Pedicle Fixation Screw with Helical Grooves for Easy Removal
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Solution Overview
Problem
Existing medical devices and screws are inadequate for combined vertebroplasty and pedicle formation, as they are not designed to be easily removable after bone cement hardens, posing a risk of complications such as infection and difficulty in removal due to strong engagement with the cement.
Innovation Solution
A cylindrical internal fixation device with helical grooves on a proximal side and threads on a distal side, allowing for easy insertion and removal by rotating opposite to the screwing direction, and a treatment device with a screwdriver and inner cylinder for secure fixation and removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the screw is designed to be tightly engaged in the bone cement for secure fixation, then the internal fixation strength is improved, but the ease of removal deteriorates
Solution Approach 1:
The screw shaft is divided into two distinct functional segments: a proximal portion with external threads for engagement with bone cement, and a distal portion with internal threads for engagement with the pedicle. This segmentation allows each portion to serve its specific function optimally - the proximal threads provide secure fixation in the bone cement while the distal threads enable controlled engagement with the pedicle, and the separate design allows for planned removal through the proximal engagement mechanism.
Solution Approach 2:
The screw design incorporates a reverse thread configuration where the proximal external threads are designed to engage with the bone cement in a manner that allows for controlled disengagement. The thread geometry and engagement mechanism are inverted compared to conventional screws, enabling the screw to be easily removed after serving its fixation purpose, thus resolving the contradiction between secure fixation and ease of removal.
2Stability of the object's composition
If the screw is threaded into the bone cement for fixation, then the fixation stability is improved, but the time required for surgery increases
Solution Approach 1:
The bone cement is injected into the vertebral body cavity before the screw is inserted. This preliminary action creates a pre-prepared fixation medium that is ready to receive the screw threads. The screw can then be directly threaded into the already-injected bone cement without requiring additional steps, thereby maintaining fixation stability while minimizing surgical time.
Solution Approach 2:
The procedure merges the vertebroplasty (bone cement injection) and pedicle screw fixation steps into a single integrated operation. By combining these two procedures that were traditionally performed separately, the invention reduces the total surgical time while achieving both the stabilization effect of bone cement and the mechanical fixation of the screw.
3Strength
If conventional screws are used for vertebroplasty, then the fixation function is provided, but the adaptability for combined procedures deteriorates
Solution Approach 1:
The screw is designed with multi-functionality to serve both vertebroplasty and pedicle formation procedures. The proximal external threads enable engagement with bone cement for vertebroplasty, while the distal internal threads enable engagement with the pedicle for spinal fusion. This universal design allows a single screw to perform multiple functions that were previously requiring separate devices, thereby improving adaptability for combined procedures.
Solution Approach 2:
The screw design incorporates dynamic engagement capabilities where the thread configurations allow for flexible adaptation during surgery. The proximal threads can engage with the bone cement to provide fixation, while the distal threads can engage with the pedicle to provide anchoring. This dynamic design enables the screw to adapt to different surgical scenarios and combined procedures, enhancing versatility.
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 secure internal fixation equivalent to screws while being easy to remove, reducing the risk of postoperative complications and facilitating quicker surgery by allowing immediate screwing into bone cement before it hardens.
Implementation Method 1
the shaft has helical grooves (4) on a proximal side
Implementation Method 2
A cylindrical internal fixation device with helical grooves on a proximal side and threads on a distal side
Implementation Method 3
allowing easy insertion and removal by rotating in the opposite direction
Data Source
Figure 1(A)~1(C)
Figure 2
Figure 3(A)~3(B)
AI summary
An internal fixation device that is inserted through the pedicle into bone cement pre-filled into the vertebral body, the device being easy-to-remove, but exhibiting internal fixation performance equivalent to that of a screw is provided. An internal fixation device to be inserted through a pedicle into bone cement filled into a vertebral body, the device comprising a columnar shaft and a connection at a distal end of the shaft that can be connected to a screwdriver, and the shaft has helical grooves on a proximal side. More suitably, the internal fixation device is provided with threads on the distal side of the shaft, the threads and the grooves formed to have the same lead.