(based on classification of King et al) assistance provided by Ben Allen Jr. M.D.
- See: Selection of Fusion Level:
- Discussion:
- "S" shaped thoracolumbar curve crosses midline;
- thoracic curve is larger and stiffer than lumbar curve;
- selective arthrodesis of the thoracic curve in King type II curves may lead to larger residual lumbar and loss of balance;
- over correction of main thoracic curve may be one of problems, because in lumbar curve, spontaneous correction is not sufficient to restore balance;
- treatment:
- the goal w/ this type of curve is to preserve lumbar lordosis along w/ a motion segment;
- usually w/ flexible curves less than 45 deg, lumbar fusion can be limited to L3 or higher;
- distally the up-going convex lumbar hook and the down going concave hook are placed at the same level;
- convex lumbar curve:
- down going proximal hook and up going distal hook;
- concave lumbar curve:
- down going distal hook, at same level as convex distal hook;
- concave thoracic curve:
- down going distal hook (which is also the down going hook of the upper lumbar curve;
- up going hook at apex of the curve;
- up going hook above end vertebrae;
- convex thoracic curve:
- up going hook at apex of curve which is staggered from the apex concave up going hook
- up going hook above proximal end vertebrae, which is staggered from opposite concave hook;
- if the shoulder is high on the concave side, then the convex up-going hook is placed one level caudad relative to the concanve hook;
- w/ severe asymmetry, the hook is placed two levels caudad;
- note: distraction on the concave side may elevate the ipsilateral shoulder;
- in this case, the shoulder will be low on the concave side, and therefore, the convex up-going hook is placed on level cephalad relative to the concanve hook;
- w/ severe asymmetry, the hook is placed two levels cephalad
The selection of fusion levels in thoracic idiopathic scoliosis.