Pedicle Screw U-Shaped Cavity for Vertebral Derotation
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Solution Overview
Problem
Current pedicle screws face challenges in effectively treating scoliosis and other spine degenerative diseases due to issues like stress concentration, vertebral fracture, and difficulty in assembling with rods, particularly in the axial plane, leading to complications such as loose screws and loss of reduction.
Innovation Solution
A pedicle screw design featuring a screw head with a U-shaped cavity, first and second grooves, and an arc-shaped dimple allows for adjustable angle insertion of a screw rod, enabling self-rotation and pendulum motion, which limits the screw body to the axial plane, facilitating vertebral derotation and reducing assembly difficulties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a polyaxial pedicle screw is used to allow easy assembly with rod and reduce stress concentration, then the ease of operation and stress distribution are improved, but the ability to achieve vertebral body derotation in the axial plane is lost
Solution Approach 1:
The screw head is designed with a U-shaped cavity that allows dynamic adjustment of the screw rod angle while maintaining axial plane limitation. The screw body can rotate within the U-shaped cavity to achieve vertebral body derotation, while the cavity structure itself provides the adaptability needed for both polyaxial and monoaxial configurations
Solution Approach 2:
The design allows changing the degree of freedom parameter by adjusting the orientation and constraints of the U-shaped cavity. When the cavity is oriented to allow rotation, it provides polyaxial movement for easy assembly; when constrained to limit movement to axial plane, it enables vertebral body derotation
2Adaptability or versatility
If a monoaxial pedicle screw is used to achieve vertebral body derotation in the axial plane, then the treatment effect is improved, but the difficulty of assembling with rod increases resulting in vertebral fracture and stress concentration
Solution Approach 1:
The screw head incorporates a U-shaped cavity that provides dynamic adaptability, allowing the screw to function as either monoaxial or polyaxial depending on the surgical requirements. This dynamic structure eliminates the need to choose between derotation capability and assembly ease
Solution Approach 2:
The pedicle screw design achieves multi-functionality by combining features of both monoaxial and polyaxial screws. The U-shaped cavity structure allows the same screw to provide vertebral body derotation when needed while also allowing easy assembly with rod through controlled movement, making it universally applicable to different surgical scenarios
3Ease of operation
If the screw body is allowed free movement to facilitate assembly, then the ease of operation is improved, but the stability and reliability of the screw fixation is reduced leading to loose screws and loss of reduction
Solution Approach 1:
The screw head features a U-shaped cavity that provides controlled dynamic movement during assembly, allowing the screw body to adjust its position and rotate as needed for easy insertion. Once assembled, the cavity structure maintains appropriate constraints to ensure stable fixation and prevent loosening
Solution Approach 2:
The U-shaped cavity is designed with predetermined geometry that anticipates and accommodates the movement needed during assembly while built-in constraints prevent excessive movement that could lead to loosening. The structure provides built-in protection against both insufficient movement (assembly difficulty) and excessive movement (loosening)
Data Source
AI summary
The present invention provides a pedicle screw, which includes a screw head, a screw body, a screw rod and a screw cap. The screw body includes a ball-liked arc-shaped buckle portion and a column-liked thread portion. The screw head includes a semi-sphere part with an arc-shaped dimple on one end and a U-shaped cavity on the other end. The U-shaped cavity connects with the arc-shaped dimple. Furthermore, the Arc-shaped dimple connects with the arc-shaped buckle portion. The Arc-shaped dimple includes an opening on its top to allow the screw body passing through. The U-shaped cavity includes an opening, which includes a female thread to fix the screw rod in the U-shaped cavity by a male thread on the screw cap.