Retractable Flange Instrument for Orthopaedic Cup Positioning
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Solution Overview
Problem
Existing instruments for positioning orthopaedic joint prostheses risk damaging the smooth, polished bearing surfaces of cup components during implantation due to improper contact, which can impair the prosthesis's articulation and longevity.
Innovation Solution
A retractable flange instrument with a spring element and a transverse support system allows secure engagement and accurate positioning of the cup component, minimizing contact with the internal surface and enabling precise alignment and force application without scratching the bearing surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the instrument contacts the internal bearing surface of the cup component during positioning, then secure fixation and accurate alignment can be achieved, but the smooth polished bearing surface may be scratched or damaged, impairing the prosthesis's articulation and longevity
Solution Approach 1:
A retractable flange acts as an intermediary element between the instrument shaft and the cup component's groove. The flange can be extended to engage the groove for secure positioning, then retracted to clear the bearing surface, allowing force application without direct contact between the instrument and the polished bearing area.
Solution Approach 2:
The flange is designed to be movable between extended and retracted positions. When extended, it provides secure engagement with the groove for accurate positioning. When retracted, it clears the bearing surface to prevent damage. This dynamic adjustment allows the instrument to adapt its contact points based on the operational phase.
2Strength
If considerable force is applied to the cup component during positioning to ensure accurate placement, then reliable fixation is achieved, but the risk of damaging the bearing surface or shell increases
Solution Approach 1:
The flange serves as a mediator that transmits positioning forces through the groove engagement rather than directly to the bearing surface. This allows considerable force to be applied for secure fixation while the force transmission path avoids the polished bearing area, preventing damage.
Solution Approach 2:
The instrument is segmented into distinct functional elements: the shaft for force application, the retractable flange for groove engagement, and the bearing surface protection zone. This segmentation allows force to be applied through the flange-groove interface while keeping the bearing surface isolated from damaging contact.
3Strength
If the flange is made entirely of metal to provide sufficient strength for positioning, then adequate fixation force can be applied, but the material cannot be optimized for both strength and spring properties
Solution Approach 1:
The flange is constructed as a composite assembly with a metal portion providing structural strength and attachment to the shaft, and a separate elastomeric portion providing spring properties for engagement and retention in the groove. This composite structure allows each material to be optimized for its specific function.
Solution Approach 2:
Different portions of the flange have different material properties optimized for their specific functions. The metal portion near the shaft provides strength and rigidity for force transmission, while the elastomeric portion at the engagement end provides flexibility and spring properties for secure retention in the groove without permanent deformation.
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 instrument ensures secure fixation and accurate alignment of the cup component, maintaining the integrity of the bearing surface and facilitating successful implantation of orthopaedic joint prostheses while allowing for sufficient articulation range.
Implementation Method 1
the retractable flange portion being biassed towards the in-use position by means of a spring element
Data Source
AI summary
An instrument for positioning a cup component of an orthopaedic joint prosthesis includes a shaft, and a flange located near an end of the shaft on which the cup component can be fixed. The flange extends from the shaft transversely, and can be retracted from an in-use position wherein the flange is received in a groove in the internal surface of the cup component when positioned over the said end of the instrument, and a retracted position in which the flange is withdrawn toward the axis of the shaft from the in-use position, allowing the cup component to be released from the instrument.