Intramedullary Nail Shape Memory Fixation
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Solution Overview
Problem
Intramedullary nails face challenges with incomplete stability under axial stresses and the need for X-ray exposure during surgical operations due to the absence of visible distal holes, which can compromise osteosynthesis and healing.
Innovation Solution
A cannulated intramedullary nail with a tubular sleeve and shape-memory elements that project from slots to provide stability and grip within the medullary canal, using a single stabilizing screw and distal shape-memory elements for secure fixation, allowing for easier insertion and removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional intramedullary nails with bone screw holes are used, then stable fixation is achieved, but X-ray exposure and surgical complexity increase due to the need for drilling holes in correspondence with nail holes
Solution Approach 1:
The invention extracts and eliminates the need for distal bone screw holes by using shape-memory elements that provide fixation through expansion within the medullary canal. The shape-memory elements replace the function of distal bone screws, removing the requirement for distal holes and thereby eliminating the associated X-ray exposure and surgical complexity.
Solution Approach 2:
The shape-memory elements utilize phase transformation (parameter change) of the material structure to achieve fixation. The elements transform from a compressed state during insertion to an expanded state at body temperature, providing stable fixation without requiring pre-drilled holes. This parameter change enables fixation stability while avoiding the harmful effects of multiple drilling operations.
2Ease of operation
If shape-memory elements alone are used for fixation, then surgical simplicity is improved, but stability under axial stresses is insufficient
Solution Approach 1:
The invention merges two fixation approaches: proximal bone screw fixation through traditional holes and distal fixation through expanding shape-memory elements. This combination provides both the surgical simplicity of shape-memory technology and the stability of mechanical bone screw fixation, resolving the contradiction between ease of operation and strength under axial stress.
3Ease of operation
If shape-memory elements are housed in seats on the rod, then insertion is facilitated, but structural complexity increases with the addition of tubular sleeve and seat structures
Solution Approach 1:
The shape-memory elements are nested within seats on the cannulated rod, and the entire assembly is inserted into the medullary canal. This nesting approach facilitates insertion by containing the shape-memory elements within the rod structure during insertion, while the elements expand after insertion to provide fixation. The tubular sleeve provides a protective housing that simplifies the overall construction while enabling the complex function of shape-memory fixation.
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 enhances stability and reduces X-ray exposure by using shape-memory elements to grip the bone, providing improved fixation and ease of removal, combining the benefits of shape-memory materials and traditional bone screws.
Implementation Method 1
shape-memory elements housed in corresponding seats on said rod; each of the elements being able to assume a configuration in which it is retractably housed in its respective seat, so as to allow the insertion of the nail in the bone, and another configuration in which said elements project from slots in said sleeve
Data Source
Figure 1
Figure 2~3
Figure 4A~4D
AI summary
The invention concerns an intramedullary nail to be inserted into a fractured elongated bone and comprising: a cannulated rod (2) extending between a proximal end (3) and a distal end (4); an outside tubular sleeve (5) for receiving said rod (2), the rod (2) being coaxial with the sleeve (5) and axially guided inside the tubular sleeve (5); shape-memory elements (7) housed in corresponding seats (6) of said rod (2); each of the shape-memory elements (7) able to assume a configuration of rest in which said shape-memory elements (7) are housed in their respective seats (6) to allow the nail to be inserted into the bone, and a configuration of use in which said shape-memory elements (7) are projecting from slots (8) in said sleeve (5).