Flex-BAC Artificial Spinal Disc. The Flexure-based Bi-Axial Contact-aided (Flex-BAC) compliant-mechanism-based spinal arthroplasty device (artificial disc) has the potential to closely mimic the physiological motion profile of the natural spinal disc. The Flex-BAC compliant mechanism offers the potential to restore both the kinematics and kinetics of a damaged spinal disc, and has the ability to eliminate wear. The Flex-BAC is composed of two convex surfaces of varying curvatures. These surfaces may be a series of one or more circular, elliptical, or flat segments. The curvature and length of a surface may vary in order to obtain the desired resistance to force, range of motion, location of the instantaneous axis of rotation, and kinetics. The device’s center is connected via one or more flexures as to constrain the device to roll. The endplates to which the center is connected may also contain multiple circular, elliptical, or flat segments.
Lower back pain (LBP) will afflict as much as 80% of the adult population at some point during their lifespan. Conservative estimates show that spinal arthroplasty is a viable alternative to 47.9% of the 450,000 spinal fusions that occur each year in the United States. The spinal arthroplasty market is therefore expected to encompass a 2.18 billion dollar market. A common surgical treatment for degenerative disc disease is lumbar spinal fusion. However, fusion has the several drawbacks, including less than ideal clinical success rates, inferior quality of the restored motion, increased stress on adjacent levels, and long recovery time. Similar to the paradigm shift away from hip and knee arthrodesis towards total joint replacement, there is justification for a shift from disc fusion to reconstruction. Compliant mechanisms have properties that make them uniquely suited for next-generation total disc replacements.
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Halverson, P., Bowden, A., and Howell, L.L., “Wearless Total Disc Arthroplasty through Compliant Mechanism Design,” abstract accepted for publication in Proceedings of the Eighth Annual Meeting of The Spine Arthroplasty Society, 2008.
Halverson, P.A., Howell, L.L., and Bowden, A.E., “A Flexure-based Bi-Axial Contact-aided Compliant Mechanism for Spinal Arthroplasty,” accepted for publication in Proceedings of the 32nd Annual Mechanisms & Robotics Conference at the 2008 ASME International Design Engineering Technical Conferences, Brooklyn, NY, August 3-6, 2008, DETC2008-50121.