Measuring movement at the low back

The clinical importance of movements of the human spine is increasingly being realized but their measurement is difficult to carry out. Traditionally, measurement of spinal motion focuses on the lumbar spine as the mobile region and movement at the lower thoracic spine is largely ignored. The aim of this study was to test the hypothesis that sagittal movement at the low back is not confined to the lumbar spine. The range of sagittal movement and the amount of skin distraction during trunk flexion was studied in 10 normal subjects. Angular movement in the sagittal plane between the vertebra prominens and S2 ranged between 40° and 83° among the subjects. Concomitant skin distraction showed that a mean of 32% (range 20-41%) of the movement between the upper thorax and sacropelvis occurred cranial to T12. We therefore suggest that the term "low back" should be applied to a series of mobile vertebrae in the lower thoracic and lumbar spines and that motion of this region in the sagittal plane should be considered as the movement of an immobile upper thoracic spine relative to the sacropelvis.