Metatarsal Compression Nail Asymmetric Thread Design
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Solution Overview
Problem
Existing metatarsal compression nails lack an effective compression mechanism and stability, leading to inadequate anchoring and difficulty in removal.
Innovation Solution
A surgical metatarsal compression nail with a conical rear external thread and a tapered middle section, providing improved compression and stability, along with a cylindrical core area for guided screwing using a Kirschner wire, and automatic thread formation for secure anchoring and easy removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the rear external thread has a cylindrical contour like the front thread, then the structure is simple and easy to manufacture, but the compression effect is insufficient
Solution Approach 1:
The patent applies asymmetry by giving the rear external thread a conical contour while the front thread remains cylindrical. This asymmetric design allows the rear thread to generate compression force through its tapering geometry, improving the compression effect without complicating the overall structure excessively.
Solution Approach 2:
The patent applies local quality by differentiating the contours of the front and rear external threads. The front thread has a cylindrical contour for stable insertion, while the rear thread has a conical contour specifically designed to generate compression. This localized differentiation optimizes each thread's function for its specific purpose.
2Device complexity
If the rear and front threads are directly connected without a middle section, then the structure is compact, but automatic twisting during screwing in cannot be avoided and fixation position is poorly defined
Solution Approach 1:
The patent applies segmentation by dividing the nail into distinct sections: a front threaded section, a conical middle section, and a rear threaded section. The conical middle section acts as a transition zone that guides the nail during insertion, preventing automatic twisting and ensuring precise fixation position, while still maintaining overall structural compactness.
3Ease of manufacture
If the thread pitch of front and rear threads is equal, then the manufacturing is simpler, but compression effect is not achieved
Solution Approach 1:
The patent applies local quality by assigning different thread pitches to the front and rear threads. The rear thread has a smaller pitch than the front thread, which is specifically designed to generate compression force. This localized differentiation in thread parameters enables the compression function while keeping the manufacturing process relatively simple.
Data Source
Figure 1~9
AI summary
The nail (1) has a core area, a front threaded portion (6) with a front external thread, and a rear threaded portion with a rear external thread. A central section (8) is arranged between the front and rear threaded portions, where a pitch of the front external thread is greater than that of the rear external thread. The rear external thread includes a conical envelope contour (11), which tapers toward a front end of the compression nail, where a cone angle of the conical envelope contour is 2 degrees.