Threaded Bone Implant With Segmented Pitches for Low-Torque Extraction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current threaded bone implants face challenges in minimizing articular cartilage damage during insertion and removal, particularly in small bones like those in the hand and foot, due to the need for larger diameters that can cause joint damage and require high torque for extraction, leading to potential implant and tool failure.
Innovation Solution
A method and tool system that includes an implant with axially spaced threaded lengths and a removal tool with opposite-handed threads, allowing for controlled advancement and withdrawal of the implant by turning the tool in opposite directions, minimizing the need for high torque and reducing articular cartilage damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the implant diameter is increased to provide adequate thread engagement and stability, then the fixation strength is improved, but the articular cartilage damage increases and the required insertion torque increases
Solution Approach 1:
The implant is divided into multiple threaded sections with different pitch characteristics. The leading end has a first pitch and the trailing end has a second pitch, allowing different portions of the implant to engage bone at different rates during insertion, enabling controlled advancement with reduced cartilage damage
Solution Approach 2:
Different portions of the implant have different thread pitches tailored to local requirements. The leading end uses a first pitch optimized for initial penetration and the trailing end uses a second pitch optimized for final engagement, with each section's properties matched to its specific function in the bone
2Strength
If the implant diameter is increased to maintain thread engagement, then the fixation strength is improved, but the required extraction torque increases causing tool failure
Solution Approach 1:
The threaded sections are segmented with different pitches, where the trailing end's second pitch is designed to disengage more easily than the leading end's first pitch, reducing the torque required for extraction while maintaining adequate fixation during use
Solution Approach 2:
The thread pitches are designed non-uniformly with the trailing end having a smaller pitch than the leading end, which is counterintuitive but enables easier extraction by reducing the mechanical interlocking at the trailing end where removal torque is applied
3Manufacturing precision
If a guide pin is used to facilitate implant placement, then the placement precision is improved, but the device complexity increases
Solution Approach 1:
The implant body itself serves as the guide pin through its cannulated construction with an axial passage, eliminating the need for a separate guide pin while maintaining placement precision. The same component that provides structural support also guides insertion
Solution Approach 2:
The guide pin function is merged with the implant body by providing a cannulated construction with an axial passage through which the implant can be advanced, combining two separate functions (guidance and structural support) into one component
Data Source
AI summary
The combination of: a) an implant having a body with a leading end and a trailing end and external threads extending around a lengthwise axis, the body having an axial through passage and configured to be directed into a bone passage whereby upon turning the body in a first direction around the lengthwise axis, the external threads engage a surface bounding the bone passage and cause the implant to be advanced in an assembly direction into an operative position; and b) a removal tool with a first component that is configured to be engaged with the body with the implant in the operative position in such a manner that the body will follow movement of the first component as the first component is: a) turned in a direction opposite to the first direction; and b) drawn in a direction oppositely to the assembly direction to thereby allow the implant to be separated from the bone.