Polyaxial Bone Plate Locking Mechanism with Tapered Apertures
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Solution Overview
Problem
Current bone plate systems in orthopedic surgery lack a locking mechanism that combines the stability of traditional locking screws with the variable orientation of non-locking screws, necessitating either compression of the bone plate to the bone or relying solely on friction for fixation.
Innovation Solution
A polyaxial locking mechanism featuring tapered apertures and fasteners with mismatched taper angles and circumferentially spaced recesses, allowing for insertion at various angles while maintaining a secure locking engagement, and optionally using materials with different hardness for deformation during insertion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional locking screws are used, then stable locking engagement is achieved, but screw orientation is fixed and lacks variability
Solution Approach 1:
The aperture is segmented into multiple zones with different taper angles, allowing the fastener to be inserted at various angles while maintaining locking engagement. The aperture contains a first zone with a first taper angle and a second zone with a second taper angle, enabling polyaxial insertion while preserving stable locking.
Solution Approach 2:
The taper angle parameter varies within the aperture structure. The aperture transitions from a first taper angle in the first zone to a second taper angle in the second zone, allowing the fastener to accommodate different insertion angles while maintaining reliable locking engagement through the varying geometric parameters.
2Adaptability or versatility
If non-locking screws are used, then variable screw orientation is achieved, but compression to the bone is required and friction-based fixation is less stable
Solution Approach 1:
The aperture is divided into zones with different taper characteristics, allowing the fastener to achieve both orientation variability through the first zone and stable locking engagement through the second zone, eliminating the need for compression while maintaining fixation stability.
Solution Approach 2:
The fastener system transitions from a fixed-orientation locking mechanism to a dynamic polyaxial system where the fastener can be inserted at multiple angles. The tapered aperture with varying angles provides dynamic adaptability while the locking engagement provides static stability.
3Adaptability or versatility
If tapered apertures with mismatched taper angles are used, then polyaxial insertion is enabled, but manufacturing precision requirements increase
Solution Approach 1:
The aperture is segmented into zones with different taper angles, where the first zone has a larger taper angle for easier polyaxial insertion and the second zone has a smaller taper angle for stable locking. This segmentation allows each zone to be optimized for its specific function while maintaining overall manufacturability.
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
Enables secure attachment of bone plates to bones at multiple angles without requiring compression, enhancing surgical flexibility and stability while allowing for easy replacement of fasteners without damaging the apertures.
Implementation Method 1
the threaded head can deform during insertion within the threaded aperture of the bone plate
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3
AI summary
A bone plate system comprises a bone plate including a first surface and a second surface, the bone plate including at least one threaded aperture, the threaded aperture being tapered between the first surface and the second surface. The bone plate system further comprises at least one fastener including an elongate shaft and a threaded head, the threaded head being tapered between a proximal end of the threaded head and a distal end of the threaded head, wherein a plurality of circumferentially spaced recesses are formed in the threaded head and define a plurality of threaded tabs. The at least one fastener is configured for insertion within the at least one threaded aperture at a plurality of different insertion angles while achieving a locking engagement between the threaded head and the threaded aperture.