External Fixation Strut Attachments for Tighter Ring Spacing
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Solution Overview
Problem
Existing external fixation systems face challenges in adjusting strut attachments, particularly when struts reach their minimum length, limiting the ability to achieve desired bone deformity corrections, and require improvements in precision and ease of adjustment.
Innovation Solution
The introduction of strut attachments that allow for two degrees of freedom between the strut and the ring, utilizing pivot and hinge joints, and a threaded rod that rotates with respect to a telescopic tube, enabling variable attachment points on the strut body and providing additional degrees of freedom.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the strut is completely collapsed to achieve minimum length, then the ring-to-ring distance is minimized, but the strut runs out of its minimum length and cannot achieve tighter distances
Solution Approach 1:
The strut attachment system is divided into separate components: a ring attachment member with a pivot joint and a strut attachment member with a hinge joint. This segmentation allows independent adjustment of each joint's position and orientation, enabling the system to achieve tighter ring-to-ring distances by reconfiguring the attachment geometry rather than relying solely on strut collapse.
Solution Approach 2:
The attachment system incorporates two degrees of freedom through pivot and hinge joints, making the attachment points dynamically adjustable. This dynamic capability allows the attachment points to be repositioned along the strut and ring surfaces, enabling the system to adapt to varying distance requirements and overcome the fixed minimum length limitation.
2Measurement precision
If the strut attachment point is fixed at the end of the strut, then the assembly is simple, but the adjustment precision and range are limited
Solution Approach 1:
The attachment mechanism transforms the fixed attachment point into a dynamic one with two degrees of freedom. The pivot joint in the ring attachment member and the hinge joint in the strut attachment member enable precise positioning along the strut length and ring circumference, achieving high adjustment precision while maintaining a relatively simple modular structure.
Solution Approach 2:
The attachment system serves multiple functions: it provides precise attachment point positioning, enables angular adjustment through two degrees of freedom, and maintains structural integrity. The pivot and hinge joints collectively achieve both precision and versatility without requiring complex mechanisms for each function separately.
3Adaptability or versatility
If the threaded rod is fixed relative to the telescopic tube, then the structure is stable, but the additional degree of freedom is lost
Solution Approach 1:
The threaded rod is made rotatable relative to the telescopic tube, adding a degree of freedom to the strut assembly. This rotational capability allows the threaded rod to self-align and accommodate angular variations in the attachment points while maintaining the telescopic adjustment function, thereby enhancing adaptability without compromising structural stability through proper mechanical design.
Data Source
AI summary
Disclosed herein are strut attachments for external fixation frames. The strut attachments provide solutions for frame configurations in which it is not possible to attach a strut at its ends to corresponding rings. The strut attachments may be considered an outrigger type of mechanism that achieves more travel out of completely collapsed struts. The strut attachments, each having a pivot and a hinge joint, allow a strut to be attached on the level of a first ring and extend at least partially proximally or distally to a second ring depending on the frame of reference of the ring system. These strut attachments may be used when the fully collapsed length of the strut will not allow the rings to get any closer to one another than is needed or proscribed. In such cases, the strut attachments allow for even tighter ring to ring distance.