Spinal Bone Anchor With Adjustable Saddle For Rod Alignment
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Solution Overview
Problem
Existing bone anchor systems for spinal stabilization often result in less than optimal fit between the anchor and the rod, leading to undesirable stress concentrations due to the need for contouring, bending, and angling of the rod through the channel of the bone anchor, which can compromise the transfer of corrective and stabilizing forces to the vertebrae.
Innovation Solution
A bone anchor assembly featuring an adjustable saddle that supports an elongated connecting element, allowing for pivoting within a defined plane, coupled with a receiver that maintains a fixed relationship with the bone anchor, ensuring optimal alignment and force transfer while accommodating varying orientations of the connecting element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the rod is contoured, bent, and angled to fit through the channel of the bone anchor, then the rod can be positioned to connect the anchor to the spine, but this creates stress concentrations and compromises force transfer
Solution Approach 1:
The bone anchor channel is designed with multiple degrees of freedom, allowing the rod to pivot and adjust its orientation dynamically. The channel includes a first degree of freedom for pivoting about a first axis and a second degree of freedom for pivoting about a second axis, enabling the rod to achieve optimal alignment without excessive bending or contouring, thereby reducing stress concentrations while maintaining effective force transfer to the vertebrae
Solution Approach 2:
The patent changes the geometric parameters of the bone anchor channel by introducing multi-axis pivoting capabilities. This allows the rod's orientation parameters (angle, position) to be adjusted within the channel, transforming the rigid fit requirement into a flexible alignment system that reduces stress while maintaining structural integrity
2Strength
If the bone anchor receiver and bone engaging portion are fixed relative to one another, then force transfer is improved, but this requires precise contouring and bending of the rod which creates stress concentrations
Solution Approach 1:
The bone anchor incorporates a receiver with a channel that provides multi-degree-of-freedom pivoting motion. This dynamic capability allows the rod to adjust its orientation independently, reducing the need for extreme contouring and bending. The fixed relationship between the receiver and bone engaging portion is maintained while the channel geometry accommodates rod orientation variations, thereby reducing stress concentrations without compromising force transfer
3Reliability
If the rod is contoured and bent to achieve optimal alignment, then the fit between anchor and rod is improved, but this creates undesirable stress concentrations
Solution Approach 1:
The channel geometry is designed to provide multi-degree-of-freedom pivoting motion, allowing the rod to achieve optimal alignment through controlled pivoting rather than extreme contouring and bending. This dynamic adjustment capability maintains reliable anchor-rod interface fit while significantly reducing stress concentrations in the rod and surrounding bone structure
Data Source
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AI summary
A bone anchor assembly is provided, which may be used in cervical, thoracic, lumbar or sacral areas of the spine or other orthopedic locations. The anchor assembly includes a bone anchor, a receiver mounted to the bone anchor, a saddle within the receiver, a spacer within the receiver, and an engaging member. The receiver extends along a central longitudinal axis proximally away from the bone anchor. A rod or other elongated connecting element is received in a passage of the receiver in contact with the saddle, and the engaging member engages the connecting element against the saddle, which engages the saddle against the spacer, which in turn engages the proximal head of the bone anchor in the receiver. The orientation of the saddle in the receiver is adjustable to correspond to the orientation of the connecting element relative to the central longitudinal axis of the receiver.