Telescopic Bone Lengthening Nail With Rotary Oscillation Mechanism
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Solution Overview
Problem
Current lengthening nail technologies for long bones face issues such as bulkiness, infection risks, limited support during elongation, and difficulties in positioning and extraction, with existing solutions either being external and cumbersome or internal and requiring multiple surgical interventions with uncertain elongation results.
Innovation Solution
A lengthening nail design featuring a first hollow tube with a second solid or hollow tube slidably and rotatably mounted inside, coupled by means that allow step-wise longitudinal translation through rotary oscillations, with a tip for blocking and extraction assistance, and indexing mechanisms for precise positioning, along with pawls and springs for controlled elongation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external fixators are used for bone lengthening, then progressive elongation can be controlled and adjusted, but the device becomes bulky and unattractive with increased infection risks
Solution Approach 1:
The patent implements a telescopic structure where an inner tube is nested within an outer tube, both housed inside a single medullary canal. This nested configuration allows the lengthening mechanism to be contained entirely within the bone, eliminating external components that would expose soft tissues to infection while preserving the progressive elongation capability through controlled rotation of the inner tube relative to the outer tube.
2Object-affected harmful factors
If internal fixators are used for bone lengthening, then no element appears outside the limb, but multiple surgical interventions are required with limited elongation gain per intervention
Solution Approach 1:
The patent employs a dynamic lengthening mechanism where the inner tube can rotate continuously or repeatedly relative to the outer tube, enabling progressive elongation to occur over an extended period. This dynamic system allows multiple small increments of lengthening to accumulate into significant total elongation, eliminating the need for repeated surgical interventions while maintaining an entirely internal implant configuration.
3Object-affected harmful factors
If the lengthening nail is entirely buried in the bone, then it provides internal fixation, but extraction becomes difficult
Solution Approach 1:
The patent incorporates a retrieval tool that can be inserted through the medullary canal to engage with the inner tube. This tool enables the inner tube to be extracted separately from the outer tube, which remains embedded in the bone to maintain structural support. This selective extraction mechanism resolves the contradiction by allowing removal of the lengthening component while preserving the stabilizing structure.
4Reliability
If pawls with teeth are used for translation, then controlled elongation is achieved, but rattling occurs during operation
Solution Approach 1:
The patent introduces a viscoelastic element positioned between the pawl and the teeth on the helical groove. This cushioning element absorbs impacts and dampens vibrations that occur during engagement and disengagement of the pawl with the teeth, thereby eliminating rattling sounds and patient discomfort while preserving the controlled incremental elongation mechanism.
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
This design enhances clinical outcomes by reducing rattling, improving support and control during elongation, simplifying positioning and extraction, and reducing the risk of ossification, while allowing for safer and more controlled elongation maneuvers.
Implementation Method 1
at least one spring (37) arranged to act on the at least one pawl (34, 35)
Implementation Method 2
at least one other pawl (35) in engagement with at least one other tooth (28) on the second tube (20)... each tooth (27, 28) having a frustoconical shape
Data Source
Figure 1~2
AI summary
The present invention relates to elongation nails for long bones or similar. The elongation nail according to the invention is principally characterized in that it comprises a tube (10), another tube (20) mounted slidably and rotatably in the tube (10) in such a way that the end (21) of the tube (20) emerges from the end (11) of the tube (10), means (30) for coupling the two tubes (10, 20) in such a way that successive rotational oscillations of the two tubes with respect to each other about their longitudinal axis (100) cause a step-by-step translation of the two tubes with respect to each other. The nail also comprises an insert (40), mounted in a completely recessed position in the open end (12) of the first tube (10), and means (41) for locking the insert (40) with respect to the first tube, this insert having means (42) for cooperating with a lug of an ancillary instrument used to position the nail, said lug being able to be introduced into the end (12) of the tube (10) so as to cooperate with this insert (40).