Fenestrated Bone Anchor With Pear-Shaped Channels for Stable Infiltration
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Solution Overview
Problem
Existing fenestrated bone anchors face challenges in achieving homogeneous material infiltration and mechanical stability, particularly when using thermoplastic materials for anchoring, leading to uneven stress distribution and reduced load-bearing strength.
Innovation Solution
The design of fenestrated bone anchors with pear-shaped lateral channels and gradually increasing wall thickness ensures homogeneous material flow and stress distribution, maintaining mechanical stability by optimizing the cross-sectional shape and wall thickness to minimize stress variation along the anchor length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional lateral channels with uniform cross-section are used, then the anchor structure is simple, but material infiltration is uneven and stress distribution is non-uniform
Solution Approach 1:
The lateral channels are designed with a pear-shaped cross-section that is asymmetric, featuring a wider distal end and a narrower proximal end. This asymmetric geometry optimizes material flow from the longitudinal cavity into the surrounding bone tissue while distributing mechanical stresses more uniformly along the anchor length, resolving the contradiction between manufacturing simplicity and homogeneous material infiltration.
Solution Approach 2:
The wall thickness of the anchor shaft is varied locally, being greater in regions corresponding to the lateral channels and thinner in intermediate regions. This local variation in wall thickness creates a gradient structure that enhances material infiltration at the channel locations while maintaining overall structural integrity, achieving homogeneous material distribution without requiring complex overall geometry.
2Strength
If lateral channels are positioned proximally for cortical bone anchoring, then anchoring strength in dense bone is improved, but stress concentration increases at the channel locations
Solution Approach 1:
The anchor shaft features localized wall thickening at the regions where lateral channels are positioned, creating local reinforcement zones. This local quality variation allows the anchor to achieve strong anchoring in cortical bone through proximal channel placement while the thickened walls prevent stress concentration and maintain structural integrity at these critical locations.
Solution Approach 2:
The design incorporates pre-positioned wall thickening at the lateral channel regions before the anchor is subjected to load. This beforehand cushioning in the form of geometric reinforcement prepares the structure to withstand the stress concentrations that would otherwise occur at the channel locations, allowing proximal placement for optimal cortical bone anchoring.
3Strength
If wall thickness is increased for mechanical stability, then load-bearing capacity is improved, but material flow through lateral channels is restricted
Solution Approach 1:
The anchor employs a gradient wall thickness design where the shaft wall is thickest at the lateral channel locations to facilitate material flow, and thinnest in intermediate regions to maintain flexibility and reduce stress. This local differentiation allows the structure to optimize both material infiltration and load-bearing capacity without compromising either function.
Solution Approach 2:
The solution addresses the two-dimensional conflict between wall thickness and channel flow by introducing a longitudinal dimension to the wall thickness variation. The wall thickness changes along the length of the anchor, being greater at channel locations and thinner elsewhere, thereby resolving the contradiction through three-dimensional geometric optimization.
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 allows for efficient and stable anchoring by ensuring uniform material infiltration and stress distribution, enhancing the anchor's ability to withstand bending loads, especially when proximally fixed to denser bone structures.
Implementation Method 1
energy, in particular vibration energy (in particular ultrasonic vibration energy) is applied to the thermoplastic element for liquefying the material having thermoplastic properties
Data Source
Figure 1A~4
Figure 5A~6C
Figure 7A~7C
AI summary
Disclosed is a fenestrated bone anchor (210) suitable for being anchored in live bone tissue of a human or animal patient. The bone anchor comprises a shaft with a proximal end and a distal end and a circumferential surface extending from the proximal end to the distal end. The shaft further comprises a longitudinal cavity extending from the proximal end towards the distal end and a plurality of lateral channels extending through a wall of the shaft from the axial cavity to the circumferential surface. The lateral channel has a pear-shaped cross section and/or the thickness of the wall increases gradually in selected ones of directions towards the lateral channels. The fenestrated bone anchor is e.g. a component of a surgical system comprising an interbody fusion device of the stand-alone type.