Abstract: Spinal curvature modulation systems, methods and related devices and instrumentation are disclosed, which include a flexible tether, a tether tensioning unit and bone anchors for the flexible tether that allow the tether to be secured across multiple vertebrae in a region of treatment. When the flexible tether is attached to multiple vertebrae, it can be used to correct spinal deformities. Tension in the flexible tether is adjustable transcutaneously without invasive surgical procedures by use of remotely driven actuators, such as a magnet-driven motor, or by a small tool insertable through a small incision. Disclosed systems and methods thus allow for multiple adjustments of tether tension, and spinal curvature, over time without repeated, highly invasive, spinal surgeries.