Viscoelastic Longitudinal Member for Dynamic Bone Stabilization
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Solution Overview
Problem
Existing dynamic stabilization systems for bones or vertebrae face challenges in matching the shape of longitudinal members to pedicle screws, leading to potential loosening due to creep of biocompatible plastics materials under mechanical stress, and lack of flexibility in adapting to various anatomical conditions.
Innovation Solution
A viscoelastically deformable longitudinal member made from a combination of biocompatible plastics material, such as polycarbonate-urethane, and metal, specifically titanium, which allows for bending resilience and creep-proof clamping sites, enabling the member to be matched to the pedicle screws and maintain stability over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If longitudinal members are made from biocompatible high-performance plastics material, then flexibility in bending is improved, but resistance to shear and buckling deteriorates
Solution Approach 1:
The longitudinal member is constructed as a composite structure with a plastics material outer layer providing flexibility and a metal core providing rigidity. This composite design allows the member to simultaneously achieve bending flexibility from the plastics material and resistance to shear and buckling from the metal core.
2Adaptability or versatility
If longitudinal members are made from biocompatible high-performance plastics material, then flexibility in bending is improved, but dimensional stability under load deteriorates due to creep
Solution Approach 1:
The composite structure combines plastics material for flexibility with a metal core that provides dimensional stability and resistance to creep under load. The metal core maintains the structural integrity while the plastics outer layer provides the necessary bending flexibility.
Solution Approach 2:
Different portions of the longitudinal member have different material properties: the outer plastics layer provides flexibility and comfort, while the inner metal core provides dimensional stability and creep resistance. This local differentiation of material qualities resolves the contradiction between flexibility and stability.
3Strength
If longitudinal members are made thicker to increase resistance to shear and buckling, then strength is improved, but flexibility deteriorates
Solution Approach 1:
The composite design allows achieving high strength and resistance to shear and buckling through the metal core without increasing the overall thickness of the longitudinal member. The plastics outer layer maintains flexibility while the metal core provides the necessary structural strength.
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 solution provides a dynamic stabilization system that is flexible enough to adapt to various anatomical conditions, resistant to creep, and maintains stability, reducing the risk of loosening and promoting healing by evenly distributing loads and reducing inflammation.
Implementation Method 1
the plastics material provides for viscous deformability
Implementation Method 2
the metal provides for resiliently flexible deformability
Data Source
AI summary
A device for dynamic stabilization of bones or bone fragments comprising at least one anchor member for attachment to vertebrae having an opening configured to receive a longitudinal member; and the longitudinal member being viscoelastically deformable and having a predetermined bending resilience.