Transdiscal Screw Non-Linear Trajectory
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Solution Overview
Problem
Existing screw systems for transdiscal fixation of vertebral bodies face challenges in achieving high pull-out resistance without requiring high installation torque or excessive material usage, and they struggle with navigating non-linear paths within anatomical constraints.
Innovation Solution
A transdiscal screw assembly capable of following a non-linear configuration, featuring a joint that allows independent rotation of the screws and a flexible sleeve with interlocking teeth, enabling the screw to maintain pull-out resistance while accommodating curved or angled paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If screw diameter or thread depth is increased to achieve higher pull-out resistance, then pull-out resistance is improved, but installation torque increases and material usage increases
Solution Approach 1:
The patent employs a non-linear curved trajectory for the screw instead of a straight linear path. The screw follows a curved path through the vertebral body that arches away from the entry point and returns, creating a longer engagement path within the bone. This curved configuration increases the effective pull-out resistance by extending the thread engagement length without requiring increased screw diameter or thread depth, thereby avoiding the trade-off with installation torque.
2Reliability
If screw diameter or thread depth is increased to achieve higher pull-out resistance, then pull-out resistance is improved, but manufacturing material increases
Solution Approach 1:
The curved non-linear trajectory extends the screw path through the vertebral body in an arching pattern, increasing the engagement length and surface area of thread-bone contact. This approach achieves enhanced pull-out resistance by optimizing the geometric path rather than increasing the screw's cross-sectional dimensions, thereby reducing the quantity of manufacturing material required while maintaining or improving reliability.
3Ease of operation
If a linear screw path is used, then installation is simple, but pull-out resistance is reduced and anatomical constraints cannot be accommodated
Solution Approach 1:
The patent implements a curved non-linear screw trajectory that arches away from and returns to the entry point, creating a longer engagement path within the vertebral body. This curved path increases pull-out resistance by extending thread engagement while still allowing for relatively simple installation through pre-drilling and guided insertion. The curved path also enables navigation around anatomical constraints that would block straight linear paths.
Solution Approach 2:
The screw trajectory transitions from a one-dimensional linear path to a two-dimensional curved path within the vertebral body. By adding the dimensional complexity of curvature, the screw achieves longer engagement length and better anatomical accommodation without proportionally increasing installation complexity, as the curved path can be pre-planned and drilled.
4Ease of manufacture
If a linear screw path is used, then manufacturing is simple, but anatomical constraints cannot be accommodated and fixation versatility is limited
Solution Approach 1:
The screw is designed with a curved non-linear trajectory that can be manufactured as a straight screw with a predetermined bend or as a flexible screw. The curved path allows the screw to navigate around anatomical constraints such as nerves, vessels, or bone structures that would block straight linear paths. The manufacturing process remains relatively simple using standard bending or forming techniques applied to the screw shaft, while greatly enhancing adaptability to various anatomical configurations.
Data Source
AI summary
This invention relates to a transdiscal screw capable of following a non-linear trajectory. The screw assembly includes a first screw and second screw coupled at a poly-axial joint. The first screw and the second screw capable of rotating independently of each other. The screw can also include a third screw coupled to the second screw at a poly-axial joint such that the first screw, second screw and third screw can rotate independently of each other.