Implant Fixation Design for Heterogeneous Bone Adaptation
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Solution Overview
Problem
Variations in bone properties, such as density and elastic modulus, affect the stability and performance of cementless orthopedic implants, leading to variable implant stability and increased risk of failure during loading scenarios due to excess micromotion and stress transmission.
Innovation Solution
A method involving the use of image data to derive bone property information, creating a virtual bone model, and simulating the implantation of a virtual implant with finite element analysis to determine optimal fixation feature parameters, such as peg location and geometry, to minimize micromotion, stress transmission, and strain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fixation features with designed surface textures are used to increase friction, then implant stability is improved, but variability in bone properties causes variable effect on fixation and decreased implant stability
Solution Approach 1:
The patent applies local quality by customizing fixation features according to local bone properties. Different regions of the implant are designed with specific fixation features (pegs, keels, holes) whose geometry, location, and distribution are tailored to match the heterogeneous bone density and porosity at each location, ensuring optimal adaptation to local bone conditions
Solution Approach 2:
The patent utilizes parameter changes by modifying fixation feature parameters (size, shape, location, distribution) based on bone property parameters (density, porosity, elastic modulus). The design process involves adjusting these parameters to optimize the match between implant fixation features and the specific bone quality of the patient
2Reliability
If fixation features are designed to provide press-fit, then implant stability during first 6-8 months is improved, but excess micromotion occurs under increased loading scenarios
Solution Approach 1:
The patent applies preliminary action by performing virtual simulations and finite element analysis during the design phase to predict and optimize fixation feature performance before actual implantation. This allows the fixation features to be pre-configured with optimal parameters that anticipate and prevent excessive micromotion under future loading conditions
Solution Approach 2:
The patent utilizes composite materials by combining multiple fixation feature types (pegs, keels, holes with bone ingrowth surfaces) with different surface textures and geometries in a single implant design. This composite approach creates a synergistic effect that enhances overall fixation strength and reduces micromotion under various loading scenarios
3Reliability
If heterogeneous bone properties are accounted for in design, then optimized fit is achieved, but design complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the implant design into distinct fixation features (pegs, keels, holes) that can be independently optimized according to local bone properties. This segmentation allows complex heterogeneous bone adaptation to be achieved through modular design elements rather than a monolithic complex structure
Solution Approach 2:
The patent utilizes copying by creating virtual models and simulations of the implant-bone interface during design. These virtual copies allow for iterative optimization of fixation features based on patient-specific bone properties without requiring physical prototypes, reducing actual manufacturing complexity while maintaining design optimization
Data Source
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AI summary
An implant (300), and a method of designing the implant, takes into account heterogeneous bone properties. The method may be directed to designing a fixation feature (310, 320, 330, 340) of the implant using a virtual bone model (100). Bone property information (101, 102) derived from image data may be mapped to the virtual bone. A virtual model of the implant (401) may be created, including a virtual fixation feature characterized by an input parameter. One or more simulations (400) may be performed, the simulations being of an implantation of the virtual implant on the virtual bone. Values for at least one input parameter may be used for each simulation, each simulation resulting in a value for an output parameter. The input and output values may be analyzed to derive a relationship between the values, the relationship being used to design the fixation feature of the implant.