Spinal Elastic Constraint for Motion Restriction
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Solution Overview
Problem
Current spinal implants that restrict flexion for discogenic pain often provide inconsistent elastic tension, risk damage to vertebrae, and are bulky, making them difficult to implant and prone to failure, while existing treatments for discogenic pain are limited and ineffective.
Innovation Solution
The development of spinal implants with elastic constraints that increase bending stiffness during flexion by coupling compliance members with inelastic tethers between spinous processes, providing controlled elastic resistance and minimizing risk to vertebrae, with a design that allows for dynamic flexion inhibition and reduced complexity for easier implantation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bone cerclage devices are applied to restrict spinal motion, then motion restriction is improved, but device complexity and ease of operation deteriorate due to bulky design and difficult implantation
Solution Approach 1:
The implant is divided into three functional segments: compliant members (providing elastic tension), tethers (providing directional constraint), and spinous process engagement structures. This segmentation allows each component to be optimized independently, reducing overall device complexity while maintaining motion restriction effectiveness.
Solution Approach 2:
The implant transitions from static bone cerclage devices to a dynamic system where compliant members provide elastic tension that adapts to spinal motion. The device allows controlled flexion through a defined range of motion while maintaining restriction, making implantation and adjustment more straightforward compared to rigid static devices.
2Reliability
If high tension is applied to fix the spinal segment, then motion restriction is improved, but harmful factors increase due to risk of vertebrae damage
Solution Approach 1:
The compliant members are pre-configured with elastic properties that provide cushioning protection to the vertebrae. Instead of applying high tension directly to fix the segment, the elastic compliant members absorb and distribute forces, preventing concentrated stress on vertebral structures while maintaining effective motion restriction.
Solution Approach 2:
The implant changes the mechanical parameters of spinal constraint from high-force static restriction to low-force dynamic elastic restraint. The compliant members provide sufficient tension to restrict pathological motion while maintaining forces within safe limits for vertebral health, effectively changing the force magnitude parameter from harmful to therapeutic levels.
3Reliability
If static devices are used to restrict motion, then motion control is improved, but adaptability deteriorates due to inability to allow dynamic flexion
Solution Approach 1:
The implant replaces static motion restriction with dynamic control through elastic compliant members. These members provide consistent restraining force throughout the range of motion, adapting to different spinal positions and movements. The device maintains reliable motion control during flexion while naturally allowing extension and neutral positions, providing adaptability that static devices cannot achieve.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The implants effectively limit flexion-related pain by increasing bending stiffness within specific ranges, reducing the risk of injury, and maintaining functionality over millions of cycles with minimal plasticity and creep, while allowing controlled flexion to prevent adjacent segment morbidity.
Implementation Method 1
The compliance member will comprise a body having a first tether attachment element and a second tether attachment element, where the body defines an axial tension spring between said attachments
Implementation Method 2
The tethers will have a central region adapted to be received over the spinous processes
Implementation Method 3
The elastic constraint may have an elastic tensile stiffness in the range from 7.5 N/mm to 40 N/mm
Data Source
AI summary
A system for restricting spinal flexion includes superior and inferior tether structures joined by a pair of compliance members. Compliance members comprise tension members which apply a relatively low elastic tension on the tether structures. By placing the tether structures on or over adjacent spinous processes, flexion of a spinal segment can be controlled in order to reduce pain.