Intramedullary Stem With Transverse Through-Openings
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing intramedullary implant assemblies for long bones are prone to failure due to aseptic loosening, osteomyelitis, resorption, and mechanical fatigue, particularly when direct implant contact or press-fit cannot be achieved, and they fail to accommodate dynamic compressive loading and resist motion under axial, torsional, and bending loads.
Innovation Solution
An implant assembly with a stem having transverse through-openings that allow axial movement relative to fasteners, accommodating subsidence while resisting tensional and torsional loads, and promoting bone ingrowth through a porous surface, thereby enhancing stability and integration with the bone.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional intramedullary implant assemblies are used without transverse through-openings, then the structure is simpler and manufacturing is easier, but the implant is prone to aseptic loosening due to micromotion and cannot accommodate dynamic compressive loading
Solution Approach 1:
The stem is segmented by incorporating transverse through-openings that divide the continuous structure into distinct sections. These openings allow the stem to be divided functionally into regions that can move independently, enabling accommodation of subsidence while maintaining overall structural integrity and reducing micromotion-related loosening.
Solution Approach 2:
The stem structure is made dynamic by introducing transverse through-openings that permit controlled movement and adjustment. The stem can dynamically adapt to subsidence and loading conditions through the ability of implant components to move relative to each other within the opening structures, transitioning from a rigid fixed structure to a flexible adaptive one.
2Adaptability or versatility
If the implant assembly uses fixed fasteners without axial movement capability, then resistance to axial distraction is improved, but the ability to accommodate subsidence and dynamic compressive loading is reduced
Solution Approach 1:
The fastener system transitions from a static fixed connection to a dynamic adjustable connection. The transverse through-openings allow fasteners to move axially within the opening, enabling the system to adapt to subsidence while maintaining strength through the ability to reposition and redistribute loads dynamically.
Solution Approach 2:
The system allows changes in positional parameters of the fasteners relative to the stem. By permitting axial movement within the transverse through-openings, the fastener position parameter can change to accommodate subsidence, while the overall structural parameters maintain sufficient strength through the engineered geometry of the openings and fastener-stem interaction.
3Adaptability or versatility
If the implant assembly permits axial movement to accommodate subsidence, then adaptability to dynamic loading is improved, but resistance to torsional and bending loads may be reduced
Solution Approach 1:
The stem is segmented by incorporating transverse through-openings that divide the continuous structure into distinct sections. These openings allow the stem to be divided functionally into regions that can move independently, enabling accommodation of subsidence while maintaining overall structural integrity and reducing micromotion-related loosening.
Solution Approach 2:
The implant assembly utilizes a composite structure combining the stem material with the fastener system and bone interface. This composite construction allows different components to have optimized properties - the stem provides torsional and bending strength, while the fastener system within transverse through-openings provides axial movement capability for subsidence accommodation, achieving both requirements through material and structural composition.
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 implant assembly provides improved stability and integration by allowing axial movement to accommodate subsidence and resist external loads, reducing the risk of failure and promoting bone remodeling, thus addressing the limitations of existing implant designs.
Implementation Method 1
promoting bone ingrowth through a porous surface, thereby enhancing stability and integration with the bone
Implementation Method 2
Each transverse through-opening has a longitudinal dimension, measured relative to the longitudinal axis of the stem, that is sufficient to permit axial movement, relative to the longitudinal axis of the stem, of the stem relative to each fastener within the at least one transverse through-opening
Implementation Method 3
The at least one transverse through-opening of the stem of the implant assembly can be configured to permit axial movement of the implant assembly relative to the at least one fastener to accommodate subsidence of the implant assembly while resisting tensional and torsional loads
Data Source
Figure 1
Figure 2A~2L
Figure 3A~3L
AI summary
An implant assembly for a long bone having a longitudinal axis. The implant assembly has a stem that is received in a surgically prepared medullary canal of the long bone. The stem defines at least one transverse through-opening that extends through the stem from a first portion of the outer surface of the stem to an opposed second portion of the outer surface of the stem. Each transverse through-opening has a central axis that is substantially perpendicular to the longitudinal axis of the stem. Each transverse through-opening receives a fastener and has a longitudinal dimension, measured relative to the longitudinal axis of the stem, that is sufficient to permit axial movement, relative to the longitudinal axis of the stem, of the stem relative to each fastener.