**1. Introduction**

Adolescent idiopathic scoliosis (AIS) is a condition that affects 1–3% of children aged 10–16 years [1]. A structural lateral curvature of the spine with a rotational component develops in

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2017 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

otherwise healthy teenagers during puberty. Mild or moderate curves pose no health threats but may be associated with cosmetic concerns. Teenagers with mild deformities are placed under clinical surveillance and are encouraged to exercise, those with larger curves (more than 25°) are braced, while skeletally immature patients with thoracic curves exceeding 45° are candidates for surgical intervention [2]. Patients with thoracolumbar or lumbar curves usually undergo surgery with a lower than the traditional 45°Cobb angle threshold [3]. The standard surgical procedure for AIS is a spinal fusion of 8–10 vertebrae. Although surgical fusion is a successful solution for progressive spinal deformity, fusion leads to loss of spine mobility and may cause painful disc degeneration at the junctions of the mobile spine with the fused segments.

Non-fusion surgical solutions addressing moderate AIS curves may, therefore, be desirable alternatives to the traditional standard care of fusion. To this end, growth-modulating nonfusion procedures have been developed such as convex vertebral body stapling and/or convex vertebral body tethering as a surgical alternative for idiopathic scoliosis [4–6]. Stapling or tethering necessitate an anterior surgical approach to the spine and are both relatively extensive procedures. An intermediate posterior fusionless and less complex surgical approach for moderate AIS may be helpful. The ApiFix® system was developed to fill this missing gap [7].

ApiFix® is a new posterior dynamic device consisting of an expandable ratcheting rod anchored by two pedicle screws to the concave side of the scoliotic spine. Surgery is performed without the addition of spine fusion of the instrumented segments. Deformity correction is achieved by distraction leading to rod elongation. Curve correction is achieved not only during surgery but also after the surgical procedure by performing scoliosis specific exercises. These exercises activate the ratchet with further rod expansion and curve reduction.Early experience with the ApiFix® device showed it to be a viable alternative to fusion in reducing and maintaining correction of moderate AIS curves [7].
