Modular External Fixator with Adjustable Stiffness Clamp
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Solution Overview
Problem
Conventional external fixators face challenges in modulating stiffness to match the different biological phases of bone healing, leading to uncertain and uneven bone healing progress, increased risk of infection, and high production costs, making them less viable in developing countries and less preferred in developed countries due to unpredictable outcomes and high costs.
Innovation Solution
A novel external fixator design that allows bone pins to be inserted in parallel and oblique angles, with a clamp system that modulates stiffness by locking pins, providing higher stiffness when needed and reducing it as healing progresses, using a yoke-shaped clamp with simple and lightweight components made from materials like titanium or aluminum alloys, which are MRI-compatible.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional external fixators are used with fixed stiffness, then the structure is simple to manufacture, but bone healing progress becomes uncertain and uneven due to inability to match different biological phases of healing
Solution Approach 1:
The external fixator employs adjustable stiffness through modular connection elements that can be configured in different positions and orientations. The connection elements allow dynamic adjustment of the fixator's mechanical properties to match different phases of bone healing, transitioning from higher stiffness in early healing to lower stiffness in later remodeling phases.
Solution Approach 2:
The fixator system enables changing mechanical parameters (stiffness, stability) by adjusting the configuration of connection elements between bone anchors. This allows the same fixator structure to provide different levels of stability throughout the healing process, adapting to the evolving biological requirements without requiring multiple different devices.
2Strength
If bone pins are inserted only in parallel fashion with conventional fixators, then the device structure is simple, but the stiffness of the construct is insufficient for effective fracture stabilization
Solution Approach 1:
The fixator system allows asymmetric arrangement of bone pins relative to the fracture line, enabling insertion at oblique angles rather than only parallel configurations. This asymmetric pin placement creates more favorable mechanical leverage and increases the overall stiffness of the fixation construct, better resisting bending and rotational forces at the fracture site.
3Reliability
If external fixators are kept on patients for long periods to ensure bone healing, then the fracture stabilization is maintained, but the risk of infection increases due to pin passage through soft tissue and skin
Solution Approach 1:
The adjustable stiffness capability allows the fixator to be dynamically adapted as healing progresses. By reducing stiffness in later phases when biological healing is underway, the device can be removed earlier than with conventional fixed-stiffness fixators, thereby reducing the duration of pin exposure and associated infection risk while maintaining adequate mechanical support throughout the healing process.
4Reliability
If conventional external fixators are used with complex stiffness modulation measures, then the bone healing can be optimized for different phases, but the measures required are tedious and complex
Solution Approach 1:
The fixator is divided into modular components (bone anchors, connection elements, adjustable joints) that can be independently configured. This segmentation allows stiffness modulation through simple repositioning or reconfiguration of individual modules rather than complex global adjustments, making the adaptation process more straightforward and clinically feasible.
Data Source
AI summary
The invention relates to an external fixator device and a method of its use in treating bone fractures and in orthopedic interventions, such as corrective osteotomies.