Vertebral Growth Modulation Through Periosteal Resection and Fixed Length Deformity Overcorrection: Computational and In Vivo Pilot Study.

Abstract

Vertebral body tethering (VBT) is a fusionless surgical technique for correcting spinal deformities through asymmetric growth inhibition. Standard VBT often relies on intraoperative overcorrection with an anterior center of rotation, which may decrease disc height and inhibit vertebral growth. Strategies that promote, rather than inhibit, growth could expand the vertebral growth modulation toolkit. Determine how the center of rotation location during overcorrection influences vertebral growth, and to evaluate the feasibility of growth-promoting techniques, including anterior vertebral periosteal transection and a novel uniplanar, unidirectional, length-stable posterior implant. Validated finite element model (FEM) simulated anterior versus posterior centers of rotation, assessing effects on disc height, physeal stress, and sagittal vertebral growth. Six swine underwent anterior periosteal transection, with growth rates measured against adjacent vertebrae. In a kyphotic swine model, a posterior fixed-length implant was applied across the most kyphotic disc space, shifting the center of rotation posteriorly; growth modulation was compared to non-operative controls. Computational analysis and large animal study. FEM predicted that a posterior (convex) center of rotation increased disc height, redistributed physeal stress to promote growth, and improved deformity correction, whereas an anterior center of rotation decreased disc height and inhibited growth. Periosteal transection did not accelerate vertebral growth (170 ± 19 μm/day control vs. 155 ± 25 μm/day treated; <i>p</i> = 0.054). In contrast, the posterior implant achieved overcorrection and induced corrective % appositional metaphyseal growth modulation (+24% ± 10% vs. -11% ± 13% in controls; <i>p</i> = 0.001). Periosteal resection/transection did not reliably enhance vertebral growth. Shifting the corrective center of rotation posteriorly using a fixed-length, uniplanar device preserved disc height and promoted corrective growth. Posterior, length-stable implants may serve as a viable alternative to standard VBT, especially when conventional techniques fail to shift the center of rotation away from the deformity's concavity.