A Flexure-Based Bi-Axial Contact-Aided Compliant Mechanism for Spinal Arthroplasty

A healthy spinal disc is capable of 3 degrees of rotation and has a force-deflection response that helps to stabilize the spine. Age or trauma can cause the stability of the spine to decrease. Spinal fusion, the current surgical treatment of choice, stabilizes the spine by rigid fixation, reducing spinal mobility at the cost of increased stress at adjacent levels. This paper introduces a compliant mechanism that has the potential to closely mimic the physiological motion profile of the natural spinal disc. Compliant mechanisms have properties that make them well suited for spinal implants that restores the range of motion and the forcedeflection response of the spine. This paper presents an introduction to the biomechanics of the spinal disc, reviews the state of the art in spinal care, and proposes the use of the Flexure-based Bi-Axial Contact-aided (Flex-BAC) compliant mechanism as a spinal arthroplasty device (artificial disc). The Flex-BAC compliant mechanism offers the potential to restore both the kinematics and kinetics of a damaged spinal disc. The disc provides the ability to eliminate wear through rolling. An overview of the device and a preliminary kinematic and kinetic analysis are given.