Telescoping IM Nail Magnetic Actuation Mechanism
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Solution Overview
Problem
Current limb lengthening techniques, such as those using external fixators and implanted mechanical devices, are invasive and cumbersome, lacking a non-invasive, efficient method for adjusting the length of intramedullary nails to address limb length discrepancies.
Innovation Solution
A telescoping intramedullary nail system with a magnetic actuating mechanism, featuring a proximal outer body, a distal body, and a threaded shaft, where rotation of inner and outer magnets imparts axial movement to the nail, allowing for non-invasive lengthening or shortening through a rotating mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external fixators or implanted mechanical devices are used for limb lengthening, then the bone can be distracted to achieve lengthening, but the procedure becomes invasive and cumbersome with increased surgical complexity
Solution Approach 1:
The patent replaces complex mechanical actuation systems (motors, hydraulics, pneumatics) with a magnetic field-based actuation system. External magnets interact with an internal magnet through magnetic attraction/repulsion forces to actuate the telescoping mechanism, eliminating the need for invasive mechanical drive trains while maintaining reliable bone distraction capability
Solution Approach 2:
The patent employs a telescoping intramedullary nail structure where one nail segment is inserted within another segment. This nested configuration allows the nail to change length through relative telescoping motion of the segments, driven by the magnetic actuation system, thereby achieving length adjustment without external mechanical complexity
2Adaptability or versatility
If traditional mechanical actuation mechanisms are implanted, then the IM nail can be adjusted for length, but the device becomes more invasive and less comfortable for the patient
Solution Approach 1:
The patent substitutes implanted mechanical actuators (motors, pumps, ratchets) with a non-invasive magnetic actuation system. The external magnet application allows length adjustment without surgical implantation of complex mechanical devices, significantly improving patient comfort while preserving full length adjustment capability
Solution Approach 2:
The patent introduces a magnetic field as an intermediary between the external actuator and the internal IM nail mechanism. The magnetic field transmits actuation forces through tissue without physical contact or invasive mechanical connections, enabling comfortable non-invasive operation while maintaining adaptability
3Force
If invasive mechanical devices are used for IM nail actuation, then the distraction force can be applied, but the surgical procedure becomes more complex and time-consuming
Solution Approach 1:
The patent replaces invasive mechanical drive mechanisms with a magnetic actuation system that can be applied externally. This eliminates the need for complex surgical implantation of mechanical actuators, significantly reducing surgical time while maintaining the capability to generate and control distraction forces for bone lengthening
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
Enables non-invasive and efficient length adjustment of the intramedullary nail, reducing surgical complexity and improving patient comfort by utilizing a magnetic actuating mechanism that allows for distraction or contraction of the nail without the need for external fixators.
Implementation Method 1
The outer magnet is rotatably accommodated in its own housing, equipped with a drive mechanism for rotating the outer magnet about an axis that is parallel to the axis of the inner magnet of an IM nail. Imparting rotation to the outer magnet imparts rotation to the inner magnet disposed within the proximal outer body of the IM nail.
Data Source
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AI summary
A length-adjustable IM nail system includes a telescoping IM nail with proximal and distal bodies. An inner magnet within the proximal body is connected to a threaded rod which, in turn, is connected to the distal body. The threaded rod passes through a threaded block which is connected to the proximal body. The position of the distal end of the threaded rod is fixed with respect to the distal body, but may rotate freely within this fixed position. An actuator is also disclosed that includes a pair of rotating magnets disposed in an angular relationship with each other and the axis of the IM nail and the patient's limb. Rotation of these outer magnets in the same direction results in rotation of the inner magnet and threaded rod and a telescoping axial movement of the threaded block and proximal body with respect to the distal body.