Surgical aspects of spinal growth modulation in scoliosis correction.

Spine growth modulation for scoliosis correction is a technique for slowing growth on the convex side of the curve and enhancing growth on the concave side by using the Heuter-Volkmann principle; this results in gradual deformity correction. The theoretic advantages include speedier recovery because of the minimally invasive approach used, as well as motion preservation. Several devices have been used in humans, including vertebral body stapling, with either a flexible titanium clip or a nitinol staple, and anterior spinal tethering. Prerequisites for the use of these devices are a relatively flexible curve and sufficient remaining growth in the patient. Although vertebral body stapling is effective for moderate curves of less than 40°, anterior spinal tethering can be used for curves greater than 40°. The titanium clip and spinal tethers are used exclusively for thoracic scoliosis, whereas nitinol staples can be used for the thoracic spine or the lumbar spine. The thoracoscopic technique is used for thoracic instrumentation, and the mini-open retroperitoneal technique is used for lumbar staple insertion. The insertion of a titanium clip and an anterior spinal tether requires sacrifice and mobilization of the segmental vessels, whereas nitinol staples can be inserted without such sacrifice. Single lung ventilation and CO2 insufflation are used to improve visualization with the thoracoscope. The curve should be instrumented from an end vertebra to an end vertebra. Postoperative immobilization depends on the type of device used. Most complications are approach related, such as atelectasis caused by a mucus plug, pain at the chest tube site, and pneumothorax. Device-related complications are rare. Overcorrection is a concern. In patients with early onset scoliosis, a hybrid construct with vertebral stapling and growing rods or a vertical expandable prosthetic titanium rib has been suggested. A failure of the spinal growth modulation procedure does not preclude spinal fusion. None of the devices for spine growth modulation have been approved by the FDA for human use and are still investigational. Early results are promising, and continued clinical studies are necessary.