Triple Helical Thread Bone Screw for Pull-Out Strength
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Solution Overview
Problem
Bone screws used in surgical applications lack sufficient pull-out strength under natural movement loads and have complex and time-consuming implantation and removal processes.
Innovation Solution
A bone screw design featuring a triple helical thread with symmetrically aligned threads and a constant diameter shank, along with a self-tapping tip and driver-receiving head for easier insertion and removal, providing improved pull-out strength and facilitating quicker implantation and potential revisions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a conventional bone screw design is used, then the implantation process is simple, but the pull-out strength under natural movement loads is insufficient
Solution Approach 1:
The thread structure is divided into multiple independent helical threads (first, second, and third helical threads) that are symmetrically arranged around the shank. Each helical thread acts as an independent load-bearing element, distributing the pull-out forces across multiple threads rather than relying on a single thread structure, thereby increasing overall pull-out strength.
Solution Approach 2:
The invention transitions from a conventional single-thread or double-thread design to a triple helical thread configuration, adding dimensional complexity to the thread arrangement. The three helical threads are offset by approximately 120 degrees from one another, creating a three-dimensional load distribution pattern that enhances pull-out resistance in multiple directions simultaneously.
2Strength
If a complex bone screw design is used to improve pull-out strength, then the insertion time increases
Solution Approach 1:
The bone screw incorporates a self-tapping tip that automatically creates its own threading in the bone during insertion. This self-tapping mechanism eliminates the need for pre-drilling or separate threading operations, allowing the complex triple helical thread structure to be formed in a single insertion motion, thereby reducing insertion time despite the complexity of the thread design.
Solution Approach 2:
The self-tapping tip performs the thread-cutting action simultaneously with the insertion process itself. As the screw is driven into the bone, the self-tapping tip pre-creates the threading path ahead of the main threads, enabling the complex triple helical thread structure to engage the bone immediately without requiring separate preparatory steps.
3Ease of operation
If a self-tapping tip is added to enable easier insertion, then the device complexity increases
Solution Approach 1:
The self-tapping tip is integrated as an integral component of the shank, merging the thread-cutting function with the main body of the screw. This integration eliminates the need for separate tapping tools or multi-step insertion procedures, allowing the self-tapping capability to be achieved through a single unified device structure.
Data Source
AI summary
A bone screw is disclosed. A head includes a driver-receiving element formed thereon. A shank having a proximal portion, which is integrally connected to the head, and a distal portion maintains a constant diameter from the proximal portion to the distal portion. Three helical threads extend around the shank from the proximal portion to the distal portion. The three helical threads are symmetrically and helically aligned and advance uniformly along the length of the shank for each revolution to define a thread depth that remains constant along the length of the shank. The three helical threads respectively include three leads, which are offset by approximately 120° from each another. A tip is integrally connected to the distal portion of the shank and the tip intersects with a flute to define a self-tapping point.