Bone Plate Oblong Holes With Sloping Guideway For Screw Alignment
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Solution Overview
Problem
Existing bone fixing systems face issues with hidden gaps between the bone screw and plate, which can lead to liquid penetration and complications during implantation and removal, and are difficult to unthread due to poor thread engagement and manufacturing tolerances.
Innovation Solution
The bone plate features oblong holes with a first cylindrical thread region, a second semi-circular smooth bearing surface region, and a transitional region forming a sloping guideway, allowing for relative lateral movement and minimizing gaps between threads, enabling better thread engagement and easier screw unthreading.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If standard bone screws with rounded shoulder heads are used with smooth conical bearing surfaces in the bone plate, then the screws can be inserted at various angles, but hidden gaps form between the threads allowing liquid penetration
Solution Approach 1:
The patent applies different surface qualities to different regions of the hole: the upper region has a smooth conical or spherical bearing surface for angular adaptability, while the lower region has threaded portions with enhanced gripping effect. This local differentiation allows the hole to provide both angular insertion capability and secure thread engagement without gaps.
2Strength
If threads are produced on conical surfaces of bone screws and bone plates, then engagement is achieved, but manufacturing tolerances create gaps between meshing threads
Solution Approach 1:
The sloping guideway is formed in advance during manufacturing, creating a pre-guided path that directs the screw head into proper alignment with the threaded portion. This preliminary guiding action ensures that when the screw is inserted, the threads engage immediately with minimal gap, compensating for manufacturing tolerances.
Solution Approach 2:
The sloping guideway acts as an intermediary element between the smooth bearing surface and the threaded portion. It provides a transition zone that guides the screw head laterally and vertically into the correct position, ensuring precise thread engagement while maintaining the benefits of both smooth and threaded regions.
3Measurement precision
If combination holes with tips are used to prevent screw movement between hole portions, then position control is improved, but lateral movement for compression is restricted
Solution Approach 1:
The patent creates a dynamic system where the screw can move laterally along the sloping guideway during insertion to achieve compression, but once positioned, the threaded portion provides stable position control. The system transitions from a static blocked configuration to a dynamic guided compression mechanism.
4Ease of manufacture
If tolerance gaps are increased to facilitate manufacturing, then production ease improves, but liquid penetration and solidification problems occur
Solution Approach 1:
The patent changes the geometric parameters of the hole structure by adding the sloping guideway and optimizing the transition between smooth and threaded regions. This parameter modification allows for larger manufacturing tolerances in thread production while maintaining minimal gaps, as the guideway ensures proper alignment that compensates for dimensional variations.
Data Source
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AI summary
A system for fixating fractured bones comprising a bone plate (1) and bone screws. The bone plate includes oblong holes (4) with hole portions that are free from any barrier for a screw shaft moved between the hole portions. The hole portions also include support structures for the screw heads and a sloping guideway between the hole portions. One of the hole portions has an upper segment (50) with cylindrical thread on an arc of about less than 180, preferable 175 or most preferable 179 degrees and to which the guideway is sloping. An adapted screw (20) with cylindrical thread, when mounted in the bone plate, minimizes the gap between the threads.