Bearing Surfaces in Spinal Arthroplasty

Disc degeneration and associated disorders are among the most debated topics in the orthopedic literature over the past few decades. These may be attributed to interrelated mechanical, biochemical, and environmental factors. The treatment options vary from conservative approaches to surgery, depending on the severity of degeneration and response to conservative therapies. Spinal fusion is considered to be the “gold standard” in surgical methods till date. However, the association of adjacent level degeneration has led to the evolution of motion preservation technologies like spinal arthroplasty and posterior dynamic stabilization systems. These new technologies are aimed to address pain and preserve motion while maintaining a proper load sharing among various spinal elements. This paper provides an elaborative biomechanical review of the technologies aimed to address the disc degeneration and reiterates the point that biomechanical efficacy followed by long-term clinical success will allow these nonfusion technologies as alternatives to fusion, at least in certain patient population.

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

Volume 2: 32nd Mechanisms and Robotics Conference, Parts A and B ◽

10.1115/detc2008-50121 ◽

2008 ◽

Cited By ~ 3

Author(s):

Peter A. Halverson ◽

Larry L. Howell ◽

Anton E. Bowden

Keyword(s):

Compliant Mechanisms ◽

Compliant Mechanism ◽

Spinal Mobility ◽

Rigid Fixation ◽

Spinal Disc ◽

Spinal Arthroplasty ◽

Physiological Motion ◽

The Stability ◽

The Cost ◽

Kinetics Of

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.

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