Poly(diol citrate)-hydroxyapatite composite for orthopedic fixation
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Solution Overview
Problem
Current orthopedic devices made from biodegradable polymers like PLLA have slow degradation rates, fracture during fixation, and fail to fully integrate with bone, while composites with high HA content are brittle and difficult to process.
Innovation Solution
Development of a composite material comprising a citric acid polyester and a bioceramic, such as hydroxyapatite, with a weight ratio of less than 75% bioceramic, which enhances osteointegration, mechanical properties, and processability, allowing for the creation of orthopedic fixation devices like bone screws with improved strength and degradation rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PLLA is used for biodegradable fixation devices, then biocompatibility is improved, but degradation rate is too slow (5 years)
Solution Approach 1:
The patent creates a composite material system combining poly(diol citrate) polymer matrix with bioceramic particles (hydroxyapatite, tricalcium phosphate, beta-tricalcium phosphate). This composite approach allows the polymer to provide biocompatibility while the bioceramics accelerate degradation and provide osteoconductivity, resolving the contradiction between slow degradation of pure PLLA and need for faster degradation.
Solution Approach 2:
The patent modifies the polymer composition by using citric acid polyester instead of traditional PLLA, and adjusts the bioceramic content (30-70 wt%) to optimize degradation rate. The specific parameter changes in polymer chemistry and composite formulation enable controlled degradation within 1 year while maintaining biocompatibility.
2Reliability
If HA content is increased to improve osteointegration, then osteoconductivity is improved, but mechanical strength decreases (material becomes brittle)
Solution Approach 1:
The patent develops an optimized composite where bioceramic particles (30-70 wt%) are dispersed in a poly(diol citrate) polymer matrix. The polymer matrix provides ductility and mechanical strength while the bioceramics provide osteoconductivity. This composite structure resolves the contradiction by allowing high bioceramic content for osteointegration without sacrificing mechanical strength, as the polymer matrix prevents brittleness.
Solution Approach 2:
The patent creates a heterogeneous composite structure where bioceramic particles are distributed within the polymer matrix, providing local osteoconductivity where needed while the polymer matrix provides continuous mechanical support. This local differentiation of functions allows simultaneous achievement of high osteointegration and maintained mechanical strength.
3Reliability
If HA content is increased to improve osteointegration, then bone integration is improved, but processability worsens (difficult to process into fixation devices)
Solution Approach 1:
The patent creates a composite material system where the poly(diol citrate) polymer matrix acts as a binder holding bioceramic particles together. This composite structure provides sufficient mechanical strength and ductility for processing into fixation devices like screws and plates, while maintaining high bioceramic content (30-70 wt%) for osteointegration. The polymer matrix enables conventional manufacturing processes that would be impossible with pure brittle ceramics.
4Reliability
If PLLA composite with HA is used, then osteointegration is improved, but degradation rate remains slow
Solution Approach 1:
The patent changes the polymer chemistry from PLLA to poly(diol citrate), which has inherently faster degradation characteristics. Additionally, the inclusion of bioceramic particles (30-70 wt% HA, TCP, or β-TCP) creates pathways for water penetration and accelerates hydrolysis. These parameter changes in polymer composition and composite formulation enable degradation within 1 year while maintaining osteointegration capabilities.
Solution Approach 2:
The patent develops a composite where the polymer matrix composition is specifically designed for faster degradation compared to traditional PLLA. The bioceramic particles contribute to degradation by creating porosity and facilitating water access to the polymer matrix. This composite approach achieves both osteointegration and accelerated degradation, resolving the contradiction present in PLLA-HA composites.
Data Source
AI summary
The present invention is directed to a novel poly(diol citrates)-based bioceramic composite materials created using completely biodegradable and a bioceramic material polymers that may be used in implantable devices. More specifically, the specification describes methods and compositions for making and using bioceramic composites comprised of citric acid copolymers and a bioceramic material.