Growth modulation techniques: Tethering

Abstract

The current standard of care for severe progressive spinal deformity in growing children is deformity correction with spinal fusion and instrumentation, sacrificing both motion and further spinal growth. A possible etiology of idiopathic scoliosis is associated with disproportionate overgrowth of the anterior spinal column compared to the posterior column creating deformity in the sagittal plane (hypokyphosis) that ultimately leads to coronal (scoliosis) and axial plane (rib and lumbar prominence) deformities. In theory, application of compression to the convex and anterior sides of the vertebrae decreases anterolateral growth (Hueter–Volkmann principle), while allowing growth on the concave and posterior side. Animal models and preliminary clinical experience suggest that spinal growth can be modulated in this way using a flexible tether applied to the convex side of scoliotic vertebra, spanning the intervening disks. Experimental studies suggest that disk health is preserved with a flexible tether as disk motion is maintained during the growth period. The dawn of 3-dimensional imaging to potentially plan for precise placement of a tether to address the specific deformity is arriving. Anterolateral tethering may be performed via a thoracoscopic spinal approach, thus reducing surgical morbidity related to thoracotomy or the posterior approach. Initial results of anterolateral tethering in growing patients with spinal deformities are promising.