Bone Fixation Screw with Deployable Anchors for Cortical Engagement
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Solution Overview
Problem
Current bone screw fixation systems face challenges in providing adequate multi-directional pull-out strength and durability, particularly in osteoporotic and elderly patients, leading to increased screw loosening and bone fusion failures due to poor bone quality and increased rigidity.
Innovation Solution
A transcortical fixation pedicle screw with deployable anchors that utilize a screw body with outer threads and apertures, allowing anchors to extend into the cortical bone rim for enhanced fixation, distributing forces across a more rigid bone surface and reducing the reliance on softer cancellous bone.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional bone screw systems rely on outer screw threads to engage cortical bone and center the screw in cancellous bone, then the screw fixation depends on the quality of the cortical bone rim, but in osteoporotic and elderly patients, the cortical bone becomes less rigid and durable, leading to screw loosening and fixation failure
Solution Approach 1:
The invention divides the fixation function into two separate components: the screw body engages the cancellous bone centrally, while deployable anchors engage the cortical bone rim. This segmentation allows each component to optimize its fixation mechanism independently, with anchors providing dedicated cortical engagement without relying on the screw threads alone.
Solution Approach 2:
The invention transitions from a single-point fixation approach to a multi-directional fixation system by deploying anchors that extend radially outward from the screw body in multiple directions. This dimensional change creates fixation in both the radial (cortical) and axial (cancellous) dimensions, providing comprehensive stability.
2Force
If the inner cortical bone wall-screw thread interface is used to maximize fixation force, then optimal screw thread-inner cortical bone rim purchase is attempted, but this interface often provides sub-optimal screw fixation that allows bidirectional screw movement when stressed
Solution Approach 1:
The fixation function is segmented between the screw body (providing axial engagement in cancellous bone) and the deployable anchors (providing radial engagement in cortical bone). This separation ensures that cortical engagement is dedicated and optimized, preventing bidirectional movement by anchoring the screw laterally while the threads provide axial stability.
Solution Approach 2:
The anchors are deployed after screw insertion to preliminarily secure the screw in position by engaging the cortical bone rim. This preliminary anchoring action prevents bidirectional movement before the screw is fully stressed during patient mobility, establishing stable fixation from the outset.
3Reliability
If bone cement augmentation or increased thread count is used to improve purchase in osteoporotic bone, then some fixation improvement is achieved, but screw loosening and pseudo arthrosis remain common complications
Solution Approach 1:
The invention segments the fixation mechanism into screw body engagement (cancellous bone) and deployable anchor engagement (cortical bone). This provides a mechanically robust solution that does not rely on bone cement augmentation or increased thread count, thereby improving durability without significantly increasing system complexity.
Solution Approach 2:
The deployable anchors provide a dynamic fixation system that can adapt to patient movement and stress. The anchors are deployed after insertion to lock the screw in place, providing progressive stabilization that maintains fixation durability through the healing process without requiring complex additional components.
Data Source
AI summary
A bone fixation screw device for implantation into a bone of a patient is disclosed. The screw device includes a screw body having an outer surface. A plurality of outer screw threads extends around the outer surface of the screw body. A plurality of apertures or passages is defined through the outer surface. A plurality of anchors can extend out of corresponding apertures in the screw body. The anchors can be inserted into a patient's bone to further fixate and purchase the bone screw within the patient's bone. The screw body can include an inner cavity, the plurality of apertures each being open to the inner cavity. The anchors can extend out of corresponding apertures from the inner cavity.