Orthopedic Screw Bioresorbable Layer Rigid Flexible Transition
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Solution Overview
Problem
Current bone fixation technologies face challenges in providing a fixation system that can transition from rigid to flexible osteosynthesis, as existing systems either lack sufficient compression or inhibit micromotion necessary for bone healing, leading to issues like loosening and non-unions.
Innovation Solution
An orthopedic fixation device featuring a screw with a bioresorbable layer that initially fixes the screw at a desired angular position relative to a bone plate or body, allowing angular movement upon resorption, enabling a transition from rigid to flexible osteosynthesis and promoting micromotion for bone healing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a locking screw is used to provide fixed angular relationship and high resistance to shear force, then stability at the bone screw/plate hole interface is improved, but the capability to compress bone fragments is limited and micromotion across the fracture site is impeded
Solution Approach 1:
The screw/plate connection transitions from a static locked state to a dynamic flexible state. The bioresorbable layer initially provides rigid locking to stabilize the fracture, then progressively degrades to allow controlled micromotion that stimulates callous formation and bone healing.
Solution Approach 2:
The mechanical properties of the screw/plate interface change over time through bioresorption of the coating layer. The connection evolves from high rigidity and strength to increased flexibility and micromotion capability, matching the healing process requirements.
2Ease of operation
If a non-locking screw is used to allow micromotion and promote callous formation, then flexible osteosynthesis is improved, but resistance to shear force is low leading to loosening
Solution Approach 1:
The bioresorbable layer is applied to the screw before implantation to provide immediate locking capability. This preliminary rigid fixation ensures stability during the critical initial healing phase before the layer degrades to allow flexible osteosynthesis.
3Reliability
If rigid osteosynthesis is used to provide stable fixation, then loosening is reduced, but non-unions may occur due to inhibition of micromotion
Solution Approach 1:
The fixation system continuously adapts its mechanical properties to match the healing process. The bioresorbable layer maintains rigid fixation during the stabilization phase, then progressively degrades to enable micromotion for callous formation, ensuring continuous useful action throughout the healing timeline.
4Ease of operation
If flexible osteosynthesis is used to promote bone healing through micromotion, then callous formation is stimulated, but fixation stability is reduced leading to loosening
Solution Approach 1:
The system dynamically transitions from rigid to flexible fixation based on the healing stage. The bioresorbable coating degrades over time, allowing the screw to move from a locked state providing stability to a flexible state enabling micromotion for bone healing.
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 device provides stable initial fixation followed by controlled micromotion, enhancing bone healing by allowing the screw to move angularly relative to the body once the bioresorbable layer is resorbed, thus addressing the limitations of both rigid and flexible osteosynthesis systems.
Implementation Method 1
A layer of bioresorbable material is positioned surrounding a second portion of the shaft... The screw is angularly movable with respect to the body upon resorption of at least a portion of the bioresorbable layer
Data Source
AI summary
The device has a body with holes to accept the bone screws. The bone screws have a layer of bioresorbable material on a surface portion of the head of the screw contiguous with the shaft. Engagement between the bone screws and the body is initially through the bioresorbable material, which engagement rigidly fixes the relative angular orientation between the bone screws and the body when the device is applied to a bone. As the bioresrobable material is resorbed the angular relation between the bone screws and the body is no longer rigidly fixed, thereby effecting a transformation from rigid osteosynthesis to flexible osteosynthesis to allow micromotion between the bone fragments which promotes healing.