Vascular-Safe Pedicle Screw with Self-Tapping Flutes
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Solution Overview
Problem
Conventional spinal support systems face issues with pedicle screws damaging vascular vessels during tapping and loosening due to creep stresses, and existing extension systems require modification of the existing spinal support structure, leading to increased surgical trauma and recovery times.
Innovation Solution
The development of a 'vascular-safe' pedicle screw with self-tapping flutes that minimize tissue damage and a 'extension ready' spinal support system that allows for extension without disturbing the existing structure, using a unitary reinforcement cap for enhanced strength and a polyaxial or monoaxial extension assembly to maintain structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional pedicle screws with continuous threads are used for tapping into vertebrae, then effective anchoring is achieved, but vascular vessels may be sliced or torn during the tapping process
Solution Approach 1:
The continuous thread is divided into discrete segments by introducing self-tapping flutes that interrupt the thread at several points along its length. These flutes create terminated threads that push soft tissue aside rather than slicing through it, reducing the risk of vascular damage while maintaining anchoring effectiveness through the segmented threading pattern.
Solution Approach 2:
Self-tapping flutes are introduced as intermediary structures between the thread and the soft tissue. These flutes act as mediators that redirect the interaction between the pedicle screw and vascular vessels, causing the soft tissue to be pushed aside by the flute structures rather than being cut by the thread edges.
2Loss of time
If extension systems are designed to add spinal support rods to existing structures, then surgical trauma and recovery times are reduced, but the existing spinal support structure must be modified
Solution Approach 1:
The rod receptacle is designed with dual functionality: it can receive and secure a primary spinal support rod through interior threads, and simultaneously provide exterior threads that enable attachment of extension assemblies. This multi-functional design allows the same structure to serve both as the original anchor point and as a platform for extension, eliminating the need to remove or modify the existing rod receptacle.
Solution Approach 2:
The rod receptacle is pre-configured with exterior threads during its manufacturing, enabling future extension capabilities to be built-in advance. This preliminary preparation allows extension assemblies to be attached without requiring modification of the existing structure during subsequent surgery, reducing surgical trauma and recovery time.
3Force
If set screws are used to hold spinal rods within rod receptacles, then initial clamping force is achieved, but creep stresses cause wall segments to deform radially outward over time, leading to loosening
Solution Approach 1:
The rod receptacle wall segments are designed with curved surfaces that conform to the spinal rod. This curved geometry increases the contact area between the wall segments and the spinal rod, distributing creep stresses more effectively and reducing the likelihood of radial deformation and loosening over time.
Solution Approach 2:
The rod receptacle is constructed from composite materials or multi-layer structures that combine different material properties to resist creep deformation. This composite construction provides enhanced stability over time by utilizing the creep-resistant properties of the material composition to counteract the radial outward deformation caused by creep stresses.
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 vascular-safe pedicle screw reduces the risk of tissue damage during implantation, and the extension ready system enables seamless extension of spinal support without altering the existing structure, reducing surgical trauma and recovery time.
Implementation Method 1
The self-tapping flute is less likely to slice into vascular vessels, while still effectively tapping into bone tissue
Implementation Method 2
The curved terminations define a convex profile that extends in a tangential direction from proximate a root of the threads at the face of the self-tapping flute to a crest of the threads at the face of the self-tapping flute
Data Source
AI summary
A “vascular-safe” pedicle screw and extension-ready spinal support system. The pedicle screw includes a self-tapping flute that recessed into a threaded shaft to define terminations of the threads at a face of said self-tapping flute. The terminations are curved to define a convex profile that extends from a root to a crest of the threads at said face of said self-tapping flute. The curved terminations tend to push soft tissue aside as opposed to slicing or tearing through the soft tissue, so that the self-tapping flute is less likely to slice into vascular vessels. The distal portion of the pedicle screw may also include depressions that reduce the circumferential contact area of the pedicle screw in the direction of rotation, which increases the applied pressure to the soft tissue for a given applied rotational force. The increased pressure augments penetration of the pedicle screw through tissue without resort to sharp cutting edges.