Multi-Axial Bone Fixation Locking via Compression Deformation
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Solution Overview
Problem
Existing multi-axial connection systems for bone fixation lack efficient mechanisms to securely engage pedicle screws with rods, particularly in providing stable angular relationships and ease of assembly, especially for cannulated fasteners.
Innovation Solution
A multi-axial connection system comprising a body with a tapered fastener head receiving chamber and a rod receiving channel, a retention ring, and a compression element that deforms to securely fix the pedicle screw's angular relationship with the rod, utilizing an interference fit and a deformation element to enhance locking stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a multi-axial connection system uses a tapered fastener head receiving chamber with a retention ring and compression element, then the locking stability and angular fixation of pedicle screws relative to rods is improved, but the device complexity increases
Solution Approach 1:
The retention ring is disposed within the fastener head receiving chamber, and the compression element is received within the body and engages with the retention ring and rod. This nested arrangement allows multiple functional components to be integrated within a compact structure, achieving stable locking without excessive device complexity
Solution Approach 2:
The fastener head receiving chamber is tapered to receive the fastener head, and the retention ring has a curved configuration that interacts with the fastener head and compression element. The tapered and curved geometries provide self-centering and stable angular fixation while maintaining smooth load transfer
2Adaptability or versatility
If the system allows adjustable angles and lateral offsets for spinal fixation, then the adaptability and ease of operation are improved, but the manufacturing precision requirements increase
Solution Approach 1:
The system allows the fastener head to be positioned at various angles within the tapered receiving chamber before final locking. The compression element can be adjusted to secure the rod at different angular positions, providing dynamic adjustability during surgery while maintaining precise locked positions
Solution Approach 2:
The multi-axial connection system divides the fixation function into separate adjustable components: the fastener head orientation, the retention ring position, and the compression element adjustment. This segmentation allows independent adjustment of each parameter to achieve the desired spinal alignment
3Strength
If a compression element deforms to securely fix the pedicle screw's angular relationship with the rod, then the strength of fixation is improved, but the difficulty of assembly increases
Solution Approach 1:
The compression element is designed to deform elastically under compression load, changing its shape to lock the rod against the retention ring and fastener head. This deformation provides strong fixation while the elastic nature of the material allows for controlled assembly and potential adjustment
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 system provides a secure and stable angular fixation of pedicle screws relative to rods, improving locking mechanisms, especially for cannulated fasteners, and simplifies assembly by allowing for adjustable angles and lateral offsets, enhancing the stability and adjustability of spinal fixation.
Implementation Method 1
a compression element configured to cooperate with the body to urge a rod, when the rod is disposed within the body rod receiving channel, into contact with at least part of the pressure cap
Implementation Method 2
utilizing an interference fit and a deformation element to enhance locking stability
Data Source
AI summary
A system and method for a multi-axial connection of an apparatus to bone. The system may include a fastener inserted into a body and a head of the fastener held within a chamber of the body through a combination of a retention ring, a pressure cap, a rod, and a compression element. The compression element applies force to the rod which, in turn, pushed on the pressure cap. The force on the pressure cap urges it against the head of the fastener and pushed it against the retention ring. The force on the retention ring causes it to expand to the walls of the chamber. Once the ring can no longer expand within the chamber, the head of the fastener is wedged between the retention ring and the pressure cap.