Hybrid Cannulated Orthopedic Screw Interrupted Thread Design
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Solution Overview
Problem
Hybrid orthopedic screws face handling and performance drawbacks due to the inclusion of multiple materials in their construction, which affects their functionality and usability in orthopedic applications.
Innovation Solution
The development of orthopedic screws with a combination of an inner core member and an outer body member, where the inner core member and outer body member form an interrupted thread configuration, allowing for improved handling and performance by optimizing the thread diameters and flange widths, and using a manufacturing method involving machining and overmolding to create a cannulated screw with enhanced cutting and implantation capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple materials are used in the construction of hybrid orthopedic screws, then the functional performance is improved, but the handling and operation become more difficult
Solution Approach 1:
The patent combines multiple materials (metal inner core member and polymer outer body member) into a single integrated hybrid screw structure. The metal inner core provides structural strength and thread formation, while the polymer outer body provides bone engagement and reduced friction, achieving both improved functional performance and manageable handling characteristics.
Solution Approach 2:
The hybrid orthopedic screw utilizes composite material construction with a metal inner core member and a polymer outer body member. This composite structure allows each material to contribute its superior properties: the metal provides high strength and cutting capability, while the polymer provides low friction and bone compatibility, resolving the contradiction between performance and handling.
2Strength
If the outer body member is made larger to improve bone engagement, then the cutting capability is improved, but the insertion torque increases
Solution Approach 1:
The patent applies local quality by giving different regions of the screw different properties: the outer body member has a larger diameter for bone engagement and compression, while the inner core member has a smaller diameter optimized for cutting. The polymer outer body's larger size provides bone engagement without proportionally increasing insertion torque due to the material's low friction characteristics.
Solution Approach 2:
The patent changes material parameters by using a polymer outer body member with low friction properties instead of metal. This allows the outer body to have a larger diameter for improved bone engagement and compression while the low friction coefficient of the polymer material prevents proportional increase in insertion torque.
3Manufacturing precision
If the inner core member and outer body member form an interrupted thread, then the manufacturing precision is improved, but the structural complexity increases
Solution Approach 1:
The patent segments the screw into two distinct members: an inner core member with internal threads and an outer body member with external threads. The interrupted thread configuration is achieved by having the outer body member's external threads discontinue where they would interfere with the inner core member's internal threads, allowing independent manufacturing and assembly of precisely threaded components.
Solution Approach 2:
The patent implements a nested structure where the inner core member with internal threads is positioned within the outer body member with external threads. The interrupted thread design allows the inner core to be nested within the outer body without thread interference, achieving precise manufacturing through separate threading processes while the nested configuration provides structural integrity.
Data Source
AI summary
The disclosure relates to medical devices and methods of manufacturing medical devices. An orthopedic screw includes an inner core member having a head having a first outer diameter, a tip having a second outer diameter, and a body extending between the head and the tip and having a third outer diameter that is less than the first outer diameter and the second outer diameter. An outer body member is disposed circumferentially around the body of the inner core member and defines an outer body member external thread. The tip of the inner core member can define an inner core member external thread that forms an interrupted thread with the outer body member external thread.