Joint Prosthesis Head with Expandable Conjoining Member
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Solution Overview
Problem
Current prosthetic joint systems face challenges in adjusting and locking the angular position of the joint head without external fasteners, particularly after implantation, and often require complex instrumentation, which can complicate surgery and affect biomechanics.
Innovation Solution
A joint prosthesis with an expandable conjoining member that provides a friction fit within a socket of the stem, allowing infinite angular positioning and locking of the joint head without external fasteners, using a tapered stem and bore interaction to secure the head in place.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a locking screw mechanism is used to fix the joint head position, then the head can be locked in place, but access to the locking mechanism is lost once the stem is cemented, eliminating post-implantation adjustment capability
Solution Approach 1:
A polymeric locking medium is introduced as an intermediary substance between the head and stem. This medium cures to form a bonded connection that provides reliable fixation while allowing for post-implantation adjustment by the surgeon, as the bond can be broken and reformed without requiring access to mechanical fasteners
Solution Approach 2:
The mechanical locking screw system is replaced with a chemical bonding system using a polymeric locking medium. This substitution eliminates the need for mechanical fasteners that require access holes, allowing for reliable bonding while maintaining the ability to adjust the head position after implantation by simply breaking and reforming the chemical bond
2Reliability
If external fasteners are used to secure the joint head, then secure fixation is achieved, but the surgical procedure becomes more complex and requires additional instrumentation
Solution Approach 1:
External fasteners and complex locking mechanisms are completely removed from the system. The patent uses a polymeric locking medium that is applied directly to the interface between the head and stem, eliminating the need for screws, bolts, or other mechanical fastening devices and their associated instrumentation
Solution Approach 2:
The fixation function is merged with the bonding function of the polymeric locking medium. The same material that bonds the head to the stem also provides the fixation security, eliminating the need for separate fastening components and simplifying the overall system
3Reliability
If the stem is cemented in place, then stable fixation is achieved, but access to the glenoid is limited by the protrusion on the humeral stem
Solution Approach 1:
The system allows for dynamic adjustment of the head position after implantation. The polymeric locking medium enables the surgeon to modify the head orientation even after the stem is cemented, providing adaptability that accommodates both stable stem fixation and the need for glenoid access and adjustment
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
Enables easy and precise adjustment and locking of the joint head during and after surgery, improving biomechanics and reducing the need for complex instrumentation, while ensuring secure fixation without external locking devices.
Implementation Method 1
Expansion of the conjoining member is achieved through coupling interaction of a stem of the head with the conjoining member
Implementation Method 2
using a tapered stem and bore interaction to secure the head in place
Data Source
AI summary
A joint prosthesis, as a replacement for a ball and socket type joint, has a head that allows for infinite dialability and/or angular orientation with respect to an implanted stem, particularly during a procedure for implanting the prosthesis. The angular orientation is positionable and fixed or locked in a set position without utilizing external or separate fasteners. An expandable conjoining member associated with the prosthesis stem receives the head and allows for the positioning thereof. The expandable conjoining member is fixed in position through expansion of the expandable conjoining member to produce a friction fit (wedging) of the expandable conjoining member within a receiving socket of the stem. Expansion of the expandable conjoining member is achieved through coupling interaction of a stem of the head with the conjoining member.