Resorbable Self-Tapping Screw for Stronger Bone Fixation
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Solution Overview
Problem
Resorbable screws used in cranio-maxillofacial surgeries often provide inadequate fixation and may weaken or dislodge over time, leading to post-surgical complications and the need for additional surgery, and require pilot hole tapping, increasing surgical time and complexity.
Innovation Solution
A fastener with a shaft that changes configuration under predetermined torque, featuring a distal portion that transforms from a static to a movable state, allowing self-tapping into bone without pre-drilling, and is designed to improve anchorage and load-bearing capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If resorbable screws are used for fixation, then the need for removal surgery is avoided, but the fixation strength and reliability deteriorate over time
Solution Approach 1:
The screw transitions from a static structure to a dynamic one through the formation of longitudinal channels that allow the distal portion to expand radially. This dynamic transformation enables the screw to adapt its shape during insertion, improving fixation reliability while maintaining resorbability. The channels act as expansion spaces that activate under insertion torque, allowing the screw to engage bone more effectively.
Solution Approach 2:
The physical parameters of the screw change during insertion through a transformation process. The distal portion changes from a compact cylindrical shape to an expanded configuration with increased radial dimensions. This parameter change is triggered by the torque applied during insertion and allows the screw to achieve better mechanical interlocking with the bone, thereby improving fixation strength.
2Ease of operation
If pilot hole tapping is performed prior to screw installation, then screw insertion is facilitated, but surgical time and procedural complexity increase
Solution Approach 1:
The screw performs its own hole preparation function through the longitudinal channels formed in its shaft. These channels allow the distal portion to expand and cut its own insertion path in the bone without requiring a separate pilot hole tapping step. The screw essentially prepares its own receiving space during the insertion process itself, eliminating the need for preliminary hole preparation.
Solution Approach 2:
The pilot hole tapping step is completely removed from the surgical procedure. The longitudinal channels in the screw shaft extract the need for pre-drilling by providing internal expansion spaces that allow the screw to self-tap into the bone during insertion, simplifying the overall surgical workflow.
3Adaptability or versatility
If resorbable screw materials are used, then tissue integration is achieved, but anchorage capacity and load bearing strength are reduced
Solution Approach 1:
The screw utilizes dynamic shape change to compensate for the inherently lower strength of resorbable materials. By transforming from a compact to an expanded configuration during insertion, the screw achieves superior mechanical interlocking with the bone tissue. This dynamic adaptation allows resorbable screws to achieve adequate anchorage capacity that would otherwise be unattainable with static designs.
Solution Approach 2:
The screw achieves enhanced load bearing capacity by utilizing the radial dimension through expansion. The longitudinal channels enable the distal portion to expand radially outward, increasing its engagement with the bone in the radial direction. This dimensional change compensates for the lower material strength by distributing loads over a larger effective area and creating stronger mechanical interlocking.
Data Source
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AI summary
A fastener for implantation in a bone includes a head and a shaft. A first thread and a second thread are disposed on the shaft, the second thread being parallel to and offset from the first thread. Each of the first thread and the second thread includes an interruption at every half revolution of the thread such that a first axis passes through a first plurality of interruptions and a second axis passes through a second plurality of interruptions. The first axis and the second axis are on opposite sides of the shaft. Further, each interruption extends across a lateral width of the respective thread such that a lateral edge of the thread on a first side of the interruption is laterally offset from a lateral edge of the thread on a second side of the interruption.