Tapered Collet Locking Mechanism for Spinal Implants
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Solution Overview
Problem
Current spinal implant technologies lack effective locking mechanisms that securely stabilize spinal rods, screws, or plates, leading to instability and potential failure in treating musculoskeletal disorders such as scoliosis and kyphosis.
Innovation Solution
A spinal implant with a locking mechanism featuring a tapered collet and passageway system that transitions between non-locking and locking orientations, providing an interference fit and resistance to axial translation and rotation, along with off-center axis locking nuts and spherical collars to securely fix longitudinal members.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a locking mechanism is implemented to stabilize spinal implants, then stability and reliability are improved, but device complexity increases
Solution Approach 1:
The locking mechanism employs a nested structure where the collet is disposed within the locking nut, and the spherical collar is received within the collet. This nested arrangement allows multiple functional components to be integrated in a compact configuration, achieving reliable stabilization of spinal implants while minimizing the overall device complexity and footprint.
Solution Approach 2:
The locking mechanism is divided into distinct functional segments: the locking nut with tapered interior surface, the collet with gripping surfaces, and the spherical collar. Each segment performs a specific function (threaded engagement, radial compression, and positioning), allowing the system to achieve high reliability through specialized components while managing complexity through functional decomposition.
2Strength
If a tapered collet with interference fit is used to restrict translational motion, then fixation strength is improved, but manufacturing precision requirements increase
Solution Approach 1:
The locking mechanism utilizes a tapered geometry where the diameter of the collet and corresponding recess vary along the axial direction. This parameter change creates an interference fit that generates strong frictional forces to prevent translational motion. The gradual taper allows for controlled engagement and distribution of contact stresses, achieving high fixation strength while accommodating reasonable manufacturing tolerances.
Solution Approach 2:
The spherical collar component introduces a curved geometric element into the locking mechanism. This spherical geometry provides a natural interference fit within the collet, creating radial compression forces that enhance the gripping action. The curved surfaces distribute contact stresses more evenly compared to flat interfaces, improving fixation strength while being tolerant of manufacturing variations.
3Stability of the object's composition
If off-center axis locking nuts are employed to prevent orbital motion, then stability is improved, but device complexity increases
Solution Approach 1:
The locking nut is designed with an asymmetric, off-center axis configuration where the interior tapered surface and collet positioning are offset from the central thread axis. This asymmetry creates a mechanical constraint that prevents orbital motion of the spinal implant, as the offset geometry blocks rotational displacement. The asymmetric design achieves enhanced stability while maintaining relatively simple manufacturing through standard machining operations.
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 locking mechanism effectively stabilizes spinal implants, restricting both translational and orbital motion, enhancing the stability and durability of spinal fixation systems during surgical correction of deformities and other spinal disorders.
Implementation Method 1
The tapered collet is configured to create an interference fit that restricts axial translation of the longitudinal member
Implementation Method 2
The locking mechanism is configured to rotate between a non-locking orientation in which the first and third central axes are co-axial such that the longitudinal member is movable relative to the inner and outer members and a locking orientation in which the first and third central axes are offset such that the longitudinal member is fixed relative to the inner and outer members
Data Source
AI summary
A spinal implant includes a locking mechanism. The locking mechanism includes an inner surface defining a tapered passageway. A tapered collet is configured for disposal in the tapered passageway. The tapered collet has an inner surface defining a passageway configured for disposal of a longitudinal member. The tapered collet is configured to translate within the tapered passageway between a non-locking orientation in which the longitudinal member is moveable relative to the tapered collet and a locking orientation in which the longitudinal member is fixed relative to the tapered collet.