Orthopedic Fastener Thread Geometry for Reduced Insertion Torque
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current orthopaedic fasteners face issues such as misalignment, failure to withstand multidirectional forces, high insertion torque, heat buildup, and lack of tactile feedback, leading to trauma and osteonecrosis during surgical procedures.
Innovation Solution
A new thread geometry design utilizing single-point threading and multiple form cutting tools to create independently programmable thread features, including a left-handed flute for chip dispersal and improved self-tapping features, which reduces insertion force, provides tactile feedback, and enhances bone engagement while minimizing trauma.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If buttress thread profile is designed to increase retention by increasing friction, then retention is improved, but insertion torque increases and heat generation occurs
Solution Approach 1:
The patent changes the thread profile parameters from conventional buttress to a modified geometry with optimized flank angles and pitch. This parameter optimization allows the thread to engage bone effectively for retention while reducing the cutting action and friction during insertion, thereby lowering insertion torque and heat generation.
Solution Approach 2:
The thread design incorporates dynamic characteristics where the cutting edges are optimized to efficiently remove bone debris during insertion, reducing resistance. Once inserted, the thread geometry provides stable engagement with the bone, transitioning from a high-friction insertion phase to a low-friction retained phase.
2Reliability
If high insertion torque is used to ensure proper thread engagement, then thread engagement is improved, but bone trauma and heat buildup occur
Solution Approach 1:
The patent extracts the bone debris removal function from the threading process itself by incorporating optimized chip dispersal flutes that actively evacuate bone particles away from the thread engagement zone. This separation of debris removal from thread engagement reduces friction and heat generation while maintaining reliable thread-bone contact.
Solution Approach 2:
The thread geometry acts as an intermediary that distributes insertion forces more evenly across the bone structure. The optimized flank angles and root radii reduce stress concentrations, allowing proper thread engagement with lower peak forces, thereby minimizing bone trauma and heat generation.
3Ease of manufacture
If conventional buttress thread is used for self-tapping, then self-tapping capability is achieved, but fastener tends to wander off axis during insertion
Solution Approach 1:
The patent employs asymmetric thread geometry with different flank angles on the leading and trailing edges of the thread. The leading flank is optimized for cutting and centering during insertion, providing self-aligning characteristics that prevent wandering. The trailing flank is optimized for engagement and retention, maintaining self-tapping capability while improving axial alignment accuracy.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution reduces insertion force, minimizes heat generation, prevents bone trauma, and provides better tactile feedback for surgeons, resulting in improved fixation and shorter healing times with enhanced resistance to pull-out and bending forces.
Implementation Method 1
This allows the surgeon tactile feedback and reduces the effort required to deploy the fastener. This, in conjunction with a forward chip feeder, a centering pilot, and improved thread cutting features keep friction low, the fastener aligned and directed from wandering away from the preferred path.
Implementation Method 2
A new thread geometry design utilizing single-point threading and multiple form cutting tools to create independently programmable thread features, including a left-handed flute for chip dispersal and improved self-tapping features
Data Source
Figure 1
Figure 2~3
Figure 4~7
AI summary
An orthopedic structure includes a method for making a threaded fastener with thread geometry and leading edge geometry which provides greater precision during installation. Specifically, thread pitch and tooth profiles are independently variable. A leading portion of the fastener advances bone shards forward of the forward of the fastener to reduce insertion torque and prevent the shards from residing in the upstream tooth profile for better retention.