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 cervi cal spine flexion/ extension. lateral flexion and rotation and shoulder fle xion/extension, abduction and external rotation in healthy subjects. Methods. The study was conducted in two parts. One part assessed inter-obse rver reliability with two observers measuring 40 subjects. The other part a ssessed 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 correlat ion 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, al l ICCs were above 0.70. Intraobserver ICCs for the cervical spine ranged fr om 0.54 to 0.82 and for the shoulder from 0.62 to 0.81. After removal of ou tliers, all ICCs were above 0.70 except for shoulder abduction (0.62). Conclusions. Whilst all movements measured by the FASTRAK showed good relia bility, the reliability of the whole movement in a plane (e.g. left plus ri ght 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 mo vements, 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.