Design of a minimally invasive non fusion device for the surgical management of scoliosis in the skeletally immature.

Current management of scoliosis in the skeletally immature focuses on prevention of curve progression. Progressive curves require surgical instrumentation without fusion with periodic lengthening of the construct, continuous bracing and ultimately fusion of the curve when control is lost at the adolescent growth spurt. This treatment regime has a major negative impact on the childs biopsychosocial profile and yields relatively poor longterm results. The aim of this study was to define the ideal characteristics of a growing rod and design a novel implant based on these characteristics. The method used was logical thought to define the desired implant characteristics and then design an implant which approximated the theoretical model as closely as possible. An ideal growing rod would grow with the spine, correct the deformity as growth occurred, leave no residual deformity at maturity, not require activity restriction/bracing, not require fusion at maturity and be compatible with a minimally invasive surgical technique. The ideal growing rod (IGR) is modular consisting of a number of units linked together which conform to the shape of the deformed spine. Each unit spans a disc space and consists of a telescopic rod with one end attached to the vertebra above and the other to the vertebra below. The rod is pushed apart by the force of growth but can only elongate in a predetermined direction resulting in a three dimensional realignment of the instrumented spinal segments with growth. In conclusion it is possible to design a growing rod with theoretical advantages over current constructs.