Ring External Fixator Locking Mechanism for Rotational Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current ring external fixators lack rotational stability due to the absence of locking mechanisms at the interfaces between components, leading to loosening and instability, particularly with threaded bone pins and hinges, which can result in pin site infections and compromised bone healing.
Innovation Solution
The introduction of a locking mechanism that modifies the surfaces of pin fixation bolts and ring interfaces to interlock, providing rotational stability, along with reversible locking mechanisms for hinges, allowing for variable angle and position adjustments, and the use of multipurpose posts that can function as multiple components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If threaded bone pins are attached to the ring using a pin fixation bolt secured by a nut, then the available safe corridors for insertion are increased and patient tolerance is improved, but the pin fixation bolt can rotate around its axis due to lack of locking mechanism, leading to loosening and instability
Solution Approach 1:
The pin fixation bolt is segmented into functional zones: a smooth shank portion that fits into the ring hole, a threaded portion for the nut, and a head portion with a locking mechanism. The locking mechanism includes a locking surface on the head and a corresponding locking feature in the ring hole, creating distinct functional segments that address rotation prevention separately from the insertion function.
Solution Approach 2:
The locking mechanism employs asymmetric geometry where the locking surface on the pin fixation bolt head is angled relative to the bolt axis, and the corresponding locking feature in the ring hole has a complementary asymmetric shape. This asymmetric configuration prevents rotational movement by creating a mechanical interlock that only allows insertion along the bolt axis, not rotation around it.
2Device complexity
If the ring fixator components are connected simply by tightening them against each other, then the device complexity is reduced and ease of manufacture is improved, but the components are prone to loosening over time due to rotational forces
Solution Approach 1:
The locking mechanism is pre-configured into the pin fixation bolt and ring interface during manufacturing. The locking surface and locking feature are formed as integral parts of the components, so that when assembled, the locking action occurs automatically without requiring additional steps or complex mechanisms. This preliminary integration maintains simplicity while ensuring reliability.
3Stability of the object's composition
If double column cubes are used to provide rotational stability, then the rotational stability is improved, but the ring width must be increased and the overall weight and bulk of the fixator increases
Solution Approach 1:
The locking function is extracted from the cube component itself and transferred to the pin fixation bolt and ring interface. Instead of modifying the cube to provide locking (which would require double-column design), the locking mechanism is taken out and implemented at the connection point between the pin fixation bolt and ring, eliminating the need for heavier double-column cubes.
4Adaptability or versatility
If different sizes of components and pin fixation bolts are used to accommodate various fixator configurations, then the adaptability is improved, but the quantity of components that need to be held in stock and sterilised increases
Solution Approach 1:
The locking mechanism is designed with universal geometry that can accommodate different component sizes and configurations. The locking surface angle and locking feature shape are standardized across all pin fixation bolts and rings, allowing a single design to serve multiple functions and sizes, thereby reducing the variety of components needed in stock.
Data Source
AI summary
A locking mechanism provides rotational stability to the threaded bone pins and other fixator components by modifying the opposing surfaces of the pin fixation bolt, the ring and other fixator components at their interface so that they can interlock with each other. A pin fixation bolt can be used to connect different diameter threaded bone pins. A multipurpose post enables variable angle and rotationally stable insertion of threaded bone pin and versatile use of the multipurpose post to replace currently available various fixator components. Plates enable rotationally stable, variable angle and variable position connection of the plates so that rings offset to each other can be connected without using oblique supports. Reversibly lockable hinges allow the hinge articulation to be locked or unlocked as desired, during the course of the treatment.