Nitinol Joint Spacer for Stress Distribution
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Solution Overview
Problem
Biological joints can deteriorate due to various factors, leading to pain, limited mobility, and the need for surgical intervention, with existing fusion methods causing long-term stress on adjacent joints and limiting motion.
Innovation Solution
A surgically implantable spacer made of nitinol, with martensitic properties, is designed to be inserted between bones, featuring segment defining slots, a threaded shaping passage, and a blind receptacle, allowing for superelastic expansion and shape memory recovery to enhance joint support and mobility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If joint fusion is performed to address defective inter-vertebrae discs, then joint stability is improved, but motion capability deteriorates and stress on adjacent joints increases
Solution Approach 1:
The spacer is divided into multiple segments or struts that can independently deform and distribute mechanical loads, allowing the joint to maintain stability while reducing stress concentration on adjacent joints through distributed load bearing
Solution Approach 2:
The spacer utilizes phase transformation (martensitic transformation) of nitinol material to change its mechanical properties dynamically, transitioning between rigid and flexible states to adapt to different loading conditions and reduce stress on adjacent joints
2Stability of the object's composition
If joint fusion is performed to address defective inter-vertebrae discs, then joint stability is improved, but motion capability deteriorates
Solution Approach 1:
The spacer incorporates dynamic elements that allow controlled motion and deformation under physiological loads, enabling the joint to maintain both stability and motion capability through adaptive mechanical response rather than rigid fixation
Solution Approach 2:
The nitinol material's phase transformation capability allows the spacer to dynamically adjust its stiffness and mechanical properties in response to temperature and stress changes, providing both stability and motion as needed
3Stability of the object's composition
If a rigid spacer is used to provide joint support, then joint stability is improved, but adaptability to motion deteriorates
Solution Approach 1:
The spacer utilizes phase transformation (martensitic transformation) of nitinol material to change its mechanical properties dynamically, transitioning between rigid and flexible states to adapt to different loading conditions and motion requirements
Solution Approach 2:
The spacer incorporates dynamic deformation capabilities through superelasticity and shape memory effects, allowing it to adapt its structural properties in real-time to maintain both support and motion adaptability
4Stability of the object's composition
If additional surgical procedures are performed to fuse other spinal regions, then joint stability is improved, but device complexity and surgical invasiveness increase
Solution Approach 1:
The spacer is designed to provide multiple functions including load bearing, motion control, and stress distribution within a single device, eliminating the need for additional fusion procedures and reducing overall surgical complexity
Solution Approach 2:
The segmented design of the spacer allows it to distribute mechanical loads across multiple points, providing comprehensive spinal support that prevents the need for additional fusion procedures in adjacent regions
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 spacer provides enhanced joint stability and mobility by allowing for superelastic expansion and shape memory recovery, reducing the need for additional surgical procedures and minimizing stress on adjacent joints.
Implementation Method 1
Superelasticity occurs at a narrow temperature range below its transformation temperature; in this case, no heating is necessary to cause the undeformed shape to recover, and the material exhibits enormous elasticity, some 10-30 times that of ordinary metal
Implementation Method 2
Shape memory refers to the ability of nitinol to undergo deformation at one temperature, and then recover its original, undeformed shape upon heating above its 'transformation temperature'
Implementation Method 3
One of these material compositions is Nickel titanium, also known as nitinol. Nitinol is a metal alloy of nickel and titanium, where the two elements are present in roughly equal atomic percentages. Nitinol alloys exhibit two closely related and unique properties: shape memory and superelasticity
Data Source
AI summary
A spacer formed of an intermetallic compound, such as nitinol. The spacer includes at least two segments shaped in opposing arches. The unique properties of the intermetallic compound enable the material to be deformed into a planar, insertable shape when the material is cooled below a transition temperature and returns to the undeformed shape when the material returns to an ambient, operational temperature. An expansion mechanism assembly engages with the spacer to apply an expansion force, extending the spacer longitudinally drawing the spacer into the planar configuration. The expansion mechanism assembly can be used to guide the spacer into the desired position within the patient. The spacer control mechanism assembly is subsequently removed, relieving the expansion force, returning the spacer to the natural un-deformed, arched shape as it returns to body temperature. Retention features can be integrated in the spacer to aid in retaining the spacer in location.