AN IN-VIVO STUDY OF THE PRIMARY AND COUPLED ROTATIONS OF THE THORACICSPINE

Objective. To provide preliminary data on three-dimensional thoracic s pine kinematics measured in vivo. Design. This study measured the thre e planes of thoracic spine motion in normal subjects using an external measuring device. Background. Few studies have investigated the prima ry and associated coupled rotations in the thoracic spine in vivo. Mos t knowledge of motion characteristics comes from in vitro studies whic h have limitations. There is a lack of agreement on the patterns of th oracic coupled motion especially that between lateral flexion and axia l rotation. Methods. Thoracic motion was examined in 60 normal subject s (30 males, 30 females) aged 18-24 years. The primary and coupled rot ations of the thoracic regions T-1-4, T-4-8, T-8-12 were measured usin g a 3 SPACE Fastrak system. Results. The three thoracic regions displa yed the characteristic variations in range and distribution of primary rotations previously described. The pattern of coupled motion varied between subjects but an ipsilateral pattern predominated between later al flexion and axial rotation in the middle and lower thoracic regions while the upper thoracic region was found to exhibit either a contral ateral or ipsilateral pattern. Gender did not influence results. Concl usions. The pattern of coupled motion in the thoracic spine demonstrat ed some variability between subjects in vivo. Lateral flexion and axia l rotation were strongly coupled with overall, their relationship bein g predominantly ipsilateral.