Practical Application of a Biaxial Goniometer to the Wrist Joint

The objectives of this study were: 1) to determine errors in wrist angle measurements from a commercially-available biaxial electrogoniometer and 2) to develop a calibration routine in order to correct for these errors. Goniometric measurements were simultaneously collected with true angular data using a fixture that allowed wrist movement in one plane while restricting motion in the orthogonal plane. These data were collected in two sets of trials: 1) flexion/extension with radial/ulnar deviation restricted and 2) radial/ulnar deviation with flexion/extension restricted. During these trials, discrete 30 degree increments of forearm rotation were studied. The results showed the expected cross talk and zero drift errors during forearm rotation. The application of mathematical equations that describe the effect of goniometer twist during forearm rotation resulted in significant error reduction for most trials. The calibration technique employs both a slope and a displacement transformation to improve the accuracy of angular data. The calibration technique may be used on data collected in the field if forearm rotation is measured simultaneously with the goniometer data.