Expandable Bone Core for Press-Fit Pedicle Screw Fixation
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Solution Overview
Problem
Existing pedicle screw fixation techniques face issues with screw loosening and pullout, particularly in patients with poor bone quality, leading to instability and potential failure of spinal fusion constructs.
Innovation Solution
The use of expandable pedicle screw implants with an expandable anchor and deployable teeth that create a strong press-fit in the bone, enhancing stability and osseointegration by filling unused pedicle space and engaging cortical bone.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional pedicle screw fixation is used, then the procedure is simple and widely applicable, but screw loosening and pullout occur especially in patients with poor bone quality
Solution Approach 1:
The pedicle screw incorporates an expandable proximal portion that can dynamically change volume after insertion. The expandable anchor is inserted in a collapsed state and then expanded to engage cortical bone, transforming from a static implant to a dynamic one that adapts to the bone structure, thereby improving fixation stability without requiring excessively complex initial design
Solution Approach 2:
The pedicle screw is divided into distinct functional segments: a threaded distal portion for initial anchoring and an expandable proximal portion for enhanced cortical bone engagement. This segmentation allows each part to perform its specific function optimally, improving overall reliability while maintaining reasonable device complexity through modular design
2Strength
If the pedicle screw is expanded to increase purchase in pedicle space, then primary stability is improved, but the device complexity increases
Solution Approach 1:
The expandable anchor is designed to be inserted in a collapsed, space-efficient state through the pedicle canal, then expanded in-situ to engage the cortical bone. This nesting principle allows the implant to achieve high strength and bone-implant interface integrity while minimizing the complexity of the expansion mechanism by utilizing the available space within the prepared canal
3Reliability
If expandable anchor with deployable teeth is used, then osseointegration is facilitated, but the manufacturing complexity increases
Solution Approach 1:
The expandable anchor features deployable teeth or anchors at its distal end that provide localized enhanced engagement with cortical bone. This local quality enhancement facilitates osseointegration and improves reliability specifically at the critical bone-implant interface, while the rest of the device maintains simpler manufacturing requirements, balancing ease of manufacture with improved osseointegration capability
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 expandable implants improve primary stability, reduce micro-motion, and facilitate osseointegration, thereby reducing the risk of screw loosening and construct failure, promoting successful spinal fusion.
Implementation Method 1
The expansion joints may include a malleable or flexible material. The plurality of expandable sections may be configured to radially expand outward and away from one another, thereby increasing an outer diameter of the anchor.
Implementation Method 2
The central through hole may be internally threaded and configured to engage with corresponding threads along the shaft of the pedicle screw.
Data Source
AI summary
Pedicle bone anchor implants, assemblies, and methods thereof. The implant may include an expandable anchor having a body with expandable sections separated by one or more expansion joints, a plurality of expandable teeth, or an expandable head. The expandable anchor has a collapsed configuration and an expanded configuration, thereby creating a press-fit in adjacent bone.