Total Disc Replacement Rigid Constraint Mechanism
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Solution Overview
Problem
Current total disc replacement devices fail to rigidly limit lateral motion and pivoting of apposition members relative to each other, as existing constraint mechanisms are either too elastic or not effectively designed to mimic natural intervertebral disc motion patterns.
Innovation Solution
A total disc replacement device with a central axis, featuring first and second apposition members with intermediate surfaces and an elastic spacer between them, where the intermediate surfaces of the apposition members are equipped with rigid constraint means that create a gap, allowing for dampened motion and eventual rigid limitation of lateral motion, mimicking natural spinal segment behavior.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If elastic constraint means are used in the resilient central body, then the device allows motion between apposition members, but the lateral motion cannot be rigidly limited
Solution Approach 1:
The constraint means are divided into two distinct segments: rigid constraint means arranged on the apposition members for reliable lateral motion limitation, and elastic constraint means arranged on the resilient central body for dampened motion. This segmentation allows each segment to perform its specific function optimally without compromise.
Solution Approach 2:
The resilient central body acts as an intermediary element between the rigid constraint means on opposing apposition members. It transmits and dampens forces while allowing controlled motion, bridging the gap between rigid structural requirements and flexible motion requirements.
2Device complexity
If rigid constraint means are arranged only on the resilient central body, then the device structure is simplified, but the lateral motion limitation is not rigid
Solution Approach 1:
Instead of placing constraint means only on the resilient central body as conventionally done, the invention inverts the arrangement by placing rigid constraint means on the rigid apposition members themselves. This inversion ensures that the rigid structural elements directly provide the rigid motion limitation required.
3Reliability
If the gap between constraint means is closed in the unloaded state, then rigid lateral limitation is achieved, but dampened motion is lost
Solution Approach 1:
The gap width between constraint means is optimized to a specific parameter range (0.1-5mm) that allows the system to transition between two states: dampened motion when the gap is open under normal loads, and rigid limitation when the gap closes under extreme loads. This parameter optimization resolves the contradiction between the two opposing requirements.
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 device effectively limits lateral and antero-posterior translation of vertebral bodies, protects facet joints, dampens motion, acts as a soft break during extreme bending, restores the lordotic curve, and allows for superposed motion similar to natural intervertebral discs, while maintaining structural integrity.
Implementation Method 1
an elastic spacer (4) disposed between said intermediate surfaces (8, 10) of said first and second apposition members (2, 3)
Data Source
AI summary
An intervertebral implant for implantation between an upper vertebra and a lower vertebra having a central axis. The implant may have a first member with a top surface for contacting at least a portion of the upper vertebra and a bottom surface as well as a second member with a top surface and a bottom surface for contacting at least a portion of the lower vertebra. An elastic spacer may be disposed between the first member and the second member. Contraints may be employed to to limit the amount of lateral movement between the first and second members.