Crown-Partitioned Spherical Shell Prosthesis for Stable Bone Anchoring
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Solution Overview
Problem
Surface replacement prostheses for ball-and-socket joints face challenges in attachment stability, bone necrosis, and bone material removal, with existing solutions either lacking in force distribution or being prone to loosening due to lever forces.
Innovation Solution
A prosthesis design featuring a spherical shell section with a cavity partitioned by a crown, where the crown engages directly into load-bearing bone structures, providing a large contact surface for stable attachment, and is designed to minimize bone resection with a conical crown that increases in thickness for improved stability and blood infusion, allowing for controlled pressure and bone growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If a surface replacement prosthesis with a cap is used, then force distribution is improved, but more bone material must be removed and attachment stability deteriorates
Solution Approach 1:
The prosthesis is divided into two functional parts: a spherical shell section (cap) that covers the articular surface and a separate crown that anchors into the bone. This segmentation allows the cap to be optimized for force distribution while the crown is optimized for stable attachment, resolving the contradiction between force distribution and bone preservation.
Solution Approach 2:
Different parts of the prosthesis have different geometries and functions: the spherical shell section has a specific curvature to match the articular surface and distribute forces, while the crown has a conical shape with increasing thickness to engage load-bearing bone structures. This local differentiation allows each part to optimize its specific function without compromising the other.
2Stress or pressure
If a surface prosthesis with a handle is used, then force distribution to additional contact surfaces is improved, but the handle is subject to lever forces causing loosening
Solution Approach 1:
Instead of extending the attachment element (handle) outward to distribute forces, the invention inverts the approach by having the crown engage directly into the load-bearing bone structures. The force distribution is achieved through the large contact surface of the spherical shell section, while the crown provides stable anchoring without creating lever forces.
3Reliability
If a threaded bolt attachment is used, then attachment stability is improved, but the procedure complexity and operation time increase
Solution Approach 1:
The invention extracts the threading mechanism from the attachment system, using instead a simple press-fit or interference fit between the crown and the prepared bone cavity. This eliminates the need for threading operations, reducing surgical complexity and operation time while maintaining attachment stability through the conical crown geometry that engages load-bearing bone structures.
Data Source
AI summary
A prosthesis for replacing a surface in an area of a ball of a ball-and-socket joint includes a spherical shell section having an outer surface that is configured to lie in an articular fossa and is for attachment to a surface. The shell section having a cavity for receiving a bone end. The prosthesis also includes a crown that partitions the cavity of the shell section into a first cavity and a second cavity, wherein a shape of the shell section is at least a section of a hemisphere and a free edge of the crown lies in the same plane as a free edge of the shell section.