• Criteria for selective TL/L scoliosis instrumentation:

• The standard technique is to include the entire Cobb measurement.

• Hall et al. (1997) described a technique for short-segment selective instrumentation. In their initial discussion, structural curvatures greater than 60° and thoracic curvatures that did not correct to 20° or less on the corrective radiographs were excluded. The criteria are based on both the standing posteroanterior (PA) and the supine anteroposterior (AP) bend radiographs.

 Standing PA radiograph: Select the apex. If this is a disk space, include the two cephalad and caudal vertebral bodies (four bodies, three disks). If a vertebral body, include one cephalad and one caudal segment (three vertebrae and two disks).

 Supine AP active bend: Include those interspaces that do not “reverse.”

 When levels between the two views differ, choose the longer of the constructs.

 This technique will often save one or even two motion segments.

 An example of the short-segment technique is shown in Figure 1. The end vertebrae are T11 and L3. On the standing PA view (Fig. 1A), the apex is the T12-L1 disk. The levels are two above and two below: T11-L2. On the supine bend view, the thoracic curvature is flexible (Fig. 1C). The T10-11 and L2-3 disks reverse, and can be excluded (Fig. 1D). Here the method spares two motion segments. The curvature has been reversed, and there is spontaneous improvement of the thoracic deformity and excellent balance (Fig. 1E). Normal sagittal alignment is maintained (Fig. 1F).

• The end instrumented vertebrae are often short of the Cobb terminals. In order to avoid imbalance, the deformity must be overcorrected by about 10°. This will frequently create an adjacent wedged disk space.

 In Figure 2A and 2B, use of the short-segment technique with the overcorrection required to balance the spine produced subjacent disk wedging.

 In Figure 3A–D, the lowest end vertebra (LEV) and lowest instrumented vertebra (LIV) coincide. There is no subjacent disk wedging. Note that the preoperative thoracolumbar kyphosis has been corrected by a single rod with structural interbody graft.

 In Figure 4A and 4B, the LIV is clearly short of the LEV, but there is only mild subjacent disk wedging.

• Either single-rod or dual-rod instrumentation may be used. In the patient in Figure 5A–D, the dual-rod system required no structural graft to maintain the sagittal alignment. We have not been able to obtain the same amount of coronal plane correction (overcorrection) with the present dual-rod systems.

• Once they leave the ribs and costal cartilage, the intercostal neurovascular bundles pass obliquely across the abdominal wall in the interval between the internal oblique and transversalis muscles. The 10th bundle is directed to the level of the umbilicus, the 9th several centimeters above, the 11th between the umbilicus and pubis, and the 12th toward the inguinal area.

• The musculophrenic branch of the internal mammary artery and its vein lie behind the costal arch between ribs 7–10 and anastomose with the intercostal vessels. It must be cauterized or ligated when the arch is divided.

• Intercostal nerves 7–12 innervate the rectus muscle, penetrating it at its lateral border. Incisions along this semilunar line will denervate the muscle.

• The flat radiolucent table shown in Figure 9 permits biplanar imaging. The patient is placed in the lateral decubitus position with bolsters holding the pelvis. The upper torso is taped. A roll is positioned several fingerbreadths below the axilla.

• A conventional table permits better support via kidney rests and may first be flexed to facilitate the approach and then lowered to allow the spine to fall into a corrected position prior to instrumentation manipulation.

• Entry level selection: A horizontal line is drawn from the curve apex (see dashed line in Fig. 1A). The rib on the convexity of the deformity that is intersected at the lateral-most portion of the standing PA radiograph is selected. In general, the 9th rib is used when exposure of the T11-12 level is required, and the 10th rib for the T12-L1 level.