Capture Element for Prosthetic Knee Distraction Control
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Solution Overview
Problem
Constrained knee prostheses with hinge posts often face issues with distraction and luxation due to insufficient soft tissue, leading to pain and complications for patients, as existing designs do not adequately limit the movement of the femoral component relative to the tibial baseplate and bearing component.
Innovation Solution
The development of a prosthesis system that allows for selection between configurations to limit or allow full distraction, utilizing a combination of bushings and capture elements to restrict movement, with the ability to switch between these configurations intraoperatively based on the patient's anatomy and soft tissue availability, using a minimal number of components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the femoral component is allowed to move freely relative to the tibial baseplate and bearing component, then the knee joint has greater range of motion and flexibility, but distraction and luxation occur leading to pain and complications
Solution Approach 1:
The hinge post is designed with selective mobility: it allows proximal/distal movement when soft tissue is sufficient to maintain stability, but becomes constrained when soft tissue is insufficient. The capture element engages with the hinge post only when needed, dynamically adapting the degree of freedom based on actual joint conditions.
Solution Approach 2:
The system changes the parameter of distraction limitation based on soft tissue adequacy. When soft tissue is sufficient, full distraction is permitted; when insufficient, the capture element engages to limit distraction to a safe range, preventing luxation while maintaining functional movement.
2Reliability
If a capture element is added to limit distraction of the femoral component, then joint stability is improved and luxation is prevented, but device complexity increases
Solution Approach 1:
The capture element serves multiple functions: it limits distraction when soft tissue is insufficient, allows full movement when soft tissue is sufficient, and can be selectively engaged or disengaged based on intraoperative assessment. This multi-functionality reduces the need for entirely different prosthesis designs for different patient conditions.
Solution Approach 2:
The system allows the surgeon to assess soft tissue adequacy intraoperatively and selectively engage the capture element based on actual patient anatomy and tissue condition, making the stability adjustment self-adaptive to individual patient needs without requiring complex pre-planning or multiple component sets.
3Reliability
If the prosthesis is designed to limit distraction, then luxation is prevented in patients with insufficient soft tissue, but full distraction capability is lost for patients with adequate soft tissue
Solution Approach 1:
The prosthesis transitions from a static design to a dynamic system where the capture element can be selectively engaged or disengaged based on intraoperative assessment of soft tissue adequacy, allowing the same device to adapt to different patient anatomies and tissue conditions.
Solution Approach 2:
The system changes the operational parameter of distraction limitation based on patient-specific factors. The capture element modifies the range of motion parameter dynamically: permitting full distraction when soft tissue is adequate, and limiting distraction when soft tissue is insufficient, thus accommodating different patient anatomies with a single device design.
Data Source
AI summary
A prosthesis system may include a femoral component, a tibial bearing component configured to articulate with the femoral component, a baseplate, a plurality of bushings, one or more hinge posts and a capture element. The capture element can be configured to couple with the baseplate and can have a thru hole configured to allow at least a portion of the one or more hinge posts to pass therethrough. When coupled to the baseplate, the capture element is configured to be engaged by at least one of the plurality of bushings or one of the one or more hinge posts to limit distraction of the femoral component from the tibial bearing component and baseplate.