Anterior Spinal Fusion for Thoracolumbar Idiopathic Scoliosis

Anterior Spinal Fusion for Thoracolumbar Idiopathic Scoliosis

Franklin Keith Gettys

Daniel J. Sucato


Patients who plan to undergo an anterior spinal fusion and instrumentation (ASFI) for thoracolum-bar/lumbar curves should be evaluated both clinically and radiographically. The clinical examination should focus on the patient’s trunk balance, spinal deformity, waistline asymmetry, and neurologic status. Assessment of trunk balance should determine whether a trunk imbalance is present and its direction. If a thoracic curve appears to have some structural characteristics clinically, then an ASF of a thoracolumbar/lumbar curve would accentuate the prominence and result in a poor cosmetic result (2). The typical patient with a thoracolumbar/lumbar curve who would require surgery will have a trunk shift to the convexity of that curve (usually left side), which can be quantified by measuring the deviation from a plumb bob to the center of the sacrum. This is also associated with significant waistline asymmetry. Neurologic examination is always important in these patients to ensure that there is no indication to obtain an MRI to assess for neural axis abnormalities (3). The abdominal reflexes are especially important in the assessment of the patient with presumed idiopathic scoliosis and should be symmetric (bilaterally absent or present).

Radiographic assessment should rely on the periapical (PA) as well as the lateral radiograph. The PA radiograph is used to measure the coronal measurements of the upper thoracic, main thoracic, and thoracolumbar/lumbar curves. It should be used to assess the apical vertebral translation to ensure that this is truly a structural thoracolumbar/lumbar curve without a structural thoracic curve. The skeletal maturity can be assessed by evaluating the status of the triradiate cartilage and the Risser sign. The lateral radiographs should be used to measure the amount of lumbar lordosis. Junctional kyphosis between the main thoracic and thoracolumbar/lumbar curve would indicate structurality of both curves and preclude isolated fusion and instrumentation of the thoracolumbar/lumbar curve. The supine bend radiographs can be used to assess the flexibility of the curve. This is important in preoperative planning and may dictate the extent of the discectomy and whether resection of the posterior annulus and the posterior longitudinal ligament (PLL) is necessary to obtain satisfactory correction.

The PA radiograph is the main imaging study to plan surgical levels (Fig. 37-1). The most accepted fusion level planning is to include all vertebrae within the thoracolumbar/lumbar curve (inclusion
from proximal to distal end vertebrae). The most common thoracolumbar/lumbar curve is measured from T11 to L3, and they are the most common fusion levels. Supine best-bend radiographs do not generally assist in choosing fusion levels but are utilized to ensure that the thoracic curve is not structural.

FIGURE 37-1 A. AP radiograph of a patient with a left thoracolumbar/lumbar (T/L) idiopathic scoliosis. The left T/L curve is measured from T11 to L3 to be 50 degrees. The planned fusion levels would be from T11 to L3 (the Cobb end vertebrae). The right thoracic compensatory curve does not cross the midline and measures 20 degrees. B. Lateral radiograph reveals normal sagittal contour.

Hall et al. have popularized the concept of a short anterior fusion. The criteria for this technique included curves less than 60 degrees, which were relatively flexible, and fusion levels were based upon whether the apex was at the disc or at a vertebral body. If it were at a vertebral body, then fusion one segment above and one segment below this apical vertebral body would yield a satisfactory correction. When the apical segment is a disc, then fusion and instrumentation would occur two segments above and two segments below this apical disc. It is important to understand that overcorrection of the curve would be necessary to achieve good results using this strategy (4).

Jun 13, 2016 | Posted by in ORTHOPEDIC | Comments Off on Anterior Spinal Fusion for Thoracolumbar Idiopathic Scoliosis

Full access? Get Clinical Tree

Get Clinical Tree app for offline access