Anterior spinal tethering is a technique designed to alter the growth of an immature patient with thoracic scoliosis. The basic premise is that vertebral growth and alignment can be mechanically altered in a positive way by applying a flexible tether along the lateral aspect of the vertebral bodies. Much the way stapling and plating asymmetrically across the physis of long bones in children has been used to correct limb alignment, so have tethering procedures been applied in the setting of scoliosis. Altered growth of the scoliotic spine results in a three-dimensional deformity of the spine associated with a coronal plane curvature, axial plane rotation, and frequently a loss of thoracic kyphosis. Tethering the anterior column via the chest on the convex side of the curve is performed in hopes of directly addressing the coronal and sagittal deformities and ultimately leading to couple rotational correction.

The indications for such a procedure have not been clearly established, and there are various opinions on which curves in which patients made ideal candidates for this relatively new approach to managing scoliosis. If the goal is growth modulation, then clearly “significant” growth should be remaining. It is my intention to grow the spine into an improved alignment as I have little faith that long-term correction can be achieved with an unfused instrumentation procedure. As the indications for this approach are defined, I prefer to limit such a growth-modulating approach to patients who are Risser stage 0 with greater than 2 years of growth remaining. On the other hand, juveniles may have relatively small vertebrae in the thoracic region compared with available tethering implants. A lower age limit of approximately 9 years is suggested.

Curve size is also critical—too large a curve and the instrumentation may not be able to alter the mechanics of growth sufficiently to create improvement; too small a curve may result in rapid overcorrection or unnecessary surgery. Only patients with curves that would otherwise require spinal fusion procedures are those considered for surgical tethering. This sets the lower limit at approximately 45 degrees for those patients progressing despite bracing. The upper limit is poorly defined at present but likely is in the 60- to 70-degree range.

The tether seems most appropriate for single major thoracic curves, although the magnitude of compensatory curves that will respond spontaneously as the thoracic curve improves is unclear both for the upper thoracic and lumbar regions. Curves in the upper thoracic and lumbar spine should not be so large as to be indicated for spinal fusion on their own. The formation and segmentation of the vertebrae should be normal.