Parallel External Fixator Asymmetric Strut Design
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Solution Overview
Problem
Current parallel external fixators for fracture reduction face challenges such as interference between struts and bone pins, low adjustment accuracy due to circularly symmetric strut connections, and instability from unlocked driving joints, as well as errors in manual measurement and visualization of fracture reduction movements from X-ray images.
Innovation Solution
A method using three-dimensional medical CT imaging and sphere fitting algorithms to accurately determine the position and pose of fixation rings, allowing for precise adjustment of strut lengths through a kinematic algorithm, and a driving joint with a locking mechanism to enhance stability, while avoiding strut interference through flexible strut configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If struts are arranged in a circularly symmetric manner, then the fixator structure is simplified and easier to manufacture, but interference between struts and bone pins occurs during clinical mounting
Solution Approach 1:
The patent changes the circularly symmetric arrangement of struts to an asymmetric configuration where struts are positioned at different angles and distances from the fixation ring center. This asymmetric layout allows struts to be routed away from the paths of bone pins, eliminating interference during clinical mounting while maintaining structural integrity and adjustability of the fixator.
2Device complexity
If the driving joint in the strut uses a simple adjustment mechanism, then the device complexity is reduced, but the scale resolution and strut adjustment accuracy are low
Solution Approach 1:
The patent replaces the traditional purely mechanical adjustment mechanism with a hybrid system that incorporates a scale resolution indicator mechanism. This mechanism includes a graduated scale or digital indicator that provides precise visual feedback on strut length adjustments, allowing for high-resolution measurement and control of strut positioning without significantly increasing the overall device complexity.
3Ease of operation
If the driving joint of the strut is designed for easy adjustment, then the ease of operation is improved, but the driving joint cannot be locked in the fracture fixation state, leading to decreased stability
Solution Approach 1:
The patent implements a dynamic locking mechanism in the driving joint that can transition between two states: an unlocked state for easy adjustment during positioning, and a locked state for stable fixation once the desired strut length is achieved. This dynamic system allows the joint to be easily adjusted during operation and then securely locked to maintain the fracture fixation state, combining ease of operation with structural stability.
4Device complexity
If manual measurement of X-ray images is used to determine fracture parameters, then the device complexity is minimized, but there are many subjective and objective errors in measurement
Solution Approach 1:
The patent introduces a specialized measurement tool or digital imaging system as an intermediary between the X-ray images and the fracture parameter determination. This intermediary provides standardized reference markers, measurement grids, or computer-aided measurement software that eliminates subjective errors in manual measurement while maintaining relative simplicity of the overall system. The intermediary translates complex X-ray image analysis into precise, objective fracture parameter data.
Data Source
AI summary
A fracture reduction method and a parallel external fixator for fracture reduction for realizing the method, the fracture reduction method being used for existing six-chain ring-shaped parallel external fixators in minimally invasive fracture reduction or osteotomy of limbs. The parallel external fixator comprises two fixation rings, six struts and six markers, the fixation rings are arranged with a plurality of connecting holes, the struts are arranged with a spherical hinge, a driving joint (1302), a quick-mounting component and a universal hinge, the markers comprise marker balls and a pin shaft. The parallel external fixator can improve the treatment accuracy, reliability and operation convenience.