Polyaxial Bone-Anchoring Device for Cement-Free Pedicle Fixation
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Solution Overview
Problem
Current bone anchoring methods, particularly using pedicle screws, are inadequate for structurally weakened spinal columns due to insufficient load-bearing capacity, and the use of bone cement poses risks such as tissue necrosis and embolism, while existing alternatives are not suitable for posterior pedicle canal insertion.
Innovation Solution
A bone anchoring device with a U-shaped fork head and polyaxially pivotable bone anchoring element featuring helical wings for rotational stability, which is hammered into the pedicle canal, and includes features like teeth, grooves, and porosity to enhance pull-out strength and bone integration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If pedicle screws with bone cement are used for fixation, then anchoring strength is improved, but the risk of tissue necrosis and embolism increases
Solution Approach 1:
The invention extracts and eliminates the bone cement component from the fixation system, replacing it with a purely mechanical anchoring mechanism. The hollow pedicle screw design allows bone fragments to be captured and retained mechanically without requiring cement augmentation, thereby removing the source of harmful effects while maintaining anchoring strength.
Solution Approach 2:
The hollow interior of the pedicle screw creates a porous-like structure that allows bone fragments to penetrate and become mechanically interlocked. This hollow cavity system provides structural integration with the bone without using bone cement, achieving strong anchoring while avoiding the harmful effects of PMMA cement.
2Strength
If bone cement is injected for augmentation, then load-bearing capacity is improved, but the complexity of revision surgery increases
Solution Approach 1:
By removing the bone cement component entirely from the system, the invention eliminates the need for complex revision procedures to remove hardened cement. The mechanical anchoring system can be revised by simply removing or adjusting the screw without the additional complexity of cement removal, while maintaining adequate load-bearing capacity through mechanical interlocking.
3Stability of the object's composition
If a blade-like bone anchor is used for anterior approach, then fixation stability is improved, but suitability for posterior pedicle canal insertion deteriorates
Solution Approach 1:
The invention introduces polyaxial pivotability that allows the bone anchoring element to adapt its orientation dynamically. The distal blade can be oriented at different angles relative to the pedicle canal axis, enabling insertion through the posterior approach while maintaining optimal fixation stability. This dynamic adjustment capability makes the device versatile for different surgical approaches.
Solution Approach 2:
The invention adds an angular dimension of freedom through polyaxial pivotability, allowing the blade component to be oriented in multiple directions. This dimensional flexibility enables the same blade-like structure to be effectively used in both anterior and posterior approaches by adjusting the orientation angle, rather than requiring separate devices for each approach.
4Strength
If pedicle screws are used in weakened bone, then fixation is achieved, but rotational stability deteriorates
Solution Approach 1:
The hollow interior of the pedicle screw creates a structure that can capture and retain bone fragments, providing mechanical interlocking that resists rotational forces. This hollow cavity system enhances rotational stability in weakened bone by creating a mechanical key-lock mechanism without requiring additional rotational features.
Solution Approach 2:
The invention creates a composite structure where the metal screw combines with captured bone fragments within the hollow cavity. This composite anchoring system provides superior rotational stability compared to a pure metal screw, as the bone-metal composite structure resists rotational forces more effectively in weakened bone.
Data Source
AI summary
A bone anchoring device for anchoring and fixing vertebrae and for insertion into a pedicle canal is disclosed. A fork head having a U-shaped cut-out in a side view for a correction element, a connecting rod with two legs which terminate proximally and form a threaded section which engages with an adjusting means, wherein the legs have a radially outer circumferential area in which at least one retaining groove or other instrument attachment point is formed for gripping the fork head by a handling instrument, and a bone anchoring element with a proximal end facing away therefrom in the axial direction such that a distal direction and a proximal direction are also defined. The bone anchoring element has a spherical head at the proximal area, and the bone anchoring element is polyaxially pivotable with respect to the fork head, and has a pressure piece distally partially surrounds the bone anchoring element at the ball head, and proximally forms a seat for the connecting rod.