Multi-Axis Glenoid Fixation for Pull-Out and Translation Resistance
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Solution Overview
Problem
Existing glenoid components in shoulder arthroplasty experience failures due to axial pull-out, rotational pull-out, and side-to-side translation, particularly when the implant peg or keel is smaller than the bone tunnel, leading to loosening and instability.
Innovation Solution
The development of anchoring elements with multi-directional fixation, featuring dowels and reinforcement plates oriented at acute angles and surface features that provide resistance to motion in three orthogonal planes, enhancing the glenoid component's stability by resisting axial pull-out, rotational pull-out, and translation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single-axis fixation peg or keel is used, then the implantation procedure is simple, but the implant is vulnerable to axial pull-out and loosening
Solution Approach 1:
The patent transitions from single-axis fixation to multi-axis fixation by adding surface features that extend in directions other than the primary insertion axis. The anchoring element includes surface features that extend perpendicular to the central longitudinal axis, providing resistance to pull-out forces from multiple directions rather than just along the insertion axis.
Solution Approach 2:
The fixation structure is divided into multiple functional components: the central longitudinal axis provides primary anchoring, while multiple surface features (ridges, grooves, flanges) extend in different directions to provide segmented resistance against pull-out forces from various vectors.
2Ease of manufacture
If the implant peg is smaller than the bone tunnel, then cement injection is facilitated, but the implant experiences side-to-side translation and instability
Solution Approach 1:
Surface features extend perpendicular to the central longitudinal axis, creating multi-directional resistance to translation. These features project laterally to engage with the bone tunnel walls in directions other than the primary insertion axis, preventing side-to-side movement while maintaining space for cement flow.
Solution Approach 2:
Different portions of the anchoring element have different properties: the central axis allows cement flow, while specific surface features (ridges, flanges) provide localized resistance to translation and rotation, creating zones of different mechanical behavior along the anchoring element.
3Strength
If surface features extend perpendicular to the peg axis, then axial pull-out resistance is enhanced, but resistance to rotational pull-out and multi-vector forces is insufficient
Solution Approach 1:
Surface features are oriented in multiple non-parallel directions rather than all perpendicular to the axis. Some features extend perpendicular to resist axial pull-out, while others extend at angles to resist rotational and lever-out forces, creating a multi-vector resistance system.
Solution Approach 2:
The surface features are asymmetrically arranged with different orientations relative to the central axis. This asymmetric configuration provides differential resistance to forces from different directions, particularly enhancing resistance to rotational pull-out and lever-out mechanisms that symmetric features would not address.
4Area of stationary object
If multiple parallel pegs are used, then fixation coverage is improved, but resistance to lever-out failure and multi-directional forces remains insufficient
Solution Approach 1:
Instead of relying solely on multiple parallel pegs, each peg is equipped with surface features that extend in multiple non-parallel directions. This adds dimensional complexity to each fixation point, enabling resistance to lever-out and rotational forces that parallel pegs alone cannot prevent.
Data Source
Figure 1A~1B
Figure 1C~1H
Figure 2A~2B
AI summary
Arthroplasty components include an articular surface (3604, 3704, 3804) and a bone-facing surface (3606, 3706, 3806). In some examples, the bone-facing surface bears at least one anchoring element adapted for an oblique implantation trajectory. The anchoring element includes a reinforcement plate, a dowel, and surface features. Each surface feature resists forces acting along a different direction. In other examples, the bone-facing surface bears anchoring elements that deform along the primary or longest axis of the anchoring element during insertion. In yet other examples, the bone-facing surface is enlarged relative to the articular surface so that at least a portion of the perimeter of the articular surface is circumscribed by the perimeter of the bone-facing surface.