Intramedullary Nail Shape Memory Elements Fixation
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Solution Overview
Problem
Existing intramedullary nails face issues with incomplete stabilization within the medullary canal due to the absence of bone screws, leading to potential instability and anomalies in the healing process, particularly under axial stress, and pose challenges during surgical operations with cumulative X-ray exposure.
Innovation Solution
A simplified intramedullary nail design featuring a cannulated rod with shape memory elements hosted in seats at the proximal and distal ends, secured by corresponding covers, allowing for angular positioning without the need for bone screws, utilizing Stress Induced Martensite materials like Nitinol for enhanced stability and gripping within the bone.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If shape memory elements are used to fix the intramedullary nail without bone screws, then the device complexity is reduced and surgical operation is simplified, but the stabilization reliability under axial stress deteriorates
Solution Approach 1:
The shape memory elements change their physical state from austenite (rigid, gripping configuration) to martensite (flexible, retracted configuration) in response to temperature or stress changes. This parameter change allows the elements to provide strong stabilization when needed while enabling easy insertion when retracted, resolving the contradiction between stabilization reliability and device complexity
Solution Approach 2:
The intramedullary nail combines traditional metallic rod material with shape memory alloy elements (such as Nitinol) to create a composite structure. The shape memory elements provide enhanced stabilization capability without requiring additional bone screws, maintaining reliability while reducing overall device complexity
2Ease of operation
If shape memory elements are retracted in seats during insertion, then the ease of operation during insertion is improved, but the stabilization capability under axial stress worsens
Solution Approach 1:
The shape memory elements transition dynamically between two states: retracted within seats during insertion (flexible, low profile) and extended through slots during stabilization (rigid, gripping). This dynamic state change allows the system to optimize for ease of operation during insertion and for stabilization strength during use, resolving the contradiction between these two requirements
3Reliability
If multiple shape memory elements are distributed at proximal and distal ends, then the stabilization distribution is improved, but the device complexity increases
Solution Approach 1:
The shape memory stabilization system is segmented into multiple discrete elements distributed at the proximal and distal ends of the intramedullary nail. This segmentation provides balanced stabilization distribution along the bone length without requiring complex control mechanisms, as each element operates independently based on its local stress/temperature conditions
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 design provides stable fixation within the medullary canal without bone screws, reducing production costs and eliminating the need for surgical insertion of stabilizing elements, while ensuring effective osteosynthesis and minimizing risks of bone dysmetria and rotation.
Implementation Method 1
shape memory elements hosted in corresponding seats of said rod; each elements being able to assume a configuration wherein is retractably housed in its respective seats, so to allow the insertion of the nail in the bone
Implementation Method 2
another configuration wherein said elements are projecting from slots opening of said sleeve
Implementation Method 3
utilizing Stress Induced Martensite materials like Nitinol for enhanced stability and gripping within the bone
Data Source
AI summary
An intramedullary nail for a fractured elongated bone, comprising a cannulated rod having proximal and distal ends; an outside tubular sleeve for coaxially hosting and guiding the rod; and shape memory elements hosted in corresponding seats of the rod. Each shape memory element can be retractably housed in its respective seat in a first configuration, allowing insertion of the nail into the bone, and can project from a sleeve opening in another configuration. Proximal and distal pairs of the elements are provided at the proximal and distal rod ends. The proximal element pair lie on a same plane and are kept in their seats by a proximal cover. The distal element pair lie on an offset plane to the plane of the proximal element pair and are kept in their seats by a distal cover. This removes the need for bone screws to stabilize the nail inside the medullary canal.