Polyaxial Spinal Rod Connectors for Non-Parallel Alignment
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Solution Overview
Problem
Existing spinal fixation systems face challenges in connecting two spinal fixation rods that are not in generally planar or parallel alignment, necessitating an apparatus that can accommodate non-parallel and non-planar configurations.
Innovation Solution
A polyaxial rod connector with a connector body intersected by imaginary reference planes, featuring spinal rod passages and set screw openings that allow for variable orientations, including hourglass-shaped cross-sections and spinal rod cradles to secure rods at angles up to 40 degrees relative to each other.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional spinal rod connectors are used to connect two spinal fixation rods, then the connection is simple and straightforward, but the rods must be in generally planar and parallel alignment, limiting adaptability to non-parallel configurations
Solution Approach 1:
The connector body incorporates a polyaxial mechanism that allows dynamic adjustment of the second rod's orientation relative to the first rod. The set screw and bearing assembly enable the second rod to be positioned at various angles (including up to 40 degrees of angular misalignment) and locked in place, transforming a static connector into a dynamically adjustable one that adapts to non-parallel rod configurations
Solution Approach 2:
The invention introduces an additional degree of freedom by allowing the second rod to be oriented not only in the plane of the first rod but also at angles relative to it. The polyaxial connector body with its inclined set screw axis and bearing assembly adds rotational capability in multiple dimensions, enabling connection of rods that are misaligned in both plane and angle
2Adaptability or versatility
If the connector allows for variable orientations to accommodate non-parallel rods, then adaptability is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The connector is designed with specific geometric parameters that enable variable orientations. The inclined set screw axis (at a specific angle relative to the rod passage axis) and the bearing assembly geometry are carefully parameterized to allow controlled angular adjustment. By optimizing these parameters, the connector achieves a balance between adaptability and manufacturability, allowing variable orientations without requiring extreme manufacturing precision
3Ease of operation
If the connector body includes multiple passages and set screw mechanisms for polyaxial adjustment, then the ease of operation for securing rods at angles is improved, but the device complexity increases
Solution Approach 1:
The invention merges multiple functions into a single integrated connector body. The bearing assembly, set screw mechanism, and rod passages are combined into one unitary structure rather than separate components. This merging reduces the overall number of parts while maintaining the capability for polyaxial adjustment, improving ease of operation without proportionally increasing device complexity
Data Source
AI summary
A polyaxial rod connector comprising a body having an external surface. The connector body is intersected by an imaginary first reference plane and an imaginary second reference plane perpendicular to the first plane. The first body portion is on one side of the first plane and defines a first spinal rod passage defining a first passage axis and a first set screw opening defining a first axis perpendicular to the first passage axis. A second body portion is adjoined to the first body portion, defining a second spiral rod passage defining a plurality of passage axes, and a second set screw opening defining a second axis perpendicular to the plurality of second passage axes. The first passage axis is non-parallel with one of second passage axes in the second plane. Either the first or second spinal rod passage have an hourglass shaped cross-section parallel to the second plane.