Hinged Articulating Knee Spacer for Revision Arthroplasty
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Solution Overview
Problem
Current revision total knee arthroplasty (TKA) methods, particularly in two-stage procedures, face challenges with static and articulating spacers, as they either restrict mobility or are prone to dislocation, leading to inadequate weight-bearing capacity and prolonged recovery.
Innovation Solution
A hinged articulating spacer system comprising a hinged rod assembly and articulating component assembly, where the femur and tibia rods are hingedly coupled to allow rotational motion, providing stability and mobility while being secured with antibiotic-loaded bone cement, allowing for better weight-bearing and reduced dislocation risk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a static spacer with rigid intramedullary rod is used, then joint stability is improved, but joint mobility is restricted and weight-bearing capacity is reduced
Solution Approach 1:
The patent applies the dynamics principle by transitioning from a static rigid rod system to a dynamic hinged rod assembly that permits controlled rotational motion. The hinged connection between femoral and tibial rods allows the spacer to adapt its configuration during knee flexion and extension, maintaining stability while enabling natural joint movement patterns and weight-bearing capabilities.
Solution Approach 2:
The patent applies segmentation by dividing the single rigid intramedullary rod into separate femoral and tibial rod components connected by a hinge joint. This segmentation allows each rod to be independently positioned and secured to its respective bone, while the hinge connection between them provides rotational freedom, resolving the contradiction between stability and mobility.
2Ease of operation
If a conventional articulating spacer is used, then joint mobility is improved, but dislocation risk increases
Solution Approach 1:
The hinged rod assembly provides controlled dynamic motion that allows physiological knee movement while the hinge mechanism inherently guides and constrains the range of motion. This controlled dynamics approach prevents excessive or abnormal movements that could lead to dislocation, while still permitting adequate mobility for rehabilitation and weight-bearing.
Solution Approach 2:
The hinge joint acts as an intermediary mechanism between the femoral and tibial rods, mediating their relative motion. This intermediary connection permits controlled rotation while maintaining a reliable mechanical link that prevents complete dislocation, bridging the gap between mobility requirements and stability needs.
3Strength
If a hinged rod assembly is used, then weight-bearing capacity is improved, but device complexity increases
Solution Approach 1:
By segmenting the rod system into separate femoral and tibial components connected by a hinge, the patent distributes mechanical loads more effectively across the joint. Each rod can be optimized for its specific bone interface, while the hinge connection manages rotational forces, improving overall weight-bearing capacity despite the increased number of components.
Solution Approach 2:
The hinged rod assembly performs multiple functions simultaneously: it provides structural support for weight-bearing, enables controlled joint motion, and maintains proper alignment between femur and tibia. This multi-functionality justifies the increased complexity by delivering comprehensive performance that simpler spacers cannot achieve.
Data Source
AI summary
A hinged articulating spacer system for revision knee arthroplasty includes a femur rod for a femur, and a tibia rod for a tibia. The tibia rod is hingedly couplable to the femur rod to form a hinged rod assembly. A pre-formed femoral spacer component includes bone cement impregnated with an antibiotic. The pre-formed femoral spacer defines an opening that receives the hinged rod assembly. A pre-formed tibial spacer component includes bone cement impregnated with an antibiotic. The pre-formed tibial spacer defines an opening that receives the hinged rod assembly.