step down. In addition the asymmetry between both legs (ASS) was calculated for each parameter. Group differences were tested (t-test) and the diagnostic value determined by the area under the curve (AUC) of the ROC-curve.Introduction
Methods
