Stemless Humeral Implant Anchor Structure for Bone-Preserving Stability
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Solution Overview
Problem
Stemmed prostheses often require significant bone removal, compromising natural bone stock and complicating revision surgeries, while stemless prostheses may lack sufficient anchorage and stability, posing challenges in shoulder arthroplasty procedures.
Innovation Solution
A stemless shoulder implant design featuring a base member with a proximal collar, central anchor, and peripheral supports, including enhanced fixation surfaces and chisel slots, which minimizes bone removal and enhances bone ingrowth for improved anchorage and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If stemmed prostheses are used, then anchorage and stability are improved, but bone removal increases and natural bone stock is compromised
Solution Approach 1:
The invention extracts and removes the stem component from the prosthesis, retaining only the base member that interfaces with the bone. This eliminates the need for a long stem that requires extensive bone removal, while the base member maintains sufficient anchorage through its optimized geometry and bone-engaging surfaces.
Solution Approach 2:
The base member incorporates localized bone-engaging surfaces with enhanced fixation properties at specific contact points with the bone. This concentrated local quality provides sufficient anchorage and stability without requiring widespread bone removal throughout the implant length.
2Loss of substance
If stemless prostheses are used, then bone removal is reduced and natural bone stock is preserved, but anchorage and stability are compromised
Solution Approach 1:
The base member geometry is optimized with specific dimensional parameters including a collar portion with outer diameter matching the humeral shaft, a body portion with reduced diameter, and angled bone-engaging surfaces. These parameter changes enable the stemless design to achieve sufficient anchorage through geometric fit and bone contact areas without a stem.
Solution Approach 2:
The implant utilizes composite construction with a base member made of cancellous bone-engaging material and an articulating component made of durable material. This composite approach allows the base member to provide biological integration through bone ingrowth while maintaining mechanical stability.
3Reliability
If significant proximal humeral bone is removed for stemless prosthesis, then implant stability is improved, but revision surgery becomes more challenging
Solution Approach 1:
The base member is segmented into distinct functional zones: a collar portion for proximal humeral engagement, a body portion for articulation, and bone-engaging surfaces for distal fixation. This segmentation allows the collar to maintain proximal bone stock while the body provides stability through alternative bone contact points, preserving options for revision surgery.
Data Source
AI summary
A stemless prosthetic shoulder joint may include a prosthetic humeral head and a stemless base. The stemless base may include a collar and an anchor extending from the collar intended to anchor the base into the proximal humerus. The base may include a proximal collar having a proximal surface and a bone-engaging surface opposite the proximal surface. The collar may have a superior portion and an inferior portion, the superior portion defining an arc shape and the inferior portion defining a substantially triangular shape.