One-Piece Intramedullary Nail Coupling for Lag Screw Stability
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Solution Overview
Problem
Conventional intramedullary nails and set screws for femur fractures face challenges such as cumbersome preassembly, potential jamming during insertion, and inadequate mechanical stability due to uncontrolled medial deviation of the lag screw, leading to increased operation time and reduced load stability.
Innovation Solution
An implant system featuring a one-piece coupling member with a drive portion and bone fastener engagement portion, preassembled within the intramedullary nail, which prevents rotation of the bone fastener by engaging its grooves, allowing for simplified surgical procedures and enhanced mechanical stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional two-piece set screw structure is used, then the bone fastener can be engaged, but the preassembly becomes cumbersome and increases the risk of jamming during insertion
Solution Approach 1:
The patent combines the drive portion and bone fastener engagement portion into a single integrated coupling member. This one-piece structure eliminates the complexity of assembling multiple components and prevents jamming that occurs with conventional two-piece set screws during insertion into the intramedullary nail.
2Ease of operation
If a conventional set screw with guiding structure is used, then the bone fastener can be engaged, but the operation time increases due to additional operation steps
Solution Approach 1:
The coupling member is preassembled within the intramedullary nail before surgery, with the drive portion and bone fastener engagement portion already positioned correctly. This preliminary preparation eliminates the need for complex intraoperative assembly steps, reducing operation time while maintaining ease of use during the actual surgical procedure.
3Reliability
If a conventional set screw with prongs or rims is used, then the lag screw can be engaged, but uncontrolled medial deviation of the lag screw cannot be prevented
Solution Approach 1:
The coupling member acts as an intermediary between the drive mechanism and the bone fastener. Its specific engagement portion with grooves or ramps interfaces with the bone fastener to prevent uncontrolled medial deviation, while the drive portion allows controlled rotation. This intermediary structure provides both stability and controllability that conventional direct engagement cannot achieve.
4Ease of manufacture
If a conventional two-piece set screw is preassembled, then the components can be prepared in advance, but the small set screw gets stuck or jammed during sliding within the intramedullary nail
Solution Approach 1:
By merging the drive portion and bone fastener engagement portion into a single coupling member, the patent eliminates the sliding interface between separate components that causes jamming. The integrated structure maintains preassembly capability while ensuring reliable sliding within the intramedullary nail during insertion.
Data Source
AI summary
An implant system for use in orthopaedic surgery for fixation of bone includes an intramedullary nail and a coupling member. The intramedullary nail includes a proximal portion defining a longitudinal axis. The proximal portion includes an axial bore defining an axis substantially parallel to the longitudinal axis of the proximal portion and a transverse bore configured to receive a bone fastener. The coupling member includes a through hole and is movably arranged within the axial bore of the proximal portion. Further, the coupling member includes a drive portion and a bone fastener engagement portion. The drive portion is in one variant non-rotatably coupled to the bone fastener engagement portion. The bone fastener engagement portion is configured to engage the bone fastener penetrating the transverse bore. In one variant the engagement is realized via an extended contact region.