Abstract
Introduction
Surgical correction of spinal deformities is a challenge; segmental instrumentation controlling almost every level is the most recent approach. Correction of the deformity only through apical manipulation has many potential advantages, including little tissue disruption, less invasive intervention, preservation of spinal mobility, and vertebral growth. However, quantification of the amount of force needed to pull on the apex and its effect on translation, de-rotation, and overall correction of the curve needs to be studied. The purpose of this study is to determine the effect and amount of force needed to pull on the apex of a scoliotic deformity towards the midline, and the feasibility of use of this novel potential method of correction in the treatment of patients with adolescent idiopathic scoliosis (AIS).
Methods
Measurements were taken from 20 patients with AIS treated between June, 2009, and January, 2010. There were 16 female and 4 male patients with an average age of 14.2 years (range 11–20); the coronal preoperative Cobb angle was 67° (42–108°), decreasing on bending to 39° (8–83°), and the apex of the deformity was between T6 and L2. All patients had proximal and distal anchors spanning two levels on each end; the anchors were connected by a concave rod to which the apical vertebra was pulled. We measured the distance between the rod and the apical vertebra and the rotation of the apical vertebrae.
Results
In 17 patients a force of 30 lb was applied and in 14 patients the force reached 40 lb. The apical baseline distance was 20.9 mm (10–40); at 30 lb of pull it decreased to 11.9 mm (0–27) and at 40 lb it was 9.4 mm (0–23) or 55% translation. The change in apical rotation was measured in 12 patients. The apex de-rotated in 10 of 12 patients, with a mean rotation of 5.2° (2–10°).
Conclusions
Apical translation, vertebral de-rotation, and scoliosis correction can be done by application of a force pulling on a convex anchor at the apex of the curve towards a concave rod. With suitable instrumentation, deformity correction via manipulation of the apical vertebral body can be a valid treatment alternative through a less invasive approach, with little anatomical, biomechanical, and growth potential disruption.
