External Fixation Strut Control for Manual and Automated Adjustment
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Solution Overview
Problem
Existing external fixation systems face challenges in achieving precise and user-friendly adjustment of struts for bone deformity correction, particularly in terms of ease and precision, with existing technologies requiring separate types of struts for manual and automated operation.
Innovation Solution
An external fixation system with adjustable length struts that can operate in both manual and automated modes, featuring a strut knob that transitions between axial positions for discrete or infinitesimal length adjustments, and a controller module that interfaces with a strut gear for automated operation, allowing for stable and precise length adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If manual adjustment mechanism is used for strut length adjustment, then ease of operation is improved, but manufacturing precision and adjustment precision deteriorate
Solution Approach 1:
The single strut design incorporates both manual adjustment capability (via thumbwheel and gear mechanism) and automated adjustment capability (via motor adapter interface) within the same structure. The thumbwheel assembly can operate independently for manual precision adjustment, while the motor adapter can couple to the gear mechanism for automated control, allowing the same strut to serve both manual and automated functions without requiring separate strut types.
2Manufacturing precision
If automated adjustment mechanism is used for strut length adjustment, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The adjustment system is segmented into distinct functional modules: the thumbwheel assembly for manual operation, the motor adapter for automated operation, and the gear mechanism that both modules share. This segmentation allows each module to be independently designed and optimized, reducing overall system complexity while maintaining high precision. The motor adapter couples to the existing gear mechanism rather than requiring a completely separate automated system.
Solution Approach 2:
The gear mechanism serves dual purposes: it transmits rotation from the thumbwheel during manual operation and from the motor during automated operation. This multi-functionality eliminates the need for separate drive mechanisms for manual and automated modes, thereby reducing device complexity while maintaining precision adjustment capabilities.
3Ease of operation
If discrete length increments are used for manual adjustment, then ease of operation is improved, but measurement precision deteriorates
Solution Approach 1:
The patent replaces the traditional direct-threaded rod mechanical system with a gear-based mechanical advantage system. The gear mechanism with multiple teeth allows the thumbwheel to rotate through larger angles for each discrete increment, making manual operation easier while the fine pitch of the threaded rod (when engaged) provides precise incremental control. The gear acts as an intermediary that amplifies user input while maintaining precise control over the actual strut length changes.
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
The system provides a stable construction for precise, automated strut length adjustments, minimizing user error and enabling seamless transitions between manual and automated modes, ensuring accurate bone deformity correction.
Implementation Method 1
a spring positioned between the strut gear and the strut knob, the spring configured to bias the strut knob to the first axial position
Implementation Method 2
The at least one prong may include a tip portion with a ramped surface, the ramped surface configured to drive the strut knob to the second axial position as the controller module is coupled to the strut
Data Source
Figure 1
Figure 2A~2B
Figure 2C~2D
AI summary
An external fixation system (10) includes first and second fixation rings (20, 30) and a plurality of adjustable-length struts (200) that have two joints (210, 270), a rod (250), a tube (260), and an actuator (220) configured to drive the rod axially relative to the tube to change an effective length of the strut. The system has a plurality of controller modules (300) each configured to couple to a corresponding strut. In a manual mode of operation, the controller modules are not coupled to the struts, and manual actuation the actuators changes the effective lengths of the struts in discrete length increments. In an automated mode of operation, the controller modules are coupled to the struts and automated actuation of the actuators is configured to change the effective lengths of the struts in infinitesimally small length increments.