Bone Screw Double-Conical Thread for Angular Locking Stability
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Solution Overview
Problem
Existing osteosynthesis devices face challenges in achieving a favorable insertion torque and high locking stability, especially when bone screws are inserted at angles other than perpendicular to the bone plate, which can lead to reduced stability and increased screwing resistance.
Innovation Solution
The osteosynthesis device features a bone plate with a conical internal thread and a bone screw with a conical external thread, where the thread in the screw head has a first section with a first conicity and a second section with a second conicity, including a point of discontinuity, allowing for a variably angularly stable connection. The bone screw is designed with a double-conical or multiple-conical thread, where the smaller cone corresponds to the conicity of the plate's thread, enabling secure locking and reduced insertion torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional single-conical thread is used in the bone screw head, then the screw can be inserted into the bone plate, but the locking stability decreases and screwing resistance increases when inserted at angles other than perpendicular
Solution Approach 1:
The thread in the screw head is divided into multiple sections (first section with first conicity, second section with second conicity) with different conical angles. This segmentation allows each section to perform different functions: one section facilitates easier screwing-in while the other provides enhanced locking stability, thereby resolving the contradiction between ease of operation and reliability.
Solution Approach 2:
Different sections of the thread are given different local properties through varying conicity. The first section has a conicity optimized for insertion, while the second section has a conicity optimized for locking. This local differentiation enables the single thread structure to simultaneously address both screwing resistance and locking stability requirements.
2Adaptability or versatility
If the bone screw is inserted at an angle other than perpendicular to the bone plate, then angular variability is achieved, but stability and screwing resistance are compromised
Solution Approach 1:
The dual-conicity thread design dynamically adapts to different insertion angles. When the screw is inserted at an angle, the appropriate thread section engages with the bone plate thread, maintaining stable connection through the geometric properties of the conical sections. This dynamic adaptation preserves connection stability across various angular positions.
3Power
If a multi-conical thread with different conicities is used, then favorable insertion torque and high locking stability are achieved, but the thread structure becomes more complex
Solution Approach 1:
Multiple functional requirements (favorable insertion torque and high locking stability) are merged into a single integrated thread structure on the screw head. The first and second thread sections are combined in one continuous thread form, eliminating the need for separate thread components while achieving both torque optimization and locking stability.
Data Source
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AI summary
The invention relates to an osteosynthesis device with a bone plate and with at least one bone screw, wherein the bone plate has at least one through-hole with a conical inner thread formed at least in part in the through-hole. Moreover, the bone screw has a screw shank and also a screw head with a conical thread, with the possibility of forming a connection at a variable and stable angle between bone screw and bone plate by receiving the screw head with conical outer thread in the respective through-hole of the bone plate. According to the invention, the thread in the screw head has a first portion A with a first conicity and a second portion B with a second conicity, wherein a zone of discontinuity with respect to the conicity is present between the first portion A and the second portion B.