The reliability of the three-dimensional FASTRAK measurement systemin measuring cervical spine and shoulder range of motion in healthy subjects

Objectives. To assess the inter-observer and intra-observer reliability of a new three-dimensional measurement system, the FASTRAK, in measuring cervical spine flexion/ extension. lateral flexion and rotation and shoulder flexion/extension, abduction and external rotation in healthy subjects. Methods. The study was conducted in two parts. One part assessed inter-observer reliability with two observers measuring 40 subjects. The other part assessed intra-observer reliability with one observer measuring 32 subjects on three occasions. All subjects had unrestricted, pain-free cervical spine and shoulder movement. Reliability was measured by the intraclass correlation coefficient [ICC(2,1)]. Results. The inter-observer ICCs for the cervical spine ranged from 0.61 to 0.89 and for the shoulder from 0.68 to 0.75. After removal of outliers, all ICCs were above 0.70. Intraobserver ICCs for the cervical spine ranged from 0.54 to 0.82 and for the shoulder from 0.62 to 0.81. After removal of outliers, all ICCs were above 0.70 except for shoulder abduction (0.62). Conclusions. Whilst all movements measured by the FASTRAK showed good reliability, the reliability of the whole movement in a plane (e.g. left plus right lateral flexion) was better than for the separate movements (e.g. left and right lateral flexion taken separately). Interobserver reliability was generally better than intra-observer reliability for most cervical spine movements, suggesting that variability of movement within subjects (e.g. over a period of days) for these movements was greater than variability between measures on the same occasion.