Polyaxial Bone Anchor Locking Structure With Flexible Head Wall
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Solution Overview
Problem
Existing polyaxial bone anchoring devices are complex and lack simplicity and safety in use, with limited features and applications.
Innovation Solution
A polyaxial bone anchoring device featuring a receiving part with a head receiving portion and a locking member that allows for easy pivoting and locking of the head, utilizing a cavity for enhanced flexibility and stability, and potentially incorporating a pressure member for pharmaceutical substance delivery or a spring connection, manufactured through additive manufacturing methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing polyaxial bone anchoring devices use multiple locking mechanisms and flexible portions, then the locking reliability is improved, but the device complexity increases
Solution Approach 1:
The receiving part is divided into a rigid portion and a flexible portion, with the flexible portion containing circumferential grooves that create segmented locking zones. This segmentation allows the head to be locked at discrete angular positions while maintaining overall structural integrity and simplifying the locking mechanism.
Solution Approach 2:
Different portions of the receiving part have different mechanical properties - the rigid portion provides structural strength and stability, while the flexible portion with circumferential grooves provides the locking function. This local differentiation of material properties resolves the contradiction by assigning specific functions to specific regions.
2Strength
If the head receiving portion uses a uniform wall thickness, then the structural strength is improved, but the ease of assembly and flexibility is reduced
Solution Approach 1:
The wall thickness of the head receiving portion varies locally - thicker in regions requiring strength and stability, thinner in regions requiring flexibility for assembly. This local variation in geometric properties allows the structure to simultaneously achieve both strength and ease of assembly.
Solution Approach 2:
The flexible portion with circumferential grooves allows dynamic adjustment and compression during assembly, enabling the receiving part to adapt to the head geometry. This dynamic flexibility during assembly is then converted to static locking strength through the rigid portion.
Data Source
AI summary
A polyaxial bone anchoring device includes a receiving part with a rod receiving portion defining a recess for receiving a rod, and a head receiving portion with a wall that defines an accommodation space for accommodating a head of an anchoring element, and a locking member positionable at least partially around the head receiving portion and movable from a first position where the head can pivot in the accommodation space to a second position where an angular position of the head is locked. The wall of the head receiving portion further defines at least one cavity in communication with the accommodation space that reduces a radial thickness of at least part of the wall located between the accommodation space and the locking member, and at least part of the cavity is separated radially from the accommodation space by a portion of the wall.