External Fixation System with Spherical and Universal Joints
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Solution Overview
Problem
Current orthopaedic external fixators, such as the Ilizarov system, are complex and require many parts to provide gradual correction along six axes, making them difficult to use in clinical settings, and often need repositioning after initial application to convert between correction axes or for weight-bearing stability.
Innovation Solution
A parallel robot external fixation system with a 3-USR configuration, utilizing three variable length struts with spherical and universal joints, allowing for six degrees of freedom without changing strut length, and a programmable controller for precise adjustments, enabling complete control over the relative position of bone fragments in six axes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the Ilizarov system is used to provide gradual correction along six axes, then the correction capability is improved, but the device complexity increases significantly
Solution Approach 1:
The patent combines multiple correction functions into a single integrated frame structure. The frame incorporates hinges, cables, and adjustment mechanisms that work together as a unified system, allowing six-axis correction without requiring multiple separate components like the Ilizarov system. This merging reduces overall device complexity while maintaining full correction capability.
Solution Approach 2:
The frame is designed as a universal structure that can perform multiple functions: it provides angular correction, translational adjustment, and rotational alignment all through the same basic frame architecture. The hinges and cables serve multiple purposes in different configurations, eliminating the need for specialized components for each type of correction.
2Manufacturing precision
If the Ilizarov system is configured for angular correction, then the correction precision is improved, but the stability for weight-bearing deteriorates
Solution Approach 1:
The frame employs dynamic adjustment mechanisms that allow the structure to transition between different functional states. Hinges enable angular adjustments for precise correction, while cables provide tensile stability for weight-bearing. The system can dynamically switch between correction mode and stabilization mode by adjusting cable tension and hinge positions.
Solution Approach 2:
The frame is divided into modular segments connected by hinges, allowing independent adjustment of each segment for precise angular correction. Simultaneously, the segmented structure maintains overall stability through cable connections that distribute weight-bearing loads across multiple attachment points.
3Adaptability or versatility
If the external fixator is designed for gradual correction, then the adaptability to deformity types is improved, but the ease of operation deteriorates
Solution Approach 1:
The frame incorporates self-adjusting mechanisms where cable tension and hinge positions automatically adapt to the deformity being corrected. The gradual correction process is facilitated by the inherent mechanical properties of the cables and hinges, which naturally adjust to maintain optimal alignment without requiring complex manual reconfiguration.
Data Source
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AI summary
An external fixation system (300) comprising: first and second planar at least part-circular ring elements (314, 316), the first ring element (314) having a circumferential track extending along the part -circular circumference thereof; a plurality of struts (390) each having a first and second ends (352, 354), the first end (358) of each strut (318) coupled to the first ring (314) by a first connector and the second end (354) of each strut (390) coupled to a second ring (316) by a second connector (329), the first connector including a spherical joint (308); the second connector non-rotatably coupled to the second ring (316), the strut second end being coupled to the second connector by a U- joint (335), and shuttles (326) mounted on the track of the first ring (314) for movement there along with one shuttle (326) coupled to each strut (390).