Staggered Tooth Anchoring Shell for Hip Joint
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Solution Overview
Problem
Existing hemispherical anchoring shells for pelvic implants face challenges in achieving optimal retention force due to the mutual influence of tooth rows, leading to reduced holding forces and stability, especially in the equatorial region where the greatest clamping force is required.
Innovation Solution
A new tooth pattern is introduced where teeth in one row are positioned exactly in gaps, with a decrease in tooth depth from the equator towards the pole, and a transition to smaller, non-undercut teeth and grooves near the pole for stabilization, allowing for symmetrical milling trajectories that enhance the barb effect and reduce tooth width loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If traditional tooth rows are arranged in parallel lines on the anchoring shell, then the structure is simple to manufacture, but the retention force is reduced due to mutual influence between adjacent teeth
Solution Approach 1:
The patent applies asymmetry by arranging tooth rows in a non-parallel, staggered configuration where teeth in one row are offset relative to adjacent rows. This asymmetric arrangement prevents the mutual influence and interference that occurs with parallel tooth rows, thereby increasing retention force while remaining manufacturable through standard milling processes.
Solution Approach 2:
The patent transitions from a simple linear arrangement of teeth to a multi-dimensional staggered pattern. By introducing offset positioning in multiple directions rather than simple parallel lines, the tooth rows utilize additional spatial dimensions to maximize bone engagement and retention force without significantly complicating the manufacturing process.
2Stability of the object's composition
If tooth depth is uniform across the entire surface, then manufacturing is simplified, but the anchoring width is lost near the pole reducing stability
Solution Approach 1:
The patent applies local quality by varying the tooth depth according to the specific location on the anchoring shell. Teeth near the equator have greater depth to maximize clamping force where it is most needed, while teeth near the pole have reduced depth. This localized differentiation optimizes anchoring stability at each position without requiring complex multi-step manufacturing processes.
3Force
If the anchoring shell is designed with maximum clamping force at the equator, then primary stability is improved, but the pole region lacks sufficient stabilization
Solution Approach 1:
The patent applies local quality by differentiating the tooth characteristics between the equatorial and polar regions. The equatorial region features deeper, more numerous teeth to maximize clamping force for primary stability, while the polar region incorporates smaller stabilization teeth that provide adequate fixation without compromising the overall reliability of the implant.
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 significantly increases the retention force of the anchoring shell by maintaining effective anchoring width and reducing the loss of retaining force, resulting in higher primary stability and improved bone growth for permanent fixation.
Implementation Method 1
The clamping effect is supported by a rough surface and, in some versions, through small-dimensioned geometric elements that penetrate into the bone structure.
Implementation Method 2
This primary stability is supported by clamping through a rough surface and, in some versions, through small-dimensioned geometric elements that penetrate into the bone structure.
Implementation Method 3
A targeted design of the surface structure creates directional properties for the holding force. An example of this is the tooth-like structure described in WO 02/064066, which is produced by a machining process.
Implementation Method 4
either a left-handed or right-handed trajectory of the tooth-producing milling tool is selected so that in the clamping area of the anchoring shell the teeth of one row of teeth following towards the pole are placed exactly in gaps
Implementation Method 5
In the secondary fixation phase, a stable connection is then formed through 'interlocking' of the growing bone with the structured surface.
Data Source
Figure 1a~4b
AI summary
The fastening shell has a teeth structure arranged in an external side of a semi shell, and a milling tool for forming a shape of teeth flanks (21). The equator-side oriented flanks of the individual teeth form an angle of less than 90 degrees with a component axis such that barbed hook effect is developed in an equator. A path of the tool is curved for forming teeth gaps and formed such that the teeth of a teeth row are consecutively arranged in the teeth gaps and cutting edges of the teeth from the equator towards a pole do not overlap or have a gap of around 2mm.