Variable-Pitch Fixation Screw for Low-Force Compression Insertion
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Solution Overview
Problem
Conventional fixation devices face challenges in accurately locating and inserting screws without causing undue tissue damage, requiring significant urging force, and leading to errors due to surgeon fatigue, especially during multiple operations.
Innovation Solution
A fixation device with a screw thread that has a varying pitch at the tip end and a constant pitch along another region, allowing for easy and accurate starting, reduced axial urging force, and minimized tissue damage, featuring a cannulated design with visible indicators for precise orientation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If conventional interference screws are used, then fixation can be provided between components, but significant urging force is required to start the screwing process
Solution Approach 1:
The screw thread is designed with different pitch characteristics at different locations: a first pitch at the tip end for easy starting, and a second pitch along the main body for secure fixation. This local differentiation allows the screw to require less urging force during insertion while maintaining strong fixation capability.
Solution Approach 2:
The screw thread is segmented into two distinct regions with different pitch values. The first region (tip end) has a pitch optimized for easy engagement with minimal force, while the second region (main body) has a pitch optimized for fixation strength, allowing each segment to perform its specific function optimally.
2Measurement precision
If conventional interference screws are used, then fixation can be provided, but accurate location and orientation are difficult to achieve
Solution Approach 1:
A guide wire is inserted into the bone tunnel beforehand to establish the correct path and orientation. The interference screw is then threaded onto this guide wire, which preliminarily positions the screw at the correct location and angle before final insertion, ensuring accurate placement without requiring complex alignment maneuvers.
Solution Approach 2:
The guide wire acts as an intermediary element that mediates between the surgeon's positioning intent and the final screw placement. It provides a physical reference that guides the screw into the correct position and orientation, translating the desired anatomical alignment into actual screw placement.
3Object-affected harmful factors
If conventional interference screws are used, then fixation can be provided, but tissue damage may occur during insertion
Solution Approach 1:
The screw thread pitch is optimized locally at the tip end to be more gradual, which allows the screw to cut into the bone more smoothly and progressively. This reduces sudden tissue displacement and damage during insertion while maintaining the ability to provide reliable fixation once inserted.
4Productivity
If conventional interference screws are used, then fixation can be provided, but surgeon fatigue and errors increase during multiple operations
Solution Approach 1:
The screw thread pitch parameter is changed along the length of the screw, with a coarser pitch at the tip for easier starting and a finer pitch along the body for better fixation. This parameter variation reduces the urging force required during insertion, making the procedure less physically demanding for surgeons performing multiple operations while maintaining fixation reliability.
Data Source
AI summary
A method and apparatus are disclosed for providing a compression fixation between a first and further component. The apparatus comprises an elongate body having a head end and a tip end and comprising a screw thread including a first region in which the screw thread has a corresponding first pitch and a further region, extending from the tip end, in which the screw thread is tapered and has a corresponding farther pitch that continually decreases away from the tip end.