Self-Balancing Bone Fixation Tangs for Intramedullary Canal Adaptation
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Solution Overview
Problem
Existing bone implant fixation mechanisms in intramedullary canals face issues with tang extension, as they either cause unnecessary trauma through over-extension or compromise mechanical strength due to under-extension, failing to adapt to the varying internal bone structure.
Innovation Solution
The use of self-balancing bone fixation tangs with asymmetric extension, where one set of tangs moves linearly with the actuation shaft and the other set remains fixed, allowing for balanced extension by utilizing threaded hubs with non-zero and zero lead threads, respectively, to accommodate varying bone cavity shapes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If symmetric extension mechanism with threaded hubs is used, then equal and matching linear movement of tangs is achieved, but the mechanism cannot adapt to varying internal bone structure causing over-extension or under-extension
Solution Approach 1:
The patent applies asymmetry by providing at least one hub with non-matching thread characteristics relative to the central screw thread. This allows different tangs to extend by different amounts, enabling adaptation to varying internal bone structures while preventing both over-extension and under-extension. The asymmetric thread design enables each tang to be independently adjusted to achieve optimal extension depth.
2Strength
If tangs extend too deeply into the bone wall, then fixation strength is improved, but unnecessary trauma is caused and bone strength is weakened
Solution Approach 1:
The patent implements a feedback mechanism where the central screw acts as both an actuator and a stop mechanism. As the central screw is rotated, it drives the hubs and tangs outward. When a tang reaches the optimal extension depth and contacts the bone interior surface, further rotation of the central screw is prevented by the tang acting as a stop. This provides automatic feedback control, ensuring tangs extend to the precise depth needed for fixation strength without causing unnecessary bone trauma.
3Object-affected harmful factors
If tangs stop extension before locking into bone surface, then bone trauma is reduced, but mechanical strength is compromised
Solution Approach 1:
The patent employs a self-service mechanism where each tang, upon contacting the bone interior surface, automatically becomes a stop for the central screw. This self-regulating feature ensures that the extension process automatically terminates when the optimal depth is reached, eliminating the need for external control or estimation. The system self-adjusts to achieve both adequate mechanical strength and minimal bone trauma.
Data Source
AI summary
The bone fixation tangs with self-balancing extension compensate for the internal cavity shape of the intramedullary canal, thus avoiding the related issues of over-extension and under-extension of tangs. Over-extension, or pushing the tangs too deeply in the inner wall of the bone, is unnecessarily traumatic to the patient and may weaken the bone. Under-extension, or stopping extension before the tangs have locked into the interior surface of the bone, results in reduced mechanical strength, thus compromising the ability of the nail to provide support to the bone. The bone fixation tangs with self-balancing extension address this issue by allowing the tangs to balance their extension.