Pedicle Screw Assembly with Lateral Bone Anchor
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Solution Overview
Problem
Pedicle screw failure and pull-out are common complications in spinal fixation surgeries, leading to pseudarthrosis and adjacent segment disease, with existing solutions like increased screw sizes, alternative thread shapes, and bone-cement augmentation being unreliable.
Innovation Solution
A pedicle screw assembly featuring a pedicle screw with external threads and a bone anchor that extends outwardly from the screw to engage the vertebra, utilizing a driveshaft to actuate the bone anchors for enhanced fixation, and various embodiments with angled or perpendicular lateral channels to improve anchoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If increased screw sizes are used to increase axial resistance, then the resistance to pull-out is improved, but the device complexity and surgical difficulty increase
Solution Approach 1:
The bone anchor is inserted through the pedicle screw and deployed within the vertebral body, creating a nested configuration where the anchor is housed inside the screw structure. This allows the smaller screw to achieve enhanced axial resistance through the additional anchoring mechanism without requiring oversized screws.
Solution Approach 2:
The invention transitions from a single-point anchoring (screw in pedicle) to a multi-dimensional anchoring system by deploying the bone anchor laterally through the pedicle wall into the vertebral body. This adds a lateral dimension to the anchoring, significantly increasing axial resistance without increasing screw dimensions.
2Strength
If alternative core shapes and thread shapes are used to increase axial resistance, then the fixation strength is improved, but the manufacturing complexity increases
Solution Approach 1:
The fixation system is divided into two separate functional components: the pedicle screw that provides initial anchoring and the bone anchor that provides enhanced axial resistance. This segmentation allows each component to have optimized, simpler geometries that are easier to manufacture while achieving superior overall fixation strength through their combined action.
3Reliability
If bone-cement augmentation is used to increase axial resistance, then the fixation reliability is improved, but the surgical procedure complexity and time increase
Solution Approach 1:
The invention extracts the bone-cement augmentation function and replaces it with a mechanical bone anchor system. The anchor provides immediate mechanical interlocking with the vertebral bone through lateral deployment, eliminating the need for bone cement injection, curing time, and associated surgical complexity while maintaining or improving fixation reliability.
4Strength
If larger screw sizes are used to prevent pull-out, then the axial resistance is improved, but the ease of operation during surgery decreases
Solution Approach 1:
The bone anchor is designed to be deployed dynamically after the pedicle screw is initially inserted and secured. The anchor can be actuated to extend laterally through the pedicle wall into the vertebral body, providing enhanced axial resistance only when needed. This dynamic deployment allows standard-sized screws to achieve superior fixation without increasing surgical difficulty during the initial insertion phase.
Data Source
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AI summary
Various embodiments of a pedicle screw assembly having a pedicle screw defining an axial channel in communication with a pair of lateral channels configured to receive a bone anchor therein that extends outwardly from the pair of lateral channels in a post-deployment position for anchoring the pedicle screw to bone tissue are disclosed.