Implantable spinal assist device

A compliant implantable device for restoring normal biomechanical function to a motion segment unit of the spine comprising a flexible body having a longitudinal axis, said body being curved along said longitudinal axis and being composed of a composite material comprising a fiber material interspersed in a matrix material, said body comprising a curved central section unattached to a motion segment unit and a pair of opposed terminal sections, each terminal section having respective end portions for attaching the implantable device to adjacent motion segment units, said central section being free to move in response to pressure applied to the motion segment unit to provide support for and restore normal biomechanical function to the motion segment unit.