Magnetic Intramedullary Distraction for Controlled Bone Alignment
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Solution Overview
Problem
Existing bone distraction methods, such as external fixators and intramedullary nails, are cumbersome, painful, invasive, and difficult to control, leading to complications like nonunion, early consolidation, pin track infections, and unmatched bone lengths, especially in complex fractures.
Innovation Solution
A rotational correction system using an intramedullary implant with a rotatable permanent magnet and external adjustment device, allowing controlled rotational alignment of bone sections through magnetic coupling, enabling precise and controlled bone lengthening or compression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external fixators are used for bone distraction, then bone lengthening can be achieved, but the device becomes cumbersome and invasive causing patient discomfort and complications
Solution Approach 1:
The patent replaces the mechanical external fixator system with an intramedullary implant containing a magnetically-driven distraction mechanism. The implant uses a permanent magnet coupled with an external magnetic field generator to produce controlled distraction forces internally within the bone, eliminating the need for external pins and frames that cause patient discomfort and complications.
Solution Approach 2:
The distraction mechanism is nested within the intramedullary implant structure. The permanent magnet is housed inside the implant body, which itself is inserted into the bone's medullary canal. This nested configuration allows the distraction function to be integrated within the bone rather than applied from outside, reducing invasiveness.
2Productivity
If automatically lengthened intramedullary nails are used, then bone lengthening occurs, but the process becomes uncontrolled and painful
Solution Approach 1:
The external magnetic field generator allows for controlled adjustment of the magnetic field strength and duration, enabling precise control over the distraction rate. The system can be adjusted to match the optimal bone healing rate (typically 1mm per day), preventing both nonunion from excessive distraction and premature consolidation from insufficient distraction.
Solution Approach 2:
The permanent magnet within the implant automatically responds to the external magnetic field by rotating and driving the distraction mechanism without requiring manual intervention or surgical adjustment. This self-actuating mechanism eliminates the need for painful manual rotation of the limb while maintaining controlled distraction rates.
3Ease of operation
If motorized intramedullary nails with implanted motors are used, then controlled bone lengthening is achieved, but the surgical procedure becomes more invasive and complex
Solution Approach 1:
The patent extracts the motor function from the implanted portion of the device and relocates it to an external magnetic field generator. This eliminates the need to implant complex motor assemblies, batteries, and control electronics within the bone, significantly simplifying the surgical procedure while maintaining controlled lengthening capability through non-invasive magnetic actuation.
Solution Approach 2:
The patent introduces a magnetic field as an intermediary between the external controller and the internal distraction mechanism. Instead of directly implanting motors and electrical connections, the system uses magnetic fields to transmit energy and control signals across the skin boundary, reducing surgical invasiveness while enabling precise control.
4Power
If large electromagnet stators are used for electromagnetic distraction, then bone lengthening can be driven, but the device size and complexity increase making it impractical for home use
Solution Approach 1:
The patent changes the magnetic field generation approach from using large, power-intensive electromagnet stators to using a compact external magnetic field generator that produces pulsed magnetic fields. This parameter change allows sufficient distraction force to be delivered while reducing device size and power requirements, enabling home use.
Solution Approach 2:
The external magnetic field generator delivers distraction forces through periodic pulsed magnetic fields rather than continuous electromagnetic forces. This periodic action achieves the required bone distraction over time while significantly reducing the power requirements and device size compared to continuous electromagnet systems, making the device portable and suitable for home use.
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
Provides a non-invasive, controlled, and cost-effective method for bone lengthening or compression, minimizing complications and patient discomfort, while allowing for precise alignment and distraction rates.
Implementation Method 1
A rotational correction system using an intramedullary implant with a rotatable permanent magnet and external adjustment device, allowing controlled rotational alignment of bone sections through magnetic coupling
Implementation Method 2
the rotatable permanent magnet mechanically connected to a nut operatively coupled to the second section of the implant
Data Source
AI summary
The disclosure describes systems and methods for altering bone sections in a patient. In one embodiment, a system may include an intramedullary implant including: a housing configured to be secured to a first section of bone, where the housing may include one or more shaft engaging grooves axially extending along an inner surface thereof; a distraction shaft configured to be secured to a second section of bone, where the distraction shaft may include one or more grooves axially extending along an inner surface thereof. The system may further include an actuator disposed within the housing and operably coupled to the distraction shaft, and in response to rotation of the actuator, the one or more grooves of the distraction shaft may engage with the one or more shaft engaging grooves of the housing, causing axial displacement of the distraction shaft relative to the housing.