Anchor-in-anchor bone fixation stability
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Solution Overview
Problem
Existing bone fixation systems face challenges in securely attaching fixation devices to underlying bone, as screws can become dislodged during normal anatomical function, leading to compromised attachment and instability.
Innovation Solution
The anchor-in-anchor system, which consists of a first bone anchor with a shaft and head, and a second bone anchor that is inserted through the head of the first anchor at various angles, providing a stable triangular load-bearing plane that resists migration and subsidence by angling the bone anchors relative to each other.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single bone anchor (screw) is used to attach fixation devices to underlying bone, then the device complexity is low, but the reliability of attachment is compromised as the screw can become dislodged during normal anatomical function
Solution Approach 1:
The patent implements an anchor-in-anchor system where a second bone anchor is inserted through the head of a first bone anchor, creating a nested configuration. The second anchor passes through the head portion of the first anchor and engages the bone at a different location, forming an interconnected assembly that significantly improves attachment reliability while maintaining reasonable system complexity
Solution Approach 2:
The patent introduces angular orientation between the first and second bone anchors, with the second anchor inserted at an angle relative to the first anchor's longitudinal axis. This angular configuration creates a triangular load-bearing plane that distributes forces across multiple dimensions, preventing dislodgement and enhancing attachment reliability
2Strength
If bone anchors are inserted at angles to create a triangular load-bearing plane, then the stability and force resistance are improved, but the manufacturing precision and insertion accuracy requirements increase
Solution Approach 1:
The patent incorporates a bore through the head of the first bone anchor that is pre-configured at a specific angle relative to the longitudinal axis. This preliminary angular configuration guides the insertion of the second bone anchor, ensuring the desired angular relationship and triangular load-bearing plane are achieved without requiring complex intraoperative alignment procedures
Solution Approach 2:
The head of the first bone anchor serves as an intermediary structure that facilitates the angular insertion of the second anchor. The bore through the head acts as a guiding feature, mediating the angular relationship between the two anchors and enabling precise angular positioning while simplifying the overall insertion process
Data Source
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AI summary
An anchor-in-anchor fixation system is provided for securing underlying structure, such as bone. The fixation system includes a first bone anchor having a shaft for fixation to underlying bone, and a head that defines an internal bore. A second bone anchor extends through the bore and into underlying bone. A fixation assembly is also provided that includes one or more fixation systems coupled to an auxiliary attachment member configured for long bone fixation, spinal fixation, or fixation of other bones as desired.