A system for differential realignment of vertebra under tension is provided. It provides a tensioning device (10) including a patient positioning means (100) a tension producing actuator (170) a positioning device (140) a patient interface device (120) and a control system (190). The control system (190) with feedback on the resultant tension vector applied to patient spine allows for adjustment of either tension producing actuator (170) position or patient position or both while applying therapeutic tension levels to the patient spine. The tensioning device (10) automatically adjusts the resultant tension vector angle such that the resultant tension vector magnitude remains ideally constant during the adjustment of the tension producing actuator (170) position or the patient position facilitating flexion of spinal segments while reducing the risk of eliciting paraspinal muscle contraction due to changes in resultant tension vector magnitude.
