Reverse Spiral Cut Pedicle Screw for Spinal Fixation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Traditional pedicle screws are rigid, leading to stress shielding and potential bone fracture due to uneven loading, and have low pull-off strength, which can result in loosening and instability in spinal fixation, especially in osteoporotic spines.
Innovation Solution
A bone screw with a reverse spiral cut design that allows for automatic and self-managed expansion after insertion, reducing bending stiffness and enhancing osteointegration by increasing loading on the bone and promoting bone fusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional rigid pedicle screws are used, then structural strength and fixation stability are improved, but stress shielding and bone fracture risk increase due to uneven loading
Solution Approach 1:
The patent changes the structural parameters of the pedicle screw by introducing a reverse spiral cut that creates a flexible hinge region. This modification transforms the screw from a completely rigid structure to one with controlled flexibility, allowing it to adapt to bone movement while maintaining sufficient strength for fixation.
Solution Approach 2:
The reverse spiral cut effectively segments the screw body into distinct regions: a flexible hinge region with the cut and rigid anchor regions with threads at each end. This segmentation allows different parts of the screw to perform different functions - the hinge region provides flexibility to reduce stress shielding, while the threaded regions maintain anchoring strength.
2Stability of the object's composition
If rigid pedicle screws are used, then fixation stability is improved, but pull-off strength is reduced leading to loosening in osteoporotic spines
Solution Approach 1:
The reverse spiral cut introduces dynamic flexibility to the screw structure, allowing it to adapt to the mechanical environment of osteoporotic bone. The flexible hinge region enables the screw to accommodate bone movement and maintain optimal contact pressure, thereby improving pull-off strength without compromising fixation stability.
3Strength
If high structural stiffness is used, then screw strength is improved, but bone loading is reduced causing stress shielding and bone degradation
Solution Approach 1:
The patent optimizes the stiffness parameter by introducing the reverse spiral cut, which reduces bending stiffness in the hinge region while maintaining adequate strength. This parameter change allows the screw to transmit appropriate loads to the bone, preventing stress shielding and promoting bone health.
Solution Approach 2:
The screw exhibits local quality differentiation through the reverse spiral cut, creating a flexible hinge region with reduced stiffness contrasted with rigid threaded anchor regions. This local flexibility allows the screw to shield specific areas from excessive stress while maintaining overall structural integrity and promoting bone loading in critical regions.
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 reverse spiral cut bone screw increases pull-off strength, reduces the risk of loosening and fracture, and facilitates bone growth and fusion by distributing load more naturally, improving spinal fixation stability and longevity.
Implementation Method 1
a reverse spiral cut into the outer surface in a second direction... allows for increased loading on the bone and increased osteointegration through automatic and self-managed expansion after the bone screw is inserted into the bone
Data Source
AI summary
A pedicle screw with reverse spiral cut that allows for increased loading on a bone and increased osteointegration through automatic and self-managed expansion after the bone screw is inserted into the bone. The bone screw may be a fixation device comprising an elongated body having proximal and distal ends, said elongated body including an outer surface adapted to penetrate and anchor within a bone, and a head affixed to the distal end of the elongated body and adapted to receive a drive component, wherein the outer surface of the elongated body comprises threads extending from the outer surface in a first direction, and further wherein at least a portion of the outer surface of the elongated body comprises a reverse spiral cut into the outer surface in a second direction.