Multi-Start Thread Closure Assembly for Bone Anchoring Stability
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Solution Overview
Problem
Existing closure assemblies for bone anchoring devices in orthopaedic spinal surgery face challenges in force distribution and locking force, leading to potential splaying or twisting of components during screwing and tightening.
Innovation Solution
A closure assembly featuring a first closure member with a multi-start external thread and a second closure member with a corresponding multi-start internal thread, along with a pressure member to distribute force evenly and reduce component distortion, allowing for improved force distribution and locking stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a single-start thread is used in the closure assembly, then the structure is simpler and easier to manufacture, but the force distribution is uneven causing splaying or twisting of components during tightening
Solution Approach 1:
The patent applies parameter changes by transitioning from a single-start thread to a multi-start thread configuration. This changes the geometric parameters of the thread structure, specifically the number of starts, which directly improves force distribution during tightening while managing the increased structural complexity through standardized multi-start thread designs.
2Force
If the closure assembly is tightened to generate high locking force, then the stabilization element is secured more firmly, but the components are more likely to splay or twist during the process
Solution Approach 1:
The patent applies segmentation by dividing the force application into multiple parallel thread starts. Instead of concentrating the tightening force on a single thread path, the multi-start thread configuration segments the force distribution across multiple threads, allowing high locking force to be generated while maintaining even force distribution that prevents component splaying or twisting.
Data Source
AI summary
A closure assembly for securing an elongate stabilization element in a receiving part of a bone anchoring device includes a first closure member and a second closure member. The first closure member is receivable between legs of the receiving part, has an axis of rotation, and includes an outer surface with an engagement portion configured to engage the legs of the receiving part, and an inner surface having at least a portion that is threaded and that defines a central passage that passes axially through the first closure member. The second closure member has an axis of rotation and an outer surface having a threaded portion configured to cooperate with the threaded portion of the inner surface of the first closure member. The threaded portion of the outer surface of the second closure member includes a multi-start thread with at least two starts.