Stemless Humeral Anchor System for Bone Preservation
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Solution Overview
Problem
Conventional stemless humeral components for shoulder joint prostheses face challenges in initial stability and long-term fixation due to lack of adequate bone ingrowth, leading to potential dislodgement during early recovery or revision surgeries.
Innovation Solution
A stemless humeral shoulder assembly with a base member and anchor system that provides enhanced initial pull-out resistance and long-term fixation, featuring a central lumen with a peripheral portion and an anchor with threads extending outward, allowing for secure embedding in bone and integration with the humeral head.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If a stemless humeral component is used, then bone loss is decreased and surgical complexity is reduced, but initial stability and pull-out resistance are insufficient
Solution Approach 1:
The implant is divided into two separate components: a base member that is driven into the humeral head and an anchor member that is advanced into the base member. This segmentation allows each component to have specialized functions - the base member provides bone engagement while the anchor member provides securement, resolving the contradiction between minimizing bone loss and ensuring initial stability.
Solution Approach 2:
The base member acts as an intermediary between the bone and the anchor member. It is driven into the humeral head to create a secure foundation, then the anchor member is advanced into the base member to provide additional securement. This intermediary structure enables both bone preservation and initial stability without requiring bone removal.
2Duration of action of stationary object
If conventional stemless designs relying on bone ingrowth are used, then long-term fixation is achieved, but dislodgement risk during early recovery is high
Solution Approach 1:
The base member is driven into the humeral head before the anchor member is advanced, creating a preliminary secure foundation. This preliminary action ensures that the implant is securely positioned in bone before the final anchor member installation, providing both early stability and the conditions for long-term bone ingrowth.
Solution Approach 2:
The implant system transitions from initial mechanical securement by the driven base member to long-term biological fixation through bone ingrowth. The dynamic design allows the implant to be securely held in place mechanically during early recovery while simultaneously promoting biological integration for long-term stability.
3Reliability
If a stem is inserted into the intramedullary canal, then implant security is achieved after bone ingrowth, but bone must be removed to fit the stem
Solution Approach 1:
The design extracts the problematic stem component that requires bone removal and replaces it with a base member that is driven into the humeral head. This eliminates the need for intramedullary canal preparation and bone removal while maintaining secure implant fixation through the combination of the driven base member and advanced anchor member.
4Duration of action of stationary object
If a stem is used for humeral component, then long-term fixation through bone ingrowth is achieved, but removal becomes difficult when replacement is needed
Solution Approach 1:
The segmented design with a driven base member and an advanced anchor member allows for easier removal compared to a monolithic stem. The anchor member can be extracted from the base member, and the base member can be removed from the humeral head, providing a less invasive removal process while maintaining long-term fixation through bone ingrowth of the driven base member.
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
The assembly minimizes bone loss, increases rotational and longitudinal stability, and encourages bone ingrowth, providing excellent initial and long-term fixation, reducing the risk of dislodgement during early recovery and revision surgeries.
Implementation Method 1
The anchor member can include a helical structure advanceable to engage corresponding surfaces of the arms
Implementation Method 2
Advancement of the anchor member can cause friction between the anchor member and the base member that can help to maintain positional stability of the anchor member relative to the base member
Data Source
AI summary
A stemless humeral shoulder assembly having a base member and an anchor advanceable into the base member. The base member can include a distal end that can be embedded in bone and a proximal end that can be disposed at a bone surface. The base member can also have a plurality of spaced apart arms projecting from the proximal end to the distal end. The anchor can project circumferentially into the arms and into a space between the arms. When the anchor is advanced into the base member, the anchor can be exposed between the arms. A recess can project distally from a proximal end of the anchor to within the base member. The recess can receive a mounting member of an anatomical or reverse joint interface.