Nitinol Joint Spacer for Motion Preservation
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Solution Overview
Problem
Biological joints, such as inter-vertebrae discs, hips, and shoulders, deteriorate over time due to various factors, leading to pain, limited mobility, and the need for surgical intervention, which often results in temporary motion limitation and long-term stress on adjacent joints requiring additional surgeries.
Innovation Solution
A surgically implantable spacer made of nitinol, a material with shape memory and superelasticity properties, is designed to be inserted between bones. It features segment defining slots, a threaded shaping passage, and a blind receptacle, allowing it to be shaped and inserted in a planar configuration, then returning to its original form to provide support and stability within the joint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a joint fusion procedure is performed to address defective inter-vertebrae discs, then joint stability is improved, but motion capability deteriorates and additional surgical procedures are required over time
Solution Approach 1:
The spacer is divided into multiple segments through slot formations, allowing independent movement of each segment while maintaining overall structural integrity. This segmentation enables the spacer to provide stability to the joint while preserving natural motion capabilities, avoiding the complete motion restriction caused by traditional fusion procedures.
Solution Approach 2:
The spacer utilizes phase transformation properties of nitinol material, transitioning between martensitic (deformed) and austenitic (recovered) phases. This parameter change allows the spacer to be inserted in a deformed state and then automatically return to its original shape inside the body, providing progressive stabilization while maintaining flexibility and natural joint motion.
2Stability of the object's composition
If traditional rigid spacers are used to maintain joint alignment, then joint stability is improved, but adaptability to physiological motion deteriorates
Solution Approach 1:
The spacer transitions from a static rigid structure to a dynamic adaptive structure through the use of nitinol's phase transformation properties. The material can dynamically adjust its shape and stiffness in response to physiological conditions, allowing the spacer to maintain joint alignment while adapting to natural physiological motions and loading patterns.
Solution Approach 2:
By utilizing the temperature-dependent phase transformation of nitinol, the spacer's mechanical parameters (stiffness, shape) change in response to body temperature and physiological conditions. This allows the device to be inserted in a compliant deformed state and then transform to a stabilizing recovered state, providing both alignment and adaptability.
3Ease of operation
If the spacer is inserted in its original curved configuration, then insertion ease is improved, but functional effectiveness deteriorates
Solution Approach 1:
The spacer is pre-formed with a curved configuration and segmentation slots before insertion. The preliminary curved shape allows easy insertion through the delivery system, while the pre-configured slots are positioned to segment the spacer into functional portions that will provide joint support once the material recovers its shape inside the body.
Solution Approach 2:
The spacer undergoes a parameter change from its deformed martensitic state during insertion to its recovered austenitic state after implantation. This transformation occurs automatically at body temperature, converting the easily inserted curved configuration into the functionally effective shape that provides joint support and alignment.
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 enhances joint stability and mobility by providing a durable, biocompatible solution that reduces pain and minimizes the need for additional surgical procedures by maintaining joint alignment and distributing stress effectively.
Implementation Method 1
a spacer member formed of a material having martensitic properties; Nitinol is a metal alloy of nickel and titanium... Nitinol alloys exhibit two closely related and unique properties: shape memory and superelasticity... 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 2
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
Data Source
AI summary
A spacer formed of an intermetallic compound, such as nitinol. The spacer includes 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 can engage with the spacer to apply an expansion force. The expansion force extends 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. The spacer returns to the natural undeformed shape as it returns to body temperature. Retention features can be integrated in the spacer to aid in retaining the spacer in location.