Viscoelastic behaviour of deformed spines under correction with halo pelvic distraction

The applied tensile tractive force between skull and pelvis of the Halo Pelvic Distraction appliance has been measured using a simple compression spring device. Details of these external force measurements with daily distraction and correction of spinal deformity are illustrated for 10 patients which include tuberculous kyphoses, paralytic scolioses, and congenital and idiopathic scolioses. The relationships between applied load, time, amount of distraction, and extent of spinal curvature were studied in terms of the biomechanical proerties of elasticity and plasticity. A linear relationship exists between the total distraction distance and the reduction in the angle of the spinal deformity. For this correction procedure the rates of distraction, the total distraction amount, the total duration of the distractional period, and the maximum load depend on each individual spinal deformity with its particular peculiarities.