Converging Screw Glenoid Frame Anchorage
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Solution Overview
Problem
The challenge in securing a glenoid component of a shoulder joint prosthesis to the scapula is ensuring proper anchorage, especially during revision procedures where bone integrity is compromised, leading to inadequate fixation of the frame.
Innovation Solution
The use of converging bone screws with bores in the frame part that guide screws to converge toward each other away from the medial surface, improving anchorage by targeting structurally sound portions of the scapula, such as the lateral border and spine pillars, and employing a frame design with inclined bore axes and countersunk bores for secure screw placement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional parallel bone screws are used to fasten the frame part to the scapula, then the fixation is simple to implement, but the anchorage is insufficient especially in revision procedures where bone integrity is compromised
Solution Approach 1:
The bores in the frame part are configured with asymmetric convergence - their axes are not parallel but converge toward each other as they extend into the scapula. This asymmetric arrangement allows screws to target structurally sound portions of the scapula (such as the lateral border and spine pillars) more effectively, improving anchorage reliability without requiring complex additional components
Solution Approach 2:
The screw axes are arranged in three-dimensional convergence rather than simple parallel alignment. The bores extend at angles relative to the plane of the frame part, creating a convergence pattern in multiple dimensions that enhances bone purchase while maintaining a relatively simple overall frame structure
2Ease of operation
If multiple holes are created in the scapula for revision procedures, then the frame can be re-anchored, but the structural integrity of the bone deteriorates further
Solution Approach 1:
The converging bore configuration allows screws to be directed toward specific structurally sound portions of the scapula (such as the lateral border and spine pillars) rather than distributing holes uniformly. This localized targeting preserves bone integrity in critical load-bearing areas while still enabling revision capability
Solution Approach 2:
The frame part is designed with pre-configured converging bores that guide screw placement into optimal positions before revision is needed. This preliminary design consideration ensures that even during revision procedures, new screws will converge toward sound bone portions, preventing further deterioration
3Stability of the object's composition
If the frame part is securely anchored to prevent movement, then fixation stability is improved, but the risk of causing additional damage to the scapula increases
Solution Approach 1:
The converging bore configuration acts as an intermediary mechanism that distributes mechanical loads more evenly across the bone-screw interface. By directing screws toward structurally sound portions, the design mediates between the need for stable fixation and the risk of bone damage, achieving stability without excessive stress concentration
Data Source
Figure 1~5
Figure 2~4
Figure 6
AI summary
A glenoid component (2) of a shoulder joint prosthesis for fixation to the glenoid region of a scapula, comprises a body part (16) of the prosthesis which presents a surface for articulation with the corresponding articulating surface of a humeral component, and a frame part (4). The frame part has a lateral surface (20) on which the body part can be mounted, and a medial surface (22) generally opposite the lateral surface. First and second bores (24,26) extend between the lateral and medial surfaces for receiving screws (16,18) so as to fasten the frame part to the scapula. The bores are configured so that their axes (28,30) converge, so that the distance measured between the axes decreases with increasing distance away from the medial surface of the frame towards the scapula. A method of planning a shoulder joint replacement surgical procedure is disclosed.