Polyaxial Bone Anchor Preload Structure for Low-Friction Alignment
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Solution Overview
Problem
Existing polyaxial bone anchoring devices face challenges in achieving a reliable and reproducible friction fit between the head and the receiving part, which affects handling during surgical procedures.
Innovation Solution
A polyaxial bone anchoring device with a pressure element featuring flexible sections and inclined surface portions that exert a pre-load onto the head, allowing for a low-friction fit and balanced tolerances, enabling easy alignment and secure attachment of the bone anchoring element to a stabilization rod.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pressure element is used to exert pre-load onto the head to achieve friction fit, then the reliability of the friction fit is improved, but the device complexity increases due to additional components
Solution Approach 1:
The pressure element is integrated into the receiving part as a unified structure, where the pressure element and receiving part form a single component. This merging eliminates the need for separate additional components while maintaining the pre-load function, thus improving reliability without increasing device complexity
Solution Approach 2:
The receiving part is designed to perform multiple functions: it accommodates the head, provides the friction fit through the pressure element, and enables polyaxial movement. By making the receiving part multi-functional, the patent avoids adding separate components for each function, thereby maintaining simplicity while achieving reliable friction fit
2Ease of operation
If additional elements are added to achieve low-friction fit, then the ease of operation is improved, but the device complexity increases
Solution Approach 1:
The low-friction mechanism is achieved through the integrated design of the pressure element and receiving part, where the inclined surface and flexible section work together within the single receiving part structure. This eliminates the need for additional elements while providing easy handling during surgery
Solution Approach 2:
The friction characteristics are optimized by changing the geometric parameters of the inclined surface and the flexibility of the sections within the pressure element. By adjusting these parameters in the existing structure, the patent achieves low-friction fit without adding complexity
3Device complexity
If the pressure element is integrated into the receiving part, then the device complexity is reduced, but the manufacturing precision requirements increase to ensure proper pre-load
Solution Approach 1:
The patent employs standardized geometric parameters for the inclined surface angle and section dimensions that are optimized to provide the correct pre-load within normal manufacturing tolerances. This approach reduces the need for high-precision manufacturing while maintaining the integrated design benefits
Solution Approach 2:
The flexible sections of the pressure element automatically adjust during assembly to accommodate minor dimensional variations, self-correcting for normal manufacturing tolerances. This self-adjusting mechanism allows the integrated design to function correctly without requiring extremely tight manufacturing precision
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 device provides improved handling and secure attachment with a low-friction fit, allowing for precise alignment and a wide range of angulation without additional components, enhancing surgical efficiency.
Implementation Method 1
a pressure element (6) for exerting pressure onto the head (3) is arranged in the receiving part (4)... the flexible sections (6a, 6b) each have an inclined surface portion (69a, 69b) that cooperates with a corresponding inclined surface portion (15a, 15b) provided at the receiving part (4)... when the pressure element (6) moves downward, the inclined surface portion of the pressure element and the corresponding inclined surface portion of the receiving part are in contact with each other
Data Source
AI summary
A polyaxial bone anchoring device is provided includinga bone anchoring element (1) comprising a head (3) and a shank (2);a receiving part (4, 4′) for receiving a rod (100) for coupling the rod to the bone anchoring element, the receiving part comprising a first end (4a), an opposite second end (4b) and a central axis (C) extending through the first end and the second end, anda channel (9) for receiving the rod and an accommodation space (11) for receiving the head;a pressure element (6, 6′) arranged in the receiving part and configured to exert pressure onto the head;wherein the pressure element (6) comprises flexible sections (66a, 66b) facing away from the head (3), characterized in that the flexible sections (66a, 66b) comprise a free end portion (69a, 69b) with respect to the central axis (C) that cooperates with an inclined surface portion (15a, 15b) of the receiving part (4) such as to hold the pressure element (6) in a position in which it exerts a pre-load onto the head before the head is locked.