Hinged Knee Spacer Assembly for Stable Revision Arthroplasty Motion
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Solution Overview
Problem
Conventional revision total knee arthroplasty (TKA) spacers, both static and articulating, fail to provide adequate joint stability and mobility during the infection-treatment phase, leading to increased pain and dislocation risks, which hinder patient mobility and the success of subsequent surgical procedures.
Innovation Solution
A hinged articulating spacer system comprising a hinged rod assembly with a femur and tibia rod, coupled by a hinge pin, and articulating components secured with bone cement, allowing for limited knee motion and load-bearing capabilities, reducing dislocation risks.
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
Solution Approach 1:
The patent applies the dynamics principle by transitioning from a static rigid rod system to a dynamic hinged rod assembly that allows controlled motion. The hinged connection between femoral and tibial rods enables the spacer to adapt its configuration, providing stability when needed while permitting mobility during knee flexion and extension, thus resolving the contradiction between joint stability and mobility.
Solution Approach 2:
The patent segments the single rigid rod into separate femoral and tibial rod components connected by a hinge joint. This segmentation allows each component to perform its specific function independently while the hinge coordination provides overall stability, eliminating the need for a completely rigid structure and enabling controlled 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 dynamic control over articulating spacer movement, allowing mobility while preventing dislocation. The hinge mechanism coordinates the relative motion between femoral and tibial components, ensuring that the spacer articulates within safe limits and maintains proper alignment, thus reducing dislocation risk while preserving mobility.
Solution Approach 2:
The hinged connection acts as a mechanical feedback system that monitors and controls the position and motion of the articulating spacer components. The hinge geometry and constraints provide inherent feedback that guides the spacer through appropriate motion arcs and prevents positions that would lead to dislocation, enhancing reliability while maintaining mobility.
3Reliability
If antibiotic-loaded bone cement is used to secure spacer components, then infection treatment is improved, but weight-bearing capability is reduced
Solution Approach 1:
The patent separates the infection treatment function (antibiotic-loaded bone cement) from the primary weight-bearing function (metal hinged rod assembly). The bone cement is used only to secure the spacer components to the bone surfaces for antibiotic delivery, while the metal rod structure provides the necessary mechanical strength for weight-bearing, thus resolving the contradiction between infection treatment and load-bearing capability.
Solution Approach 2:
The patent employs composite construction by combining antibiotic-loaded bone cement with metal rod components. The bone cement serves as both a bonding agent and an antibiotic delivery vehicle, while the metal rods provide structural strength. This composite approach allows simultaneous achievement of infection treatment and weight-bearing requirements without compromising either function.
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.