Bone-Polyurethane Composites for Stress Shielding and Remodeling
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Solution Overview
Problem
Current bone grafts and substitutes face limitations in mechanical strength, degradation rate, and shape variability, leading to suboptimal support and healing in orthopedic applications, particularly due to their permanent nature and inability to remodel with the patient's bone.
Innovation Solution
Development of injectable and moldable composites comprising bone particles and biodegradable polyurethanes, which promote cellular infiltration and bone remodeling by creating a porous structure that supports mechanical strength and degrades over time, allowing for integration with native bone.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If metal implants are used to replace injured bone, then mechanical support is provided, but bone density decreases around the implant site due to stress shielding
Solution Approach 1:
The invention uses composite materials combining biodegradable polymer matrix with bone graft particles or bone marrow aspirate. This composite structure provides mechanical support comparable to metal implants while being biocompatible and stress-distributing, eliminating the stress shielding effect. The polymer matrix degrades over time as bone regenerates, transferring load gradually to the healing bone.
Solution Approach 2:
The invention changes the material parameters from permanent metal to biodegradable polymer with controlled degradation rate. The mechanical properties of the implant evolve over time as the polymer degrades and bone regenerates, providing initial mechanical support then gradually transferring load to the healing bone, avoiding stress shielding.
2Reliability
If bone grafts are used to promote cellular healing, then bone remodeling occurs, but the available shape and size are limited by donor tissue
Solution Approach 1:
The invention changes the form factor from fixed donor bone shapes to moldable and injectable polymer-based composites. The material can be delivered in liquid or paste form through minimally invasive techniques, then molded in situ to match any anatomical defect shape and size, while maintaining bone remodeling capabilities.
Solution Approach 2:
The invention uses injectable formulations that can be delivered through catheters or syringes to the target site. The material flows in liquid state, is injected into the defect cavity, and then sets or cures in place, enabling minimally invasive delivery and precise placement in complex anatomical locations.
3Strength
If cortical bone grafts are used to support physiological stresses, then mechanical strength is provided, but remodeling occurs slowly
Solution Approach 1:
The invention creates local quality differentiation within the graft material by combining fast-degrading components (bone marrow aspirate, demineralized bone particles) with slower-degrading structural support (polymer matrix). This allows simultaneous provision of mechanical strength and promotion of rapid remodeling through localized biological activity at the cellular level.
Solution Approach 2:
The composite structure combines synthetic polymer matrix providing structural integrity with biological components (bone particles, marrow aspirate) that actively promote osteogenesis and remodeling. This dual-function composite enables both mechanical support and accelerated bone regeneration compared to cortical bone alone.
4Loss of time
If bone substitute materials are used for quick remodeling, then bone regeneration occurs rapidly, but mechanical support cannot be provided immediately
Solution Approach 1:
The composite material combines fast-acting bone substitute particles (demineralized bone, bone marrow aspirate) with a structural polymer matrix. The polymer provides immediate mechanical strength and load-bearing capacity, while the bone substitute particles actively promote rapid remodeling and regeneration. Both functions operate simultaneously rather than sequentially.
Solution Approach 2:
The invention changes the degradation kinetics parameters of the graft material to match the bone regeneration timeline. The polymer matrix degrades at a controlled rate that maintains mechanical support while allowing rapid bone ingrowth, creating a temporal gradient where structural support precedes and enables rapid remodeling.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The composites accelerate bone remodeling and integration, providing immediate mechanical support while degrading to allow new bone growth, thus improving patient outcomes and addressing the limitations of traditional bone grafts.
Implementation Method 1
biodegradable polyurethanes
Implementation Method 2
degrades over time, allowing for integration with native bone
Data Source
AI summary
Present inventions present composites of bone particles and polyurethane(s), as well as methods of making such composite and uses thereof. A porous composite comprises a plurality of bone particles; and polyurethanes with which the bone particles are combined. To prepare a porous composite, a composition comprise a plurality of bone particles, polyurethane precursors including polyisocyanate prepolymers and polyols, water and catalyst. A composition is either naturally moldable and/or injectable, or it can be made moldable and/or injectable. After implantation or injection, a composition may be set to form a porous composite that provides mechanical strength and supports the in-growth of cells. Inventive composites have the advantage of being able to fill irregularly shape implantation site while at the same time being settable to provide the mechanical strength for most orthopedic applications.