Cementless Prosthetic Joint With Threaded Stem Fixation
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Solution Overview
Problem
Current elbow prostheses rely heavily on bone cement for fixation, which leads to complications such as loosening, infection, and difficulty in removal, and lack the ability to easily transition between hemiarthroplasty and total arthroplasty during surgery.
Innovation Solution
A prosthetic joint design featuring externally threaded intramedullary stems that pivotally secure connection portions, allowing for cementless installation and ligament reconstruction to provide stability, enabling interchangeable use between hemiarthroplasty and total arthroplasty with easily replaceable wear components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If bone cement is used for fixation, then initial stability is improved, but long-term reliability deteriorates due to loosening and infection
Solution Approach 1:
The patent removes bone cement entirely from the fixation system, replacing it with a threaded intramedullary stem that achieves direct mechanical engagement with the bone. This extraction of the harmful cement material eliminates the source of loosening and infection while maintaining initial stability through thread-bone engagement.
Solution Approach 2:
The patent replaces the chemical-bonding mechanism of bone cement with a mechanical threading system. The externally threaded stem engages with internally threaded bone channels, creating a mechanical interlock that provides both initial stability and long-term reliability without the biological complications of cement.
2Ease of manufacture
If bone cement is used for fixation, then ease of installation is improved, but ease of repair deteriorates due to difficulty in removal
Solution Approach 1:
By removing bone cement from the system, the patent eliminates the material that makes removal difficult. The threaded stem can be unscrewed and removed without the need for cement removal techniques, significantly improving ease of repair and revision surgery.
Solution Approach 2:
The fixation system transitions from a permanent, irreversible cement bond to a dynamic, reversible threaded connection. The stem can be easily inserted by threading and just as easily removed by unscrewing, providing flexibility for future revisions while maintaining secure initial fixation.
3Adaptability or versatility
If custom made hinges are used, then adaptability is improved, but device complexity increases leading to poor clinical results
Solution Approach 1:
The patent divides the prosthesis into separate modular components: a humeral component and an ulnar component that can be independently selected and combined. This segmentation allows adaptability to different patient anatomies and injury patterns while keeping each individual component relatively simple in design.
Solution Approach 2:
The patent creates a universal prosthesis system where the same basic components can be used for different elbow replacement scenarios (primary replacement, revision, partial or total replacement). The modular design with various stem options and articulation surfaces provides versatility without requiring custom-made hinges for each case.
Data Source
AI summary
A prosthetic joint is secured to the bones forming the original joint by utilizing strictly mechanical fasteners, for example, a threaded rod engaging a tapped intramedullary canal. Cross locking members may be provided. The need for bone cement is avoided. The prosthetic joint may be used to replace one end of one bone forming the joint, utilizing the naturally occurring end of the other bone. Alternatively, both bone ends may be replaced with prosthetic joint portions. The decision to replace one or both bone ends may be made mid-surgery. The prosthetic joint portions are secured together utilizing ligament reconstruction members made from portions of the patient's tendons or allograft tendons. A bearing forming the interface between the two joint portions is designed to wear in order to protect the remaining components from wear, and to be easily replaced in relatively simple future surgeries.